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13 LIGHTING ENGINEERING 2002 Chapter 1. THE LIGHT 1.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.2. Wave characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.3. Frequency spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.4. Dual nature of light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Transcript
Page 1: 38 Lighting Handbook

13LIGHTING ENGINEERING 2002

Chapter 1.

THE LIGHT

1.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.2. Wave characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

1.3. Frequency spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

1.4. Dual nature of light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Page 2: 38 Lighting Handbook

14 LIGHTING ENGINEERING 2002

Page 3: 38 Lighting Handbook

1.1. General remarks

It is well known that there are several types of energy: mechanical, thermal, electrostatic and electromagnetic.

• If mechanical energy is applied to a body at rest, it tends to set into motion, thus, transforming the energy applied into kinetic energy.

This energy is taken along and is also transmitted to other bodies, in case it collides with them.

• Heat is a form of energy which diffuses through convection, conduction or radiation.

• When a switch is "turned on", the metallic filament of an incandescent lamp is connected by means of a potential difference. Thus,

electric charge flows through the filament in a similar way pressure difference in a hosepipe makes water flow through it. Electron flow

constitutes the electric current. Current is usually associated to charge movement in bridge conductors, but electric current emerges

from any charge flow. When electric current diffuses through conductors and reaches a receptor, this receptor is transformed into

another type of energy.

• If the body or the emitting source irradiates energy, propagation takes place by means of radiation in the form of waves* which are

those physical disturbances which diffuse in a certain medium or in the vacuum.

Mechanical waves diffuse this kind of energy through an elastic material medium. They are longitudinal sound waves because particle

vibration coincides with their propagation direction. Two examples of this phenomenon are vibrations of spring and sounds. In a spring,

vibrations propagate in only one direction. In the case of sound, vibrations propagate in three different dimensions.

Electromagnetic waves propagate the energy produced through oscillations of electric and magnetic fields and do not need a

propagation material medium. For example, the light.

Out of the different ways waves propagate, there are several regimes. From the point of view of lighting engineering, the periodical

regime is the one which interests us. It may be defined as regular time interval repetitions and expressed graphically as several wave

forms.

Thus, wave form represents oscillations as phenomena in which physical quantity is a periodical function of an independent variable (time),

whose average value is null. That is to say, we are talking about simple or fundamental harmonic functions, like the sine or the cosine, of a

single, one-dimensional and transversal variable (propagated perpendicularly to the direction in which particles vibrate). In short, there is a

wide range of physical, electric and electromagnetic phenomena, among which electricity, light, sound, hertzian waves or sea waves are

included. Their characteristics are determined by studying sine waves. This is the reason why the concept of wave radiation and

characteristics to define them is used.

1.2. Wave characteristics

Wavelength ()It is defined as the distance travelled by a wave in a period. For a transversal wave, it may be defined as the distance between two

consecutive maximums or between any other two points located in the same phase (Fig. 1).

Figure 1. Wavelength .

* Wave: Graphic expression of a periodic variation represented in amplitude and time. Amplitude is the maximum value or ordenate taken by the wave.

λ λ

λ λ

15LIGHTING ENGINEERING 2002

Chapter 1. THE LIGHT

Page 4: 38 Lighting Handbook

16 LIGHTING ENGINEERING 2002

Chapter 1. THE LIGHT

Wavelength is a highly important characteristic in order to classify the visible radiation spectrum, object of study in this section of

LIGHTING ENGINEERING 2002.

This parameter is determined by the result of propagation velocity (), multiplied by the time it takes to cover one cycle (T Period):

= · (m/s · s = m)

Frequency ( f )It is defined as the number of periods that take place in a time unit.

Since period is inverse to frequency, , the equation above is transformed into:

(m/s · 1/s-1 = m)

and, therefore, frequency is directly proportional to propagation velocity, and inversely proportional to wavelength.

(s-1 = cycles/second = Hz)

Wavelength decreases when frequency increases.

Frequency is stable and independent from the medium through which the wave propagates. This constitutes an important characteristic

to classify electromagnetic waves.

Propagation velocity ()Propagation velocity depends on wave type, elasticity of the medium and rigidity. If the medium is homogeneous and isotropic,

propagation velocity is the same in all directions.

For example, sound propagation velocity in the air, at 20 ºC, is that of 343.5 m/s, whereas electromagnetic waves propagation velocity

in the vacuum is equivalent to 300 000 km/s = 3 · 108 m/s.

The fundamental equation which relates propagation velocity to wavelength and frequency is

= · f (m · s-1 = m/s)

1.3. Frequency spectrum

Given the fact that electromagnetic radiations share the same nature and they all propagate in the vacuum at the same velocity

( = 3 · 108 m/s), those characteristics that make them different are their wavelength, that is to say, their frequency ( = · f).Electromagnetic radiations are the following: gamma rays, X-rays, ultraviolet radiation, light, Infrared rays, microwaves, radio waves and

other radiations. The human eye is sensitive to electromagnetic radiation with wavelengths ranging approximately between 380 and 780

nm. This interval is known as visible light. Shortest wavelengths of the visible spectrum correspond to violet light, and the longest, to

red light. Between these two extremes are all the colours found in the rainbow (Fig. 2). Electromagnetic waves have slightly shorter

wavelengths when compared to visible light and are known as ultraviolet rays. Those with slightly longer wavelengths are known as

infrared waves. Thermal radiation emitted by bodies at a normal temperature is placed in the infrared region of the electromagnetic

spectrum. There are no limits in electromagnetic radiation wavelength, which is the same as stating that all wavelengths (or frequencies)

are possible from a theoretical point of view.

It must be taken into account that those wavelength intervals (or frequency ones) in which the electromagnetic spectrum divides

sometimes are not well defined and often, they overlap. For example, electromagnetic waves with wavelengths of the order of 0.1 nm.

are frequently named X-rays. Nevertheless, if originated from nuclear radioactivity, they are called Gamma rays.

f =

= f

= 1f

Page 5: 38 Lighting Handbook

Figure 2. Classification of visible spectrum.

Lamp manufacturers usually give radio spectrometrical curves with values raging between 380 nm. and 780 nm. As we have shown,

apart from the meter, nanometer (nm.) is also used in order to express wavelengths, as well as other units like Angstrom (Å) and micron

(m.).

1 m. = 10-60 m

1 nm. = 10-90 m

1 Å. = 10-10 m

Radiation of a continuous spectrum sourceAll bodies radiate energy in an ample field of wavelength at any temperature except for absolute zero. This radiation is known as

incandescence or temperature radiation. Sources of incandescent artificial light are:

- A flame from combustion, like a candle, oil candle, etc.

- A red-hot ingot or steal bar.

- An incandescent lamp filament, as the most common source to produce artificial light.

Incandescence is applied to types of radiation associated with temperature.

The spectroradiometer is used to know how the radiated potency is distributed between wavelengths. The spectroradiometrical function

or spectral distribution curve obtained is indicated in Fig. 3. Wavelengths in nm. are placed in the abscissas, and values related to energy,

with respect to the maximum radiated understood as 100%, are placed in the ordinates.

300 nm.Black light

Infrared

Violet

Indigo

Blue

Green - Blue

Green

Green - Yellow

Yellow

Orange

Red

Ultraviolet rays790x1012 Hz

400x1012 Hz

384x1012 Hz370x1012 Hz

320340360380400 nm.420440460480500 nm.520540560580600 nm.620640660680700 nm.720740760780800 nm.

Visi

ble

light

spe

ctra

l dis

trib

utio

n

DSp

ectr

al d

istr

ibut

ion

acco

rdin

g to

lam

p m

anuf

actu

rer

17LIGHTING ENGINEERING 2002

Chapter 1. THE LIGHT

Page 6: 38 Lighting Handbook

18 LIGHTING ENGINEERING 2002

Figure 3

Radiation of a discontinuous spectrum sourceRadiant energy of a gaseous discharge source, such as the ones of high pressure sodium, high pressure mercury, argon, neon, etc.,

consists in a radiation integrated by small wavelength intervals which may be called emission peaks.

Each gas has a wavelength characteristic of its own radiation which depends on the gas molecular structure through which discharge

takes place. This kind of discharge is usually called luminescence and it is characterised by temperature independent radiation types.

The most common luminous sources or discharge lamps are fluorescent tubes: high pressure mercury, high pressure sodium and

induction ones.

As for incandescence, the spectroradiometer is used to obtain the spectral distribution curve. The spectroradiometer function obtained

is indicated in Fig. 4. Wavelengths in nm. are placed in the abscissas, and values related to energy, with respect to the maximum radiated

understood as 100%, are placed in the ordinates.

Also, the specific potency in mW/nm.wavelength is usually given in the ordinates.

Figure 4

1.4. Dual nature of light

Light has intrigued humankind for centuries. The most ancient theories considered light as something emitted by the human eye. Later

on, it was understood that light should come from the objects seen and that it entered the eye producing the feeling of vision. The

question of whether light is composed by a beam of particles or it is a certain type of wave movement has frequently been studied in

the history of science. Between the proponents and defendants of the corpuscular theory of light, the most influential was undoubtedly

Newton. Using the above mentioned theory, he was able to explain the laws of reflection and refraction. Nevertheless, his deduction of

the law of refraction was based on the hypothesis that light moves more quickly in water or in glass than in air. Some time later, the

hypothesis was proved to be wrong. The main proponents of the wave theory of light were Christian Huygens and Robert Hooke. Using

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

380

nm.

20

40

60

80

100

%%

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

Spectral distribution for a cold white coloured fluorescent lamp Spectral distribution for a high pressure mercury lamp of corrected colour

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

Spectral distribution for a normal day light Spectral distribution for an incandescent lamp

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

380

nm.

20

40

60

80

100

400

nm.

500

nm.

600

nm.

700

nm.

780

nm.

%%

Chapter 1. THE LIGHT

Page 7: 38 Lighting Handbook

their own theory of wave propagation, Huygens was able to explain reflection and refraction supposing that light travels more slowly in

glass or in water than in air. Newton realized about the advantages of the wave theory of light, particularly because it explained colours

formed by thin films, which he had studied very thoroughly. Notwithstanding, he rejected the wave theory due to the apparent rectilinear

propagation of light. In his time, diffraction of the luminous beam, which allows to evade objects, had not yet been observed.

Newton's corpuscular theory of light was accepted for more than a century. After some time, in 1801, Thomas Young revitalized the

wave theory of light. He was one of the first scientists to introduce the idea of interference as a wave phenomenon present both in the

light and in the sound. His observations of interferences obtained from light were a clear demonstration of their wave nature.

Nevertheless, Young's research was not known by the scientific community for more than ten years. Probably, the most important

breakthrough regarding a general acceptance of the wave theory of light is due to the French physicist Augustin Fresnel (1782-1827),

who conducted thorough experiments on interference and diffraction. He also developed a wave theory based on a solid mathematical

foundation. In 1850, Jean Foucault measured the speed of light in water and checked that it is slower than in air. Thus, he finally

destroyed Newton's corpuscular theory of light. In 1860, James Clerk Maxwell published his electromagnetic mathematical theory which

preceded the existence of electromagnetic waves. These waves propagated with a calculated speed through electricity and magnetism

laws which was equivalent in value to 3 x 108 m/s, the same value than the speed of light. Maxwell's theory was confirmed by Hertz

in 1887 who used a tuned electric circuit to generate waves and another similar circuit to detect them. In the second half of the 19th

century, Kirchoff and other scientists applied Maxwell's laws to explain interference and diffraction of light and other electromagnetic

waves and support Huygens' empirical methods of wave construction on a solid mathematical basis.

Although wave theory is generally correct when propagation of light is described (and of other electromagnetic waves), it fails when other

light properties are to be explained, specially the interaction of light with matter. Hertz, in a famous experiment in 1887 confirmed

Maxwell's wave theory, and he also discovered the photoelectric effect. Such an effect can also be explained by means of a model of

particles for light, as Einstein proved only a few years later. This way, a new corpuscular model of light was introduced. The particles of

light are known as photons and energy E of a photon is related to frequency f of the luminous wave associated by Einstein's famous

ratio E = h · f (h = Planck's constant). A complete understanding of dual nature of light was not achieved before the 20's in the 20th

century. Experiments conducted by scientists of the time (Davisson, Germer, Thompson and others) proved that electrons (and other

"particles") also had a dual nature and presented interference and diffraction properties besides their well-known particle properties.

In brief, the modern theory of quantum mechanics of luminous radiation accepts the fact that light seems to have a dual nature. On the

one hand, light propagation phenomena find a better explanation within Maxwell's electromagnetic theory (electromagnetic wave

fundamental nature). On the other hand, mutual action between light and matter, in the processes of absorption and emission, is a

photoelectric phenomenon (corpuscular nature).

19LIGHTING ENGINEERING 2002

Chapter 1. THE LIGHT

Page 8: 38 Lighting Handbook

20 LIGHTING ENGINEERING 2002

Chapter 1. THE LIGHT

Page 9: 38 Lighting Handbook

21LIGHTING ENGINEERING 2002

Chapter 2.

THE EYE

2.1. Human eye as a light reception organ . . . . . . . . . . . . . . . . . . . . . . . . 23

2.2. Structural description of the eye . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.3. Image formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.4. Eye sensitivity curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2.5. Accommodation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.6. Contrast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

2.7. Adaptation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

2.8. Glare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Page 10: 38 Lighting Handbook

22 LIGHTING ENGINEERING 2002

Page 11: 38 Lighting Handbook

2.1. Human eye as a light receptor organ

The eye is the physiological organ of sight through which light and colour feelings are experienced. For the lighting process to take place,

as action and effect of illuminate and see, three agents are required:

1) A source producing light or luminous radiation.

2) An object to be illuminated so that it is visible.

3) The eye, which receives luminous energy and transforms it into images which are sent to the brain for their interpretation.

The study and description of eye components, together with the process which takes place since the moment in which light arrives and

goes through the paths and visual centers, until it is interpreted by the brain, would take us to the field of neurophysiology. Some

behaviour and concepts related to the sense of sight will be described and exposed in the present chapter. Their knowledge is

indispensable and contributes to a better design of lighting installations.

2.2. Structural description of the eye

In Fig. 1, a schematic longitudinal section of the human eye is represented, where its anatomic constitution may be observed.

Figure 1. Human eye constitution.

The eye is mainly constituted by the following elements:

a) Eye globe: whose primary function is to form the image on the retina.

b) Cornea: receives and transmits visual impressions and constitutes the eye fundamental optical refractor component.

c) Crystaline lens: is a biconvex, transparent and colorless lens located behind the iris. This elastic membrane changes its form to focus

objectives.

d) Iris: circular lamina located in front of the crystalline lens, and highly pigmented. It can contract the pupil controlling the amount of

light that passes to the crystalline lens.

e) Pupil: circular orifice situated in the center of the iris, and through which light rays pass. The opening of this orifice is controlled by

the iris. Its contraction is called meiosis and its extension, mydriasis.

f) Retina: is the eye inner back film constituted by a nervous membrane, expansion of the optical nerve, whose function is to receive

and transmit visual images or impressions. It contains an extremely thin layer of photosensitive cells, cones and rods, which diverge

from the optical nerve and which are in the external layer, next to the pigmented layer.

Visual axis

Crystalline lens

Vitreous humor

Upper eyelid

Aqueous humor

Cornea

Iris

Ciliary muscle

Lower eyelid Blind spot

Yellow spot

Ophthalmic muscles

Ophthalmic muscles

Optical nerve

Retina

ChoroidsSclera

23LIGHTING ENGINEERING 2002

Chapter 2. THE EYE

Page 12: 38 Lighting Handbook

24 LIGHTING ENGINEERING 2002

g) Cones: photosensitive or photoreceptive cells of the retina which are mainly located in the fovea. They are very sensitive to colours

and almost insensitive to light. Hence, their function is to discriminate fine details and to perceive colours (Fig. 2).

h) Rods: photosensitive or photoreceptive cells of the retina which are only outside the fovea and more concentrated in the periphery.

They are very sensitive to light and movement, and almost insensitive to colour. Thus, their function is to perceive more or less

brightness with which objects are illuminated (Fig. 2).

i) Macule: yellow spot situated in the rear part of the retina, on the optical axis, where a precise and sharp fixation of details and colours

take place. The fovea is in its center which is only formed by cones.

j) Blind spot: a spot in the retina through which the optical nerve drives images or feelings of light to the brain. At this point, there are

no photoreceptors.

Practical consequences of the cone and rod functionWhen we look at a dimly illuminated space, for example, in the twilight at night, visual acuity is low, because cones do not function and

neither colours nor details are distinguished. This is the reason for the famous saying "no-one will notice in the dark". This type of night

vision is called scotopic and essentially rods intervene, which collect the greater or lesser amount of light and objects movement with

extreme sensitivity.

This justifies the fact that some public lighting of avenues, roads, and department stores is done with high pressure sodium lamps which

reproduce colours badly, but contribute with a great amount of light.

On the contrary, with daily light or when illumination level increases the necessary amount, objects are seen with precision and detail

also cones, mainly. This way, colours may be distinguished. Daily light is called photopic vision. In this case the quantity requires to be

accompanied by quality, since only quantity would produce irritability in eyes and very disturbing glares.

Figure 2. Eye photosensitive part. Behaviour of cones and rods.

2.3. Image formation

Human beings’ visual field is limited by an angle of about 130º degrees in a vertical way and about 180º degrees in a horizontal way.

From illuminated objects or those with their own light located in the visual field, luminous rays emerge that go through the cornea and

the aqueous humor. The iris, by means of the opening of the pupil, controls the amount of light which is refracted through the crystalline

lens to reach the retina finally. In this place, the photosensitive pigment of photoreceptors registers in inverted images much smaller

than in reality, as it happens in the photographic camera. Once images are received and formed in the retina by means of the optical

nerve, they are sent to the brain, which is in charge of interpreting them and modifying their position (Fig. 3).

Pigmented cellCone

Rod

Pigment grains

Nerve cell

Retina enlargement

Eye globe

Chapter 2. THE EYE

Page 13: 38 Lighting Handbook

Figure 3. Image formation and its rectification in the brain.

The following chart compares the human eye to the photographic camera.

Chart 1

2.4. Eye sensitivity curve

Wavelength radiations ranging between 380 nm. (ultraviolet) and 780 nm. (infrared) are transformed by the eye into light. Out of this

range, the eye cannot see: it is blind and does not perceive anything. All luminous sources have their own radiation or a mixture of them

included within such limits.

A sunny midday white light is the sum of all wavelengths of the visible spectrum. If we try to make them reach the eye independently

and with the same amount of energy, a curve like the one in Fig. 4 is obtained. It has been elaborated by the C.I.E.* measuring a great

number of people.

* C.I.E.: International Commission on Illumination (Commission Internationale de l´Eclairage).

Human eye Photographic camera

Crystalline lens (controls accommodation) Lens (adjusts distance between lens and film)

Pupil (controls adaptation) Diaphragm - shutter (adapts exposition and amount of light)

Pigment of photoreceptors Film emulsion

Retina (creates images) Film (creates images)

25LIGHTING ENGINEERING 2002

Chapter 2. THE EYE

Page 14: 38 Lighting Handbook

26 LIGHTING ENGINEERING 2002

Figure 4. Eye sensitivity curve to monochromatic radiations.

In this curve, the maximum eye sensitivity for day white light (photopic) corresponds to a 555 nm. wavelength and to the yellow colour.

The minimum sensitivity corresponds to the red and violet colours.

Hence, luminous sources whose wavelength corresponds to yellow - green are the ones with highest efficacy and worst quality, the

reason being that such light is not appropriate for our eye, which is accustomed to the sun white light. Thus, in premises where there

is a high illumination level orange and red colours are highlighted.

In the case of night light (scotopic), the maximum of sensitiveness moves towards shorter wavelengths (Purkinje's effect). Consequently,

those radiations with a shorter wavelength (blue- violet) produce greater intensity of sensation with low illumination. Such an effect is

very important when illuminating premises with a low illumination level where blue and violet colours can be seen better.

2.5. AccommodationIt is the eye capacity to adjust automatically to different distances of objects, and, this way, to obtain sharp images on the retina. This

adjustment takes place by modifying the crystalline curvature and, thus, the focus distance by contracting or relaxing ciliary muscles.

Provided that the objective is close to the eye, the crystalline curvature is greater than when it is far. In the photographic camera, the

lens and the film.

Accommodation or focus is easier with high luminances * (lighting) which oblige the pupil to adapt or modify the diaphragm towards a

closing position. The common result of this action is the increase of the field depth, or what is the same, a sharp vision of objects at

different distances from the eye or camera.

The eye accommodation capacity decreases with age, as a result of a hardening of the crystalline.

2.6. Contrast

All objects are perceived by contrasts of colour and luminance which different parts of their surface present among themselves and in

relation to the background in which the object appears.

* Luminance: Luminosity effect which a surface produces on the eye retina, whether it comes from a primary source of light or a reflecting surface.

20

40

60

80

100

20

0

40

60

80

100

Wavelength nm.

NIGHT DAY

%

400 500 600 700

Chapter 2. THE EYE

Page 15: 38 Lighting Handbook

For high enough lighting levels, the normal eye is colour sensitive, whereas for low lighting ones, objects are fundamentally perceived

by luminance contrast which is present against the background. The luminance difference between the observed object and its

immediate space is known as contrast.

Figure 5

In Fig. 5, the surface of the object has a luminance "L0" and the background surface has a luminance "Lf". Therefore, contrast "K" is the

difference between these two luminances, divided by their background one, that is to say:

"K" is, thus, a relative value between luminances.

As we have commented, the visibility of an object over a background, depends on the luminance difference between the object and

the background. For a light coloured object over a dark background, its contrast will be positive (values between 0 and infinitum).

However, an object darker than its background will be seen as a silhouette, and its contrast will be negative, varying between 0 and (-

1).

Contrast K may be positive or negative:

If L0 > Lf K > 0 contrast is positive (the object is lighter than its background).

If L0 < Lf K < 0 contrast is negative (the object is darker then its background).

Contrast K may acquire the following values:

Positive contrast (light object) 0 < K < e

Negative contrast (dark object) -1 < K < 0

Example a) in Fig. 6 presents an easily distinguished contrast, whereas b) and c) offer greater difficulty.

Figure 6

There is also a colour contrast. Chart 2 shows some examples.

a b c

K = L0 – Lf

Lf

L f

L o

ω

27LIGHTING ENGINEERING 2002

Chapter 2. THE EYE

Page 16: 38 Lighting Handbook

28 LIGHTING ENGINEERING 2002

Chart 2. Colour contrasts.

Contrast sensitivity It is a concept derived from the former one which is equivalent to the minimum contrast of luminances that may be perceived by the

human eye. Mathematically speaking, it would be the inverse of contrast.

Therefore, the greatest sensitivity to contrast possible is approximately:

However, in normal practical conditions, sensitivity to contrasts is quite smaller because of the reasons exposed above.

2.7. Adaptation

It is the ability of the eye to adjust automatically to different lighting degrees for objects. It consists of the adjustment of the size of the

pupil so that luminance projected in the retina is equal to a value bearable by sensitive cells. If compared to a photographic camera, it

would be the greater or lesser opening of the diaphragm.

If lighting is very intense, the pupil contracts, decreasing the amount of light that reaches the crystalline. If lighting is scarce, it expands

to capture more of it.

In high value illuminations, the pupil reduces to a diameter of approximately 2 mm. In very low value illuminations, the pupil expands

up to about 8 mm.

When a person moves from a place with high illuminance to another which is completely dark, the eye undergoes an adaptation process.

In order to adjust totally to the new situation, the eye needs 30 minutes. The opposite process, when a person goes from a completely

dark place into another with high illuminance, the adaptation period lasts for only a few seconds (Fig. 7).

G = 1

= 1000.01

G = Lf =

1

L0 – Lf K

Object colour Background colour

black yellow

green white

red white

blue white

white blue

black white

yellow black

white red

white green

white black

Chapter 2. THE EYE

Page 17: 38 Lighting Handbook

Figure 7. Eye relative photosensitive curve regarding adaptation time.

2.8. Glare

It is a phenomenon that produces disturbance or decrease in the capacity to distinguish objects, or else, both things at the same time.

This could be due either to an inadequate luminance distribution or phasing or to excessive contrasts in space or time.

This phenomenon affects the retina of the eye: an energetic photochemical reaction is produced which desensitizes it for a certain period

of time, after which, it recovers.

Effects produced by glare may be classified as psychological (discomfort) or physiological (disability). It may be produced in different

ways: direct glare, like the one from sources of light (lamps, luminaires or windows), which are located within the field of vision. Reflected

glare specially from surfaces with great reflectance, specular surfaces like polished metal.

Sources of light generally give rise to a disability glare which is proportional to the lighting produced by the source of light on the eye

pupil, as well as to a factor dependent on the “q” angle. Such an angle is formed by both the straight line “R” which joins the eye with

the “F” focus and the “H” horizontal plane which goes through the eye in a working position. In Fig. 8, different glares are indicated,

depending on the angle function. A minimum value of 30° has been taken as admissible.

Figure 8. Glare according to the q angle.

0 10 20 30 40 50 60

Values for the angle

Gla

re

H

R

θ

F

20

40

60

80

100

20

0 10 20 30 40 50

40

60

80

100

Adaptation time (min.)

Rela

tive

phot

osen

sitiv

ity

%

29LIGHTING ENGINEERING 2002

Chapter 2. THE EYE

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30 LIGHTING ENGINEERING 2002

Surfaces which are not completely matte give rise to more or less sharp images of their sources of light due to light reflection. Even if their

luminance is not excessive, such images are almost always discomforting when found in the field of vision, and specially, in its central area.

According to these lines, all unnecessary polished surfaces will be avoided as far as possible (glass over tables, for example.). In case semi-

polished surfaces are used (blackboards), sources of light will have the least possible luminance and their position will be calculated bearing

in mind reflexes that may occur (filters, grids, diffusers, etc.). In special cases, images which provide reflection will be useful (silhouette effect

vision, flaw inspection in polished surfaces, typesetting, etc.).

Figure 9. Surfaces which reflect light.

Chapter 2. THE EYE

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31LIGHTING ENGINEERING 2002

Chapter 3.

MATTER OPTICAL PROPERTIES

3.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.2. Reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.3. Transmmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.4. Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.5. Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

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32 LIGHTING ENGINEERING 2002

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3.1. General remarks

When a light ray propagates along a medium and reaches the limit which separates it from the second one, it may return to it (reflection),

it may strike it and become part of the second medium, where it will be converted into a different form of energy (absorption), and

some will not change (transmission).

Out of these phenomena, two or three take place simultaneously. Following the fundamental principle of energy, the sum of reflected,

absorbed and transmitted radiation must equal the incident radiation.

Therefore, the use of light in the most convenient way requires control and distribution achieved by modifying its characteristics through

the physical phenomena of light reflection, absorption and transmission, without leaving aside the fourth factor known as refraction.

3.2. Reflection

When any type of waves strikes a flat surface like a mirror, for example, new waves that move away from the surface are generated. This

phenomenon is known as reflection.

When light is returned by a surface, a certain amount of light is lost due to the absorption phenomenon. The ratio between the reflected

flux and the incident flux is called surface reflectance

Any surface which is not completely dark may reflect light. The amount of reflected light is determined by the surface reflection

properties. There are four kinds of reflection, namely: specular, composed, diffused and mixed. Reflector systems are based on these

reflection properties.

Specular reflection (Fig. 1): It takes place when the reflecting surface is flat. This kind of reflection is based on two fundamental laws:

1. The incident ray, the reflected ray and the normal to the surface at the point of incidence lie in the same plane.

2. The angle of incidence (i) is the same as the angle of reflection (r).

Figure 1. Specular reflection.

Composed reflection (Fig. 2): Contrary to specular reflection, there is no mirror image of the light source, but the maximum angle of

reflected intensity is the same as the angle of incidence. This type of reflection takes place when the surface is irregular or rough.

i r

N

33LIGHTING ENGINEERING 2002

Chapter 3. MATTER OPTICAL PROPERTIES

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34 LIGHTING ENGINEERING 2002

Figure 2. Composed reflection.

Diffused reflection (Fig. 3): This takes place when the light that strikes a surface is reflected in all directions, the normal ray to the surface

being the most intense one.

This kind of reflection takes place on surfaces such as matt white paper, walls, plaster flat ceilings, snow, etc.

Figure 3. Diffused reflection.

Mixed reflection (Fig. 4): This is an intermediate kind of reflection between the specular and the diffused reflection, in which some of

the incident beam is reflected and some, diffused. This kind of reflection takes place with non polished metals, glossy paper and

barnished surfaces.

Figure 4. Mixed reflection.

Chapter 3. MATTER OPTICAL PROPERTIES

Page 23: 38 Lighting Handbook

Chart 1. Reflection coefficient for white daylight.

3.3. Transmmission

Radiation passes through a medium without a change in the frequency of monochromatic radiations. This phenomenon can be seen

on certain kinds of glass, crystal, water and other liquids, and air, of course.

However, when passing through the material, some of the light is lost due to the reflection on the medium surface and through

absorption. The relation between the transmitted light and the incident light is known as material transmittance.

Transmission falls into three categories: spread, diffused and mixed.

Spread transmission (Fig. 5): The beam strikes a medium and passes through it. The media which fulfill this property are called

“transparent materials” and allow a sharp view of objects on the opposite side.

Reflecting surface % reflection index

Gloss silver 92 - 97

Gold 60 - 92

Matte silver 85 - 92

Polished nickel 60 - 65

Polished chrome 60 - 65

Polished aluminium 67 - 72

Electropolished aluminium 86 - 90

Vaporised aluminium 90 - 95

Copper 35 - 80

Iron 50 - 55

Enamelled porcelain 60 - 80

Mirrors 80 - 85

Matte white paint 70 - 80

Light beige 70 - 80

Yellow and light cream 60 - 75

Accoustic ceilings 60 - 75

Light green 70 - 80

Light green and pink 45 - 65

Light blue 45 - 55

Light grey 40 - 50

Light red 30 - 50

Light brown 30 - 40

Dark beige 25 - 35

Dark brown, green and blue 5 - 20

Black 3 - 4

35LIGHTING ENGINEERING 2002

Chapter 3. MATTER OPTICAL PROPERTIES

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36 LIGHTING ENGINEERING 2002

Figure 5. Spread transmission.

Diffused transmission (Fig. 6): The incident beam spreads through the medium, coming out of it in scattered directions. These

transmitting media are called “translucent”. The most common ones are ground glass and opalized organic glass. Objects situated behind

them appear blurred.

Figure 6. Diffused transmission.

Mixed transmission (Fig. 7): This is a kind of combination between spread and diffused transmission. It is produced with organic,

polished and carved surface glass. Although beam spread is not complete, objects situated behind them appear blurred, but their

position is relative.

Figure 7. Mixed transmission.

Chapter 3. MATTER OPTICAL PROPERTIES

Page 25: 38 Lighting Handbook

3.4. Absorption

Process by which radiant energy is converted into a different form of energy, mainly in the form of heat. This phenomenon is

characteristic both of all surfaces which are not completely reflective and of materials which are not totally transparent. The ratio between

absorbed flux to incident flux is known as absorptance.

Absorption of certain light wavelengths is called selective absorption. Generally speaking, objects take their color from selective

absorption.

3.5. Refraction

The direction of the light beam may change when passing from one medium to the other. This is a result of a change in the light speed

of propagation. Speed decreases if the new media density is higher, and increases if it is lower. This change in speed and direction is

known as refraction.

There are two laws of refraction:

1. When the wave goes from one medium to another, the incident ray, the reflected ray and the normal to the separating surface of

the media on the incidence point, are on the same plane.

2. The ratio between the incidence angle sine and the refraction angle sine is a constant for the given pair of media.

The above mentioned constant is known as the index of refraction n, for the given media. The second law of refraction is usually known

as Snell’s law.

Figure 8. Refraction in the boundary bewtween two media.

n1* = angle of refration for the first medium.

n2* = angle of refraction for the second medium.

a1 = angle of incidence.

a2 = angle of refraction.

When the first medium is the air, n1 = 1 and the formula is:

sin a1 = n2 · sin a2

The distance D in figure 8 is known as displacement. Such a displacemnt depends on the angle of incidence and on the index of

refraction. When the incident ray is perpendicular to the surface, refraction and displacement equal zero.

n1 · sin a1 = n2 · sin a2 csin a1 =

n2 = nsin a2 = n1

α2

α1

α1

D

n1

n2

n1

37LIGHTING ENGINEERING 2002

Chapter 3. MATTER OPTICAL PROPERTIES

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38 LIGHTING ENGINEERING 2002

Refraction varies according to wavelength. Short waves (like blue and violet) are transmitted better than long waves (for example red).

This phenomenon is used to decompose white light into its component colours when passing through a refraction prism. The degree

to which color is decomposed depends on the angle of incidence and the refraction properties of the prism material. This is called

dispersion.

* “ni” is calculated by the quotient between the speed of light in the air and the speed of light in the medium “i”.

Chapter 3. MATTER OPTICAL PROPERTIES

Page 27: 38 Lighting Handbook

39LIGHTING ENGINEERING 2002

Chapter 4.

THE COLOUR

4.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4.2. Colour classification according to the C.I.E. chromatic diagram . . . . . . 41

4.3. Colour temperature (Tc) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

4.4. Colour rendering index (R) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

4.5. Colour and harmony psychic effects . . . . . . . . . . . . . . . . . . . . . . . . . . 44

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40 LIGHTING ENGINEERING 2002

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4.1. General remarks

Colour is a subjective psycho physiologic interpretation of the visible electromagnetic spectrum.

Luminous sensations or images, produced in our retina, are sent to the brain and interpreted as a set of monochromatic sensations

which constitute the colour of the light.

The sense of sight does not analyze each radiation or chromatic sensation individually. For each radiation there is a colour designation,

according to the frequency spectrum classification.

It is important to indicate that objects are distinguished by the colour assigned depending on their optical properties. Objects neither

have nor produce colour. They do have optical properties to reflect, refract and absorb colours of the light they receive, that is to say:

the set of additive monochromatic sensations that our brain interprets as colour of an object depends on the spectral composition of

the light that illuminates such an object and on the optical properties possessed by the object to reflect, refract or absorb.

Newton was the first one to discover the decomposition of white light in the group of colours that forms a rainbow. When a white light

beam went through a prism, the same effect as that indicated in Fig. 1 was obtained.

Figure 1. White light decomposition in the rainbow spectrum.

4.2. Colour classification according to the C.I.E. chromatic diagram

Subjective evaluations of object surfaces, in the same way they are perceived by the human eye, are interpreted bearing in mind colour

attributes or qualities. They are the following:

a) Lightness or brightness: Luminous radiation received according to the illuminance possessed by the object. The further from black in

the grey scale, the lighter the colour of an object. It refers to intensity.

b) Hue or tone: common name for colour (red, yellow, green, etc.). It refers to wavelength.

c) Purity or saturation: proportion in which a colour is mixed with white. It refers to spectral purity.

In order to avoid a subjective evaluation of colour there exists a chromaticity diagram in the shape of a triangle, approved by the C.I.E.

It is used to treat sources of light, coloured surfaces, paints, luminous filters, etc. from a quantitative point of view.

All colours are ordered following three chromatic coordinates, x, y, z, whose sum is always equivalent to the unit (x + y + z = 1). When

each of them equals 0.333, they correspond to the white colour. These three coordinates are obtained from the specific potencies for

each wavelength. It is based on the fact that when three radiations from three sources of different spectral composition are mixed, a

radiation equivalent to another with a different value may be obtained. The result is the triangle in Fig. 2, in which any two coordinates

are enough to determine the radiation colour resulting formed by the additive mixture of three components.

White light

Prism380 nm.400 nm.

500 nm.

600 nm.

700 nm.

780 nm.

41LIGHTING ENGINEERING 2002

Chapter 4. THE COLOUR

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42 LIGHTING ENGINEERING 2002

Figure 2. C.I.E. Chromaticity diagram

4.3. Colour temperature (TC )

In the C.I.E. chromaticity diagram in Fig. 2, a curve has been drawn representing the colour emitted by a black body according to its

temperature. It is known as black body colour temperature curve, TC..

Colour temperature is an expression used to indicate the colour of a source of light by comparing it with a black body colour, that is to

say, a "theoretical perfect radiant" (object whose light emission is only due to its temperature). As any other incandescent body, the

black body changes its colour as its temperature increases, acquiring at the beginning, a red matte tone, to change to light red later on,

orange, yellow and finally white, bluish white and blue. For example, colour of a candle flame is similar to the one of a black body heated

at about 1 800 K*. Then, the flame is said to have a "colour temperature" of 1 800 K.

Incandescent lamps have a colour temperature which ranges from 2 700 to 3 200 K, depending on their type. Their fleck is determined

by the corresponding coordinates and is located virtually on the black body curve. Such temperature bears no relation at all with that of

an incandescent filament.

Therefore, colour temperature is, in fact, a measure of temperature. It only defines colour and it can be applied exclusively to sources

of light which have a great colour resemblance with the black body.

The practical equivalence between colour appearance and colour temperature is established arbitrarily according to Chart 1.

* K = Kelvin. Temperatures of Kelvin’s scale exceed in 273 °C the corresponding ones in the centigrade scale.

520

510

500

490

480

470460450

400-380

530

540

550

560

580

590

24.000

10.000 6.500

5.000

3.200

2.500800

600

610620

630650

700750

570

Chapter 4. THE COLOUR

Page 31: 38 Lighting Handbook

Chart 1

4.4. Colour rendering index (R)

Colour temperature datum is only referred to the colour of light, but not to its spectral composition which is decisive for colour

reproduction. Thus, two sources of light may have a very similar colour and possesses, at the same time, very different chromatic

reproduction properties.

The colour rendering index (R) characterizes the chromatic reproduction capacity of objects illuminated with a source of light. The R

offers an indication of the capacity of the source of light to reproduce normalized colours, in comparison with the reproduction provided

by a light as reference pattern.

Chart 2

Luminous sources Tc (°K) R.C.

Blue sky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 000 a 30 000 85 to 100 (group 1)

Cloudy sky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 000 85 to 100 (group 1)

Daylight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 000 85 to 100 (group 1)

Discharge lamps (except for Na) . . . . . . . . . . . . . .

Daylight (halogene) . . . . . . . . . . . . . . . . . . . . . . . . 6 000 96 to 100 (group 1)

Neutral white . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 000 a 5 000 70 to 84 (group 2)

Warm white . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lower than 3 000 40 to 69 (group 3)

Discharge lamp (Na) . . . . . . . . . . . . . . . . . . . . . . . 2 900 Lower than 40

Incandescent lamp . . . . . . . . . . . . . . . . . . . . . . . . . 2 100 a 3 200 85 to 100 (group 1)

Photographic lamp . . . . . . . . . . . . . . . . . . . . . . . . . 3 400 85 to 100 (group 1)

Candle flame or oil candle . . . . . . . . . . . . . . . . . . . 1 800 40 to 69 (group 3)

Colour appearance group Colour appearance Colour temperature (K)

1 Warm Below 3 300

2 Intermediate From 3.300 to 5 300

3 Cold Above 5 300

43LIGHTING ENGINEERING 2002

Chapter 4. THE COLOUR

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44 LIGHTING ENGINEERING 2002

Lamps colour rendering groupsIn order to simplify the specifications for lamp colour rendering indexes of those used in lighting, colour rendering groups have been

introduced as indicated in Chart 3.

Chart 3. Lamp colour rendering groups.

4.5. Colours and harmony psychic effects

It has been proved that colour in the environment produces psychic or emotional reactions in the observer. Hence, using colours in the

adequate way is a very relevant topic for psychologists, architects, lighting engineers and decorators.

There are no fixed rules for choosing the appropriate colour in order to achieve a certain effect, since each case requires to be given a

particular approach. However, there are some experiences in which different sensations are produced in the individual by certain colours.

One of the first sensations is that of heat or coldness. This is the reason why the expression "hot colours" and "cold colours" is

mentioned. Hot colours are those which go from red to greenish yellow in the visible spectrum; cold colours the ones from green to

blue.

A colour will be hotter or colder depending on its tendency towards red or blue, respectively.

On the one hand, hot colours are dynamic, exciting and produce a sensation of proximity. On the other hand, cold colours calm and

rest, producing a sensation of distance.

Likewise, colour clarity also produces psychological effects. Light colours cheer up and give a sensation of lightness, while dark colours

depress and produce a sensation of heaviness.

When two or more colours are combined and produce a comfortable effect, it is said that they harmonize. Thus, colour harmony is

produced by means of selecting a colour combination which is comfortable and even pleasant for the observer in a given situation.

From all the above mentioned, it may be deduced that a knowledge of the spectral distribution curve of sources of light is necessary to

obtain the desired chromatic effect.

Rendering group Rendering range in Colour appearance Examples for preferible uses Examples for acceptable usein colour

colour (R or Ra)

WarmColour equalness, medical

1 A R ≥ 90 Intermediateexplorations, art galleries

Cold

Warm Houses, hotels, restaurants,

Intermediate shops, offices, schools, hospitals1 B 90 > R ≥ 80

Intermediate Printing, painting and textile industry,

Warm industrial work

Warm

2 80 > R ≥ 60 Intermediate Industrial work Offices, schools

Cold

3 60 > R ≥ 40 Rough industries Industrial work

Rough work, industrial work

4 40 > R ≥ 20 with low requisites for

colour rendering

Chapter 4. THE COLOUR

Page 33: 38 Lighting Handbook

45LIGHTING ENGINEERING 2002

Chapter 5.

LUMINOUS MEASUREMENTS

5.1. Luminous flux (luminous output) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.2. Amount of light (luminous energy) . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5.3. Luminous intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5.4. Illuminance (luminous level) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.5. Luminance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

5.6. Other interesting luminous measurements . . . . . . . . . . . . . . . . . . . . . 51

5.7. Luminous measurement graphic representation . . . . . . . . . . . . . . . . . 52

5.8. Luminous measurement summary chart . . . . . . . . . . . . . . . . . . . . . . 56

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46 LIGHTING ENGINEERING 2002

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Two basic elements intervene in lighting engineering: both the source of light and the object to be illuminated.

In the present chapter, we will deal with fundamental measurements and units used to evaluate and compare the quality and effects of

sources of light.

5.1. Luminous flux (luminous output)

Energy transformed by light sources cannot be totally taken advantage of for light production. For example, an incadescent lamp

consumes a certain amount of electric energy which is transformed into radiant energy. Out of this, only a small amount (about 10%)

is perceived by the human eye as light, while the rest of it is lost as heat.

A luminous flux produced by a source of light is the total amount of light, either emitted or radiated in all directions in one second.

More precisely, a source of light luminous flux is radiated energy received by the human eye depending on its sensitivity curve, and

which is transformed into light for a second.

Luminous flux is represented by the Greek letter F and is measured in lumens (lm). Lumen is the luminous flux of the monochromatic

radiation characterised by a value frequency of 540 · 1012 Hz. and a radiant power flux of 1/683 W. One 555 nm. wavelength radiant

energy watt in the air equals 683 lm approximately.

Luminous flux measurementLuminous flux measurement is conducted by means of an adjusted photoelement depending on the phototopic sensitivity curve of the

standard eye to the monochromatic radiations, incorporated to a hollow sphere known as Ullbricht’s sphere (Fig. 1). The source to be

measured is placed inside it. Manufacturers provide lamp flux in lumens for nominal potency.

Figure 1. Ullbricht’s sphere.

Luminous performance (Luminous efficacy)Luminous performance of a source of light indicates the flux emitted by this source per unit of electrical output consumed to obtain it.

It is represented by the Greek letter e, and it is measured as lumen/watt (lm/W).

The formula which expresses luminous efficacy is:

(lm/W)

If a lamp was to be manufactured which transformed all the consumed electrical output into light at one 555 nm. wavelength without

losses, such a lamp would have the highest performance possible. Its value would be 683 lm/W.

ε =ΦΡ

47LIGHTING ENGINEERING 2002

Chapter 5. LUMINOUS MEASUREMENTS

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48 LIGHTING ENGINEERING 2002

5.2. Amount of light (Luminous energy)

In a similar way to electrical energy, which is determined by the electrical output in the time unit, the amount of light or luminous energy

is determined by the luminous output or luminous flux emitted by the time unit.

The amount of light is represented by the letter Q, and is measured as lumen per hour (lm · h).

The formula which expresses the amount of light is the following:

Q = F · t (lm · h)

5.3. Luminous intensity

This measurement is solely understood as referred to a specific direction and contained in a w solid angle.

In the same way that a plane angle measured in radians corresponds to a surface, a solid or stereo angle corresponds to a volume

measurement and is measured in stereoradians.

The radian is defined as the plane angle within an arc of a circle, equal to the radius of the circle. (Fig. 2).

Figure 2. Plane angle.

The stereoradian is defined as the solid angle which corresponds to a spherical cap whose surface equals the square of the sphere

radius (Fig. 3).

Figure 3. Solid angle.

Luminous output of a source of light in one specific direction equals the ratio between the luminous flux contained in whatever solid

angle whose axis coincides with the considered direction. Its symbol is , and its unit of measurement is the candela (cd). The formula

which expresses it is the following:

(lm/sr)

Candela is defined as the luminous intensity of a specific source which emits luminous flux equal to one lumen in a solid angle per

stereoradian (sr).

Ι =Φω

r = 1m.

1cd

1cd

φ = 1 LmE = 1 LuxS = 1 m2

ω

ω (total) = 4π stereoradians

r = 1

α = 1 radian

α (total) = 2 π radians

δ = 1

Chapter 5. LUMINOUS MEASUREMENTS

Page 37: 38 Lighting Handbook

According to the I.S.*, candela may also be defined as the luminous intensity in a certain direction, from a source which emits

monochromatic radiation with a frequency of 540 · 1012 Hz, and whose energy intensity in the aforementioned direction is 1/683 watts

per stereoradian.

5.4. Illuminance (Luminous level)

Illuminance or luminous level of a surface is the ratio between the luminous flux received by the surface to its area. It is represented

by the letter E, and its unit is the lux (lx).

The formula which expresses illuminance is:

(lx = lm/m2)

Thus, according to the formula, the higher the luminous flux incident on a surface, the higher its illuminance. Also, for the same given

incident luminous flux, illuminance will be higher as surface decreases.

According to the I.S., lux may be defined as the illuminance of a certain surface which receives a luminous flux of one lumen, spread

over one square meter of its surface.

Lighting level measurementLuminous level measurement is conducted with a special device known as foot- candle metre. It consists of one photoelectric cell which

generates a weak eletric current when light strikes its surface, thus, increasing according to light incidence. Such current is measured by

means of an analogic or digital miliammeter, calibrated directly in lux (Fig. 4).

Figure 4. Foot- candle metre.

5.5. Luminance

Luminance is the effect which produces a surface on the retina of the eye, both coming from a primary source which produces light,

or from a secondary source or surface which reflects light.

Luminance measures brightness for primary light sources as well as for sources constituting illuminated objects. This term has substituted

the concepts of brightness and lighting density. Nevertheless, it is interesting to remember that the human eye does not perceive colours

but brightness, as a colour attribute. Light perception is, in fact, the perception of differences in luminance. Therefore, it may be stated

that the eye perceives luminance differences but not illuminance ones (provided that we have the same lighting, different objects have

different luminance since they have different reflection characteristics).

Luminance of an illuminated surface is the ratio between luminance of a source of light in a given direction, to the surface of the

projected source depending on such direction.

*I.S.c International System.

123

BBAA

Ε =ΦS

49LIGHTING ENGINEERING 2002

Chapter 5. LUMINOUS MEASUREMENTS

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50 LIGHTING ENGINEERING 2002

Figure 5. Surface luminance.

The projected area is seen by the observer in the direction of the luminous intensity. This area is calculated by multiplying the illuminated

real surface by the cosine angle forming the normal with the direction of the luminous intensity (Fig. 5).

Represented by the letter L, its unit is the candela/square metre called “nit (nt)”, with one submultiple, the candela/square centimetre

or “stilb”, used for high luminance sources.

;

The formula which expresses it is the following:

where:

S · cos = Apparent surface.

Luminance is independent from the observation distance.

Luminance measurementLuminance measurement is conducted by means of a special device called a luminancemetre or nitmeter. It is based on two optical

systems, directional and measurement systems, respectively. (Fig. 6).

The directional system is oriented in such a way that the image coincides with the point to be measured. Once it has been oriented,

the light that reaches it is transformed into electric current. Its values are measured in cd/m2.

Figure 6. Luminancemeter.

123

123

123

L =Ι

S · cosβ

1stilb =1cd

1cm21nt =

1cd

1m2

β

β

β

Viewed or apparent surface

Real surface

Apparent surface = Real surface x cosβ

Chapter 5. LUMINOUS MEASUREMENTS

Page 39: 38 Lighting Handbook

5.6. Other interesting luminous measurements

5.6.1. Utilization coefficientRatio between the luminous flux received by a body and the flux emitted by a source of light.

Unit c %

Symbol c ηRatio c

5.6.2. ReflectanceRatio between the flux reflected by a body (with or without diffusion) and the flux received.

Unit c %

Symbol c ρRatio c

5.6.3. AbsorptanceRatio between the luminous flux absorbed by a body and the flux received.

Unit c %

Symbol c αRatio c

5.6.4. TransmittanceRatio between the luminous flux transmitted by a body and the flux received.

Unit c %

Symbol c τRatio c

5.6.5. Average uniformity factorRatio between minimum to medium illuminance in a lighting installation.

Unit c %

Symbol c Um

Ratio c

5.6.6. Extreme uniformity factorRatio between minimum to maximum illuminance in a lighting installation.

Unit c %

Symbol c Ue

Ratio c

5.6.7. Longitudinal uniformity factorRatio between longitudinal minimum to maximum luminance in a lighting installation.

Unit c %

Symbol c UL

Ratio c

5.6.8. Overall luminance uniformityRatio between minimum to medium illuminance in a lighting installation.

Unit c %

Symbol c U0

Ratio c U0 =Lmin

Lmed

UL =Llongitudinal min

Llongitudinal max

Ue =Εmin

Εmax

Um =Εmin

Εmed

τ =Φt

Φ

α =Φa

Φ

ρ =Φr

Φ

η =ΦΦe

51LIGHTING ENGINEERING 2002

Chapter 5. LUMINOUS MEASUREMENTS

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52 LIGHTING ENGINEERING 2002

5.6.9. Maintenance factorCoefficient indicating the preservation degree of an installation.

Unit c %

Symbol c Fm

Ratio c Fm = Fpl · Fdl · Ft · Fe · Fc

Fpl = lamp position factor

Fdl = lamp depreciation factor

Ft = temperature factor

Fe = ignition equipment factor

Fc = installation preservation factor

5.7. Luminous measurement graphic representation

The collection of luminous intensity emitted by a source of light in all directions is known as luminous distribution. The sources of light

used in practice have a more or less large luminous surface, whose radiation intensity is affected by the construction of the source itself,

presenting various values in these scattered directions.

Special devices (like the Goniophotometer) are constructed to determine the luminous intensity of a source of light in all spatial

directions in relation to a vertical axis. If luminous intensity (I) of a source of light is represented by vectors in the infinite spatial directions,

a volume representing the value for the total flux emitted by the source is created. Such a value may be defined by the formula below:

Photometric solid is the solid obtained. Fig. 7 shows an incasdescent lamp photometric solid.

Figure 7. Incandescent lamp photometric solid.

If a plane passes through the symmetric axis of a source of light, for example, a meridional plane, a section limited by a curve, known

as photometric curve, or luminous distribution curve is obtained (Fig. 8).

0°20°

40°

80°

100°

120°

140°160°180°

60°

Φ = !ν

Ιr · dωr

Chapter 5. LUMINOUS MEASUREMENTS

Page 41: 38 Lighting Handbook

Figure 8. Photometric curve for an incandescent lamp.

By reviewing the photometric curve of a source of light, luminous intensity in any direction may be determined very accurately. This data

are necessary for some lighting calculations.

Therefore, spatial directions through which luminous radiation is irradiated may be established by two coordinates. One of the most

frequently used coordinate systems to obtain photometric curves is the “C - ” represented in Fig. 9.

Figure 9. C - coordinate system.

Photometric curves refer to an emitted luminous flux of 1 000 lm. Generally speaking, the source of light emits a larger flux. Thus, the

corresponding luminous intensity values are calculated by a simple ratio.

When a lamp is housed in a reflector, its flux is distorted, producing a volume with a marked shape defined by the characteristics of the

reflector. Therefore, distribution curves vary according to different planes. The two following figures show two examples where distribution

curves for two reflectors are represented. Fig.10 reflector is symmetric and has identical curves for any of the meridional planes. This is

inclination axis

rota

tion

axis

"C"

plan

es

γ = 180°

γ = 0°

γ = 90°

Walkway side

Roadway side

C = 0°

C = 180°

C = 90°

C = 270°

20

40

40

60

80

180°

0° 30°

150°

90°

60°

120°

60

80

100

120

140

cd

53LIGHTING ENGINEERING 2002

Chapter 5. LUMINOUS MEASUREMENTS

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54 LIGHTING ENGINEERING 2002

the reason why a sole curve is enough for its photometric identification. Fig. 11 reflector is asymmetric and each plane has a different

curve. All planes must be known.

Figure 10. Symmetric photometric distribution curve.

Figure 11. Asymmetric photometric distribution curve.

Another method to represent luminous flux distribution is the isocandela curve diagram (Fig. 12). According to this diagram, luminaires

are supposed to be in the center of a sphere where exterior surface points with the same intensity are linked (isocandela curves).

Generally, luminaires have, at least, one symmetric plane. This is the reason why they are only represented in a hemisphere.

Figure 12. Isocandela curves.

GM=0 Imax=100%10-10-20

-30

-40

-50

-60

-70

-80

-90C=0350 10 20 30 40 50 60 70 80340330320310300290280

20

30

40

50

60

70

80

90

15

10

20

30

9080

60 40

60

C=45º C=0ºC=90º

Unit = cd/1000 lm

70o

50o

30o 0o

080240320

10o

60o

30o 30o0o

225450675900

C=45º C=0ºC=90º

Unit = cd/1000 lm

Chapter 5. LUMINOUS MEASUREMENTS

Page 43: 38 Lighting Handbook

This representation is very comprehensive. However, more experience is needed to interpret it.

The flux emitted by a source of light provides surface lighting (illuminance) whose values are measured in lux. If those values are

projected on the same plane and a line links the ones with the same value, isolux curves are formed (Fig. 13).

Figure 13. Isolux curves.

Finally, luminance depends on the luminous flux reflected by a surface in the observer’s direction. Values are measured in candelas per

square metre (cd/m2) and are represented by isoluminance curves (Fig. 14).

Figure 14. Isoluminance curves.

h6h 5h 4h

1 5 2030

4050

6070

80

5

10

50

1

5

3h 2h h 0 h 2h 3h

0

h

2h

3h

A

OBSERVERS: A, B AND C

B

C

ROADWAY SIDE

WALKWAY SIDERoadway R2Qo = 0.07

Lmax=100%fl=0.152

h

6h 5h 4h

11

5

5

10

20

3040

506070

80

3h 2h h 0 h 2h 3h

0

h

2h

3h

Lmax=100%fl=0.154

WALKWAY SIDE

ROADWAY SIDE

55LIGHTING ENGINEERING 2002

Chapter 5. LUMINOUS MEASUREMENTS

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56 LIGHTING ENGINEERING 2002

5.8. Luminous measurement summary chart

Chart 1. Luminous measurement summary

Measurement Symbol Unit Ratio

Luminous flux F Lumen (lm) F = I · q

Luminous efficacy ε Lumen per watt (lm/W) ε =ΦΡ

Luminous output Q Lumen per hour (lm · h) Q = F · t

Candela (cd) Luminous intensity Ι

(cd = lm/sr)Ι =

Φω

Lux (lx)Illuminance Ε

(lx = lm/m2)Ε =

ΦS

Nit = cd/ m2

Luminance LStilb = cd/cm2

L =Ι

S · cosβ

Utilization coefficient η % η =ΦΦe

Reflectance ρ % ρ =Φr

Φ

Absorptance α % α =Φa

Φ

Transmittance τ % τ =Φt

Φ

Average uniformity factor Um % Um =Εmin

Εmed

Extreme uniformity factor Ue % Ue =Εmin

Εmax

Longitudinal luminance uniformity UL % UL =Llongitudinal min

Llongitudinal max

Overall luminance uniformity U0 % U0 =Lmin

Lmed

Maintenance factor Fm % Fm = Fpl · Fdl · Ft · Fe · Fc

Chapter 5. LUMINOUS MEASUREMENTS

Page 45: 38 Lighting Handbook

57LIGHTING ENGINEERING 2002

Chapter 6.

FUNDAMENTAL PRINCIPLES

6.1. Inverse square distance law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.2. Cosine law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

6.3. Normal, horizontal, vertical and inclined planes illumination . . . . . . . . 61

6.4. Illuminance ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.5. Lambert’s law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

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58 LIGHTING ENGINEERING 2002

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6.1. Inverse square distance law

Since early experiments, it has been confirmed that illuminances produced by the source of light decrease inversely to the square of the

distance from the plane to illuminate the source. This ratio is expressed by the following formula:

(lx)

where Ε is the illuminance level in lux (lx), Ι is the intensity of the source in candelas (cd), and d is the distance from the source of light

to the perpendicular receptor plane.

In this way, an illuminance ratio Ε1 and Ε2 may be established, between two planes separated by a distance d and D from the source

of light, respectively:

Ε1 · d2 = Ε2 · D2

Figure 1. Luminous flux distribution over different surfaces.

This law is fulfilled when we are dealing with a punctual source of perpendicular surfaces to the direction of the luminous flux. However,

the law is supposed to be accurate enough when the distance undergoing measurement is, at least, five times the maximum dimension

of the luminaire (the distance is big in relation to the size of the area of the source of light).

6.2. Cosine law

In the previous section, the surface was perpendicular to the direction of luminous rays, but when a specific angle a is formed in relation

to this, the formula for the inverse square distance law must be multiplied by the cosine of the corresponding angle. Such an expression

constitutes what is called the law of cosine, expressed in the formula below:

Ε =Ι

· cos α (lx)d2

F

d

D

E1

S1

S2

E2

Ε1=

D2

Ε2 = d2

Ε =Ιd2

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Chapter 6. FUNDAMENTAL PRINCIPLES

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60 LIGHTING ENGINEERING 2002

“Illuminance in any given point of a surface is proportional to the cosine of the angle of incidence of the luminous rays in the

illuminated point”.

In Fig. 2 two sources of light F and F´ with the same luminous intensity (I) and at the same distance (d) from point P are represented.

To the source of light F with cos0 = 1 corresponds an angle of incidence equal to zero. This source produces illuminance for the point

P with a value of:

Figure 2. Iluminance at a point from two sources of light with different angles of incidence.

c

Likewise, F´ with an angle α = 60°, corresponding cos60° = 0.5, will produce at the same point an illuminance valued as:

c

Therefore, Ε p = 0.5 · Εp, that is to say, to obtain the same illuminance at point P, the luminous intensity of the source F´ must double

that of the source F.

In practice, distance d from the source to the considered point is not known, but its height h to the horizontal of the point is. By using

a simple trigonometric relation and substituing it in the equation, a new relation where height h plays an important role is obtained:

Εp =Ι

· cos3 α (lx)h2

Ι · cos2 α · cos α

h2Εp =

Ι· cos α =

Ι· cos α =

d2 ( h )2

cos α

cos α =h

c d =h

d cos α

Ε p =1

·Ι

(lx)2 d2

Ε p =Ι

· cos 60° =Ι

· 0.5d2 d2

Εp =Ι

(lx)d2

Εp =Ι

· cos 0 =Ι

· 1d2 d2

α 60°

h

PF

F'

d

d

Chapter 6. FUNDAMENTAL PRINCIPLES

Page 49: 38 Lighting Handbook

6.3. Normal, horizontal, vertical and inclined planes illumination

In Fig. 3 the source F illuminates three planes situated in the following positions: normal, horizontal and vertical to the beam. Each will

have an illuminance called:

EN = Normal illuminance.

EH = Horizontal illuminance.

EV = Vertical illuminance.

Figure 3. Normal, horizontal and vertical illuminance.

Let us determine the normal, horizontal and vertical illuminance for point M in Fig. 3.

Normal illuminationThe inverse square distance law is applied:

where Iα is the luminous intensity under the angle a. Virtually, only normal illuminance of a point is considered whenever this point is

situated in the vertical of the source on the horizontal plane (M1 point). Thus, the previous formula is transformed into:

and also when it is situated in a straight line with the source on the vertical plane (M2 point), the illuminance is:

Horizontal illuminationIf the law of cosine is directly applied, the result is:

Such a formula may be reformulated in relation to the height h between the F source and the M point (d = h / cosα):

ΕH = Ια

· cos3 α (lx)h2

ΕH = ΕN · cos α = Ια

· cos α (lx)d2

ΕN =Ι

(lx)a2

ΕN =Ι

(lx)h2

ΕN =Ια

(lx)d2

FM2

M1 M

α

βd

Horizontal illuminance

Vert

ical

illu

min

ance

Normal

illuminan

ce

a

h

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62 LIGHTING ENGINEERING 2002

Vertical illuminationIn this case, the law of the cosine is also directly applied. The result is that:

ΕV = ΕN · cos β (lx)

Between the α and β angles, there is a simple relation since both belong to a triangle rectangle.

α + β + 90° = 180° c β = 90° - αApplying trigonometric relations:

cosβ = cos(90° - α) = cos90° · cosα + sin90° · sinαTherefore, cosβ = sinα. This value is substituted and the result is that:

ΕV = ΕN · sin α (lx)

The equation may be expressed in relation to the height h between the F source and the M point.

Inclined planes illuminationThe vertical plane may change through an angle like the one in Fig. 4. Such an angle forms the vertical plane which contains the

point P with the light incidence plane.

Figure 4. Illuminance at point P.

Taking this into account, the above mentioned expression is transformed into:

h is the vertical height of the source of light over the horizontal plane which contains point P.

6.4. Illuminance ratio

Different concepts to describe light coming from other directions different from the vertical have been proposed. These must be considered as

comfort parameters together with others like luminous level (illuminance).

Vertical / horizontalThe experience from high illuminance level installations with a very good glare control indicates that the ratio between vertical (EV) and

horizontal illuminance (EH) for a good modelling* must not be lower than 0.25 in the main directions of vision.

* Modelling: Ability of light to reveal the texture and tridimensional form of an object creating light and shade contrasts.

ΕV ≥ 0.25ΕH

ΕPI = Ια

· cos2 α · sin α · cos γ (lx)h2

α

γ P

h

I

ΕV = Ια

· cos2 α · sin α (lx)h2

ΕV = Ια

· sin α (lx)d2

Chapter 6. FUNDAMENTAL PRINCIPLES

Page 51: 38 Lighting Handbook

Vectorial /SphericalDirectional lighting effects may be described partly through vectorial illuminance and partly through the ratio between vectorial and

spherical illuminance.

The illuminance vector Ε at a point has a magnitude equal to the maximum difference in illuminance over those diametrically opposed

surface elements in a small disc (Fig. 5) located in a point, their direction being from the greatest illuminance element to the lowest

one.

Figure 5. Illuminance vector E = Ef – Er.

The spherical average at point is the average illuminance over all the surface of a small sphere located at such a point (Fig. 6).

Figure 6. Spherical medium illuminance ES.

Lighting directional intensity may be indicated by the given modelling through the ratio between vectorial illuminance and average

spherical illuminance:

If we measure it using a sphere with a radius r which receives a beam of light with an F luminous flux, it would be:

Illuminance E of an element of the radius r surface is:

In a room with a floor, walls and a flat ceiling with diffused reflection, where there is also diffused light, we have that Εjj 0 (that is to

say, there are no shadows). Under these circumstances, the modelling index is Εj / Εsj 0. However, in a completely dark room where

Ε =Φ

π · r2

ΕS =Φ

4 · π · r2

ΕΕS

Es

E

Er

Ef

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Chapter 6. FUNDAMENTAL PRINCIPLES

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64 LIGHTING ENGINEERING 2002

the light comes from one direction only (for example, sunlight), Εj= Ε (that is to say, dark shadows). Under these circumstances, the

modelling index is equivalent to Εj / Ε = Ε / Εs = 4.

Therefore, modelling index may vary between values such as 0 and 4.

Vector Εj must have a downward direction (preferibly between 45° and 75° to the vertical) in order to obtain a natural appearance of

human features.

Cylindrical / HorizontalAn alternative concept to describe the modelling effect is the ratio between cylindrical illuminance and horizontal illuminance at a certain

point.

The average cylindrical illuminance ΕC at a point is average illuminance over a curved surface of a small cylinder located at the point

(Fig. 7). Unless otherwise indicated, the cylinder axis must be vertical.

Figure 7. Average cylindrical illuminance EC.

Cylindrical illuminance at a point equals average vertical illuminance in all directions at such a point. A good modelling is achieved when

the ratio is:

Generally speaking, direction is automatically taken into account. Therefore, it is not necessary to specify it from an additional point of

view, like in the case of vectorial / spherical ratio: when light comes directly from above, ΕC = 0 and ΕC / ΕH = 0; when light is horizontal,

ΕH = 0 and ΕC / ΕH j q.

Vertical / SemicylindricalTests conducted in relation to lighting of pedestrian outodoor areas (low level lighting areas) have proved that the ratio between vertical

illuminance and semicylindrical illuminance provides a useful measure of acceptance of human features modelling, for the mentioned

application area.

Semicylindrical illuminance Εsemicyl at a point in a given horizontal direction equals the average illuminance on a curved surface of a

small vertical semicylinder located at such a point, with a curved surface focused towards the specified direction (Fig. 8).

0.3 ≤ΕC ≤ 3ΕH

EC

Chapter 6. FUNDAMENTAL PRINCIPLES

Page 53: 38 Lighting Handbook

Figure 8. Semicylindrical illuminance.

Well balanced lighting relief (neither very short nor very intense) is obtained at:

Extreme ratios are:

Zero very intense modelling.

(π/2) = 1.57 very short modelling.

6.5. Lambert’s law

There exist emitting or diffused surfaces that, when observing them from different angles, the same brightness feeling is obtained. These

surfaces are called perfect emitters or diffusers.

If L0 is luminance according to the normal and Lα is luminance according to the observation angle α, Lα = L0 is verified for any given

angle α.

Since and , the equation below is true:

Ια = Ι0 · cosα

This ratio is known as Lambert’s Law and only perfect emitters or diffusers comply to it.

Figure 9. Luminance invariability in relation to the incidence angle.

Io

α

Lo

N

Surface

Lα =Ια

S · cos αL0 =

Ι0

S

0.8 ≤ΕV ≤ 1.3

Εsemicyl

Esem

65LIGHTING ENGINEERING 2002

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66 LIGHTING ENGINEERING 2002

Chapter 6. FUNDAMENTAL PRINCIPLES

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67LIGHTING ENGINEERING 2002

Chapter 7.

LUMINAIRES

7.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.2. Luminaire classification according to the degree of protectionfrom electric contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.3. Luminaire classification according to working conditions . . . . . . . . . . . 70

7.4. Luminaire classification according to mounting surface flammability . 71

7.5. Luminaire classification according to service conditions . . . . . . . . . . . 72

7.6. Photometric basic data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

7.7. Luminaire efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

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68 LIGHTING ENGINEERING 2002

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General remarks

Due to the high luminance of lamps, it is necessary to increase the emission apparent surface in order to avoid visual problems (glare).

Also, it is necessary to shield lamps to protect them from external agents and to direct their flux in the most convenient way for visual

task.

Thus, different studies and contemporary research place great emphasis on the combination formed by the source of light and the

luminaire.

According to the UNE-EN 60598-1* Norm, a luminaire may be defined as a lighting apparatus which spreads, filters or transforms

light emited by a lamp or lamps including all components necessary for supporting, fixing and protecting the lamps, (except for the

lamps themselves). Should the need arise, also the auxiliary circuits combined with the media for the connection to the power supply.

Main components

Independently from other definitions which could be more or less descriptive, a luminaire may be defined as an object formed by a

combination of elements designed to give an appropriate luminous radiation of an electric origin. Materialization of these elements is

achieved by combining a good formal design and a reasonable economy of materials in each situation.

Formal design solves luminous control depending on needs, which is the main aim: both a thermal control which makes its functioning

stable and an electric control which offers adequate guarantees to the user. Economy of materials provides a solid and efficient product,

an easily installed luminaire, and minimum maintenance while in use.

Regarding the most fundamental characteristic components, body, control gear, reflector, diffuser, and filter among others, must be

mentioned. All of them fall into other classifications shown below.

1. Body: This is the minimum physical element which supports and defines the volume of the luminaire and contains the key

components. According to this criterion, several types may be defined:

- For indoor or outdoor areas.

- Surface or embedded mounted.

- Suspended or rail mounted.

- Wall, bracket or pole mounted.

- Open or enclosed.

- For normal or harsh environments (corrosion or explosion).

2. Control gear: Appropriate control gear would be selected to suit different sources of artificial light, according to the following

classification:

- Regular incandescent with no auxiliary elements.

- High voltage halogene to regular voltage, or low voltage with converter or electronic source.

- Fuorescent tubes. With reactances or ballasts, capacitors and starters, or electronic combinations of ignition and control.

- Discharge. With reactances or ballasts, capacitors and starters, or electronic combinations of ignition and control.

3. Reflector: A specific surface inside the luminaire which models form and direction of the lamp flux. Depending on how luminous

radiation is emitted, it may be:

- Symmetric (with one or two axes) or asymmetric.

- Narrow beam (lower than 20º) or wide beam (between 20 and 40º; greater than 40º).

- Specular (with scarce luminous dispersion) or non specular (with flux dispersion).

- Cold (with dicroic reflector) or normal.

4. Diffuser: This forms the cover of the luminaire in the direction of the luminous radiation. The most frequently found types are:

- Opal (white) or prismatic (translucent).

- Lamellae or reticular (with a direct influence on the shielding angle).

- Specular or non specular (with similar characteristics to reflectors).

5. Filters: In possible combination with diffusers, they are used to protect or lessen certain characteristics of luminous radiation.

* The UNE-EN 60598-1 Norm adopts the Internacional Norm CIE 598-1.

69LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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70 LIGHTING ENGINEERING 2002

7.2. Luminaire classification according to the degree of protection from electric contacts

Luminaires must secure protection of people from electric contacts. Depending on the degree of electric insulation, luminaires can be

classified as:

Class 0: Luminaire with basic insulation, lacking double insulation or overall reinforcement as well as an earth connection.

Class I: Luminaire with functional basic insulation and an earth connection terminal or contact.

Class II: Luminaire with double basic insulation and /or reinforced overall insulation lacking provision for earth discharge.

Class III: Luminaire designed to be connected to extra-low voltage circuits, lacking internal or external circuits not working at an extra-low

security voltage.

7.3. Luminaire classification according to working conditions

The IP system (International Protection) established by the UNE-EN 60598 classifies luminaires according to their degree of protection

from mechanical shock, dust and water. The term mechanical shock includes those elements like tools or fingers that are in contact with

energy transmiting parts

The designation to indicate degrees of protection consists in charateristic IP letters followed by two numbers (three in France) which

indicate the compliance of conditions established in charts 1., 2. and 3. The first of these numbers is an indication of protection from

dust, the second number indicates the degree of protection from water, whereas the third number, in the French system, indicates the

degree of protection from mechanical shock.

Chart 1. EN-60598 classification according to dust protection degree (1st numeral).

Chart 2. EN-60598 classification according to the degree of protection from water (2nd numeral).

Second characteristic numeral Brief description Symbol

0 Non- protected. No symbol

1 Protected against dripping water.

2 Protected against dripping water when tilted up to 15º. No symbol

3 Protected against dripping water when tilted up to 60º.

4 Protected against spraying water.

5 Protected against splashing water.

6 Protected against water jets. No symbol

7 Protected against the effects of immersion.

8 Protected against submersion. -m

First characteristic numeral Brief description Symbol

0 Non-protected. No symbol

1 Protected against solid objects greater than 50 mm. No symbol

2 Protected against solid objects greater than 12.5 mm. No symbol

3 Protected against solid objects greater than 2.5 mm. No symbol

4 Protected against solid objects greater than 1 mm. No symbol

5 Dust- protected.

6 Dust tight.

Chapter 7. LUMINAIRES

Page 59: 38 Lighting Handbook

Third numeral of the code

This numeral refers to mechanical shock tests. The following chart shows characteristic numerals accompanied by a brief description.

Chart 3. EN-60598 classification depending on protection from mechanical shock.

Instead of this third numeral, the EN-50102 Norm on “Degrees of protection against external mechanical shock provided by electric

material bulb (code IK)” may also be applied.

In the above mentioned Norm, the protection degree from mechanical shock provided by a bulb is indicated by the IK code in the way

shown below:

- Code letters (internacional mechanical shock protection): IK

- Characteristic numerals: From 00 to 10

Each characteristic numeral represents a value for impact energy, whose correspondance is summarised in chart 4.

Chart 4. Correspondence between the IK code and impact energy.

Generally speaking, protection degree is applied to the bulb as a whole. If several parts of the bulb have different protection degrees,

they must be indicated separately.

7.4. Luminaire classification according to the mounting surface flammability

Luminaires cannot be mounted on any surface at hand. The surface flammability and the luminaire body temperature impose certain

restrictions. Of course, if the surface is non-combustible, there is no problem.

For classification purposes, the EN-60598 Norm defines flammable surfaces as usually flammable or easily flammable. The usual

flammable classification refers to those materials whose ignition temperature is, at least, 200 ºC, degrees and do not weaken or deform

at that temperature.

The easily flammable classification refers to those materials which cannot be classified as usually flammable or non-combustible.

Materials in this category may be used as mounting surface for luminaires. Suspended mounting is the only option for this type of

material.

In chart 5, mounting classification based on these requirements may be observed.

Chart 5. EN-60598 classification according to the mounting surface flammability.

Classification Symbol

Luminaires suitable for direct mounting only on No symbol, but a warning notice is required.

non- combustible surfaces.

Luminaires suitable for direct mounting only On plaque.

on easily flammable surfaces.F

IK Code IK00 Ik01 IK02 IK03 IK04 IK05 IK06 IK07 IK08 IK09 IK10

Mechanical shock in Joules. * 0.15 0.2 0.35 0.5 0.7 1 2 5 10 20

Third characteristic numeral Brief description Symbol

0 Non- protected No symbol

1 Protected against a 0.225 J. mechanical shock No symbol

3 Protected against a 0.5 J. mechanical shock No symbol

5 Protected against a 2 J. mechanical shock No symbol

7 Protected against a 6 J. mechanical shock No symbol

9 Protected against a 20 J. mechanical shock No symbol

71LIGHTING ENGINEERING 2002

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72 LIGHTING ENGINEERING 2002

7.5. Luminaire classification according to service conditions

Depending on their service conditions, luminaires fall into the following types:

7.5.1. Indoor lighting luminairesWithin this group, luminaires to illuminate premises and facilities in shopping areas, industries, offices, educational buildings,

indoor sports facilities, etc. are found Therefore, this type of lighting tries to give the adecuate lighting for those working or

teaching environments.

Luminaires for general indoor lighting are classified by the C.I.E. according to the total percentage of luminous flux distributed

above and below the horizontal plane.

Chart 6. C.I.E. classification for indoor lighting luminaires.

Chart 1. Luminaire classification according to radiation of luminous flux.

In turn, with regards to the symmetric flux emitted, a classification may be considered into two groups:

1) Symmetrical distribution luminaires: Those in which the luminous flux is spread symmetrically with respect to the

symmetric axis and spatial distribution of luminous intensities. It may be represented as a single photometric curve.

2) Asymmetric distribution luminaires: Those in which the luminous flux is spread asymmetrically with respect to the

symmetric axis and the spatial distribution of luminous intensities. It may expressed by a photometric solid, or, partially, by

a flat curve of such a solid, depending on certain characteristic planes.

Photometric information which accompanies indoor lighting luminaires

Polar distribution curves

These curves are generally represented in the coordinate system C-. Since there are infinite planes, in general, three C planes

are represented, which are the following:

Direct-indirect

40~60%

40~60%

Semi-indirect

60~90%

10~40%

Indirect

90~100%

0~10%

General-diffuse

40~60%

40~60%

Semi-direct

10~40%

60~90%

Direct

0~10%

90~100%

Luminaire type % Upward flux distribution % Downward flux distribution

Direct 00 - 010 90 - 100

Semi-direct 10 - 040 60 - 090

Direct-indirect 40 - 060 40 - 060

General diffuse 40 - 060 40 - 060

Semi-indirect 60 - 090 10 - 040

Indirect 90 - 100 00 - 010

Chapter 7. LUMINAIRES

Page 61: 38 Lighting Handbook

- Plane C = 0°.

- Plane C = 45°.

- Plane C = 90°.

Polar distribution curves are in the cd units per 1 000 lumens of flux emited by the lamp. They are represented in cd/1 000

lm or cd/Klm. (Fig. 2).

Figure 2. Polar diagram in the C-γ system.

Zone flux diagram

These diagrams indicate the flux received by the surface to be illuminated directly from the luminaire, depending on angle γ.This diagram is obtained by creating cones whose axis coincide with the vertical axis of the luminaire. Generating angles with

this axis are γ angles. The percentage of light collected by each of these cones is the image represented in the diagram (Fig.

3).

Figure 3. Zone flux diagram.

For narrow beam luminaires, a high flux percentage is obtained from small angles. This is the reason why the diagram will initially

show a curve with a great slope for the first angles. From a certain angle onwards, it is virtually parallel to the abscissas axis. This

is due to the fact that almost all flux is distributed in small angles, that is to say, it is concentrated in a small angle range.

20°

20%

40%

60%

80%

100%

40° 80°60° 100° 120° 140° 160° 180°GM=0

0 100

C=90°

GM=0

C=45° C=0°

50°

10° 20° 30° 40°

60°

70°

80°

200 300 400 Cd/Klm

73LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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74 LIGHTING ENGINEERING 2002

For wide beam luminaires, the diagram will show a curve with a softer slope, since flux varies little by little, as the angle increases.

Glare diagram

These diagrams are based on the C.I.E. Glare Protection System. Curves representing these diagrams are of luminance limitation.

Such curves cover a glare index scale (quality classes from A to E established by the C.I.E.) and different illuminance values in

standard service.

Two diagrams must be used depending on luminaire type and orientation according to vision.

The required limitation of luminance depends on the luminaire type of orientation, shielding angle, acceptance degree or class

quality, as well as on the value of the illuminance in service.

In Figs. 4a and 4b, diagrams of luminance curves for the evaluation of direct glare are shown. Diagram 1 is for those directions

of vision parallel to the longitudinal axis of any elongated luminaire and for luminaires which lack luminous lateral panels,

observed from any direction. Diagram 2 is for those directions of vision in right angles to the longitudinal axis of any luminaire

with luminous lateral panels.

It is defined as:

- Luminous laterals: A luminaire has luminous laterals is it possesses a luminous lateral panel with a height of more than 30

mm.

- Elongated: A luminaire is elongated when the ratio between length and width of the luminous area is higher than 2:1.

Figure 4a. Glare diagrams.

C=270

C=90

C=0

C=180

C=90

C=270

85

GMa b c d e f g h

75

65

55

459 2 3

1

2

3

4

68

4 5 6 7 8 9 10 Cd/m2 2 3103

1.151.501.852.202.55

ABCDE

2000 10002000

50010002000

=<300500

10002000

=<300500

10002000

=<300500

1000=<300

500 =<300

a/h

G

a b c d e f g h

Quality Illuminance values in service E (lx)

Chapter 7. LUMINAIRES

Page 63: 38 Lighting Handbook

Figure 4b. Glare diagrams.

When using diagrams of Figs. 4a and 4b, luminance distribution of the luminaire in two vertical planes must be considered: the

C0 – C180 plane parallel to the inner axis. Luminance distribution of the luminaire in such a plane is used to control glare

limitation in the longitudinal direction of the room. Distribution of the luminaire in the C90 – C270 plane is used to verify glare

limitation in the transverse direction to the place to be illuminated.

When luminaires are mounted on the C90 – C270 plane parallel to the longitudinal inner axis, such a plane must be used to verify

glare limitation in the longitudinal direction of the place, and luminance distribution on the C0 – C180 plane to avoid glare

limitation in the transverse way of the place.

For elongated luminaires, the C90 – C270 plane is chosen to coincide with (or parallel to) the longitudinal axis of the lamp/s.

When such a plane is parallel to the direction of the perceived vision, it is said to be longitudinal. However, when the C90 – C270

plane is in right angles to the direction of vision, this vision is considered to be transverse.

These diagrams are generally used for indoor lighting luminaires.

7.5.2. Road lighting luminairesWithin this section, luminaires for parks and gardens as well as public road lighting are included. The first ones are frequently

installed, as indicated by their name, in parks, gardens, residential areas, etc. The second ones are installed in urban roads,

highways, tunnels, etc.

The C.I.E. has introduced a new system for the classification of road lighting luminaires, thus, substituting the system introduced

in 1965, where the classification was cut- off, semi cut- off and non cut- off. Nevertheless, the old system is still being used in

certain national recommendations for road lighting. In chart 7, the old system is shown.

Chart 7. C.I.E. classification from 1965.

Direction of Type of Allowed value for maximum intensity Allowed value for maximum intensity

maximum intensityluminaire emitted at an elevation angle of 80° emitted at an elevation angle of 90°

inferior to

Cut – off 30 cd / 1 000 lm 10 cd / 1 000 lm* 65°

Semi cut – off 100 cd / 1 000 lm 50 cd / 1 000 lm* 76°

Non cut – off Any -

C=0

C=180

a b c d e f g h85

GM

75

65

55

459 2 3 4 5 6 7 8 9 10 Cd/m2 2 3103 1

2

3

4

68

a/h

1.151.501.852.202.55

ABCDE

2000 10002000

50010002000

=<300500

10002000

=<300500

10002000

=<300500

1000=<300

500 =<300

G

a b c d e f g h

Quality Illuminance values in service E (lx)

75LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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76 LIGHTING ENGINEERING 2002

Figure 5. Examples of photometric curves accompanied by their classification.

The new C.I.E. luminaire classification, which substitutes the previous one, is based on three basic properties of luminaires:

1. The extension to which the luminaire light is distributed along a path: the “throw” of the luminaire.

2. The amount of lateral dissemination of light, widthways of a path: the “spread” of the luminaire.

3. The reaching of the installation to control glare produced by the luminaire: the “control” of the luminaire.

The reaching is defined by the angle γmax which forms the axis of the beam with the vertical plane going downwards. The axis

of the beam is defined by the direction of the angle bisector formed by two directions of 90% Ιmax in the vertical plane of maximum

identity.

Figure 6. Intensity polar curve in the plane which contains the maximum

luminous intensity, indicated by the angle used to determine the throw.

Three levels of throw are distinguished as follows:

γmax < 60° : short throw.

70° ≥ γmax ≥ 60° : intermediate throw.

γmax > 70° : long throw.

* Up to a maximum absolute value of 1 000 cd.

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

γ max

γ90% Imax

Axis of the beam

I max

Cut- off

Cut- off Semi cut- off Non cut- off

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

195

cd

130

cd

65 cd

Chapter 7. LUMINAIRES

Page 65: 38 Lighting Handbook

The spread is defined by the positioning of the line, running parallel to the axis of the path. Virtually, it does not touch the

furthest side from the 90% Imax on its path. The positioning of this line is defined by the γ90 angle.

The three levels of spread are defined in the following manner:

γ90 < 45° : narrow spread.

55° ≥ γ90 ≥ 45° : average spread.

γ90 > 55° : broad spread.

Figure 7. Spread.

Both the luminaire throw and spread may be more easily determined from an isocandela diagram in an azimuthal projection

(Fig. 8).

Figure 8. Isocandela diagram related to an azimuthal projection (sine wave) indicated by

the γmax and γ90 angles used to determine spread and throw.

In Fig. 9 the covering given by the three levels of throw and spread of the luminaire mounting height (h) is indicated on a plane

of the path.

90% Imax

γmax

γ90γ

C

h

1h

2h

3h

4h

γ 90

90% Imax

77LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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78 LIGHTING ENGINEERING 2002

Control is defined by the specific index, the luminaire SLI. This is part of the G formula of glare control, determined only by the

features of the luminaire.

where:

I80 = Luminous intensity at an elevation angle of 80°, in a parallel plane to the axis of the roadway (cd).

= Ratio between luminous intensities for 80° and 88°.

F = Light emission area for the luminaires (m2) projected on the direction of the elevation at 76°.

C = Colour factor, variable according to lamp type (+0.4 for low pressure sodium and 0 for the others).

Figure 9. In this figure, the three degrees of throw and spread defined by the

C.I.E. are shown, where “h” is the luminaire mounting height.

Control is also classified into three levels, which are the following:

SLI < 2 : limited control.

4 ≥ SLI ≥ 2 : moderate control.

SLI > 4 : tight control.

In the following chart, the C.I.E. previous definitions are summarised and shown.

Chart 8. The C.I.E. classification system depending on luminaire photometric properties.

Throw Spread Control

Short γmax < 60° Narrow γ90 < 45° Limited SLI < 2

Intermediate 70° ≥ γmax ≥ 60° Average 55° ≥ γ90 ≥ 45° Moderate 4 ≥ SLI ≥ 2

Long γmax > 70° Broad γ90 > 55° Tight SLI > 4

(90% Imax)

h

1h2.7h

1.7h

1.4 h

Short

Intermediate

Long

γmax

Spread

NarrowBroad

Average

70°

60° 45°55°

I80

I88

( I80 )0.5

I88

SLI = 13.84 - 3.31 . log(I80) + 1.3 . log - 0.08 .log ( I80 )I88

+ 1.29 . log(F) + C

Chapter 7. LUMINAIRES

Page 67: 38 Lighting Handbook

Photometric information accompanying road lighting luminaires

Diagrams of polar distribution curves

These curves are generally represented for the coordinate system C-γ. Since there are infinite planes, usually there are three C

planes represented, which are the following:

- Transverse plane (C = 90° and 270°). This plane would be perpendicular to the axis of the road for a road lighting luminaire.

- Longitudinal plane (C = 0° and 180°). This plane would be parallel to the axis of the road for a road lighting luminaire.

- The plane in which maximum intensity is found. This plane is generally called main vertical plane.

Polar distribution curves are defined in cd by 1 000 lumens of flux emitted by each lamp and it is represented by cd/1 000 lm

or cd/Klm.

Figure 10. Polar diagram in the C- system.

Isocandela diagrams

It consists of imagining that the luminaire is in the center of a sphere; in its exterior surface equal intensity points are joined by

a line. Equal surfaces in this diagram represent solid angles. Due to this reason, the diagram may be used to calculate luminous

flux for a given area, multiplying the area by the luminous intensity (bearing in mind the scale in which the diagram is

represented).

If the luminaire is installed with a δ inclination angle, strokes must be turned around the center in an angle δ to deduce the new

C-γ coordinates.

Straight lines from the center represent parallel lines to the roadway axis.

Figure 11. Isocandela diagram in azimuthal projection.

GM=0 Imax=100%10-10

-20

-30

-40

-50

-60

-70

-80

-90C=0350 10 20 30 40 50 60 70 80340330320310300290280

20

30

40

50

60

70

80

90

15

10

20

30

9080

60 40

60

GM=0-10 10

0 10080160240320 200 300 400 0 100 200 300 400

-20 20-30-40 40

50

60

70

80

90

-50

-60

-70

-80

-90

30 GM=0 10 20 40

50

60

70

80

90

30

TRANSVERSE PLANE (C=90-270) LONGITUDINAL PLANE (C=0-180) MAIN VERTICAL PLANE

C=20.0

79LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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80 LIGHTING ENGINEERING 2002

Diagram of isoluminance curves

These diagrams are frequently used for public lighting. This is due to the fact that recommendations for public lighting are not

exclusively limited to the average luminance required on the surface of the roadway, but also guidelines for their uniformity (ratio

between Lmax and Lmin) are provided. Such calculations are possible with the help of the isoluminance diagram (Fig 12).

Figure 12. Isoluminance diagram.

In the diagram, letters A, B and C appear, indicating three positions for the observer which are used in luminance performance

diagrams.

Diagram of isolux or isoilluminance curves

In practice, illuminances on the road surface and their total distribution are intended to be known in most lighting projects.

In order to ease the determination of these data in an installation, photometric sheets provide us with the isolux relative curves

for each luminaire on an illuminated plane.

Figure 13. Isolux diagram on the surface to be illuminated.

Values for each isolux line are given in Emax percentages, the highest being 100%. The lattice on which isolux lines are drawn

is measured in terms of the luminaire mounting height h.

h

6h 5h 4h

11

5

5

10

20

3040

506070

80

3h 2h h 0 h 2h 3h

0

h

2h

3h

Emax=100%fl=0.154

WALKWAY SIDE

ROADWAY SIDE

h6h 5h 4h

1 5 2030

4050

6070

80

5

10

50

1

5

3h 2h h 0 h 2h 3h

0

h

2h

3h

A

OBSERVERS: A, B AND C

B

C

WALKWAY SIDE

ROADWAY SIDERoadway R2Qo = 0.07

Lmax=100%fl=0.152

Chapter 7. LUMINAIRES

Page 69: 38 Lighting Handbook

Under the diagram, a factor for the luminaire in use () is indicated.

Maximum illuminance is calculated by means of the following formula:

where:

ϕ = factor for the luminaire in use.

Φ = lamp luminous flux.

h = interdistance between luminaires.

Performance in luminances

These diagrams are used to calculate average luminance on the surface of the roadway of a public lighting installation. If the

pavement reflection class is known, the corresponding diagram will be used.

Luminance performance diagrams are drawn in units of luminaire mounting height. Due to this reason, they are very useful for

direct graphic uses.

Figure 14. Performance in luminances with respect to three observers.

Their reading is equal to that of utilization factor curves, except that the observer’s position is important. Hence, curves are given

for three observer’s positions: A, B and C.

- A: Observer located on a side of the sidewalk at a distance h of the row of luminaires.

- B: Observer located in line with the row of luminaires.

- C: Observer located on a side of the road at a distance h of the row of luminaires.

h0.0

270°

C=

90°

180°

0.1

0.2

0.3

0.4

0.5

0.6

C

B

A

h 2h 3h

Εmax =ϕ . Φ

h2

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Chapter 7. LUMINAIRES

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82 LIGHTING ENGINEERING 2002

For other positions, it is necessary to interpolate.

Average luminance is calculated with the following formula:

where:

ηL = luminance performance factor.

Φ = lamp luminous flux.

QO = average luminance coefficient.

w = road width.

s = interdistance between luminaires.

Utilization factors

In road lighting, utilization factor (h) is defined as the fraction of the luminous flux coming from a luminaire which, in fact, reaches

the road. Utilization factor curves found on the photometric information sheets offer a simple method to calculate average

illumination, which may be determined for a certain transverse section of the road.

Utilization factor curves for a luminaire are understood as a function of transverse distances, measured in terms of h (mounting

height) on the road surface, from the center of the luminaire up to each of the two curves (Fig. 15).

Figure 15. Utilization factor as a function of h.

The easiest and quickest way to calculate average illuminance of a straight road of infinite length is by using utilization factor

curves:

where:

η = utilization factor.

Φ = lamp luminous flux.

n = number of lamps per luminaire.

w = width of the road.

s = interdistance between luminaires.

Εmed =η . Φ . n

w . s

h0.0

270°

C=

90°

180°

0.1

0.2

0.3

0.4

0.5

0.6

Walkway side Road way side

h 2h 3h

η

η =Φused

Φlamp

Lmax =ηL . Φ . Qo

w . s

Chapter 7. LUMINAIRES

Page 71: 38 Lighting Handbook

Polar diagrams are frequently used for luminaires in:

- Public lighting.

- Lighting of parks and gardens.

7.5.3. Floodlight luminairesWithin this section, those luminaires designed for installation in indoor and outdoor sports facilities, facades, working areas,

invigilance areas, etc.

A floodlight is a luminaire which concentrates the light in a solid angle determined by an optical system (mirrors or lenses), in

order to achive a high luminous intensity.

Lamps suitable for floodlights range from pressed glass lamps and halogen lamps and even high pressure mercury lamps, metal

halide lamps and low pressure and high pressure sodium lamps. They all have different voltages and each provides a kind and

special type of light, colour effects and efficiency.

Mounting, relamping and cleaning must be done at a considerable height from the ground. Thus, an ergonomic design of the

luminaire is required so that these tasks are easily taken care of.

From the point of view of light distribution, floodlights are grouped in three basic types: symmetric, asymmetric and symmetric

rotation.

Floodlights are also classified according to the opening of the beam, as shown in chart 9. The opening of a floodlight beam (or

beam angle) is defined as the angle, in a plane which contains the axis of the beam, on which luminous intensity decreases to

reach a certain percentage (generally 50% or 10%) of its peak value (Fig. 16).

Chart 9. Classification of the beam opening.

Figure 16

For a floodlight with an intensity distribution of light in a symmetric rotational way (that is to say, distribution remains unchanged

independently from the plane containing the axis of the beam under consideration), a figure for the opening of the beam may

be established, for example 28° at both sides of the axis of the beam.

For asymmetric distribution, as that given by rectangular fllodlights, two figures are given: for example 6°/24°, since the beam

is spread into two symmetric perpendicular planes (vertical and horizontal, respectively). Sometimes, distribution in the vertical

plane of such floodlights is asymmetric in relation to the beam axis. In this kind of situation, two figures are given for the opening

of the beam in this plane: for example, 5º - 8º/24º, that is to say, 5º above and 8º below the axis of the beam; and, in the

Imax

Beam opening

50% I max

50% I max

β

Description Opening of the beam (at 50% Ιmax)

Narrow beam < 20°

Medium beam 20° to 40°

Wide beam > 40°

83LIGHTING ENGINEERING 2002

Chapter 7. LUMINAIRES

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84 LIGHTING ENGINEERING 2002

horizontal plane, 12º to the left and 12º to the right of the beam.

Photometric information accompanying floodlights

Cartesian diagram

These diagrams are obtained in photometries performed on floodlights, since they provide us with information to be able to

classify them according to beam opening They are generally represented under the coordinate system B-.

Three lines representing the vertical plane, the horizontal plane and 50% of the maximum intensity (line parallel to the abscissas

axis) are represented.

Figure 17. Cartesian diagram.

Isocandela diagram

In order to avoid coordinate curves, as it happens with solid angle systems, and ease the reading of coordinates, these are drawn

in a rectangular system.

The angles of C and B planes are on the horizontal axis, γ and β angles on the vertical one.

The diagram may be compared with that of azimuthal projection, but, it must be taken into account that:

- There is no linear ratio between rectangles in the diagram and solid angles.

- The line γ = 0 or β = 0, in fact, represents a point.

-90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

100

200

300

400

500

600

700

800

Horizontal planeVertical plane

Imax/2

Chapter 7. LUMINAIRES

Page 73: 38 Lighting Handbook

Figure 18. Isocandela diagram for the B- system.

7.6. Basic photometric data

Luminaire information sheets show a series of diagrams which indicate their photometric peculiarities. In this section two terms

associated to the obtention of such curves are going to be studied.

7.6.1. Photometric center

Most calculations are done under the supposition that luminaires are specific sources of light. Thus, there is the need to search for a

point in space limited by the luminaire which will place the specific equivalent and imaginary luminous source.

For angles close to the nadir, there are virtually no differences between photometric data of the same luminaire given by different mea-

surement laboratories. For big angles, there could be differences, for example 80º and 88º, if the photometric center of a luminaire is

not clearly established.

The photometric center is a point of a luminaire or a lamp from which the Law of the inverse square of the distance in the direction of

maximum intensity is best complied. Or what is the same, it is the point where the imaginary and specific luminous source, with the

same spatial distribution of luminous intensities of the luminaire is located. The only goal is to simplify photometric calculations.

The C.I.E. has established in its publications the rules to locate such a photometric center for different types of luminaires.

7.6.2. Photometric coordinate systems Each and every one of the directions in the space through which luminous intensity is radiated is determined by two coordinates.

On photometric information sheets for indoor luminaires, public lighting and floodlights, representations obtained by means of

three coordinate systems, the most frequently used, are utilized. Such systems are A-α, B-β and C-γ.The C-γ coordinate system is defined in the C.I.E. publications. However, there is no international agreement on the definition

-80-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

70

2015

105

3

30

50% of Imax

AXIS X

Beta angles

Plan

es B

85LIGHTING ENGINEERING 2002

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86 LIGHTING ENGINEERING 2002

of the systems A-α and B-β. Tests for obtaining the last two differ depending on the country that conducts them.

When applied to the photometry of these types of luminaires, the reference axis is always vertical and directed towards the

lowest point (nadir).

All systems have a beam of planes with an intersection axis, sometimes called “rotation axis”.

In each case, a direction in space is characterized by an angle measured between two planes and an angle measured in one

of the planes.

Systems differ between themselves with regards to axis orientation of the intersection in space in relation to the luminaire axis.

To test floodlights, systems adapted to the horizontal axis are used, but their name varies in different countries.

7.7. Luminaire efficiency

Luminaire efficiency is expressed in terms of its Light Output Radio – I.o.r.)*. This radio is defined as the portion of light output of the

luminaire with regard to the sum of light individual exits of lamps when they are used outside the luminaire.

The light output radio defined this way is the total “I.o.r.” of the luminaire, and is equal to the sum of the “I.o.r.” upwards and downwards.

Chapter 7. LUMINAIRES

Page 75: 38 Lighting Handbook

* The term used in the U.S.A. is “luminaire efficiency”.

87LUMINOTECNIA 2002

Capítulo 7. LUMINARIAS

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87LIGHTING ENGINEERING 2002

Chapter 8.

LAMPS

8.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

8.2. Thermal radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

8.3. Luminescence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

8.4. Conditions to be met by lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

8.5. Incandescent lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

8.6. High pressure mercury discharge lamps . . . . . . . . . . . . . . . . . . . . . . . 100

8.7. High pressure sodium discharge lamps . . . . . . . . . . . . . . . . . . . . . . . 105

8.8. Induction lamps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

8.9. Chart with characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

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88 LIGHTING ENGINEERING 2002

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8.1. General remarks

In chapter 1, the dual nature of light was studied, and in chapter 2, the process of how visible radiations are manifested in light by means

of vision was discussed.

As it has already been mentioned, light is a form of energy represented by electromagnetic radiation, which may affect the human eye,

and is produced in many ways, depending on the causes that provoke it. If it is due to the radiant body temperature, the phenomenon

is called thermal radiation. All other examples are considered as luminiscence.

Fig. 1 gives a general idea about the main physical agents which intervene in light production and their respective sources.

Figure 1. Physical agents intervening in light production.

8.2. Thermal radiation It is the radiation (heat and light) emitted by a hot body.

The energy of this radiation depends only on the calorific capacity of the radiant body. In general, the light obtained is always

accompanied by a considerable thermal radiation that constitutes a source of energy loss when, in fact, light is trying to be produced.

When heating a piece of coal, iron, gold, wolfram or any other material, a visible radiation is obtained. It may be seen in the incandescent

colour acquired by the body and it will vary depending on temperature, as shown in Chart 1.

Chart 1. Incandescent colours at different temperatures.

All the laws studied and formulated for the ideal radiator may be summarized in a single one: the percentage of visible radiation increases

according to radiator temperature.

As it may be seen in Fig. 2, at 6,500 K the maximum performance is obtained. It would be useless to increase temperature of the

radiator with the intention of obtaining a performance greater than 40%.

Temperature °C Incandescent colour

0.400 red - incipient grey

0.700 red - grey

0.900 red - dark

1 100 red - yellow

1 300 red - light

1 500 red - incipient white

2 000 onwards red - white

Thermal radiation Luminiscence

LIGHT PRODUCTION

Incandescentcombustion

Gas discharge

Sun

Natural

Artificial

FlameGaslightElectric arcIncandescent lamp

Metallic vapor lampNoble gas lampNegative glow lampXenon lamp

Luminiscent substanceLuminous plaqueSolid body plaqueRadioactive source of light

Ray Glowworm

Solid body radiation

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Figure 2. Visible radiation depending on absolute temperature.

8.2.1. Natural thermal radiation

In nature itself, an evident example of light production at a great scale may be found by the thermal radiation offered by the

Sun or other stars similar to it. The Sun is an enormous ball of hydrogen in an incandescent state in which nuclear radiation is

constantly transforming hydrogen (H2) into Helium (He). In the process, enormous amounts of energy are expelled to the

Universe. From the energy emitted by the Sun, almost 40% of the radiation is transformed into visible light, which corresponds

to the maximum optical performance at 6,500 K.

8.2.2. Artificial thermal radiation

Light by artificial thermal radiation is obtained by heating any solid matter or body at a high temperature, either through

combustion or incandescence.

Light of the lighting flame

The oldest thermal radiator in history and also the most primitive one was the lighting flame produced by the combustion of a

lit torch, followed by the oil lamp, the petroleum one and the wax candle, which were the most widely used lighting sources in

the old times.

At the beginning of the 19th century, the mineral coal gas (coal) was used to obtain a lighting flame, instead of the solid

substances used until then (wax, grease) and liquid ones (oil, petroleum). At the beginning, light was obtained directly from the

flame. Later on, through Auer's incandescent mantle.

Electric arc light

If two coal bars in contact, through which electric current is circulating, are quickly separated up to a certain distance, a

permanent and powerful electric arc is produced between its pins.

The electric arc itself only produces 5% of the emitted light. The rest corresponds to the incandescent craters formed in both

coal bars. This kind of arc, whose current intensity is quite high, must not be confused with gas discharge arcs.

Light of an incandescent body in the vacuum

When an electric current circulates through an ohmic resistance, this is heated up and, if taking place in the vacuum, it turns

incandescent. The colour acquired is red- white at temperatures ranging between 2,000 and 3,000 ºC, in which case it emits

light and heat like a perfect thermal radiator. The first person who put this principle into practice was Henrich Goebel who made

the first electric incandescent lamps in 1854, using empty perfume bottles in which he hermetically sealed a filament made

with carbonized bamboo fibres. However, it was the American Thomas Alva Edison who discovered an incandescent lamp with

40

50%

30

20

10

0 10 5 000 10 000K

Visib

le ra

diat

ion

perc

enta

ge

Temperature

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a coal filament and gave it a practical utility as a series article in 1879. At the same time as Edison, the british Swan also achieved

a usual incandescent lamp.

The coal filament: Lamps used from 1880 to 1909, had a coal filament composed of “coked” bamboo or paper fibres.

The point of fusion of this filament was approximately of 3,700 °C, but due to its high vaporization index, lamps could also be

made for a temperature in service of about 1,900 °C. Thus, luminous performance was not more than 3 to 5 lm/W.

The metal filament: At the beginning of the past century, a search begun in order to find metals that would be able to substitute

the coal filament in a susccessful way. Among metals with a high degree of fusion were osmium, tantalium and wolfram mainly.

Wolfram point of fusion is approximately 3,400 °C, with an evaporation index slightly lower than that of coal. The lamp life is

approximately 1,000 hours, the filament incandescence temperature reached 2,400 °C and a luminous performance of 8 to

10 lm/W was obtained.

8.3. Luminescence

Those luminous phenomena whose cause does not exclussively obey to temperature of the luminescent substance. Such phenomena

are characterized because only some particles of the matter atoms, the electrons, are excited to produce electromagnetic radiations. In

order to understand such a study, Börh’s atomic model must be studied.

Figure 3. Böhr’s atomic model.

According to this model, each atom is formed by a positive atomic nucleus and by a cover of negative electrons. These are distributed

in different layers that rotate around the nucleus following certain orbits. Usually there is an electric balance in the atom, that is to say,

the number of positive charges is equal to the number of negative charges (electrons). This balance is known as fundamental state of

the electron E, and for electrons in the most internal orbit, it is identical to the base line f (Fig. 3).

If a certain amount of energy is administered to the electron from the outside, electron E is excited and moved from its regular orbit to

the next one or to another more external one. Thus, the energy supplied is absorbed. The electron is located in a superior energy level

(level lines e1, e2, e3, etc. of Fig. 3). After a short time in this level, the electron returns again to its regular initial position (line f of Fig.

3) and emits the amount of energy absorbed at the beginning, usually in the form of electromagnetic radiation.

If the amount of energy is greater, electron E may instantaneously reach a more external orbit. As a consequence of the greater range

of energy achieved, radiation emited when the electron returns to base f will be richer in energy.

Therefore, the different layers of energy correspond to a perfectly determined level of energy, and, thus, there are not intermediate

levels. Thus, it is deduced that in order to excite an atom, an exactly determined amount of energy is necessary. This is emitted in the

form of radiation and/ or heat loss when the atom recovers its fundamental shape.

e3e2e1

f1 f2

≈W

A

1

1 2 3

m

4 5 6

fE

E = Electron

Weak excitation

2 Strong excitation

6 Phosphorescence

m = Acummulation level

= Energy emission

3 Forced energetic excitation (laser)

4 5 Stages emission, W heat give- away

A= Absorption S= Emission

Electrone energy ranges

S

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The emission of energy transformed in this process from an atomic point of view takes place in portions or discontinuous parts known

as energy quants (Böhr postulated that the atom may not rotate at any distance from the nucleus, but in certain orbits only). However,

in the field of practical lighting engineering, light emitted in this tranformation is considered to be emitted in a continuous way, in the

form of electromagnetic waves, which is acceptable for normal cases of its application.

By means of the theory of energy quants formulated by Max Plank, it is proved that different chemical elements, when excited, do not

emit a continuous spectrum due to the different structure of their electronic layers, but only very particular wavelengths (lines) within all

the electromagnetic spectrum. These spectra are known as linear spectra. Each substance has a characteristic linear spectrum and also

luminescent gases like, sodium vapor, whose spectrum is composed by a double yellow line whose wavelengths correspond to 589

and 589.6 nm, respectively.

According to the physical technique used to excite atoms, the type of radiation and the form in which it is emitted, several types of

luminiscence may be distinguished.

Electric discharge light within a gas

In all gases, especially in those contained in discharge lamps, besides neutral gas atoms, some free electric charges are found

(electrons).

Figure 4. Gas discharge tube.

If a continuous current is applied to the anode A (+) and to the cathode C (-) of the discharge tube (Fig. 4), an electric field

is created between A and C which accelerates negative charges (electrons) and hurries them towards the anode. When an

electron reaches a certain speed, it has enough kinetic energy to excite a gas atom. If the speed of the electron when crashing

against the atom gas is even greater, the impact may even cause the separation of an electron from the atomic cortex, so the

atom lacks an electron in its configuration. That is to say, a positive ion is obtained. This phenomenon is known as impact

ionization. This way, the number of free electrons is even higher. It is even possible that they will increase enormously if the

electric current produced by them is not limited by means of an appropriate resistance (stabilizer).

Together with the free or separated electrons, positive ions may be also found moving in the opposite way of electrons. That is

to say, towards the cathode. Due to their small speed, they may not produce any excitation of other gaseous particles. On the

contrary, after a short period of time, they take an electron again in exchange for an energy emission.

Depending on the noble gas or metal gas with which the discharge container is filled, by means of the previously mentioned

atomic excitation, linear spectra or light colours characteristic of the chosen chemical element will be formed. For example, if

the gas is neon, the light colour is red- orangish, and if it is mercury vapor, it will be white- bluish.

All these phenomena take place within a volume ranging between two electrodes, and it is limited by the discharge container

wall. This volume forms a discharge gaseous column.

If the discharge tube receives an alternating power supply, instead of a continuous one, electrodes change their function

periodically, sometimes behaving as a cathode and some other times as an anode. Otherwise, the luminous production

phenomenon is exactly the same.

Electric discharge conditions for light production in a gas essentially depend on the gas or vapor pressure inside the discharge

tube. So, there are three kinds of discharge, namely:

- Low pressure discharge.

- High pressure discharge.

E

A CE

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- Very high pressure discharge.

The higher pressure is, the wider spectral lines, forming even greater bands, so that the chromatic spectrum improves.

Metal vapor lamps need the metal to be vaporized first since it is in a solid or liquid state when cold. This is the reason why

these lamps are filled with a noble gas which is the first one to inflame, supplying the heat necessary for metal vaporization.

High voltage electric discharge between cold electrodes (noble gas tubes)

In order to administer enough free electrons in this type of discharge, cold electrodes are used mostly built with a chromium-

nickel metal.

The filling of the discharge tube is with noble gases like neon which emits an intense red- orangish light, or helium which emits

a light pink coloured light and also with metal vapors, especially mercury vapor which emits a white- bluish light, and when

mixed with the neon gas an intense blue light.

Starting and working voltages are high, 600 to 1,000 volts being necessary for half a metre in length. The average voltage

consumption also for half a metre in length is of about 33 W, with a luminous performance of 2.5 to 5 lm/W.

Due to this low luminous performance, noble gas tubes have been barely used for indoor lighting, but they really have played an

important role in luminous advertisement due to their particular easiness to be modelled in the shape of letters.

Low voltage electric discharge between hot electrodes (metal vapor lamps)

If a certain amount of solid sodium or liquid mercury is introduced inside a glass tube previously evacuated in order to transform

metal into vapor through the electric discharge, a metal vapor discharge in gas is obtained. This may be even produced at a

regular low voltage (220 V), with prehated or heated electrodes (hot cathodes). Sodium and mercury vapor lamps work

according to this principle.

From everything that has been exposed until now, it is deduced that light emitted by metal vapor lamps especially depends on

the linear spectrum of the metal vapor chosen. Thus, sodium vapor lamps produce a monochromatic light of a yellow- orangish

light and mercury vapor lamps one of a green- bluish characteristic.

Discontinuous spectra of these lamps are improved through different ways:

Mercury lamps:

- Through combination with an incandescent lamp (blended light lamps).

- Through combination with a fluorescent layer (mercury vapor lamps, corrected colour).

- Through addition of metal halides (metal halide vapor lamps).

Sodium lamps:

- Through combination with mercury light in a metal transparent recipient, at high pressure filling (high pressure sodium

lamps).

Photoluminescence (low pressure fluorescent lamps)

Photoluminescence is fundamentally understood as the excitation of certain substances to luminescence by means of radiation,

usually produced by short wave ultraviolet radiation. The luminescent substances used only emit light while they are being

excited by short wave ultraviolet radiation which is transformed into a longer wave radiation (visible spectrum light).

Luminescent substances used are, among others, calcium wolfram, magnesium wolframite, zinc silicate, cadmium silicate,

cadmium borate, halophosphates, etc.

Each of these luminescent substances emits a certain light colour. By mixing these substances in an appropriate way, any desired

composed light colour may be obtained. If the emission light of each of these chromatic components is achieved to be

superimposed, a continuous spectrum is obtained which may also vary from daylight white to warm white.

“Fluorescence” are all those luminescent phenomena in which luminous radiation remains during the excitation. The opposite

situation is known as phosphorescence.

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Phosphorescence

Phosphorescence takes place when luminous radiation persists in certain luminescent substances even after excitation is over.

This phenomenon corresponds to the fact that under certain energy levels (belonging to certain electronic layers) of some

chemical components, like sulphures, seleniures or oxides of alkali earth metals, apart from this, there is an “acummulation level”

that prevents electrons from quickly returning to their initial position.

Electrons, that because of their excitation reach this acummulation level, can only in a slow fashion recover their fundamental

state. It is then when the substance continues emitting light. This phenomenon may last fractions of seconds or months

(depending on material type and temperature).

Electroluminance

In order to produce this phenomenon, instead of an exciting radiation, also an electric field may be directly used to “rise“

electrons at a higher level of energy. This is achieved by inserting a luminescent substance between two conducting layers

and applying alternating current to the group, as for plaque condensers.

This way to obtain light (manifested by a sparkle of a moderate splendor) has been performed in the so- called luminous

plaques to be applied in hospital rooms, building numbering, stair lighting, etc.

Injected luminescence

To a certain extent, it is the opposite case to that of the photoelectric principle, in which photometres to measure light are based.

Whereas there is a luminous energy transformation in the photometre into electric energy (in the form of a minicurrent), on

applying injected luminescence to the so- called solid body lamp of an electric energy, a luminous energy is reciprocally

produced (chromatic radiation). This kind of radiation has a very good application for simple procedures of unimportant marking.

A solid body lamp is obtained by inlay in the net of a semiconductor certain strange atoms, in such a way, that it will remain

divided into two parts, one with an excess of electrons and the other with a defect.

Radioluminescence (light produced by radioactive substances)

In this case, the luminous emission is based on radiation from a luminescent substance with rays which result from the natural

desintegration of radioactive matter, like for example, uranium and its isotopes. This light production principle, the so- called

isotope lamp, is applied which does not need power supply at all to work.

Bioluminescence

Bioluminescence is a luminous phenomenon which is weakly manifested in Nature. It consists of a sparkle emitted by light

worms, some classes of fishes, marine algae, rotten wood and similar. This phenomenon is due to the oxidation process of

some special chemical or organic substances, like the ones glow worms and photogene bacteriae have when in contact with

the air or water oxygen.

So far, it has not been possible to reproduce this phenomenon of Nature artificially.

8.4. Conditions to be met by lamps

8.4.1. Total radiation spectral distribution

For lamps as energy transformers to work with a high performance, almost all the energy absorbed should be transformed into

visible radiation. Besides, their light should be white like daylight and with a good chromatic reproduction which requires a

continuous spectrum containing all main colours from purple to red. But, since eye sensitivity is maximum for yellow- greenish

radiation, the best thing to do, as far as luminous performance is concerned, is to obtain the highest percentage possible of

radiation in the 555 nm zone.

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8.4.2. Luminance

Light lamps preferably used outside must not have a high luminance so that their glare effect is kept within bearable limits. The

admissible luminance value depends on the type of application.

On the contrary, lamps used in luminaires may have great luminances, since they trimmer the glare effect. In general, luminance

to be obtained from a lamp depends on the system adopted for light production, that is to say, on the physical nature of the

source of light and on the fact that it may be pointed, linear or plane.

Lamps luminance may never be increased by means of any optical system but it may be weakened, for example by diffusing

layers.

8.4.3. Luminous intensity distribution

Lamp radiation is not equal in all directions in the space. It is affected by the position of the base, the supports of the luminous

body, etc. All this determines that each type of lamp possesses a distribution typical of its luminous intensity.

Luminous distribution curves are essential to project lighting installations, as well as for luminaire design, because their optical

system must be adjusted in such a way to the lamp luminous distribution curve and light is directed to the place or point where

it is needed the most.

8.4.4. Emitted radiation biological effect

Lamps must not emit any unnecessary or harmful radiation for human beings, either immediately or in the long run. With

thermal radiators like incandescent lamps, this condition is observed from the beginning (most of the radiation produced is

infrared). Some gas discharges, mainly mercury vapor, naturally contain a percentage of ultraviolet radiation that may be

classified into:

- UV-A: Sun tanned or long wave (between 315 and 380 nm.).

- UV-B: Anti- rachitic or medium wave (between 280 and 315 nm.). It favours the production of vitamin D in the body.

- UV-C: Bactericide or short wave (between 200 and 280 nm.). It kills germs and organic matter. These effects may increase

due to weakening of the atmospheric ozone layer.

- UV-C: Ozonosphere or short wave (between 100 and 200 nm.). This type of radiation is able to create ozone with the same

characteristics as that of the atmosphere.

The permanent effect of UV-B or UV-C radiations produces burns on the skin and conjunctivitis in the eyes which are not

protected. In general lighting lamps, this may be avoided with the use of appropriate glass classes that absorb critical radiation.

8.4.5. Appropriate colour for each application

The light colour of a lamp is determined by the spectral composition of its radiation. In Chart 2, light groups are established for

lamps used in general lighting:

Chart 2

Whereas incandescent lamps, due to their high content in the power supply (with the exception of coloured lamps), may only

radiate a warm white colour, light colours of discharge lamps are determined by gases or vapors chosen for them. For example,

Light colour Color temperature

Incandescent-fluorescent 2 600-2 700 K

Warm white 2 900-3 000 K

White or neutral white 3 500-4 100 K

Cold white 4 000-4 500 K

Daylight white 6 000-6 500 K

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yellow for sodium vapor discharge, or pale blue for mercury vapor. Other chromatic variants may be used, combining different

metallic vapors or modifying vapor pressure. With fluorescent lamps the possibility of achieving any shade that may be desired

is offered by means of the selection or mixture of a great amount of well- known luminescent substances, in order to adapt

them to each type of application.

8.4.6. Chromatic reproduction quality

Chromatic reproduction refers to the aspect of the colour illuminated surfaces have. Their reproductive quality not only depends

on the incident light colour tone, but also on their spectral composition. Therefore, colour temperature technically refers to the

colour of light, but not to its spectral composition. Thus, two sources of light may have a very similar colour and have, at the

same time, some very different chromatic reproduction properties. Most of the times what is required from a lamp is a good

chromatic reproduction, which means a spectral distribution different from the necessary one to obtain a high luminous

performance.

8.4.7. Luminous flux constants

In practice, it is not possible to maintain the luminous flux value at a 100% during all the life of the source of light, since physical

and technological reasons are against it.

Luminous flux indicated in catalogues refer, as far as incandescent lamps are concerned, to lamps which have not been working

yet, and as far as discharge lamps are concerned, to lamps with 100 hours of working, to which this has been stabilized.

8.4.8. Luminous performance

As seen in chapter 5, the maximum luminous performance to be achieved in the most favourable situation is 683 lm/W.

Although this value may not be reached, nowadays, lamps with a quite high performance have been achieved that allow the

obtaining of high lighting in a relatively economic way.

Nevertheless, in many cases it must be decided which property of the lamp is the most priceless: whether a high luminous

performance or an extraordinarily good chromatic reproduction.

8.4.9. Average rated life and service life

Average rated life is an statistical concept which represents the arithmetic means of the duration in hours of each of the lamps

of a group representative enough of the same model and type.

Service life is a measurement referred to practice, also given in hours, after which the luminous flux of a certain lighting

installation has decreased to such a value that the lamp is not profitable although the lamp may go on working.

8.4.10. Repercussions in power supply

Any modern lamp requires its working not to have an important repercussion in the power supply. With incandescent lamps,

this repercussion is limited to an upsurge in the connection moment, due to its small resistance with the cold lamp. Electric

discharge lamps generally work in connection with an inductance, representing an apparent resistance for the circuit.

This gives rise to obtaining a low power factor (cos ), which means an additional charge for the power supply and it must be

then compensated.

8.4.11. Stabilization of lamps with negative resistance characteristics

Negative resistance is the property some electric resistances have, for example, a discharge arc one, to decrease its value as the

intensity of the current circulating through it increases. This obliges to stabilize current in discharge lamps so that it will not

acquire excessive values that may destroy it. This is easily done by locating inductive, capacitive and ohmic resistances in the

lamp circuit.

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8.4.12. Variations in power supply

Variations in power supply influence the lighting engineering data of any lamp. In incandescent lamps, they affect duration and

colour temperature very much, and in discharge ones, relations of arc pressure and also discharge conditions.

8.4.13. Time needed until the luminous flux acquires the normal regime

Incandescent lamps ignite immediataly emiting their total flux. Fluorescent lamps may also do it if quick ignition starters are used.

If not, ignition will be done later on, after one or several attempts.

The other discharge lamps require some minutes as ignition time, until metal vapor acquires the necessary pressure and the

luminous flux reaches it maximum value.

8.4.14. Possibility of immediate reignition

It is the possibility that a lamp, after having been turned off, will be immediately reignited while still hot with full emission of the

luminous flux. This condition is only met by incandescent lamps, metal vapor ones present certain differences regarding their

immediate reignition possibility, as indicated below:

- High pressure mercury lamps: They need some time (minutes) for cooling down before reignition while still hot, and

some more time to reach the total luminous flux.

- Metal halide lamps: They behave exactly like mercury ones. There are some types which may reignite while still hot

by means of special devices.

- High pressure sodium lamps: Those types which have a separated ignition device reignite while still hot within a

minute and reach their total flux virtually with no delay. Other types without a separate ignition device behave in a

similar fashion as mercury lamps.

- Low pressure sodium lamps: They behave like mercury lamps.

8.4.15. Stroboscopic effect

In all artificial sources of light which work with alternating current their emission stops every time current goes through the zero

point. This takes place twice per period, so for a 50 Hz. frequency (periods per second) corresponds 100 instants of darkness

per second. The filament of incandescent lamps has a lot of thermal inertia. Thus, a slight descend of luminous emission takes

place due to such a reason. This is not perceived by the eye except when low power lamps work with a 25 Hz voltage.

For discharge lamps working with 50 Hz. voltages, the eye is not able to appreciate such quick light variations which are

produced. It may be the case, too, that lamps illuminate zones in which rapid movements are made, these being observed as

if they were made intermittently or even as if they were stationary. This phenomenon is known as the stroboscopic effect and

it may be reduced to make it unobservable by means of a lamp special power supply mounting, or wherever a three- phased

line is available, distributing its connection between the three phases.

8.4.16. Working position

An electric lamp is generally made for a certain working position in which it has optimal working properties. Outside this position,

properties worsen, either by an excess of heating of the spiral, the base or the glass outer bulb, by deviation of the discharge

lamp arc or by variations of the surrounding heat. This is the reason why tolerances given in the corresponding lamp catalogues

must be accepted in order to avoid their premature depletion because of an inadequate working position. Abbreviations used

indicate the main working positions and the admissible tilt angle in degrees.

Main working positions:

S (s) = Vertical (standing, base downwards).

H (h) = Vertical (hanging, base upwards).

P (p) = Horizontal (base sideways).

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HS (hs) = Vertical (base upwards or sideways).

Universal = Allows any position.

Admissible tilt angles: After the main working position, there is a figure that indicates the admissible tilt in degrees in relation to it.

Figure 5. Working position sketch.

110°

45°60°

20°

p 20 p 45 p 60 h 45

h 110 h 150 hs 30 hs 45

45°

45°

150°

30°

Admissible position

NON admissible position

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8.5. Incandescent lamps

As it has been said before, the incandescent lamp is the oldest source of electric light and, nowadays, the most commonly used one. It

is also the one that possesses the widest variety of alternatives and it may be found in almost all installations, specially when a low

luminous flux is required. A relatively recent discovery is the halogene incandescent wolfram lamp, which has quickly dominated many

lighting application areas.

8.5.1. Conventional incandescent lamps

Incandescent lamps produce light through the electric heating of a wire (the filament) at a high temperature, emitting radiation

within the visible field of the spectrum.

Figure 6. Conventional incandescent lamp.

The main parts of an incandescent lamp are the filament, the filament supports, the glass bulb, the filling gas and the base.

Filament: The one used in modern lamps is made out of wolfram (high fusion point and low evaporation degree). A higher

luminous efficiency would be achieved by twisting the filament as an spiral.

Glass bulb: It is a cover of sealed glass which encloses the filament and avoids contact with the air outside (so that it does not

burn).

Filling gas: Filament evaporation is reduced filling the glass bulb with an inert gas. The most commonly used gases are argon

and nitrogen. In these lamps, luminous energy obtained is very little compared to the heat energy irradiated, that is to say, a

great amount of the transformed electric energy is lost as heat and its luminous efficacy is small (it is a waste- energy lamp).

The advantage of these lamps is that they are directly connected to the electric current without the need of an auxiliary

equipment for their working.

8.5.2. Wolfram halogen lamps

The high temperature of the filament for a normal incandescent lamp makes wolfram particles to evaporate and condense on

the wall of the glass bulb, darkening this, as a result. Halogen lamps have a halogen component (iodine, chlorine, bromine),

added to the filling gas and work with the halogen regenerative cycle to prevent darkening.

The evaporated wolfram is combined with the halogene to form a halogene wolfram compose. As opposed to wolfram vapor,

it is maintained in the form of gas, the glass bulb temperature being high enough as to prevent condensation. When such a gas

approaches the incandescent filament, it is decomposed due to the high temperature in wolfram that is again deposited in the

filament, and in halogene, which continues with its task within the regenerative cycle (Fig. 7).

Filament

Base

Filling gas

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Figure 7. Halogene cycle.

The main difference between an incandescent lamp, apart from the halogene additive mentioned before, is in the glass bulb.

Due to the fact that temperature of the glass bulb must be high, halogene lamps are of a smaller size than regular incandescent

lamps. Their tubular- shaped glass bulb is made out of a special quartz glass (which must not be touched with the fingers).

Since their introduction, wolfram halogene lamps have entered almost all applications where incandescent lamps were used.

The advantages of wolfram halogene lamps with regard to regular incandescent lamps are the following: longer duration, greater

luminous efficiency, smaller size, greater colour temperature and little or no luminous depreciation in time.

8.6. High pressure mercury discharge lamps

In this section, discharge lamps in whose discharge tube mercury is introduced, are going to be studied. Fluorescent lamps, compact

fluorescent lamps, high pressure mercury lamps, blended light lamps and metal halogene lamps are included.

8.6.1. Fluorescent tubes

Fluorescent tubes are a low pressure mercury discharge lamp in which light is produced predominantly through fluorescent

powder activated by the discharge ultraviolet energy.

The lamp, generally with a long tubular- shaped glass bulb and a sealed electrode for each terminal, contains low pressure

mercury and a small amount of inter gas for ignition and arc regulation. The glass bulb inner surface is covered by a luminiscent

substance (fluorescent powder or phosphorous) whose composition determines the amount of emitted light and the lamp

colour temperature).

Figure 8. Fluorescent lamp.

Free electron

Mercury atom

Ultravioletradiations

Visible light

Length

Wolfram electrodes with electron emitting matter

Fluorescent coat (luminophorous).Lamp holder

Transparent glass tube

12

1

Argon and mercuryatmosphere

Temperature lower than 1 400º C

Tungsten filament

Tungsten halide

Temperature higher than 1 400º C

Halogenes

Tungstene particles

Glass bulb

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The main parts of the fluorescent lamp are the glass tube, the fluorescent layer, the electrodes, the filling gas and the base.

Glass tube: The glass tube of a regular fluorescent lamp is made out of sodium- calcium glass softened with iron oxide to control

short wave ultraviolet transmission.

Fluorescent covering: The most important factor to determine the characteristics of the light of a fluorescent lamp is the type

and composition of the fluorescent powder (or phosphorous) used. This establishes colour temperature (and, as a

consequence, colour appearance), colour reproduction index (R) and, lamp luminous efficiency, to a great extent.

Three groups of phosphorous are used to produce different series of lamps with different colour qualities (standard

phosphorous, tri- phosphorous and multi- phosphorous).

Electrodes: Electrodes of a lamp which possesses an adequate layer of material emitter serve to drive electric energy to the

lamp and provide the necessary electrons to maintain discharge.

The majority of fluorescent tubes have electrodes that are preheated by means of an electrical current just before ignition (they

are given the name of preheating electrode lamps; this preheating is begun by an independent starter).

Filling gas: Filling gas of a fluorescent lamp consists in a mixture of saturated mercury and an inert gas trimmer (argon and

krypton).

Under normal working conditions, mercury is found in the discharge tube both as a liquid and as vapor. The best performance

is achieved with a mercury pressure of about 0.8 Pa., combined with a pressure of the trimmer of about 2 500 Pa. (0.025

atmospheres). Under these conditions, about 90% of the radiated energy is emitted in the ultraviolet wave of 253.7 nm.

In fluorescent lamps, colour temperature ranges between 2 700 K and 6 500 K., with a discontinuous spectral distribution curve

reproducing colours depending on the composition of the fluorescent substance that covers the inner wall of the tube.

Each resulting total luminous radiation is the sum of the radiation of discontinuous spectrum plus that of a continuous spectral

distribution, more efficient each time, with the use of special phosphorous.

Thus, fluorescent tubes with several light tones and chromatic reproduction indexes are manufactured. According to the C.I.E.

norms, these are divided into three main groups:

- Daytime white light: TC > 5 000 K.

- Neutral white: 5.000 K ≥ TC ≥ 3 000 K.

- Warm white: TC < 3 000 K.

There are several tones for each group, with a wide range of colour temperatures and chromatic reproduction indexes,

depending on each manufacturer. These cover the needs for a wide range of applications.

These lamps require an auxiliary equipment formed by a ballast and an igniter (starter), besides a compensation condenser to

improve the power factor.

Working nominal values are reached after five minutes. When the lamp is turned off, due to a great pressure in the burner, it is

necessary to cool down between four and fifteen minutes before it is turned back on.

8.6.2. High pressure mercury lamps Since their introduction, high pressure mercury lamps have been developed to a point that lighting technology cannot be

thought of without it.

In these lamps, discharge takes place in a quartz discharge tube containing a small amount of mercury and an inert gas filling,

usually argon, to help ignition. One part of the discharge radiation occurs in the visible region of the spectrum as light, but some

part is also emitted in the ultraviolet one. Covering the inner surface of the blister, in which the discharge tube is located, with

a fluorescent powder which will transform this ultraviolet radiation into visible radiation. The lamp will offer higher lighting than

a similar version without such a layer.

Working principles

When the working of the high pressure mercury lamp is examined, three well differentiated phases must be distinguished:

ignition, turn-on and stabilization.

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Ignition

Ignition is achieved by means of an auxiliary electrode, placed very close to the main electrode and connected to the other

through a high value resistance (25 kΩ). When the lamp is turned on, a high voltage gradient takes place between the main

and the ignition electrodes, which ionizes the filling gas in this area as a luminescent discharge, the current being limited by a

resistance. Luminescent discharge is then expanded through the discharge tube under the influence of the electric field between

the two main electrodes.

When luminescent discharge reaches the most distant electrode, current increases in a considerable way. As a result, the main

electrodes are heated until the emission increases enough to allow the luminescent discharge to change completely to an arch

discharge. The auxiliary electrode lacks another function in the process as a consequence of the high resistance connected

serially to it.

During this stage, the lamp works as a low pressure discharge (similar to that of a fluorescent lamp). The discharge fills the tube

and gives it a bluish appearance. la corriente limitada por una resistencia. La descarga luminiscente luego se expande por todo

el tubo de descarga bajo la influencia del campo eléctrico entre los dos electrodos principales.

Turn- on

The inert gas having been ionized, yet, the lamp does not burn in the desired way and does not offer its maximum production

of light, until mercury present in the discharge tube is completely vaporized. This does not happen until a certain amount of

time has elapsed, called turn-on time.

As a result of the arch discharge in the inert gas a heating is generated providing a quick increase of temperature inside the

discharge tube. This causes mercury gradual vaporization, increasing vapor pressure and concentrating discharge towards a

narrow band along the axis of the tube. With an increase in pressure, radiated energy progressively concentrates along the

spectral lines of greater wavelengths and a small portion of continuous radiation is introduced. This way, light turns whiter. With

time, the arc achieves a stabilization point and it is said that the lamp reaches the total thermodynamic balance point. All mercury

is then evaporated, and discharge occurs in non- saturated mercury vapor.

The turn- on time, defined as the necessary time for the lamp since the ignition moment to reach an 80% of its maximum

production of light, is approximately four minutes.

Stabilization

The high pressure mercury lamp, like most discharge lamps, has a negative resistance and, thus, it cannot work on its own in a

circuit without an adequate ballast to stabilize the flux of the current through it.

Main parts

In Fig. 9 the main parts of a high pressure mercury lamp may be observed.

Figure 9. High pressure mercury lamp.

Auxiliary electrodes

Wire beam lead

Base

Ohmic resistance for eachauxiliary electrode in series

Principal electrodes

SupportWire beam lead

Hard glass ovaloidal glass bulb

Fluorescent substance

Low pressure inert gas filling

Discharge tube

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Discharge and support tube: The discharge tube is made out of quartz. It has a low absorption of ultraviolet and visible radiation.

Also, it stands high temperatures of the work involved.

Electrodes: Each main electrode is composed of a wolfram bar, whose extreme is covered by wolfram serpentine impregnated

with a material that favors the emission of electrons. The auxiliary electrode is simply a piece of wire of molybdenum or wolfram

located near one of the main electrodes and connected to another one by means of a resistance of 25 kΩ .

Blister: For lamps up to 125 W of potency, the blister may be of glass sodium- calcium. However, lamps with higher potencies

are manufactured, generally, with hard glass of borosilicate, since higher working temperatures and thermal shock are tolerated.

The blister, which normally contains an inert gas (argon or a mixture of argon and nitrogen), protects the discharge tube from

changes in the room temperature and protects lamp components from corrosion.

Glass covering: In most high pressure mercury lamps, the inner surface of the blister is covered by white phosphorous to

improve lamp colour reproduction and to increase its luminous flux. Phosphorous transforms a great amount of ultraviolet

energy radiated by the discharge into visible radiation, predominantly in the red extreme of the spectrum.

Gas filling: The discharge tube is filled with an inert gas (argon) and a precise dosis of distilled mercury. The first is necessary

to help originate the discharge and to secure a reasonable life for the covered emission electrodes.

The blister is filled with argon or with a mixture of argon and nitrogen at atmospheric pressure. The addition of nitrogen serves

to avoid an electronic arc between the wire supports of the glass.

These lamps require an auxiliary equipment which is normally a ballast with an inductive resistance or transformer of the

dispersion field, besides a compensation condenser.

When the lamp is turned off, it will not start again until it has cooled off enough to lower vapor pressure to the point where the

arc will be turned on again. This period lasts about minutes.

8.6.3. Blended light lamps

Blended light lamps are a combination of the high pressure mercury lamp and an incandescent lamp. They are a result of one

of the tries to correct bluish light of mercury lamps, which is achieved by inclusion within the glass itself, of a mercury discharge

tube and a wolfram incandescent filament.

Mercury discharge light and that of the fired filament are combined, or mixed, to achieve a lamp with totally different operative

characteristics compared to those which have both pure mercury lamp and an incandescent lamp.

Main parts

With the exception of the filament and the gas used in the blister, parts of a blended light lamp are the same as those described

for high pressure mercury lamps (Fig. 10).

Figure 10. Blended light lamp.

Wire beam lead

Base

Tractional resistence

Discharge tube

Principal electrodes

Hard glass ovoid glass bulb

Fluorescent substance

Low pressure inert gas filling

Incandescent filament

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Filament: The filament, which also acts as a resistance ballast for the discharge tube, is a coiled wolfram wire the same as that

of the incandescent lamp. It is connected with the discharge tube in series and located next or around it, to obtain a good

blended light and to favour a quick ignition of the tube.

Filling gas blister: As for incandescent lamps, the filling gas in blended light lamps is made out of argon but adding a percentage

of nitrogen to avoid an arc in the filament. Compared with the standard high pressure mercury lamp, a greater filling pressure

to keep evaporation of wolfram to the minimum is used.

Blended light lamps have the advantage of being connected directly to the power supply system (ballast and starter for is not

required their working). Ignition takes about two minutes and re- ignition is not possible before cooling- down.

8.6.4. Metal halide lamps

High pressure mercury lamps also contain rare earths like Dysprosium (Dy), Holmium (Ho) and Thulium (Tm). These halides

are partly vaporized when the lamp reaches its normal working temperature. Halide vapor is later on dissociated, within the hot

central zone of the arc, into halogene and metal, achieving a considerable increase of luminous efficacy and approaching colour

to that of daylight. Different halide combinations (sodium, iodine, ozone) are used to which scandium, thallium, indium, lithium,

etc. is added.

Main parts

Figure 11. Metal halide lamps.

Discharge tube: It is made out of pure quartz. Sometimes, a white layer of zirconium oxide is applied to the outer part of the

electrode cavities, to increase wall temperature at that point.

Electrodes: They are similar to those of the high pressure mercury lamp.

Blister: The blister of metal halide lamps is made out of hard or quartz glass. Some do not even have an blister.

The inner surface of blisters with an ovoid shape has a phosphorous layer to transform discharge ultraviolet radiation into visible

radiation. However, halides used for the metal halide lamp produce only a small amount of ultraviolet, and mainly, it is radiated

in the ultraviolet spectrum wavelength zone, where conversion into visible radiation is poor.

Filling gas in the discharge tube: The discharge tube is filled with a mixture of inert gases (neon and argon or krypton- argon),

a dosis of mercury and appropriate halides, depending on the type of lamp.

Filling gas of the blister: The blister of a metal halide lamp whose discharge tube is filled with a mixture of neon- argon, must

also be filled with neon so that neon pressure inside and outside the tube is the same. In case the discharge tube is filled with

a mixture of krypton- argon, nitrogen may be used in the blister, or else, the latter may be eliminated, too.

Working conditions of metal halide lamps are very similar to those of conventional mercury vapor. They are prepared to be

connected in series with a ballast to limit current, a compensation condenser being necessary.

Electrodes

Clear tubular glass bulb

Base

Ellipsoidal diffuser glass bulb

Base

Quartz discharge tube

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Due to metal halides, the ignition voltage for these lamps is high. The use of a starter or ignition device with shock voltage of

0.8 to 5 KV is needed.

Most lamps allow for immediate re- ignition with hot lamps (right after being turned- off), by using shock voltage of 35 to 60

KV. If not, they must cool- down between four and fifteen minutes before being turned back on.

8.7. High pressure sodium discharge lamps

This section deals with those lamps with a discharge tube where sodium vapor is introduced. Low pressure sodium lamps and high

pressure sodium lamps are included.

8.7.1. Low pressure sodium lamps

There exists a great similarity between the working of a low pressure sodium lamp and a low pressure mercury lamp (or a

fluorescent one). However, while light in the latter is produced by transforming ultraviolet radiation of the mercury discharge into

visible radiation, using fluorescent powder in the inner surface, visible radiation in the former is produced by direct discharge of

sodium.

Working principle

The discharge tube of a low pressure sodium lamp is usually U- shaped and is located inside an empty tubular glass cover, with

indio oxide coat on the inner surface. The empty part, together with the layer, which behaves as an infrared selective reflector,

helps keep the discharge tube wall at an adequate working temperature. Such measurements are necessary for the sodium,

which is deposited in slits of the glass when condensed, and it evaporates with a minimum heat loss. Due to this fact, the most

luminous efficiency possible is achieved.

The neon gas inside the lamp is used to begin the discharge and to develop enough heat to vaporize the sodium. This responds

for the red- orangish luminescence during the firsts few working minutes. The metallic sodium is gradually evaporated, producing

the characteristic monochromatic yellow light, with 589 nm. and 589.6 nm. lines in the spectrum. The red colour, initially

produced by the neon discharge, is energetically suppressed during the working because sodium excitation and ionization

potentials are much lower than those of neon.

The lamp reaches its luminous flux established in approximately ten minutes. It will re- ignite immediately in case power supply

is momentarily interrupted, since vapor pressure is quite low and the voltage applied enough to reestablish the arc.

The lamp has a luminous efficiency up to 200 lm/W and a long life.

Therefore, this lamp is applied to those places where colour reproduction is of less importance and mainly where contrast

recognition matters, for example: motorways, ports, beaches, etc. Low pressure sodium lamps range from 18 W to 180 W.

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Main parts

Figure 12. Low pressure sodium lamp.

Discharge tube and supports: The discharge tube of a high pressure sodium lamp is U- shaped, to make the most out of space

and provide a better thermal isolation. It is made out of sodium- calcium glass, and has an inner surface covered with borate

glass to form a protective layer against sodium vapor.

The tube also contains a number of small slits or holes, where sodium is deposited during manufacturing.

Discharge tube filling: The discharge tube filling consists of metallic sodium of high purity and of a mixture of neon and argon,

which behaves as an ignition and trimmer gas.

Electrodes: Low pressure sodium lamps possess cold ignition electrodes. These consist of a triple wolfram wire, in such a way

that a great amount of emitter material may be maintained.

Blister: It is empty and covered by a thin film of infrared material reflector in its inner surface. The infrared reflector serves to

reflect most part of the heat radiation which returns to the discharge tube, keeping it, at the desired temperature, this way, while

visible radiation is transmitted.

These lamps precise an auxiliary equipment formed by a power supplier with an autotransformer or ballast and igniter with

impulse voltage depending on type. A compensation condenser is required.

Nominal values are reached after fifteen minutes after re- ignition. When the lamp is turned off, a few minutes are necessary

before re- ignition.

8.7.2. High pressure sodium lamps

Physically speaking, high pressure sodium lamps are quite different from low pressure sodium lamps, due to the fact that vapor

pressure is higher in the former. This pressure factor also causes many other differences between the two lamps, including

emitted light properties.

Discharge tube in a high pressure sodium lamp contains an excess of sodium to produce saturated vapor conditions when the

lamp is working. Besides, it has an excess of mercury to provide a trimmer gas, xenon excluded, to ease ignition and limit heat

conduction from the discharge arc to the tube wall. The discharge tube is housed in an empty glass cover.

High pressure sodium lamps radiate energy through a good part of the visible spectrum. Therefore, when compared to the low

pressure sodium lamp, they offer a quite acceptable colour reproduction.

Main parts

The main parts of a high pressure sodium lamp are the following:

Bayonet cap

Double or triple spiral electrodes with electrone emission matter

"U"- shaped discharge tube

Deposit area for nonvaporised sodium Clear blister bulb

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Figure 13. High pressure sodium lamp.

Discharge tube: The discharge tube is made out of aluminium oxide ceramics (sintered aluminium) very resistant to heat and

to chemical reactions with sodium vapor.

Electrodes: Electrodes, covered by a layer of emitter material, consist of a twisted serpentine wolfram rod around it.

Filling: In the inside of the discharge tube are sodium, mercury and noble gases (xenon or argon) out of which sodium is the

main producer of light.

Blister: This glass is generally empty.

The shape must be either ovoid or tubular. The first one has an inner covering. However, since the discharge tube of the high

pressure sodium lamp does not virtually produce any ultraviolet radiation, the covering is simply a diffused layer of white powder,

to decrease the high brightness of the discharge tube. The tubular glass is always made out of clear glass.

Starters and auxiliary starters: Many of the high pressure sodium lamps have an incorporated auxiliary starter, which helps

reduce the measure of the ignition peak voltage needed for the lamp ignition. Sometimes, both the incorporated starter and

the auxiliary starter are in the lamp itself.

These lamps precise of an auxiliary equipment formed by a ballast and an igniter with impulse tension depending on type. A

compensation condenser is also needed. Nominal values are reached five minutes after ignition. When a lamp is turned off, due

to a great pressure of the burner, it needs to cool down between four and minutes before turning it back on.

8.8. Induction lamps

The most vulnerable parts of all discharge lamps are the electrodes. During their average rated life, lamps reduce and lose their emit-

ting voltage by the impact of quick ions or by chemical reactions with energetic vapors in the discharge tube. Electrodes in high pres-

sure discharge lamps also produce a great amount of infrared wasted radiation, which decreases efficiency of the lamp.

The induction lamp introduces a completely new concept in light generation. It is based on the low pressure discharge gas principle. The

main characteristic of the new lamp system is that it does not need electrodes to originate gas ionization. Currently, there are two dif-

ferent systems to produce this new ionization of gas without electrodes.

Base Discharge tube

Clear blister bulb

Diffused blister bulb

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8.8.1. High power fluorescent lamps without electrodes

Discharge in this lamp does not begin and end in two electrodes like in a conventional fluorescent lamp. The shape of close

ring of the glass of the lamp allows to have a discharge without electrodes, since energy is supplied from the outside by a

magnetic field. Such magnetic field is produced in two ferrite rings, which constitutes an important advantage for lamp duration.

Figure 14. High voltage fluorescent lamp without electrodes.

The system has an electronic equipment (at a frecuency of approximately 250 kHz) separated from the lamp besides a

fluorescent tube without electrodes. This allows to preserve optimal energy of discharge in the fluorescent lamp and reach a

high luminous potency with a good efficacy.

The main advantages of this lamp are:

- Extremely long life: 60 000 hours.

- Lamp potency 100 and 150 W.

- Luminous flux up to 12 000 lumens.

- Luminous efficacy of 80 lm/W.

- Low geometric profile that allows the development of flat luminaires.

- Comfortable light without oscillations.

- Start without flickers or sparkles.

These lamps are essentially indicated for those applications where relamping increases maintenance expenses excesively, like

for example, illumination of tunnels, industrial premises with very high ceilings and difficult access, etc.

8.8.2. Low pressure gas discharge lamps by induction

This type of lamps consists of a discharge recipient which contains the low pressure gas and a voltage coupler (antenna). Such

a potency coupler, composed by a ferrite cylindrical nucleus, creates an electromagnetic field within the discharge recipient

inducing an electrical current in the gas generating its ionization. Enough energy to begin and maintain discharge is supplied to

the antenna by a high frequency generator (2.65 MHz) by means of a coaxial cable of a determined length, since it forms part

of the oscillating circuit.

Ferrite nucleus

CoilElectron

Mercury atom

Magnetic field

Fluorescent covering

Ultraviolet radiation

Visible light

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Figure 15. Gas discharge lamp by induction.

The main advantages of these lamps are:

- Extremely long duration: 60 000 hours.

- Voltage lamps with 55, 85 and 165 W.

- Luminous flux up to 12 000 lumens.

- Luminous efficacy between 65 and 81 lm/W.

- Instantaneous ignition free of flickers and stroboscopic effects.

- Light for a great visual comfort.

These lamps are used for many general and special lighting applications, mainly to reduce maintenance expenses, like in public

buildings, outdoor public lighting, industrial applications, etc.

8.9. Charts with characteristics

8.9.1. Fluorescent lamps

TL linear fluorescent

Average rated life : 7 500 hours

Nominal Flux Performance Diametre Length Lamp holder R.I. Chromatic

power φ (lm) Lm/W Ø in mm L in mm Ra degree

18 1350 75.00 26 0.590 G 13 85 1 B

18 1150 63.88 26 0.590 G 13 62 2 B

18 1100 61.11 26 0.590 G 13 75 2 A

18 1000 55.55 26 0.590 G 13 98 1 A

36 3350 93.05 26 1200 G 13 85 1 B

36 2850 79.16 26 1200 G 13 62 2 B

36 2600 72.22 26 1200 G 13 75 2 A

36 2350 65.27 26 1200 G 13 98 1 A

58 5200 89.65 26 1500 G 13 85 1 B

58 4600 79.31 26 1500 G 13 62 2 B

58 4100 70.68 26 1500 G 13 75 2 A

58 3750 64.65 26 1500 G 13 98 1 A

Potency coupler

Bulb

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Compact fluorescent TC-D of 2 pins

Power supply voltage: 230 V.

Average rated life: 10 000 hours.

Compact fluorescent TC-D of 4 pins

Power supply voltage: 230 V.

Average rated life: 10 000 hours.

Compact fluorescent TC-L of 4 pins

Power supply voltage: 230 V.

Average rated life: 10 000 hours.

8.9.2. High pressure mercury lampsAverage rated life: 14 000 hours.

Colour temperature: 3 500 K 4 200 K

Colour reproduction index (R): 50

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

0.050 01800 36.00 55 130 E-27

0.080 03800 47.50 70 156 E-27

0.125 06300 50.40 75 170 E-27

0.250 13000 52.00 90 226 E-40

0.400 22000 55.00 120 290 E-40

0.700 38500 55.00 140 330 E-40

1000 58000 58.00 165 390 E-40

Nominal Flux Performance Width Length Lamp holder R.I. Chromatic

power φ (lm) Lm/W in mm L in mm Ra degree

18 0.750 41.66 38 225 2G11 95 1 A

24 1200 50.00 38 320 2G11 95 1 A

36 1900 52.77 38 415 2G11 95 1 A

40 2200 55.00 38 535 2G11 95 1 A

55 3000 54.54 38 535 2G11 95 1 A

Nominal Flux Performance Width Length Lamp holder R.I. Chromatic

power φ (lm) Lm/W in mm L in mm Ra degree

13 0.900 69.23 27 131 G24q-1 85 1 B

18 1200 66.66 27 146 G24q-2 85 1 B

26 1800 69.23 27 165 G24q-3 85 1 B

Nominal Flux Performance Width Length Lamp holder R.I. Chromatic

power φ (lm) Lm/W in mm L in mm Ra degree

13 0.900 69.23 27 138 G24d-1 85 1 B

18 1200 66.66 27 153 G24d-2 85 1 B

26 1800 69.23 27 172 G24d-3 85 1 B

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8.9.3. Blended light lampsAverage rated life: 6 000 hours.

Colour temperature: 3 500 K 4 200 K

Colour reproduction index (R): 50

Power suuply voltage: 230 V.

8.9.4. Metal halide lampsAverage rated life: 2 500 14 000 hours.

Colour temperature: 3 000 K 6 000 K

Colour reproduction index (R): 60 93

Compact metal halide lamps

Double- based metal halide lamps

Metal halide lamps with a clear base and a clear tubular shape

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

0.250 020000 080.00 045 225 E-40

0.400 042000 105.00 045 275 E-40

1.000 080000 080.00 075 340 E-40

2.000 240000 120.00 100 430 E-40

3.500 320000 091.42 100 430 E-40

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

0.070 005500 078.57 20 114 RX7s

0.150 013500 090.00 24 132 RX7s

0.250 020000 080.00 25 163 Fc2

0.400 038000 095.00 31 206 Fc2

1000 090000 090.00 ≈40 - Cable

2000 220000 110.00 ≈40 - Cable

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

035 03400 97.14 19 100 G12

075 05500 73.33 25 084 G12

150 12500 83.33 25 084 G12

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

160 03100 19.37 075 180 E-27

250 05600 22.40 090 226 E-40

500 14000 28.00 125 275 E-40

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Metal halide lamps with a base in an ellipsoidal form with a diffusing layer

8.9.5. Low pressure sodium lampsAverage rated life: 14 000 hours.

Colour temperature: 1 800 K

Colour reproduction index (R): NULL.

Low pressure sodium with a clear tubular shape and an infrared reflecting layer

Low pressure sodium with a light tubular shape

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

026 03500 134.61 55 215 BY-22d

036 05750 159.72 55 310 BY-22d

066 10700 162.12 55 425 BY-22d

091 17000 186.81 70 530 BY-22d

131 25000 190.83 70 775 BY-22d

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

018 01800 100.00 55 0.215 BY-22d

035 04600 131.42 55 0.310 BY-22d

055 08100 147.27 55 0.425 BY-22d

090 13000 144.44 70 0.530 BY-22d

135 22500 166.66 70 0.775 BY-22d

180 32000 177.77 70 1120 BY-22d

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

0.070 04900 070.00 055 140 E-27

0.100 08000 080.00 055 140 E-27

0.150 12000 080.00 055 140 E-27

0.400 43000 107.50 120 290 E-40

1000 90000 090.00 165 380 E-40

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8.9.6. High pressure sodium lampsAverage rated life: 12 000 18 000 hours.

Colour temperature: 2 000 K 2 200 K

Colour reproduction index (R): 20 65

High pressure sodium lamps with a tubular shape

High pressure sodium lamps with an ellipsoidal shape and a diffusing layer

High pressure sodium lamps with two bases

Luxurious high pressure sodium lamps with a tubular shape

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

150 12.500 83.33 45 210 E-40

250 23.000 92.00 45 255 E-40

400 39.000 97.50 45 285 E-40

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

070 07000 100.00 20 115 RX7s

150 15000 100.00 25 130 RX7s-24

250 25500 102.00 25 205 Fc2

400 48000 120.00 25 205 Fc2

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

00.50 003500 070.00 070 155 E-27

00.70 005600 080.00 070 155 E-27

0.100 010000 100.00 075 185 E-40

0.150 014000 093.33 090 225 E-40

0.250 025000 100.00 090 225 E-40

0.400 047000 117.50 120 290 E-40

1000 128000 128.00 165 400 E-40

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

0.050 004000 080.00 40 155 E-27

0.070 006500 092.85 40 155 E-27

0.100 010000 100.00 45 210 E-40

0.150 017000 113.33 45 210 E-40

0.250 033000 132.00 45 255 E-40

0.400 055500 138.75 45 285 E-40

0.600 090000 150.00 55 285 E-40

1000 130000 130.00 65 400 E-40

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Luxurious high pressure sodium lamps with an ellipsoidal form and a diffusing layer

8.9.7. High powered fluorescent lamps without electrods (induction)Power supply voltage: 230 V.

Average rated life: 60 000 hours.

8.9.8. Low pressure discharge gas lamps by inductionPower supply voltage: 230 V.

Average rated life: 60 000 hours.

Nominal Flux Performance Diametre Height Lamp holder R.I.

power φ (lm) Lm/W. in mm. in mm. Ra

55 W 3500 65 85 140.5 - 80 (840/830/827)

85 W 6000 70 111 180.5 - 80 (840/830/827)

165 W 12000 70 130 210 - 80 (840/830/827)

Nominal Flux Performance Width Length Lamp holder R.I. Chromatic

power φ (lm) Lm/W in mm L in mm Ra degree

100 W 8000 80.00 139 313 - 80 (840/835) 1 B

150 W 12000 80.00 139 414 - 80 (840/835) 1 B

Nominal Flux Performance Diametre Length Lamp holder

power φ (lm) Lm/W Ø in mm L in mm

150 12.000 80.00 090 225 E-40

250 22.000 88.00 090 225 E-40

400 37.500 93.75 120 285 E-40

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Chapter 9.

CONTROL AND REGULATIONAUXILIARY EQUIPMENTS

9.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

9.2. Ballasts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

9.3. Starters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

9.4. Capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

9.5. Energy- saving equipments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

9.6. Control gears for different discharge lamps. Circuits. . . . . . . . . . . . . . . 134

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9.1. General remarksThe present chapter deals with auxiliary equipments lamps need for their correct functioning. The equipment to be installed depends

on the type of lamp.

Incandescent, halogene and blended light lamps may be connected directly to the power supply without the need for any kind of

auxiliary equipment, or by means of a transformer. Due to their characteristics, intensity going through them and tension applied are

proportional.

Discharge lamps have the particularity that the ratio between the intensity going through them and the tension applied is not

proportional. That is to say, the ratio power- current is not linear but negative. In other words, tension of the arc depends little on the

current that goes through it. Depending on the tension applied, if the start takes place, intensity of the current may increase enormously

until a destruction of the lamp takes place or current fluctuates without proportion with little power variations. Because of these reasons,

it is necessary to use some current stabilizing device if a correct working is to be achieved.

Discharge stabilizationThe most simple element that could be applied is a resistance. This solution is not recommendable for alternating current

though, because the lamp illuminates virtually when the power applied to the whole reaches instantaneous values, higher than

the power of the arc. This is translated into flickering of the lamp. Hence, this type of stabilization is almost exclusively used with

continuous current.

Another element that may be also applied to discharge stabilization is a condenser. This solution is not tolerated in a normal

frequency of 50 Hz. (let alone for continuous current) because current of the lamp is greatly distorted when strong peaks of

short duration are produced. The lamp will emit light intermittently and it will run out prematurely. However, this system may

be used with higher frequency power supplies (above 300 Hz.). The advantage being greater luminous performance of the

lamp.

The most widely known element to stabilize discharge lamps in normal practice is formed by an inductive reactance which limits

the intensity of the discharge current, quite efficiently, simply and economically. Current distortion produced in the lamp is

tolerable and generally without flickering. Although it displaces the phase between the power of the lamp and the supply net,

this may be easily corrected by means of condensers in parallel with the line.

When power available in the line is not enough to allow lamp ignition, previous transformers or autotransformers may help. In

order to simplify the set, the so called leakage autotransformers (also called dispersion autotransformers) are used, too. They

incorporate the precise inductive reactance in their secondary body. Once an adequate leakage transformer is available, if a

fluorescent lamp is to work that requires heating of its cathodes for ignition, a starter is introduced. Or it may not be necessary

means of incorporating two new coils to the autotransformer for a correct heating.

Parallel to the previous evolution, the condenser necessary to correct the power factor was used. An inductive reactance in series

with a condenser constitutes an intensity regulator. By correctly using the elements with slight alterations of these, complex

equipments are built. In them, the condenser in series with the secondary one of the transformer, and sometimes with the

primary one, improves lamp stability when compared to strong power variations in the line. Besides, it simultaneously corrects

the power factor and cos of the whole to a better value than if a simple condenser in parallel to the line is used.

Discharge lamps auxiliary equipmentsLet us analyze in a general way, equipments usually used by discharge lamps for their correct working. At the end of the present

chapter, some representative circuits of different discharge lamps will be shown.

Fluorescent lamps

A fluorescent lamp has negative resistance characteristics. Therefore, it must be operated as a whole with a limited current

device (ballast) to avoid current leakage. The ballast, which has positive resistance characteristics, may be:

- Resistive ballast: For continuous current.

- Inductive ballast: It is the most widely spread ballast used for normal alternating current applications.

- Electronic ballast: It is the most expensive, but it offers important advantages compared to the previous ones.

Power factor correction is achieved by placing a condenser in parallel to the circuit of the lamp. Also using capacitive ballasts for

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half the lamps and inductive ballasts without compensation for the other half in circuits which contain several lamps.

For lamp ignition some type of help is needed, due to the fact that the fluorescent lamp inner resistance when turned

off is too cold to be turned on automatically when the power supply is applied to it. As far as ignition is concerned,

fluorescent lamp circuits may be divided into three groups:

- Circuits with preheated starter: Ignition is controlled by a conventional or electronic starter.

- Circuits without preheated starter: These lamps may operate with two different types of circuit, instantaneous ignition

(semi- resonant circuit) and quick ignition (non- resonant circuit).

- Circuits with cold ignition: Specially designed for lamps provided with an inner band to ease immediate ignition

without preheating and without a starter.

High pressure mercury lamps

Apart from the reactance, a start equipment is not necessary for mercury lamps. Compensated inductive ballasts may be used

both in parallel compensation circuits and in compensation circuits in series. Both circuits take a condenser to compensate for

the power factor.

Metal halide lamps

Working conditions for metal halide lamps are very similar to those of conventional mercury one., They are arranged in such a

way that they may be connected in series with a current limiting ballast. Nevertheless, due to halides, power ignition of these

lamps is high and need the use of a starter or igniter.

The ballast to be connected to the metal halide lamp depends on its properties. For example, the so- called three band lamps

use ballasts designed for high pressure mercury lamps, but rare earth lamps work better with ballasts of high pressure sodium

lamps.

Low pressure sodium lamps

These lamps require an auxiliary equipment which may be:

- Ballast, with or without a separate igniter: Due to the lamp low voltage, these may operate in comparatively simple circuits

which consist, basically, in a ballast in series with the lamp and a starter in parallel. For the correction of the power factor, a con-

denser in parallel is used.

- Transformer with a separate igniter: In this circuit power of the lamp is almost always constant for all its life. It consists in a

ballast, a condenser in series for the correction of the power factor and an electronic igniter.

High pressure sodium lamps

As for metal halide lamps, high shock powers are necessary for ignition due to the high pressure to which the gas is kept. Thus,

high pressure sodium lamps operate normally with a ballast and a starter. Some lamps have an incorporated starter, but most

of them use an external ignition device.

Mainly, there are two types of circuits, either with the starter connected in series or in parallel with the lamp:

- Circuit with a starter in series: The starter is connected between the ballast and the lamp.

- Circuit with a semi starter in parallel: The starter is connected to the lamp through the reactance.

Correction of the power factor may be achieved through a condenser in the way of compensation in parallel in both circuits.

Induction lamps

Induction lamps are connected to the power supply through a high frequency generator, which is formed by a system of

electronic circuits. The connection between the lamp and the generator is achieved through a coaxial cable which forms part of

an oscillator circuit. Therefore, its length may not be modified.

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9.2. Ballasts

9.2.1. Introduction

Reactances or ballasts are accessories to be used in combination with discharge lamps. As inductive, capacitive or resistive impedances,

alone or in combination, they limit the current which circulates through them to the values required for an adequate working.

Moreover, they supply power and ignition current required when necessary, and, in the case of quick start reactances, they also supply

low power necessary for the heating of lamp cathodes.

Given the characteristics offered for correct performance and working of the lamp, the most widely used are those of an inductive type.

The combination of inductive- capacitive reactance is also used.

Resistance and capacitive ones are not used alone since the first ones produce many losses, thus, providing low performance. The

second ones provide a very low power in the lamp due to great deformation of the current wave originated by them.

According to their installation principles, they may be classified into:

- Independent reactance, which is covered by a special protection to work outside.

- Reactance to be incorporated, which requires a secondary protection like a housing, a luminaire, etc.

9.2.2. Function of the reactanceThe reactance is a fundamental element in any discharge lamp lighting installation because lamps would not work without it.

Given the great variety of lamps in the market, very different in type, size, colour, etc., adequate reactances to each of them are

required, so that the precise parameters are supplied in each case and for each situation. That is to say, starting needs and, later

on, normal operation ones are satisfactory.

Generally speaking, functions covered by reactances are the following:

- To provide cathode ignition or preheating current to achieve the initial emission of electrons in these.

- Supply enough output power in the vacuum to arc the lamp.

- Limit current in the lamp to adequate values for a correct working.

- Control variations in the lamp current, as opposed to variations in power supply. This is known as having a good

regulation.

9.2.3. Normative to be met by reactances

Reactances certification

Reactances must be manufactured according to corresponding national and international norms. As a consequence, the ones

that have been tested and certified by different organisms, will have the organization symbol printed (Fig. 1.).

Figure 1. Examples of certification brands of different organisms.

Having such certifications allows these products to circulate around countries comprised by such brands.

Reference norms

Norms regulating security and functioning of reactances for high intensity discharge lamps are the following:

AENOR SPAIN CENELEC-AENORGERMANY IMQ-ITALY SLOVAQUIAIRAM-ARGENTINA

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UNE-EN 60922: Reactances for discharge lamps (except for fluorescent tubular lamps). General and

safety prescriptions.

UNE-EN 60923: Reactances for discharge lamps (except for fluorescent tubular lamps). Working

prescriptions.

ANSI C82.4: Reactances for high intensity discharge lamps and low pressure sodium lamps.

UNE-EN 60662: High pressure sodium lamps.

UNE-EN 61167: Metal halide lamps.

UNE-EN 60188: High pressure mercury lamps.

UNE-EN 60192: Low pressure sodium lamps.

UNE-EN 60598: Luminaires.

European directives

In order to be able to use electric and electronic devices in the European Union, it is compulsory for them to have the

mark "CE" which means European Conformity, and represents the compliance with the following European Directives

to which lighting products are subjected:

- Low Voltage Directive (LV) 73/23/EEC, in force since 1-1-97 and applicable to all electric devices of nominal voltage

from 50 to 1,000 V. in alternating current and from 75 to 1,500 V. in continuous current.

- Electromagnetic Compatibility Directive (EMC) 89/366/EEC, in force since 1-1-96 and applicable to all electric and

electronic devices that may generate radio- interferences or be affected by perturbances generated by other devices

in their surroundings.

Reference norms

For the Low Voltage Directive (LV), security norms on the product are compulsory.

For those corresponding to Electromagnetic Compatibility (EMC), the following norms are applicable:

UNE-EN 50081-1: Electromagnetic compatibility. General emission norm.

UNE-EN 55015: Radioelectric perturbations of fluorescent lamps and luminaires.

EN 61000-3-2: Perturbations of power supply systems. Harmonics.

EN 61547: Luminaires for general applications. Immunity prescriptions.

The applicable harmonic and immunity requeriments of radio- interference emission must be checked with the

luminaire or in the installation where reactances are going to be used.

Harmonics

A harmonic is a perturbation introduced in the power supply by electric equipments. In lighting systems, energy is supposed to

receive a unique frequency and to be constant. Frequency constancy in energy distributions is generally achieved. However, due

to several circunstances, the fundamental wave may be polluted with undesirable harmonics (for example, produced by

associated frequency converters, etc.).

The study of such pollution produced by harmonics is very complex because its consequences depend on the harmonic

frequency amplitude and order, as well as on the situation over the fundamental.

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It is necessary to highlight that if the situation of harmonics over the fundamental wave makes composed waves to tend to be

square, impedance coils do not limit intensity received from the lamp sufficiently. Under these conditions, alternating voltage is

similar to a continuous pulsatory voltage to which inductive shocks do not respond in an efficient way.

A mathematical model may be established for the study of power in different elements of the electric circuit (lamp, ballast, etc.),

and decompose it in Fourier’s series, taking the first two terms as an acceptable approximation.

The third and subsequent harmonics produced during the use of electromagnetic nuclei (magnetic ballasts) in lighting with

discharge lamps and the generation of odd harmonics produced by the lamps themselves, have two immediate consequences:

1st- Capacitors of power factor correction are not able to correct power factor down to the unit, but, on adding capacity

to such condensers, a capacitive circuit appears.

2nd- In threephasic systems with neuter, current in the neuter becomes similar to that of phases. The reason is that

even cancelling the fundamental frequency charges being equal, that is to say, with balanced phases, the third

harmonics are in phase and, therefore, they are summed.

If devices providing power supply of the threephasic line with neuter would take only the fundamental frequency, the neuter

would not carry current in case of charge balance over the phases. However, if devices take a current containing 33.3% of the

third harmonic, the neuter wire is charged with the same current as that of the phases, although its frequency is three times the

fundamental.

In practice, so that this does not happen with lighting lines, limits have been established in admissible current distorsions for

even harmonic cases , since odd numbers are cancelled (see IEC 1000-3-2, IEC 1000-3-3 or EN 61000-3-2 and EN 61000-

3-3 Norms). Nevertheless, the neuter must be measured at the same size than those of phases, as demanded by the Low

Voltage Regulation, in order to avoid surprises with low quality materials.

Another typical problem with power supply polluted by frequency harmonics is the resonance phenomenon, which may take

place in those equipments composed by an inductive reactance and a condenser in series. These equipments are special and

known as regulators, autorregulators or constant power ballasts.

9.2.4. Electromagnetic ballasts Electromagnetic ballasts are mainly composed by a large number of copper coils over a laminated iron nucleus. A heat loss

takes place in them through the coil ohmic resistance and the hysteresis in the nucleus. This depends a lot on the mechanic

construction of the ballasts and the copper wiring diametre.

Types of reactancesShock reactance

This type of inductive reactance, formed by a simple coil with its corresponding magnetic nucleus, electrically connected in series

with the lamp, is the most comonly used. It constitutes a set of low factor power which may be corrected placing a condenser

in parallel with the power supply (Fig. 2).

Figure 2

This type of reactance, economic, light and of a small size, provides poor power regulation , as opposed to variations in the

power supply voltage (around 20% of the power oscillation, for power supply variations of 10%) and starting current is high

with respect to the functioning; circuits must be measured for that value. This makes lamp life to be considerably reduced if

Ballast

CapacitorPower supply

F

N

Lamp

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power supply volatge fluctuates more than 5%. Therefore, this type of reactances is adequate whenever adequate voltage

stability conditions are met.

Autotransforming reactance

When power supply has a voltage lower than 220 V, it is necessary to foresee an elevation system for that voltage which will

provide us with the necessary one for lamp ignition. This system may be simply an autotransformer and a normal shock

reactance, which is correct from an electric point of view, but also very costly and bulky.

Figure 3

Normally, autotransforming reactances have been built for this function, whose basic structure is shown in Fig. 3. They are

formed by two magnetically decoupled winded, even with magnetic shunts between them. So, on top of raising voltage so that

the lamp may be ignited, they also control its intensity. This type of reactances have a very small power regulation. Thus, a

voltage variation of about 5% is transformed into lamp power oscillations of 12%. Besides, we are speaking about power low

factor reactances. In order to correct this factor, bearing in mind that power supply (normally 110 or 125 V), it is obligatory to

place condensers with a great capacity, and, thus, very costly ones.

Autorregulating reactance

This reactance combines an autotransformer with a regulating circuit. Due to the fact that part of the main coil is common to

the second one, its size is reduced. Since only the secondary coil contributes to a good regulation, its degree depends on the

portion of primary power coupled to the second one (Fig. 4).

Figure 4

Bal

last

Capacitor

Power supply

F

N

Lamp

Bal

last

Power supply

F

N

Lamp

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With this type of reactance, the following advantages are achieved:

- A good regulation of current and power of the lamp, as opposed to power supply variations (about 5% in power, as

opposed to voltage variations of about 10%).

- As a consequence from the above, an important increase in lamp life, reducing installation maintenance expenses.

- Power supply starting current is not higher than the normal functioning, so protection systems and power supply

cables may be measured for a minor current than in installations with shock reactances. Due to the same reason,

protection security increases since its values correspond to those of functioning.

- Compensation of the power factor is maintained above 0.9 independently from the power supply current voltage.

- Due to the great stabilization provided by these reactances, power supply voltage is low (at this power the lamp

extinguishes). Power supply variations, very much above the usual ones, are permited without producing lamp turnoffs.

Brands and indicationsReactances, besides their electric characteristics, have a series of printed indications which is convenient to know to make good

use of them. Thus, the maximum segurity, duration and electric performances are obtained.

tW It is the maximum temperature to which coils of a reactance may be constantly working in normal

conditions, at their nominal voltage and frequency, to secure an average life of 10 years. Increases or

decreases of temperature in coils have an influence on their life.

t Coil heating of a reactance over room temperature in which they are installed, working in normal

conditions and at nominal voltage and frequency.

ta Maximum room temperature at which a reactance may work in normal conditions. It is given by: ta =

tW - t

Losses It is the autoconsumed power. If not indicated otherwise, this value is measured with nominal voltage

and frequency and with coils at a temperature of 25ºC.

It is the power factor.

Besides these, conformity prints from different organisms may appear as it was previously indicated.

9.2.5. Electronic ballastsElectronic ballasts offer important advantages with respect to conventional inductive ballasts, such as:

- They improve lamp and system efficiency.

- They do not produce flickering or stroboscopic effects.

- They provide an instantaneous start without the need of a separate starter.

- They increase lamp life.

- They offer excellent possibilities to regulate the lamp luminous flux.

- Power factor is close to the unit, although harmonics in line must be carefully observed so that maximum admited

values are not exceeded.

- Connection is simpler.

- They have a smaller temperature increase.

- They do produce neither a buzz nor other noises.

- They are lighter.

- They may be used in continuous current.

Of course, these advantages correspond to electronic ballasts correctly designed, elaborated and verified.

Electronic ballasts are generally used for fluorescent lamps metal halide and high pressure sodium lamps of up to 150 W.

The most commonly used working principle in electronic ballasts for fluorescent tubes in normal alternating current connections

(220 V and 50 Hz) is as shown in Fig. 5.

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Figure 5

As it may be seen, a narrow filter placed before reduces distorsion of the power supply current and avoids that high frequency

signals are reflected in the power supply. Besides, the electronic circuit must be protected from fortuitous impulses which appear

in 50 Hz alternating current.

Once the alternating current has been modified, and with the help of the coupling condenser, high frequency generation in

square wave is the following step, through two transistors, generally. This frequency must be higher than 20 KHz. to go over

audible limits and achieve the greatest performance.

Before applying high frequency to tubes, some solutions to limit current and ease ignition must be established.

It is also necessary to provide the necessary solutions to avoid ballast deterioration at the end of the tube life, etc.

Concepts associated to electronic ballastsPower factor: In electronic ballasts, the power factor is corrected and has a constant value very close to the unit, controlled at

any time during its functioning by the power factor correction circuit.

Protection against surges: In threephasic installations with the neuter incorrectly connected or interrupted, if there is an

unbalance of charges, there is also an unbalance of voltages, originating surges in some phases. This may create working

problems and deterioration of lamps and auxiliary equipments.

Electronic ballasts are provided with a protection system against surges, avoiding problems which may be produced in circuits

due to this reason.

Current harmonics: A pure non sine wave is formed by a fundamental wave to which frequency waves multiple of the

fundamental one are superimposed. These superimposed waves are called higher order harmonics, as previously seen.

These harmonics are produced by elements with a non- linear behaviour, overloading power supply systems. They are frequently

discarded because they become a source of perturbations for other devices in the same power supply system and reduce the

power factor of the device affected by them.

Electronic ballasts must include input filters in their circuits to limit and maintain the level of harmonics equal or under the EN

61000-3-2 Norm exigencies.

Dispersion or stray currents: In order to reduce radio electric interferences filters which originate disperse currents or non

acceptable for a good electric functioning of the equipments are used.

Electronic ballasts incorporate interference suppression condensers with an earth connection for stray currents, with values

always lower than 0.5 mA. This does not constitute a problem for protection equipments and circuit differentials.

For a correct installation, it is always necessary to use the ballast earth terminal and connect it adequately.

Radio electric interferences: Electronic equipments functioning under high frequencies emit or generate harmful radio electric

interferences for the electric surrounding and devices related to it.

These emission levels must be located under the limit tolerated by the EN 55015 Norm.

Electronic ballasts are equipped with stages and filters which suppress radio electric interferences. Hence, their emission is

always inferior to the maximum normalized limits.

Narrow filter High frequencyoscillator

Electroniccontrol

Lamp stabilizerRectifier

Power supply

F

N

Trimmercapacitor

Lamp

Lamp

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To maintain this low emission level of radio interferences, special attention must be paid to the installation wiring disposition,

following recommendations for this purpose at any time.

Normative to which high frequency ballasts must complyIn order to offer the maximum functioning and security guarantees, electronic ballasts must be designed according to the latest

European norms in order to achieve the following characteristics:

- Being electronic, they must be totally noise- free.

- Not to produce flickering during ignition.

- Corrected stroboscopic effect.

- Useful as emergency devices, admitting continuous current power supply.

- To allow a wide margin of power supply voltage.

- To have an automatic disconnection circuit as opposed to faulty or depleted lamps.

- To incorporate harmonic filters to avoid that these are introduced in the power supply.

Therefore, they must comply with or follow the norms established below:

UNE-EN 50081-1: Electromagnetic compatibility. General emission norm.

UNE-EN 55015: Radio electric perturbations of fluorescent lamps and luminaires.

EN 61000-3-2: Perturbations of power supply systems. Harmonics.

EN 60928: General and security prescriptions.

EN 60929: Working prescriptions.

UNE-EN 50082-1: Electromagnetic compatibility. General immunity norm.

Ignition through high frequency electronic equipments Ignition time for an electronic ballast is the necessary time to begin lamp ignition. Depending on this period of time,

instantaneous ignition equipments (or cold ones) and ignition equipments with cathode preheating (or hot ones) will be

distinguished.

Instantaneous ignition electronic ballasts: They produce lamp ignition almost instantaneously.

This ignition takes place with cold lamp cathodes, without a previous preheating.

The use of these ballasts is recommended in installations where a limited number of daily ignitions is required, like

offices, shopping precincts, banks, etc.

Quick ignition electronic ballasts: These ballasts, as opposed to instantaneous ignition, have a short preheating time,

of approximately 0.4 seconds.

Preheating ignition electronic ballasts: These ballasts produce lamp ignition in an approximate time of two seconds.

Previous to ignition, lamp cathodes are preheated by a initial current that goes through them, which originates a softer

ignition, but not an instantaneous one. Nevertheless, in this type of installations, the life of the lamp subjected to

frequent ignitions is much shorter than that of a lamp subjected to few ignitions and long periods of continuous

working.

HF generator for induction lamps: The HF generator provides the signal of high frequency (2.65 Mhz) to the

antenna of the lamp to begin and maintain gas discharge. The generator electronic circuit system is inside a small

metal box which protects from radio frequency interference and drives heat generated in the circuit.

9.3. StartersMercury lamps have electrodes which allow starting with a low voltage, around 220 V. Therefore, no additional starting device is required.

However, metal halide and high pressure sodium lamps need very high ignition voltage which may not be supplied by the reactance

alone.

Supplying this ignition power is the role of starters, which are also used for ignition of some low pressure sodium lamps.

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Working principlesThey are based on the principle of taking advantage of energy stored in a condenser, which is discharged by means of an

adequate shooting system in the primary coil of a transformer. Due to the brusque flux variation in its nucleus, a voltage impulse

induced in the secondary one appears. Its peak value is very high and it is of a short duration. When superimposed to the power

supply, it arcs the discharge tube.

According to its working principle three different types of starters may be distinguished: independent starter, impulse transformer

starter and independent starter from two wires.

Besides this classification according to their working, starters may have a deactivation system inside that will interrupt their

working if the lamp does not start in a period of time. These are called temporized starters.

Independent starter or impulse superimposed starter (Starter in series)

It works as shown in Fig. 6. The starter of the condenser is discharged by means of the shooting circuit on the spirals of the

primary transformer, which amplifies the impulse at the adequate value. The impulse voltage depends exclusively on the starter

itself. It is compatible with any shock reactance and it does not bear ignition impulses, whose value is high in many cases.

Figure 6

Impulse transformer starter (semi parallel starter)

It uses the reactance as an amplifier of the products by the starter and it works as shown in Fig. 7. The condenser of the starter

is discharged by means of the shooting device between points 2 and 3 of the reactance. Together with an adequate proportion

of spirals with regards to the total coil, it amplifies the impulse to the necessary value.

The value of the impulses depends both on the starter itself as well as on the reactance used. Due to this reason, it is not always

compatible with any combination of both. The reactance must have an intermediate feeding point and it must also be subjected

to high peak power voltage produced for ignition.

Figure 7

Ballast

Power supply

F

N

ResistanceShooting

circuit

Stater

Capacitor

Capacitor

1 3

2

Lamp

Ballast Transformer

Power supply

F

N

Resistance

Shooting circuit

Starter

Capacitor

Capacitor

Lamp

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Independent starter from two wires (parallel starter)

It works as shown in Fig. 8. The energy stored in condenser C is returned towards the lamp by the intervention of the shooting

circuit D, in the precise moment in which voltage reaches its maximum value. An impulse of a peak value between 2 and 4

times the instantaneous of the power supply, between 600 V and 1,200 V, is reached, but with a longer duration, and, therefore,

of more energy than those obtained with other systems of starters.

Figure 8

The may be only used for some metal halide lamps and low pressure sodium lamps of 35 W., which require voltage impulses

relatively low but of a certain duration.

Temporized starters

These starters have an inner device, which after a time previously fixed for impulse production, deactivates its working. If the

lamp does nor ignite due to exhaustion or failure, its stops subjecting all circuit to high voltage impulses.

The starter is active again after the interruption of the power supply circuit voltage, although only for a short period of time

(milliseconds).

Ballast

Power supply

F

N

Resistance

Shooting circuit

Starter Capacitor

Capacitor

Lamp

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Reference normsNorms applicable to starters are the following:

EN 60926: Starters (except for effluves). General and security prescriptions.

EN 60927: Starters (except for effluves). Working prescriptions.

EN 60662: High pressure sodium lamps.

EN 61167: Metal halide lamps.

Recommendations for the use of startersIn the first place, the adequate starter for the lamps to be installed must be chosen so that the necessary peak voltage is

provided, the number of impulses required for lamp ignition and the charge capacity born by the cables to the lamp is admitted.

Location must be carefully chosen so that there is always the minimum distance from the starter to the lamp. Thus, the capacity

of cables is minimum, securing ignition. Such a capacity depends on the separation between cables and on their length.

The conductor bearing the high voltage impulse, indicated in all starters, must be of an insulation for a voltage in service of no

less than 1 KV., and be connected to the central contact of the base to favour its ignition.

The connecting form indicated in the sketch of the starter must be always respected.

Humidity, water or condensations in the housing of the starter must be avoided. Derivations between terminals or to earth may

be produced, which would cancel the high voltage impulse, failing ignition.

An excessive room temperature must also be avoided because it may provoke an overheating in the starter and risk its average

life. Temperature at the point indicated on the surface of the starter must not exceed the value indicated for tC…ºC, when the

lamp is working and thermally stabilized.

The starter produces voltages of up to 5 KV. Thus, insulation of cables supporting them must be especially considered. It is not

advisable to work on the luminaire without being sure that power supply is off.

Connect the condenser for the voltage correction factor to avoid impulse losses towards the power supply.

StartersThis name is given to starters designed for fluorescent lamp ignition.

The most common type of starter is that called flicker, composed by a glass bulb full of neon gas at a low pressure. In its interior there

are two electrodes, one of them or both are bimetal lamellae which bend slightly by the action of heat. In parallel with the electrodes,

a condenser is connected to eliminate interferences. All this is housed in a cylindrical recipient made of aluminium or of an insulating

material. A plaque with two pins for contact and fixing are included. The starter is embedded in series with the lamp electrodes and

ballast, working automatically in the following way:

When the connection is established, a small electric discharge takes place between the lamellae through the gas, heating them enough

to bend till they get together. This union closes the circuit and eases the flow of current through the lamp electrodes for a short period

of time. When the electrodes are incandescent, they emit electrons around them in the form of a cloud. A bit later, when the lamellae

cool down, they separate opening the circuit and giving rise to the ballast spreading a power impulse tension through which discharge

of the arc and lamp working takes place. Once the lamp is turned on, the starter is out of service without an insufficient voltage reaching

it. If ignition fails, the starter behaves exactly in the same way.

However, electronic starters only make one ignition attempt (very determined) so that any flickering during the ignition stage is

eliminated. Additional advantages of electronic starters are high ignition reliability at low room temperatures and prolongation of lamp

life.

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9.4. Capacitors

9.4.1. General remarksElectric capacitors are a system formed by two conductors separated by insulation. If no element is between the two conductors,

air is the insulator. Nevertheless, generally speaking, air is substituted by another insulator with higher dielectric power. Hence,

conductors (frameworks) may be very close to one another without electric charges jumping from one to the other.

If frameworks of a capacitor are connected to the poles of an electric generator, equal and different sign charges are adquired.

So, once it has been disconnected, the capacitor stores electric charges.

The amount of charge stored by a capacitor is directly proportional to the power differential established between its plaques.

But it may also happen that two capacitors of a different form or size adquire different charges when subjected to the same

power difference.

Capacity of a capacitor is the quotient between the charge of one of its plaques and the power differential between both of

them.

where:

C = capacity of the capacitor.

q = charge of the capacitor (coulomb).

U = power differential between the capacitor (V) plaques or pins.

Pure capacitive circuitCapacity (capacitance) of an electric circuit or of an element of the circuit serves the purpose of delaying a variation in the

voltage applied between its terminals. That delay is caused by absorption or cession of energy and it is associated with the

variation in the electricity charge.

A pure capacitive circuit is that whose ohmic resistance equals zero (pure capacitance). Following the electric field laws, voltage

between the plaques of a capacitor is known to be proportional to the stored charge and that the ratio q/U is the capacity.

If instead of a continuous current, a capacitor is applied a sine alternating current, a variation of the same du will be necessary

to produce another variation in the charge dq = i · dt in an infinitesimal time dt. That is to say:

dq = i · dt = C · du

If a sine alternating voltage is applied to the circuit u = Umax · sin (t), and it is substituted in the previous equation, derivation

and operation is as follows:

i = Umax · · C · sin( · t + )

This equation indicates the advance suffered by the intensity with regards to voltage due to the capacitor effect.

Frequency effectCapacity reactance

The capacity of a circuit serves to delay the increase or decrease of voltage, but under no circumstances does it avoid or limit

change. Nevertheless, frequency limits current amplitude in a value equal to = ohms. This value is called

capacitive reactance XC, which increases when frequency decreases and it

decreases if frequency increases. Thus, for continuous current like f = 0 Hz, the capacitive reactance value is infinite and that of

current is zero amperes.

Inductive reactance

Inductance of a circuit serves the purpose of delaying the increase or decrease of current, but under no circumstances does it

avoid or limit the change. However, frequency limits amplitude of the current in a value equal to . L = 2 . . f . L ohms. This

12 . . f . C

1 . C

2

C = qU

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130 LIGHTING ENGINEERING 2002

value is known as inductive reactance XL, which increases when frequency is higher and decreases if frequency also does. Thus,

in continuous current, like f = 0 Hz., the value of inductive reactance is zero.

Resistance

Resistance offered by a conductor in alternating current may be said to be the same as that offered in continuous current (ohmic

resistance), whenever the Kelvin and corona effects, and resistance due to parasite currents, hysteresis, etc. may be disregarded.

Generalized Ohm’s lawIn circuits, the electric current is limited by the resistance value (R), the inductive reactance (XL) and the capacitive reactance

(XC) of the elements forming the circuit. All these elements may undergo a sine alternating voltage which, as a permanent

regime, makes an alternating intensity current circulate in the same form and wave frequency. Also, generalized Ohm’s law for

alternating current is verified in them. The formula is as follows:

The real part of the complex number is the measurement known as resistance, R, represented in the real axis. Its module equals:

The imaginary part of this complex number, Zr

is the reactance X, represented in the imaginary axis in such a way that if it is of

an inductive nature, it is positive, +j . XL, and if it is of a capacitive nature, it is negative,-j . XC. Its module equals:

The angle is the phase different angle between tension and intensity, in such a way that if it is positive, it corresponds to an

inductive circuit. If it is negative, it corresponds to a capacitive circuit. As it is widely known, this angle is of great importance in

alternating current. It is called power factor and provides information about reactive energy and also quantifies it.

Figure 9

If the impedance triangle of Fig. 9 is multiplied by I2, the result obtained is its corresponding power triangle, in which:

Active power P = R . I2 = U . I . cos (W)

Reactive power Q = X . I2 = U . I . sin (V Ar)

Apparent power S = Z . I2 = U . I (V A)

ϕ

0

X (inductive)

-Xc

XL

Z

R

X = Z . sin = ZZ2 - R2 ()

R = Z . cos = ZZ2 - R2 ()

Zr

= Z . (cos + j . sin) = R + j . X ()

Zr

= Ur

Ir ()

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Figure 10

9.4.2. Power factorPower factor (cos) may be defined as relative efficiency in the use of electric energy. Technically speaking, it is the ratio

between active power P (in W.) submitted to a receptor and apparent power S (in V.A.) supplied by the power line.

Figure 11

It will always be lower than the unit, but the closer to it, the more advantage we are taking out of the energy from the power

supply.

Norms for reactances specify that an equipment (set of reactance– lamp) has a high power factor when its value is equal or

greater than 0.85.

The use of high power factor reactances has the following advantages:

1- Compliance with requisites from electric energy supply companies of compensating the power factor, at least, at

0.85.

2- To avoid extra charges in light bills for reactive energy.

3- To reduce the section in power supply line conductors in installations.

4- To use high power factor equipments implies to install a larger number of luminaires per circuit so that protection

equipments are reduced and simplified (magnetothermal, differentials, etc.).

Power factor compensation

As usual, industrial use reactances are of an inductive type and their power factor is around 0.5. Reactances of a capacitive type

must be associated to them so that the power factor of the set is close to the unit. This capacitive reactance consists in one or

several capacitors, whose installation is convenient near the inductive reactance in order to measure conductors for the smallest

intensity possible. This would not be achieved if capacitors are placed at the beginning of the installation, next to the distribution

board, for example.

On selecting the necessary compensation method, location of capacitors and economic aspects should be considered (prices,

power supply parameters, acquisition initial expenses and equipment maintenance expenses). Apart from this, there are factors

such as system harmonics and surrounding conditions which may limit the effective use of capacitors.

There is not a compensation method which may be universally recommended. Nevertheless, several methods may be applied

in each case.

ϕ

0 P=UI cosϕ

QL=UI sinϕS=

UI= P2 +Q L

2

ϕ

0

S

Q

P

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132 LIGHTING ENGINEERING 2002

Compensation in parallel

Compensation in parallel is done as shown in Fig. 12 where a fluorescent lamp with ignition through a starter has been

represented as a typical example, but it may be applied to any other type of lamp.

Figure 12

The capacitor connected in parallel to the power supply, must have the adequate value so that reactive intensity ahead of the

phase absorbed by it, IC, formed by the one circulating through the lamp, IL, gives a power supply absorbed intensity, IT, whose

power factor is close to the unit (Fig. 13).

Figure 13

Power to be born by the capacitor is that of the power supply, and tolerance admitted in capacity is usually ±10% of its nominal

value.

Being:

VPOWER SUPPLY = Power supply tension.

IL = Current absorbed by the equipment without compensation.

IC = Current absorbed by the capacitor.

It = Current in power supply after compensation.

and ´ =Phase difference angles after and before compensation.

Calculation of the necessary capacitor

Calculation of capacity (C) of the necessary capacitor in an equipment may be solved with the help of the following formula:

where:

C = P . (tag - tag´)

(F) . V2

ϕ'

ϕ

Ic

It

Vpower supply

IL

Ballast

Star

ter

Lam

p

CapacitorPower supply

F

N

Ic

Iγ IL

IL

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cos = initial power factor. ( = arc cos).

cos’ = power factor to be achieved. (’ = arc cos’).

V = power supply of the line.

= frequency in radians. ( = 2. . F; F is the frequency in Hz.).

Compensation in seriesAs established before, compensation in parallel reduces the reactive power component of the power supply, and, thus, power

losses. With compensation in series reactive power is transmitted to a certain degree and the recover of the line remains

influenced when connecting capacitors in series to the power supply. The formula for the power loss in the line is given by:

This formula shows that, when XC = XL,, the power supply reactance is zero and the tension loss originated by the reactive power

transmission is also zero, as a consequence. When an adequate capacitor in series, is included, Xc may be greater than XL. In

this case, reactance of the power supply becomes negative. Thus, compensation in series may also reduce a power supply drop

caused by the transmission of active power.

9.5. Energy- saving equipmentsIn public lighting through discharge lamps, energy consumption may be reduced during early hours or in circumstances which require

less visual exigency by means of a reduction in illuminance for each point or in most of the corresponding luminous points.

In old installations, two lamps used to be mounted on each luminaire for road lighting so that two lighting levels were available

depending on conveniences. Nowadays, one luminaire with a single discharge lamp incorporated and with double level equipment is

used. This ballast allows a reduction of consumed power by means of the introduction of an additional inductance incorporated to the

iron nucleus of the main inductance in a separate nucleus in the lamp circuit. Figs. 14, 15 and 16 show three forms known of the double

level system referred to a vapor mercury lamp.

Figure 14. The relay switches the winding intake in a single nucleus.

Double level ballast

Relay

F

N

Lamp

U = Ia . R + Ir . (XL - XC)

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134 LIGHTING ENGINEERING 2002

Figure 15. The relay is inserted in series with the auxiliary shock circuit.

Figure 16. The relay opens the shock circuit derived from the main one.

In any case, lamp consumption is reduced since the relay acts, connecting with an important line existing in the installation. Also,

a temporizer in the equipment of each luminaire may be available, which programmed as required, passes from the normal

level to the reduced one.

The double level system being described may be applied to high pressure mercury lamps and high pressure sodium lamps

(having special care in ignition circuits). This system is not adequate for metal halide lamps because the colour of the light is

very much affected by the emitted power.

In energy saving systems with several lighting levels, the power factor of the installation must be carefully watched. Sometimes

it will be necessary to reduce the needed installed capacity for the maximum level in the minimum level. An added advantage

in double level equipments is the longer duration of equipments and lamps, since generally, harmful surges are produced in

lines during hours in which lighting is connected at a reduced level.

9.6. Control gears for different discharge lamps. Circuits

Fluorescent tubesFluorescent tubes are classified into two large groups, depending on whether cathodes are heated or not for ignition.

The most common ones are the hot cathode that may be ignited by means of a thermal starter (Fig. 17), heating of filaments

in the rapid ignition systems "rapid start" (Fig. 18), "trigger" ignition (the filament voltage is reduced once the tube has ignited),

semi- resonant ignition (Fig. 19) and ignition through electronic means.

Principal ballast

Auxiliary ballast

F

N

Relay

Lamp

Principal ballast Auxiliary ballast

Relay

F

N

Lamp

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Another type of tubes is that of cold cathodes, which almost exclusively ignite through tension applied between their extremes.

Figure 17. Ignition through starter. Inductive ballast. Compensation of power factor in parallel with the line.

Figure 18. Rapid ignition. Circuit with autotransformer dispersion (with heating of electrodes in parallel).

Figure 19. Rapid ignition. "Semi resonant" circuit with heating of electrodes in series.

High pressure mercury lamps Electric equipments most commonly used are those with an inductance in series with the lamp limiting ignition and normal

regime intensities. The low power factor produced by the use of the inductance is corrected using capacitors in parallel with the

line (Fig. 20).

When voltage of the line is insufficient or excessively large for the one requiring lamps, a transformer between the line and the

stabilization inductance is coupled (inductance may be incorporated to the second transformer and it is then called dispersion

or stray transformer).

F

N

Power supply Capacitor

Ballast

Lam

p

Lam

p

Capacitor

Power supply

F

N

Ballast

Capacitor

Star

ter

Lam

p

Power supply

F

N

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136 LIGHTING ENGINEERING 2002

Figure 20. High pressure mercury lamp connection scheme.

Low pressure sodium lamps Equipments used for this lamp type in the recent past have been almost exclusively constituted by a high impedance

autotransformer in the second one and a capacitor in parallel with the line to improve the power factor (Fig. 21). Recently,

inductances in series or semiresonant circuits (low voltages, Fig. 22) and hybrid circuits constituted by more complex

autotransformers associated to electronic starters (Fig. 23) are used with new lamps in order to improve lamp performance and

reduce power consumption strongly.

Figure 21. Dispersion autotransfomer.

Figure 22. Semiresonant starter.

Reactance

Power supply

F

N

Capacitor

Power supply

F

N

Bal

last

Lam

p

Capacitor

Ballast

CapacitorPower supply

F

N

Lamp

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Figure 23. Hybrid circuit. Electronic impedance and starter.

High pressure sodium lampsFor ignition of this type of lamps, electronic starters have been developed, which generate impulses lamps need for arc ignition

in combination with the ballast, or independently. These starters must stop in impulse emission once the lamp is ignited, in

order not to damage it.

There are two types of starters from the point of view of their association with the ballast: the ones which incorporate a

transformer for generation of high voltage impulses (Fig. 24) and those using inductance as a transformer (Fig. 25). The first

ones must be mounted very close to the associated lamp; the ballast may be also located far from the lamp. Those which use

impedance as a transformer are more economical and must harmonize the couple reactance- starter. The lamp may be far from

the equipment depending on the cable capacity allowed by the starter.

Anyway, stabilization in these lamps is strongly determined by the characteristic of the sodium arc, whose tension is not constant

along its life. The best stabilization system for this type of lamp is an inductance in series with constant power supply.

Figure 24. Scheme with an independent starter.

Figure 25. Scheme with a semiparallel starter.

Power supply

F

N

Starter

Ballast

Capacitor

Lam

pBallast

Capacitor

Starter

Power supply

F

N

Lamp

Ballast

Power supply

F

N

Capacitor Starter

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138 LIGHTING ENGINEERING 2002

Metal halide lampsIn general, special ballasts need not have developed for these lamps. Metal halide lamps with three bands use ballasts designed

for high pressure mercury lamps. Rare earth lamps and tin lamps work well with ballasts for high pressure sodium lamps.

Since the voltage of the ballast is not enough to start this lamp, an external starter is needed (Figs. 26., 27. and 28.)

Figure 26. Scheme with an independent starter.

Figure 27. Scheme with a semiparallel starter.

Figure 28. Scheme with a parallel starter.

Ballast

Power supply

F

N

Capacitor Starter

Lam

p

Power supply

F

N

Starter

Ballast

Capacitor

Lam

p

Ballast

Capacitor

Starter

Power supply

F

N

Lamp

Chapter 9. CONTROL AND REGULATION AUXILIARY EQUIPMENTS

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139LIGHTING ENGINEERING 2002

Chapter 10.

INDOOR AND INDUSTRIALLIGHTING

10.1. General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

10.2. Lighting levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

10.3. Glare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

10.4. Shadows and modelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

10.5. Light quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

10.6. Lighting design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154

10.7. Indoor lighting calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156

10.8. Some recommended lighting levels . . . . . . . . . . . . . . . . . . . . . . . . . . 158

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140 LIGHTING ENGINEERING 2002

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10.1. General remarksHuman beings need to be informed about their surroundings in order to perform their activities in an easy and harmless fashion.

Most information about the environment reaches human beings through their eyes. Therefore, it is of a visual nature. The term visibility

(of an object) is used as a measure of easiness, fastness and precision an object may be detected and visually recognized. In

consequence, a good visibility of the surrounding environment, and everything it contains, is essential.

Good lighting is required for good visibility. Although good visibility of relevant objects is a necessary condition, it is not always enough

to perform activities easily and comfortably. In indoor areas, where a task is performed, the main function of lighting is to provide

comfort for visual tasks in this place. However, in circulation areas, resting areas or living rooms, visual capacity criterion is not so

important. Pleasantness and visual comfort is what matters.

Thus, the most important criteria related to lighting design for a particular application are visibility and visual satisfaction. Moreover, such

factors must be well balanced in relation to installation and working costs.

10.1.1. Visibility / visual performanceWorking in indoor areas, the influence of lighting while doing the job is very important.

Performance for a specific person, for a concrete job, is esencially translated into a function of the person’s ability to perform

a task (execution potential), on the one hand. On the other hand, the person’s attitude towards the task execution (execution

attitude) is also relevant.

Attitude during execution determines, to what extent, the execution potential is efficiently used. It includes factors such as

motivation, dedication and concentration, of a social or psychological nature, and which lie outside our field of study.

Lighting, as well as other factors in the physic environment, may influence the execution potential, but, influence on real

execution also depends on the execution attitude.

Visual performance is the term used to describe the eye working speed and the accuracy with which a task is performed.

Visibility of a task is generally determined by visibility of the most difficult element which must be detected or recognized so

that work can be performed. This detail is known as critical detail. Visibility of the critical detail is a function of the difficulty

experienced in order to discriminate it visually from the background on which it is seen, from other details found in its most

immediate surroundings.

Luminance

In order to achieve good visibility at work, the most important factor is related to luminance of the task and its surroundings.

The general effect of luminance on visibility is due to the resulting adaptation, process by which properties of the visual

system are modified according to luminances of the visual field. For a given luminance distribution in the visual field, the

adaptation process reaches a final state expressed as adaptation luminance.

Visual system properties affected by adaptation to luminance are the following:

- Visual sharpness, which is the capacity of the system to discriminate between details or objects that are very close.

- Sensitivity to contrast, which is the capacity of the system to distinguish between small differences of relative luminance.

- Efficiency of eye motor functions for accommodation, convergence, pupil contraction, eye movements, etc.

Visual sharpness, sensitivity to contrast and efficiency of eye motor functions are larger with the increase of adaptation

luminance up to a maximum certain level.

For tasks where detail angular size is critical with respect to working visibility, an increase in visual sharpness due to another

increase in luminance is highly important to improve task visibility. However, when the angular size of the critical size is very

much above the threshold of visual sharpness, contribution to its increase is insignificant.

Something similar happens with the above mentioned factors. They may also be positively affected by an increase in

luminance. However, it will provide an improved visibility at work as a result, as long as such factors are critical with respect

to visibility of the task under consideration.

Diffusing objects and their surroundings

Luminance of a matte surface is proportional to the product of illuminance in the surface and its reflectance. Luminance as

a factor that influences visibility may be, in consequence, substituted by illuminance and reflectances for diffusing surfaces

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142 LIGHTING ENGINEERING 2002

and their surroundings. Reflectances form part of the intrinsic properties of the task and the indoor area. These are not

affected by lighting. Thus, for these tasks only illuminance remains a factor of the lighting system which affects visibility. It

should be born in mind that for these tasks, luminance contrast is not affected by illuminance, but it is determined by

reflectances of details and their background. Therefore, task visibility will be larger with the increase in illuminance up to a

maximum certain level. The effect of the illuminance increase over visibility will be larger as size is smaller, or the contrast

detail or the number of exigencies of the eye motor functions. For details of large angular size, with a high contrast with the

background and static in a known position, the effect of illuminance increase in visibility on a moderate level will be

insignificant.

Bright objects and their surroundings

Considering that luminance of a perfectly matt object is proportional to the product of illuminance and reflectance (diffuse),

luminance of a regular reflecting surface is proportional to the product of its reflectance (regular) and the environmental

luminance in the reflection direction.

In practice, however, most surfaces do not belong either to the perfectly diffused reflection or to the perfectly regular one.

Surfaces have mixed reflection properties in such a way that their luminance depends both on the illuminance properties of

the surface as well as on the luminances of the surroundings. In order to relate luminance of mixed reflection surfaces with

illuminance in a similar way as luminance of a matt surface is related to illuminance by its reflectance, the luminance factor

has been introduced.

Luminance factor of a surface in a given direction under certain lighting conditions, is the reason for the surface luminance

in that direction to the luminance of a perfectly diffusing white surface, when they are identically illuminated.

From this definition, it may be deduced that the luminance factor of a perfectly diffusing surface is constant and equal to its

reflectance in all directions and under all lighting conditions.

In an environment of uniform luminance L, luminance of a perfectly regular reflecting surface is L in all directions and

luminance of a perfect diffusing white surface is also equal to L. Luminance factors of that regular reflecting surface under

such lighting conditions, are equal to 1 in all directions.

In an environment of luminance equal to 0 except for a limited L luminance area (source), luminance of a perfect diffusing

white surface is smaller than L because illuminance is lower than illuminance in an environment of uniform luminance L.

Luminance of a regular perfectly reflecting surface is equal to 0 except in all reflection directions of the source in which

luminance is equal to L. Luminance factor of such regular surface, thus, is larger than 1 in the directions of reflection of the

source and 0 in all other directions.

Since bright surfaces have reflection properties partly regular and partly diffused, it may be deduced from all the above that

for such mixed reflection surfaces, luminance factor will be constant and equal to its reflectance (mixed) in all directions only

in a uniform luminance environment. In other environments, it may reach values between 0 and above 1, depending both

on reflection properties and lighting systems.

This also means that contrasts in objects which are not perfectly matt are affected by lighting because they are determined

by luminance factors of details and background. These may reach different values in different visual directions, especially in

directions of high luminance reflection.

In conclusion, for tasks and bright contours not only illuminance is important for good visibility but also lighting direction. This

is a general term which describes the special distribution of incident light in the task. It is determined by luminance

distribution of the environment and depends on factors such as geometry of installation, luminances of luminaires and indoor

reflectances.

10.1.2. Visual satisfactionVisual satisfaction is a term used to describe visual condition acceptability.

For indoor work, visual satisfaction is essentially a function of easiness of work under real conditions, and pleasant or

comfortable visual environment, when both concentrate on the task and when they are improved or seek relaxation.

Visual satisfaction is affected by the luminous environment and individual preferences.

For indoor areas with matt surfaces and tasks, influential factors of the luminous environment are illuminances in different

Chapter 10. INDOOR AND INDUSTRIAL LIGHTING

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surfaces and their task. Give origin to brightness by reflectio is. an important factor affecting visual satisfaction.

For indor areas with bright tasks or surroundings, environmental luminances reflected on surfaces and which may veil the

contrast of the task or give origin to brightness by reflection, are an important factor affecting visual satisfaction.

Much research has been conducted in order to determine a preferred range of horizontal illuminances surrounding indoor

areas. For such a purpose, carefully controlled values of surface reflectance in a room must be taken into account. Out of the

results obtained in Western Europe, for brightness free fluorescent lighting conditions, an average curve has been determined

indicating the percentage of observers which consider a particular illuminance as “satisfactory”. This curve is shown in Fig. 1,

together with the evaluation of “too dark” and “too light”.

Figure 1. Response combinations.

10.1.3. Visual capacityVisual capacities vary from one individual to another, as it happens with other individual factors characteristic of people. Visual

capacity depends on factors such as shape and transparency of elements of the eye optical system, accommodation capacity,

convergence and aligning of eyes and retina spectral sensitivity. Reduced visual capacity due to refraction errors may be

corrected using prescription glasses.

Visual capacities are reduced with aging. The most important change when the eye ages is that the range on which it is

possible to adjust accommodation exactly at a given distance is reduced. Other physical changes in the aging eyes are a

reduction of light transmission by means of optical media and an increase in media dispersion. This means that old people

may be less sensitive to central light, which may reduce visibility, and more sensitive to peripheryl light, which may cause

glares. Providing a glare free adequate lighting is even more important for elder workers than for young people.

10.1.4. Lighting parametersLevel and quality of lighting provided by a given installation may be described by means of the following parameters:

- Lighting level.

- Glares.

- Shadows and modelling.

- Quality of light.

- Lighting design.

Too dark Too lightSatisfactory

100

80

60

40

20

102 2 5 2 5103 104 (Lx)

0

%

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144 LIGHTING ENGINEERING 2002

10.2. Lighting levels

The required lighting level in a certain situation is expressed in terms of illuminance. At the end of this chapter some charts are shown

where such a level may be consulted for most of the activities.

Reference surfaceReference surface of an indoor area is the surface where the recommended appropriate illuminance is supplied, selected

from the charts shown at the end of the present chapter. The reference surface does not need to be reduced to a single

surface area, but it may include a number of separate areas. Indoor lighting specifications must always include a clear

definition of the reference surface.

In indoor working areas, the reference surface will normally be the working plane. For indoor areas where tasks are not

restricted to fixed places, the working plane is considered to be the horizontal plane limited by indoor walls at a height of

0.85 m. above the floor. For indoor areas where task localizations are known and clearly specified, the reference surface may

consist in specific areas of working or task areas.

When the task is not performed in a horizontal plane or is at a different height, the reference surface will have the angle of

the task plane and be at its height.

In indoor areas where work is not done, the reference surface may be the floor, the wall, or any important plane.

Illuminance uniformityIlluminance given on the reference surface by a lighting installation will never be totally uniform, either in space or in time.

Uniformity in space

Measurement of illuminance uniformity on the reference surface is the ratio between minimum illuminance and average

illuminance.

In general lighting, illuminance uniformity on the reference surface must not be lower than 0.8 to provide possible locations

of equivalent tasks in all the indoor areas.

In localized general lighting or lighting of general areas, average illuminance in areas surrounding tasks must not be lower

than one third of the level for task areas.

Ratio between average illuminances for two adjacent indoor areas (for example, an office and a corridor) must not exceed

5:1.

Uniformity in time

Average illuminance given by an installation will gradually decrease with time due to depreciation of the lamp luminous

flux and the accumulation of dirtiness in lamps, luminaires and surfaces in the room.

Initial lighting: it is the average illuminance when the installation is new and surfaces in the room are clean. Initial

illuminance must be chosen according to requisites imposed by the maintenance program. Its value should not be

used for illuminance recommendations.

Illuminance in service: it is the average illuminance during all maintenance cycle on the reference surface. In some

countries, it is used for illuminance recommendations.

Maintenance illuminance: it is the average illuminance on the reference surface during all the time between two

maintenance operations, substitution of lamps and/ or cleaning of luminaires and surfaces in the room. In some

countries, it is used for illuminance recommendations. In countries where recommended illuminance is established in

terms of illuminance in service, maintenance illuminance should not be under 0.8 of the recommended value.

10.3. GlareGlare is the sensation produced by an exaggerated luminance within the visual field which alters sensitivity of the eye, causing

discomfort, reducing visibility or both.

Glare may take place in two different ways. Sometimes they occur separately, but generally, they take place simultaneously. The first is

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known as physiological glare (or disability glare). It impairs visual capacity and visibility, but it does not necessarily produce discomfort.

The second is known as psychological glare (or discomfort glare). This type is discomforting but it does not necessarily impairs object

observation.

In indoor lighting, psychological glare (discomfort) is likely to be more of a problem than physiological glare (disability). Measurements

taken to control discomfort glare will have to take discomfot glare into account, too. The sensation of discomfort experimented by

discomfort glare tends to increase with the passing of time and contributes to nervous tension and fatigue.

Any given type of glare may be direct or by reflection. Direct glare is the glare directly caused by luminances of the sources of

light, such as lamps, luminaires and windows, which appear in the observer’s field of vision. Glare by reflection is the glare

produced by reflected luminances from surfaces with high reflectance, especially specular surfaces such as polished metals,

except when these form part of the luminaire. Glare by reflection must be distinguished from other types of reflection which

produce a reduction of the task contrast. They are more correctly described as veiling reflections (high luminance is reflected

by the task towards the eyes, veiling it and reducing its contrasts).

10.3.1. Glare controlControl of direct glare of lamps and luminaires consists in controlling their luminance in the direction of the observer’s eyes.

Nevertheless, the degree of experimented glare is not only a function of luminaires in the worker’s visual field, but it also

depends on the type of activity performed. The more light demanded by the visual task, and the higher the need of

concentration, the higher discomfort will be, too. However, in those situations where the worker must move to perform the

task, the experimented discomfort will be less.

Therefore, the luminance degree of control will differ according to the type of task or activity. The C.I.E. has classified tasks

and activities in five groups depending on the required luminance degree of control. In Chart 1, five groups referring to Quality

Classes are enumerated.

In general terms, the highest luminances in an indoor area produced by the lighting installation are those coming from lamps.

Generally speaking, such luminances are too high to use lamps without controlling their brightness in the direction of the

eyes. This is the reason why one of the luminaire functions is to limit luminance in the critical directions at an acceptable

level.

Chart 1. C.I.E. quality classes for glare limitation

10.3.2. Practical methods for glare control Fundamentally, glare control means control of the focus luminance in the interval between 45º and 90º (Fig. 6). There are

several methods to perform this control. Among them, two are going to be studied below, devoting more attention to the

last one in section 10.3.3.:

Quality Glare Type of task or

Class index (G) activity

A, very high quality 1.15 Visual tasks exceptionally difficult.

B, high quality 1.50 Visual tasks extremely difficult.

Tasks requiring moderate visual demand and high

concentration.

C, average quality 1.85 Visual tasks moderately difficult, moderate concentration

requirement and workers’ movement to a certain extent.

D, low quality 2.20 Visual tasks demanding low visual and concentration levels,

workers frequently confined to movement within a restricted

area.

E, very low quality 2.55 Interiors used with visual tasks not requiring a perception of

detail where workers are not confined to a specific work place

but they move freely from one place to another and not

continuously used by the same workers.

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146 LIGHTING ENGINEERING 2002

- Control with translucent materials.

- C.I.E. design system.

Control with translucent materials

This method controls visible luminance surrounding lamps with a diffuser or prismatic material. Usually, the strictest limits are

imposed in the upper part of the “” interval.

Luminaire mounting height, room dimensions, degree of control of selected glare and in some cases, luminaire orientation,

notably influence the selection of appropriate limits for each “” interval.

These factors have been born in mind for different systems developed in order to determine the appropriate luminance limit

and/ or the degree of glare a determined installation is supposed to have.

C.I.E. design system

One of the main objectives of the C.I.E. on discomfort glare has been to develop a mathematical formula which may generate

glare values for simple sources as well as for a group of sources. The formula proposed is the mathematical average term

more usually applicable between different national systems. This formula is suggested to be rigurously checked bearing in

mind its possible adoption as a formula recommended by the C.I.E.

where:

G: C.I.E. glare index.

Ed and Ei: vertical illuminances in the eye.

Ed: directly from sources of glare.

Ei: indirectly from background.

L: luminance of the source of glare.

w: size of the source of glare.

p: Guth’s position index (position index for each luminaire, which is related to the shift of the area of vision).

10.3.3. C.I.E. glare protection systemIt is the system of luminance curve used in combination with a system of protective angle as an additional verifier for

luminaires having visible lamps, or parts of them, within the zone of critical vision. It is considered to be the simplest and

most practical method, and it is the one that will be described below.

Luminance limitation curves (Fig. 2), comprise a scale of glare indexes which represent quality classes from A to E, together

with different values of standard illuminance in service. Two diagrams depending on luminaire type and orientation according

to the direction of vision must be used.

Figure 2. Diagrams of luminance curves for evaluation of direct glare.

1.151.501.852.202.55

ABCDE

2000 10002000

50010002000

=<300500

10002000

=<300500

10002000

=<300500

1000=<300

500 =<300a b c d e f g h

85GM

75

65

55

459 2 3 4 5 6 7 8 9 10 Cd/m2 2 3103

Diagram 1 L

a b c d e f g h85

GM

75

65

55

459 2 3 4 5 6 7 8 9 10 Cd/m2 2 3103

Diagram 2 L

a b c d e f g h

G Quality Values E illuminance in service (lx)

2 · 1+ Ed / 500

Ei + Ed·

L2 . w

p2G= 8 . logE R

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Diagrams of Fig. 2 are diagrams of luminance curves for the evaluation of direct glare. Diagram 1 is for those directions of

vision parallel to the longitudinal axis of any elongated luminaire and for luminaires lacking lateral luminous panels observed

from any direction. Diagram 2 is for those directions of vision in right angles to the longitudinal axis of any luminaire with

lateral luminous panels.

Limitation of the required luminance depends on the type and orientation of the luminaire, the shielding angle, the

acceptance degree or quality class, and the value of illuminance in service.

Type of luminaire

The terms “luminous laterals” and “elongated” used to describe the types of luminaire are defined in the following

way:

- Luminous laterals: a luminaire is considered to have luminous laterals if it has a luminous lateral panel with a height

of more than 30 mm.

- Elongated: a luminaire is considered to be elongated when the ratio between the length and the width of the

luminous area is higher than 2:1.

Luminaire orientation

When using diagrams in Fig. 2, luminance distribution of the luminaire in two vertical planes must be taken into account: the

C0-C180 plane and the C90-C270 plane.

Figure 3. C- planes in which luminaire luminance must be verified.

When luminaires are mounted in the C0-C180 plane parallel to the axis of the premises, luminaire distribution on such a plane

is used to control glare limitation in the longitudinal direction of the room. Luminance distribution in the C90-C270 plane is

used to verify glare limitation in the transverse direction of the room.

When luminaires are mounted on the C90-C270 plane parallel to the premises logitudinal axis, such a plane must be used to

verify glare limitation in the room longitudinal direction, and luminance distribution on the C0-C180 plane to verify glare

limitation on the room transverse way.

For elongated luminaires on the C90-C270 plane this is chosen coincident with (or parallel to) the longitudinal axis of the lamp/

s. When such a plane is parallel to the direction of perceived vision, vision is supposed to be longitudinal. However, when

the C90-C270 plane is in right angles to the direction of vision, vision is considered to be transversal.

Shielding angle

For those luminaires which, when being observed from an angle of 45º or more with respect to the vertical, lamps or parts

of them may be seen, not only the average luminance of the luminaire according to curves must be limited in Fig. 4, but

also lamps must be well shielded depending on lamp luminance and quality class chosen.

The required shielding angles (Figs. 4 and 5) are shown in Chart 2. If the shielding angle is equal or higher than the tabulated,

glare will belong to the specified class or better.0

85°

75°

45°

C90 - C270 C0 - C180

45°

75°

85°

γ γ

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148 LIGHTING ENGINEERING 2002

Figure 4. Shielding angles for several luminaires.

Figure 5. Glare control due to shielding.

Types of sources

According to statistical experience, the minimum luminance threshold is that of 10-5 cd/m2 . Glare appears from 5 000 cd/m2

onwards and, under no circumstances must it go over 20 000 cd/m2. In order to control glare, it is convinient to divide

sources into two large groups, that is to say, those which have a luminance under 20 000 cd/m2 and those with a luminance

above this value.

Sources under 20 000 cd/m2 include all normal types of fluorescent lamps. Luminaires belonging to this group of sources

use, translucent materials and shielding for glare control. In some circumstances, lamp luminance is low enough to allow

bare use.

The group of sources above 20 000 cd/m2 includes for the most part compact lamp types, with an incandescent filament

and varieties of gas discharge. Although both methods of glare control mentioned before are used in low power lamps, the

shielding method is almost excusively used to control glare in the most powerful types, as far as industrial lighting goes. In

these cases, illuminance in the observer’s eye, such as luminance, must be taken into account. Because of this reason, both

flux coming out and mounting height must be carefully considered when calculating shielding angles convenient for sources

of this class.

90° - γ < S 90° - γ = S 90° - γ > S

Shielding angle

α

α α

α

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Chart 2. Minimum shielding angles required additionally.

Glare degree or quality class

Curves comprise a scale of five degrees of glare corresponding to five quality classes (Chart 1).

Degrees of glare emerge from glare subjective evaluation performed in a laboratory by a group of observers, using a nine point

scale where the main points were marked.

Standard servicie illuminance

Standard service illuminance value, 300 lux onwards, is used together with quality class, as a parameter to select the limit

curve of the adequate luminance.

Ratio a/h

Instead of the adequate range of critical ranges, a range of critical ratios a/h may be used, where “a” represents the horizontal

distance and “h” the vertical distance between the observer’s eye and the furthest luminaire (Fig. 6). These values are

represented on the right side of glare diagrams.

Figure 6. Critical radiant and vision zones.

Luminance values

Luminance distribution of luminaires in the C0-C180 and C90-C270 planes are initial values. Average luminance of the luminaire

in a given direction may be calculated as the quotient between luminous intensity in such a direction and apparent luminous

area.

* For linear lamps seen frontways: 0°.

Critical vision zone

Critical radiant zone

a

γ

45° hs

1.20

m.

a

hstan γ =

Luminance range Quality class of glare Lamp type

lamp average (cd/m2) limitation

A B C D E

Lower than 20 000 20º 10º * Tubular fluorescent.

From 20 000 to 50 000 30º 20º High pressure discharge

diffusers or fluorescent tubes.

More than 50 000 30º 30º High pressure discharge

Light glass tubular tubes.

Light glass incandescent.

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150 LIGHTING ENGINEERING 2002

Limitation curves are valid for:

- General lighting.

- Lines of vision predominantly horizontal or downwards.

- Reflectances of 0.5, at least, for flat ceilings and walls, and, at least, 0.25 for furniture.

For a luminous ceiling, glare limitation will be enough provided luminance in angles greater than 45º does not exceed 500

cd/m2.

Process for the use of the protection system from glare

1. Determine average luminance between 45º and 85º and the type of luminaire chosen for the installation.

2. Determine the quality class and the level of illuminance required for the installation (provided it is new).

3. Select the adequate curve (class and level) of the corresponding diagram.

4. Determine the maximum angle, for the length and height of the room, between the level of the eye and the luminaire

plane.

5. Take the horizontal line of the glare limitation diagram for the value a/h found in the previous step. The part of curve over

this line may be ignored.

6. Compare luminaire luminance with the chosen part of the limitation curve.

There will not be psychological glare if the luminaire luminance value does not exceed the luminance specified by the chosen

limitation curve within the range of the emission angles. If the result is different, the design must be modified, for example,

selecting another type of luminaire. It is advisable to use this method only in indoor working areas. In other situations, that

is to say, in public places, halls and entrances, higher illuminances may be required since sources of light in these places

serve as an animation element.

New development

A new development in the area of glare systems is the C.I.E. Unified Glare Rating, UGR, which is a new evaluation system of

psychological glare in indoor lighting. Although this system has not been internationally approved, it may be adopted to

general use.

UGR formula

The formula to calculate the UGR value is the following:

where:

Lb = background luminance (cd/m2).

L = luminance of luminous parts of each luminaire in the direction of the observer’s eye (cd/m2).

=solid angle drawn by the luminous parts of each luminaire in the observer’s eye (stereoradian).

p = position index for each luminaire, which is related to the shift of the area of vision (Guth’s position

index for each luminaire)

A more exact evaluation of glare is achieved by means of a direct application of the UGR formula for the considered

installation, for which a computer program is required.

UGR Charts

A simpler UGR value may be obtained, although not as exact, using standard UGR glare charts. These charts provide

the UGR value calculated for different standard situations and for different types of luminaires.

A disadvantage of these charts is that luminaires cannot be classified. Due to this reason, UGR limitation curves have

been developed.

0.25

Lb·

L2 . w

p2UGR= 8 . logE R

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UGR limitation curves

Glare limitation curves calculated using the UGR method are slightly different to limitation curves of the C.I.E. glare

limitation described before. These comprehend five lines instead of eight, and the range of luminances covered is

considerably larger.

Figure 7

The range of the glare index extends from 13 to 28 in groups of 3 units, this being the least increase provided by a

significative change in the sensation of psychological glare.

Another difference is that for these curves, luminaire classification is independent from illuminance. Thanks to curves

luminaires may be classified. However, they are not as exact as charts, since only the luminaire effect is considered and not

the effect of all the installation.

Glare produced by windows

Sky luminance in which glare begins to be perceived is approximately 2 000 cd/m2 and corresponds to horizontal illuminance

of 10 000 lux under cloudy conditions.

Since sky luminance may not be diminished, glare produced by windows may only be prevented using curtains, blinds or

lattices. Alternatively, working positions may be established in such a way that glare from windows does not interfere with

the occupants’ field of vision.

Psychological glare produced by windows may be reduced using very light decorations on surfaces close to window openings

and spreading decorations on them, allowing incident light to reduce contrast from the window.

Veiling reflections and reflected glare

Brightness of a source of light reflected by a matte or semi-matte surface in the observer’s eyes produces a slight or

considerable discomfort. When this reflection is produced in a task is known as veiling reflection. When glare is produced

outside the task, it is reflected glare.

On top of producing discomfort, veiling reflections reduce the context of the task, and, as a consequence produce a loss of

details.

Both veiling reflections and reflected glare may be minimized in the following way:

1. Designing a lighting system or locating working areas in such a way that no part of the visual task is within or near the

reflection angle of any bright source of light with respect to the eye.

2. Increasing the amount of light in both sides on the visual task, approximately in right angles to the direction of vision.

3. Using luminaires which possess a wide range of emission and low luminance.

4. Using working surfaces, paper, stationery, office machines, etc. with a matte surface to reduce effects from reflection.

8

13 16 19 22 25

γ

28

C= 0-180

45º

50º

55º

60º

65º

70º

75º

80º

85º

2 3 4 5 6 8 2 3 4 5 6 8 2 3 4 5 6 8 2

L (cd/m2)

102 104 105103

UGRC= 90-270

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152 LIGHTING ENGINEERING 2002

10.4. Shadows and modellingThe appearance of indoor areas is improved when their structural characteristics, objects and people are illuminated in such a way that

silhouttes are seen in a clear and comfortable way, and shadows are formed with no confusion. Such a thing happens when light flows

in an evident way in one direction more than in any other. The term modelling is used to describe the form in which silhouttes

of three dimensional objects are stresssed by lighting.

Modelling may be strong or weak; the most effective degree for any indoor area depends on type of construction and activities implied.

When light comes from many directions and is too diffused, modelling may be light and the indoor area may be little interesting due

to the loss of luminance contrast. Besides, if the directional component is very strong, modelling will normally be severe and shadows

may be confused.

However, pronounced shadows, like the ones obtained with sources of light concentrated in a small area, may be used to produce

intentioned dramatic effects. Shops, art rooms and many other places will require lighting with a provision for modelled shadows in

several degrees.

A window or a big luminaire may produce good modelling without strong shadows, but if the source is very big in relation to the

distance to the illuminated object, like in the case of indirect lighting, modelling will remain weakened.

Profound shadows which produce excessive luminance contrasts may be softened by means of applying additional sources of light.

Finishes with high diffusing reflectances in the surfaces of the room result in efficient secondary sources of light also reducing shadows,

materially speaking, and reflecting a significant amount of diffused light within shadowy areas. Shadows with soft edges are obtained

with sources of large areas such as fluorescent lamp luminaires or indirect lighting systems.

10.5. Light quality

In chapter 4 devoted to The Colour, it was explained that the most important characteristics of the quality of light are Colour

Temperature (TC) and Colour Performance Index (R or Ra).

Colour Temperature (TC) has an important influence on the environment created as long as coldness or heat sensations go. At the

same time, it promotes or reduces object chromaticity in the same way. Moreover, the term TC cannot be manipulated in an

independient way, but it must be combined in an adequate way with illuminance so that disturbing effects of visual perception are not

produced. Kruithof’s curves delimit possible combinations between TC and illuminance calculation (Fig. 8).

Figure 8. Kruithof’s curves for the ratio between Tc and illuminance.

5 000

500

50

52 000 2 500 3 000

COLOR TEMPERATURE ºK

ILLU

MIN

ANCE

IN L

UX

4 000 5 000 10 000

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The Chromatic Reproduction Index (R) is extremely important as far as quality of light goes, being the first measurement in activities

where an optimal chromatic reproduction is absolutely essential (see chapter 4).

Light and colour in indoor areasApart from lamp colour properties, another aspect of colour which influences visual comfort in a room, is the colour diagram

chosen for surfaces in a room. In general terms, light colours must be chosen to achieve high luminous efficiency for main

surface areas. A white surface will reflect around 80% of the incident light, a light colour about 50%, a medium colour

between 30% and 50%, and a dark colour less than 10%.

In order to achieve the best results, materials and colours must be selected under equal or similar light to the planned one

for the designed medium, apart from other factors of a subjective kind, climat, sex, age, colour surfaces which influence the

rest of the colours, etc.

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154 LIGHTING ENGINEERING 2002

10.6. Lighting design

Lighting is an art and a science. Therefore, there cannot be rigid or light rules regulating the design process. The basic purpose for a

good lighting design is to create a lighting installation which will provide a good visibility for the task and, at the same time, a satisfactory

visual environment.

The function of a space enormely influences the way in which lighting must be applied. Therefore, spatial visual requisites have to be

determined in the first place. Later on, and taken the results of these analysis as a basis, appropriate decisions for selection of lighting

systems, lamps and luminaires will be made.

In some cases, the lighting designer may choose the lighting system type; In other cases, architectural design and structural conditions

may dictate a particular type installation.

Indoor decoration and specially reflectances of the large surface rooms have a considerable influence in the lighting appearance.

However, the most important fact is to have the design process in mind, consisting in two well- differenciated stages. The first stage

begins with the client, and includes the study of different local factors which will influence the design. The second stage is the design

process itself, and, it is in this stage where the first decision out of many more regarding design is taken.

10.6.1. Luminance distribution on surfacesLuminance distribution within a field of vision is an extremely important criterion in lighting design. It must be considered as

complementary of indoor illuminance distribution.

For a given lighting level, differences in luminance may be due to differences in surface reflectance. Although illuminance

may be appropriate for the visual task, it will not necessarily provide an acceptable luminance balance in the indoor area.

Such a balance will depend on chosen reflectances for surfaces. Lighting in this regard may contribute to improve the poorest

situation, but the result will always be visually unsatisfactory. Therefore, luminance distribution must be considered as

supplementary in indoor lighting projects.

The following aspects must be carefully considered:

1. Luminance of the task and luminance of its surroundings.

2. Extreme values of wall and ceiling luminance.

3. Glare suppression, limiting luminaire and window luminances.

In Fig. 9, the scale of luminances for indoor lighting may be observed. This is a very important fact for luminance distribution.

Figure 9. Luminance scales for indoor lighting.

1

2

5

10

20

50

100

200

500

1000

2000

5000

10000

cd/m2

Permitted luminance for general lighting luminaires

Task preferred luminance

(Recommended luminance for paths)

Satisfactorilyperceptible

Barelyperceptible

Human face features

Flat ceiling and wall preferred luminance

Permitted luminance for luminaires in

VDU working places

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Luminance distribution for working areas If possible, luminances for the immediate surroundings of the task should be lower than luminances for the task, but,

preferably, not lower than 1/3 of this value. This implies that the ratio for the immediate background reflectance of a task to

the task itself should be in the 0.3 0.5 range. This constitutes a practical or useful requisite for offices, but its application

is difficult, and sometimes, even impossible. In most factories, the task is usually dark and the lighting designer may rarely

specify the background reflectance.

10.6.2. Light emission depreciation

Illuminance provided initially by a lighting installation will decrease in a gradual way during its use due to a reduction in lamp lumens, to

lamps which burn down, and to accumulation of dirtiness in lamps, luminaires and surfaces of the room. However, it is possible to main-

tain illuminance at or above the minimum permitted value (known as maintained value) cleaning the lighting equipment and the room

surfaces as well as replacing burned down or used up lamps at adequate intervals, according to a previously agreed maintenance pro-

gram.

The value for such maintenance program is indicated in Fig.10. Clearly for the case illustrated, illuminance in the non- maintained

system will decrease up to a 40% of the initial value within the first three years and it will continue to decrease. But with a yearly cle-

aning, relamping and paint changing every three years, illuminance reaches 60% of the initial value. In three years, the maintained

system provides an illuminance 50% greater than that of the system without maintenance.

Figure 10. Depreciation combined curves showing the cleaning and renovation effect

for an installation of fluorescent lamps.

Factors to be considered in indoor lighting depreciation

Dirtiness in lamps and luminaires

For the most part, light loss may be attributed to dirtiness accumulated in lamps and light control surfaces (reflected, refracted

or diffused) of luminaires.

Depreciation speed caused by dirtiness which accumulates on light control surfaces is affected by the tilt angle, finish, and

surface temperature, by the luminaire ventilation degree or tightness, as well as by the atmospheric pollution degree

surrounding the luminaire.

Depreciation in the emission of light may be reduced selecting appropriate luminaires for each place. Those luminaires with

open bases and closed surfaces accumulate dirtiness more quickly than those with ventilation. In ventilated luminaires,

convection currents take dust and dirtiness out through holes or slits in the canopy or reflector, and out of reflection surfaces.

In highly polluted environments, it is better to use sealed or dustproof luminaires. Some of them possess a filter inside which

Cleaning twice a year and relamping

Cleaning once a year and relamping

Cleaning twice a year and initial lamps

Cleaning once a year and initial lamps

1 2 3Number of years, supposing 3 000 hours working per year

1 000 2 000 3 000 4 000 5 000 6 000 7 000 8 000 9 000 Working hours

0

10

20

30

40

50

60

70

80

90

100

Ligh

ting

perc

enta

ge

Luminaires cleanedevery 12 months

Loss for lampdirtiness

Benefit for cleaningevery six months

Benefit for cleaningevery six months

Relamping also benefitial

Luminaires cleanedevery 12 months

55

Loss due to lamp deterioration

6265

70

6271

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156 LIGHTING ENGINEERING 2002

allows the necessary “breathing” to take place.

Dirtiness on the surfaces of the room

Dirtiness accummulated on ceilings (flat ceilings) and walls reduces their reflectance value and, thus, the amount of reflected

light. The connection between this and the calculation of illuminance will obviously depend on the size of the room under

study and on the luminaire light distribution. The effect will be more pronounced in small rooms or when there is luminaires

with an indirect component.

Depreciation of the lamp flux

Luminous performance of all lamps diminishes with use, but the speed of such diminution varies greatly according to

types of lamps and manufacturers. Hence, calculations for lighting must bear in mind specified depreciation of the

luminous performance of each lamp in particular.

It must be taken into account that data shown in figures are based on certain suppositions related to working

conditions. One or more of the following factors may influence the depreciation index:

- Room temperature.

- Lamp working position.

- Supplied voltage.

- Type of control equipment used, if relevant.

Lamp failure

Average life of a lamp depends on the type of lamp used and, for discharge lamps, on the ignition cycle. Failures in lamps

cause not only a reduction in illuminance levels, but also an inacceptable reduction in the lighting uniformity degree.

Maintenance factor (fm)

fm is defined as the ratio between illuminance produced by the lighting installation at a specified time, at the illuminance

produced by the installation itself when it is new.

fm, thus, combines losses caused by lamp depreciation flux, luminaire depreciation and depreciation of the room surface. If

each of these depreciation causes is quantified by a specific period of use, a general factor product of the three factors is

obtained.

fm = lamp flux loss factor x luminaire loss factor x room surface loss factor

When the light loss factor for different maintenance situations is calculated, it is possible to predict the illuminance situation

produced by the installation in relation to the time elapsed.

10.7. Indoor lighting calculations

10.7.1. Lighting levels and recommendationsBefore beginning lighting calculations, required values will be obtained for the type of activity to be developed in the premises

to be illuminated. Such values may be found at the end of the chapter and they are:

- Average illuminance in service.

- Glare limitation quality.

Beside these requirements, values for the dimensions of the premises are fundamental, the working plane height, as well as

the luminaire mounting contour height.

10.7.2. Index of premisesPremises to be illuminated are classified according to the relation that exists between their dimensions, mounting height and

type of lighting. This is called index of the premises and it serves the purpose of determining the utilization factor.

The utilization factor is calculated in the following way:

- For direct, semidirect, direct-indirect and general diffused luminaires:

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- For indirect and semi-indirect luminaires:

In both formulas:

A = Width of the premises (m.).

L = Length of the premises (m.).

h= Mounting height (m.). The distance between the luminaire down to the useful or working plane is considered.

The height of the premises, H, is the sum of the luminaire suspension contour height, C, plus the mounting height, h,

plus 0.85* m. to which the working plane is from the ground.

Since H and C are data previous to the installation, mounting height is calculated with the following formula:

h = H – C – 0.85 (m.)

10.7.3. Light loss or maintenance factor (fm)In general terms, maintenance factors shown in Chart 3 may be established, which are the result of the working environment.

This factor is obtained by multiplication of three factors (lamp flux depreciation, luminaire depreciation and depreciation of

room surface), as it had been commented previously.

Chart 3

10.7.4. Utilization factor or coefficient of utilization (fu)Utilization factor of a lighting system is the ratio between luminous flux which reaches the working plane and the total flux

emitted by the lamps installed.

This is a very important fact for the calculation of lighting and depends on a diversity of factors, like: adequate value of lighting

level, lighting system, luminaires, dimensions of premises, reflection (ceilings, walls and floor) and maintenance factor.

In general, the reflectances method is used for its determination. Currently, there are also many situations and tabulated

values according to each manufacturer and even computer programs for their users. When this factor is to be used, whether

it is multiplied or not by the luminaire performance () must be taken into account. This will later be used in the lighting

calculation formula.

* Distance at which the working plane is from the ground according to the Construction Technological Norm.

Working environment Fm

Steel fabrication, melting areas 0.65

Welding industries, mechanized 0.70

Industrial offices, rooms 0.75

Operation patios, public premises 0.80

Offices, comercial and computing offices 0.85

Ratio of premises = 3 . A . L

2 . h . (A + L)

Ratio of premises = A . L

h . (A + L)

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158 LIGHTING ENGINEERING 2002

10.7.5. Calculation process

Currently, this process is computerised (INDALWIN program). But in this section, the process to be followed to perform an indoor ligh-

ting project is going to be indicated. This will be done bearing in mind recommendations established by the C.I.E. as far as illuminan-

ces in service are concerned, direct glare quality limitation and colour rendering group (R or Ra) more highly recommended for a con-

crete installation (warehouses, offices, classrooms, etc.). The following steps must be followed:

1) Premises geometrical characteristics.

2) Reflection characteristics of different surfaces.

3) Obtaining required values for the type of activity to be developed in the premises (average illuminance in service,

glare limitation quality, R), of the C.I.E. charts.

4) Selection of the type of luminaire to be installed according to the characteristics of the premises, which will define

whether the luminaire is to be embedded, suspended or wall mounted.

5) Check that luminaires comply with the direct glare limitation quality.

6) Since an average level will be maintained in the installation, it is necessary to apply depreciation coefficients to initial

values. These have been previously seen.

7) When lighting calculation for premises is done using the utilization factor method, it is necessary to know luminaire

performance and utilization factor (for this reason, K value and ceiling, wall and floor reflections must be known).

8) Once all the data are known, the lighting fundamental formula is applied:

where:

Ems = Average lighting in service.

= Lamp unitary luminous flux.

N = Number of lamps (to be determined).

= Luminaire performance.

fu = Utilization factor.

fm = Maintenance factor.

S = Surface to be illuminated.

10.8. Some recommended lighting levels

Construction areas in general

Kind of area Illuminance in service Quality class

Circulation areas, corridors 100 D-E

Bathrooms, restrooms 100 C-D

Businesses, warehouses 100 D-E

Stairs, Escalators 150 C-D

Ems = . N . . fu . fm

S

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Assembly workshops

Plastic, rubber and chemical industries

Clothing

Electricity industry

Food manufacture

Kind of area Illuminance in service (lux) Quality class

Automatic process 200 D-E

General work areas 300 C-D

Craft decoration 500 A-B

Kind of area Illuminace in service (lux) Quality class

Cable manufacturing 1.300 B-C

Coil winding 1.500 A-B

Assembly of telephones, radios 1 000 A-B

Evaluation, adjustment 1 000 A-B

Assembly of high precission parts 1 500 A-B

electronic components

Kind of area Illuminace in service (lux) Quality class

Ironing 1.500 A-B

Sewing 1.750 A-B

Inspection 1 000 A-B

Kind of area Illuminace in service (lux) Quality class

Automatic processes 1.150 C-D

Interior plant general area 1.300 C-D

Control rooms, laboratories 1.500 C-D

Pharmaceutical manufacturing 1.500 C-D

Pneumatic manufacturing 1.500 C-D

Inspection 1.750 A-B

Colour combination 1 000 A-B

Kind of area Illuminance in service (lux) Quality classd

Rough work: heavy machinery 1.300 C-D

assembly

Medium work: vehicle body and 1.500 B-C

engine assembly

Fine work: office machinery and 1.750 A-B

electronics assembly

Very fine work: instrument 1 500 A-B

assembly

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160 LIGHTING ENGINEERING 2002

Smelting

Ceramics and glass

Metal manufacture

Leather works

Kind of area Illuminance in service (lux) Quality class

General work area 1.300 B-C

Pressing, cutting, sewing, 1.750 A-B

shoe manufacture

Classification, piling, quality 1 000 A-B

control

Kind of area Illuminance in service (lux) Quality class

Totally automatic 50 D-E

production plants

Semi-automatic 200 D-E

production plants

Work stations with permanent 300 D-E

staff in production plants

Control and inspection platforms 500 A-B

Kind of area Illuminace in service (lux) Quality class

Furnaces/furnace rooms 1.150 D-E

Mixing rooms, rooms for 1.300 C-D

formation, moulding and furnising

Finishing, enamelling and polishing 1.300 B-C

Polishing machine engraving 1.500 B-C

Polishing and manual engraving 1.750 A-C

Fine work 1 000 A-B

Kind of area Illuminance in service (lux) Quality class

Smelting areas 200 D-E

Preliminar workbench, preliminary

nucleus construction 300 C-D

Fine workbench, nucleus

construction, inspection 500 A-B

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Machine and tool shops

Painting works and spraying cabins

Paper factory

Printing works

Textile industries

Kind of area Illuminance in service (lux) Quality class

Carding, patterned cloths 1.300 D-E

Spinning, winding, dying 1.500 C-D

Twisting, weaving 1.750 A-B

Sewing, inspection 1 000 A-B

Kind of area Illuminance in service (lux) Quality class

Printing machine 1.500 C-D

Binding 1.500 A-B

Composing, correcting, 1.750 A-B

cutting, and enhancing rooms

Retouching, etching 1 000 A-B

Colour reproduction and printing 1 500 A-B

Copper and steel etching 2 000 A-B

Kind of area Illuminance in service (lux) Quality class

Automatic processses 200 D-E

Board and paper manufacture 300 C-D

Inspection, classification 500 A-B

Kind of area Illuminance in service (lux) Quality class

Washing, rough spraying 1.500 C-D

Ordinary spraying and painting 1.750 B-C

Fine painting, spraying and 1 000 A-B

finishing, retouching and mixing

Kind of area Illuminance in service (lux) Quality class

Small part cast 1.200 D-E

Preliminar workbench and machine 1.300 C-D

work, welding

Intermediate workbench and 1.500 B-C

machine work

Fine workbench and machine work, 1.750 A-B

inspection and verification

Fine work, complicated and small 1 500 A-B

part measurement and inspection

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162 LIGHTING ENGINEERING 2002

Woodwork shops

Offices

Schools

Shopping precincts

Kind of area Illuminance in sevice (lux) Quality class

Conventional shops 300 B-C

Self- service 500 B-C

Supermarkets, department stores 750 B-C

Kind of area Illuminance in service (lux) Quality class

Workshops, libraries, reading rooms 300 A-B

Classrooms, assembly halls, 500 A-B

laboratories, art rooms, sports halls

Kind of area Illuminance in service (lux) Quality class

Archives 1.200 C-D

Conference rooms 1.300 A-B

General offices, typing, 1.500 A-B

rooms where computer- related

activities are performed

Open and deep offices 1.750 A-B

Drawing offices 1 000 A-B

Kind of area Illuminance in service (lux) Quality class

Sawmills 1.200 D-E

Assembly bench work 1.300 C-D

Wood machining 1.500 B-C

Finishing 1.750 A-B

Final inspection, quality control 1 000 A-B

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Public edifices

Houses

Hotels and restaurants

Kind of area Illuminance in service (lux) Quality class

Dining rooms 200 B-C

Bedrooms and bathrooms in 100 B-C

general

Bedrooms and private bathrooms 300 B-C

Entrance lobbies and conference 300 B-C

halls in general

Kitchens 500 B-C

Kind of area Illuminance in service (lux) Quality class

Bedrooms in general 50 B-C

Head of bedroom 200 B-C

Bathroom in general 100 B-C

Place to shave and make up in 500 B-C

the bathroom

House in general 100 B-C

Place to sew and read 500 B-C

Stairs 100 B-C

Kitchen in general 300 B-C

Kitchen’s work area 500 B-C

Desk 300 B-C

Children’s room 100 B-C

Kind of area Illuminance in service (lux) Quality class

Cinema auditorium 50 B-C

Cinema foyer 150 B-C

Theater and concert hall auditoria 100 B-C

Theater and concert hall foyers 200 B-C

Light- sensitive exhibits in museums 150 B-C

and art galleries

Exhibits insensitive to light in museums 300 B-C

and art galleries

Church naves 100 B-C

Chancel, sanctuary and platform 300 B-C

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164 LIGHTING ENGINEERING 2002

Hospitals

Kind of area Illuminance in service (lux) Quality class

Ward corridors at night 000.050 A-B

Ward corridors during the 000.200 A-B

night/afternoon

Wards’ general lighting 000.150 A-B

Lighting in examination rooms 000.500 A-B

General lighting in local 001 000 A-B

examination rooms

Intensive care and observation 000.750 A-B

Nurses’ stations 000.300 A-B

Pre- operation rooms 000.500 A-B

General lighting in 1 000 A-B

operating rooms

Local lighting in operating 100 000 A-B

rooms

General lighting in post- mortem 000.750 A-B

rooms

Local lighting in post- mortem 005 000 A-B

rooms

General lighting of laboratories 000.750 A-B

and pharmacies

Local lighting of laboratories 001 000 A-B

and pharmacies

General lighting in 000.500 A-B

consulting rooms

Local lighting in 000.750 A-B

consulting rooms

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165LIGHTING ENGINEERING 2002

Chapter 11.

FLOODLIGHTING

11.1 General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

11.2 Utilitarian lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

11.3 Amenity lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

11.4 Sports lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

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11.1. General remarks The Committee for International Lighting (C.I.E.) defines floodlighting as: lighting of a place (scene, area) or of an object by means

of floodlights in order to increase lighting strongly in relation to their surroundings.

There is a great number of totally different application fields and lighting systems to which the term “floodlighting” is frequently applied

(also the term directed lighting is used). The common technique to all floodlighting installations consists in the use of floodlights to

obtain an increase in surface illuminance with regards to its surroundings.

This important branch of lighting technique is probably the most widely linked to the development of countries and is having a

generalized and important increase.

The scale of applications open to floodlighting with amenity and utilitarian purposes is wide and varied. However, the most important

ones are listed below:

- Utilitarian lighting (large working areas).

- Amenity lighting (buildings, monuments, bridges, parks and gardens).

- Sports lighting.

For each case, floodlighting is a problem to be solved individually. Sometimes, very narrow beams will be necessary, with a great

intensity in candelas to reach areas or objects located at great distances. Some other times, certain opening angles will be required to

achieve good uniformity in the lighting of the zone or field, adjusting the floodlight to its geometrical limits as much as possible.

If the enormous variety presented by the three most important variables intervening in all cases is added (type of area, geometrical

situation of lighting equipments and conditions of the environment or surroundings), it may be easily deduced that it is virtually

impossible to establish a norm. Only for most cases of sports lighting (measure unification, rules of the game, etc.) it is possible to

establish general norms, even though there are several variables.

Therefore, to help the specialist who is going to design the lighting installation project, only the most important basic rules,

recommendations, charts or data to bear in mind may be provided, always taking into account the specialist’s criterion in order to

supply deficiencies.

Data collectionIt is the fundamental base to make ulterior decisions. The more data, the better, as far as planes, observations, possibility of locations,

lighting hours, dirtiness acummulation prediction, surroundings of the area, streets, crossings, roads or nearby roads, power supply

systems, estimate possibilities, etc. is concerned.

- Lighting hours, needs in peak hours, glares, favourable contrasts, atmospheric conditions, etc. must be carefully considered in security,

protection or production lighting.

- Possible colour effects, shadows and contrasts, floodlight angles, surface reflectance, brightness of the surroundings, etc., must not

be forgotten in decorative or architectonic lighting.

- Possible vertical lighting exigencies, avoidance of shadows and glares to users or the audience, contrasts and game features or class

(competition, club, training, leisure, etc.) will be preferably considered in sports lighting.

Illuminance determinationIn case it is not provided, the recommendable level must be fixed bearing in mind all particularities and with the help of the charts

present throughout this chapter and at the end of it.

But not only the minimum luminous level for a correct perception of the object must be taken into account (always eased by the

extraordinary eye adaptation capacity), but also the slightest visual fatigue of people subjected to the action of artificial lighting for long

periods of time must also be avoided. Thus, accidents or a decrease of faculties may be avoided.

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11.2. Utilitarian lighting This lighting system is integrated by those cases in which floodlighting is necessary because of security, protection or production

purposes, constituting the only logic system to perform lighting. Many large areas, for example road intersections, ports, classification

areas in railways, construction areas, storage areas, container complexes, etc., are illuminated using floodlighting with high columns.

Lighting with high columns is preferred, mainly due to the fewer number of lighting columns used. This factor contributes to mobility

in the illuminated area.

Generally speaking, the high column system supposes a saving in expenses if compared to a system which uses lower columns. The

saving is mainly in the total cost of columns, lamps, luminaires and cables, although there is also a reduction in maintenance expenses.

General remarks

Column height

In order to calculate the column (tower or post) height in which floodlights will be mounted, avoiding a direct glare, the

abacus in Fig. 2 will be used. It is important the fact that with excessive heights, the price of columns increases considerably.

However, if heights are lower, the number of columns, lamps and luminaires increases very much. Also, if there are relatively

high constructions in different positions within the area, mounting heights lower than those shown in the abacus must be

used in order to avoid strong shadows projected on the area. When the emphasis lies in saving space and in the flexibility

of use of the area, the columns used must be higher than those of the abacus, since an increase in height also increases

the allowed space, and, the number of obstructions in the form of columns decreases, too.

Figure 1

Figure 2

6 m.9 m.

12 m.15 m.

18 m.21 m.

24 m.27 m.

30 m.

33 m.

36 m.

39 m.

42 m.

45 m.

48 m.

51 m.

54 m.

57 m.

60 m.

MOUNTING HEIGHT

TOTAL WIDTH OF THE SURFACE TO BE ILLUMINATED

DIST

ANCE

FRO

M T

HE C

OLUM

NS TO

THE

EDG

E OF

THE

ARE

A TO

BE

ILLU

MIN

ATED

MOU

NTIN

G HE

IGHT

0 m.60 m.

54 m.

48 m.

42 m.

36 m.

30 m.

24 m.

18 m.

12 m.

6 m.

0 m.

20 m. 40 m. 60 m. 80 m. 100 m. 120 m. 140 m.

D

Mounting height will be at least H=D/4

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Lighting levels

At least the level required in the horizontal plane (horizontal illuminance) must be defined. Sometimes also vertical

illuminance must be controlled (for example, where reading tasks take place, goods are inspected or moved).

The necessary lighting levels and uniformities depend on the difficulty of the visual task, on the one hand, and on the degree

of efficiency and security required, on the other hand. In Chart 1 level and uniformity requirements for different categories

of areas are indicated.

Chart 1. Recommended illuminances and uniformities for outdoor working areas.

Glare

The degree of glare limit required depends, of course, on the category of the area under study (C.I.E.: Glare evaluation

system for and outdoor sports area lighting).

In general, discomforting glare will be reduced with an increase in the mounting height. Choosing floodlights well and having

special care when pointing them may also help to maintain glare to the minimum. Sometimes, when glare is critical, special

lattices must be placed on luminaires.

Lamps

High intensity discharge lamps are recommended as appropriate for area floodlighting. The most frequently used lamps are

high pressure sodium discharge lamps, and metal halide ones. Even though when colour discrimination is not necessary and

lighting levels are not excessively high, low pressure sodium discharge lamp offers a good solution.

Visual task and Example Horizontal illuminance Uniformity factor

category recommended

maintained average (lux)

Security

Low risk areas Industrial storage areas; 5 1:7

occasional transit only

Medium risk areas Vehicle storage areas, 20 1:4

containerterminals with

frequent transit

High risk areas Critical areas in petrochemical 50 1:2.5

works, chemical electricity

and gas plants

Movement and transit

Pedestrians Only people movement 5 1:7

Slow moving vehicles Load/ unload trucks and/ or 10 1:4

bicycles

Normal transit Public lighting in container 20 1:2.5

terminals, manouver areas

General work

Very rough Excavation, clearance 20 1:4

Rough Woodwork 50 1:4

Regular Masonery, woodwork 100 1:2.5

Fine Painting, electric works 200 1:2

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11.3. Amenity lighting This lighting system is used when an advertisement, a facade, a building, artistic fountain or monument, etc. is to be illuminated due

to purely decorative reasons, with the idea of attracting people's attention, embellishing an area or expressing civic proud, sometimes

even used as an advertising way.

In these instances, lighting belongs to the architectural vocabulary, being an art in which brightness, lights, shadows, colours and

contrasts are manipulated.

11.3.1. Design general considerations During day- time hours, a building is illuminated by direct sunlight, diffused light radiated from the sky or both. The result is

that the architectural characteristics of the building are highlighted by a varied show of lights and shadows. The design of a

good lighting installation through floodlighting requires a careful study of the most attractive characteristics of the building

and the effects of light on them. Therefore, the techniques to illuminate a building through floodlighting are not based on

lighting engineering, because feelings and understanding of aesthetical values are equally important.

Observation direction

Normally, there are several directions from which a building may be observed, but, in general, one direction in particular may

be considered as the main observation direction.

Observation distance

Observation distance is important since it determines the number of visible details on the structure to be illuminated.

Surroundings and background

If the surroundings and the background of a structure are dark, a relatively small quantity of light is necessary for the structure

to be highlighted against the background. If there are other buildings illuminated through floodlighting in the surroundings,

or buildings with illuminated windows, or a background with brightness, this will give a strong impression of luminance. Then,

more light for floodlighting to produce the desired impact will be necessary. Another solution may be to create colour

contrasts, instead of luminance differences.

Obstacles

Trees and railings surrounding a building may form a decorative element of the installation. An attractive way of doing so is

by placing the sources of light in front of them. This has two advantages: first, the sources of light are invisible for the observer

and, second, trees and railings are seen as silhouettes against the illuminated background of the facade, increasing the

feeling of depth.

Position and direction of floodlights

Once the main line of observation has been chosen, the installation and focusing of floodlights will depend on the shape

of the building or, better, on its ground plan or horizontal cross- section. Experience indicates that the best placing of

floodlights in a building with a rectangular ground plan is the one indicated in Fig. 3. The main observation line is indicated

by the arrow A and the position of floodlights by the points marked as B. Placing floodlights in the two extremes of the

diagonal, a good luminance contrast between the two neighbouring sides of the building is achieved, and also a good

perspective. Oblique beams of floodlights highlight the texture of materials forming the facade. As observed in Fig. 3, this

installation for rectangular buildings is also applicable to those of a square ground plan.

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Figure 3

Also projecting elements (like balconies), walls or balustrades may enrich the appearance of a facade and must be taken

into account, if included in the lighting structure. In this case, floodlights must be placed at a certain distance from the facade,

in order to avoid excessively strong shadows. If there is not enough space for this, small floodlights placed on the projection

itself may be used as complementary lighting (Fig. 4).

Recess or concave elements like galleries or balconies will remain in the shadow when placing floodlights at a short distance

from the facade. In these situations, complementary lighting placed on the recess parts themselves may be used. Light of

another colour may be appropriate for this purpose. Lighting through floodlighting placed at a greater distance produces less

shadows and eliminates the need for additional lighting.

Figura 4

Some of the many alternatives to place luminous sources are: on public lighting posts or on posts specifically placed for this

purpose; on the roof of a neighbouring building; on supports fixed to the facade itself or on the ground, behind low walls,

bushes or hedges.

Recommended lighting levels

In order to determine the necessary level of illuminance to provide a structure with the required visual impact, factors such

as brightness of the surroundings and background, material used in the construction, etc. must be taken into account. Three

d

d

Supplementary local lighting to reduce shadow intensityChange in the height of the shadowproduced by variation ofdistance "d"

A A

A

BB

A

B

B

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points are important:

1) The darker the material, the higher the illuminance necessary to provide an impression of satisfactory brightness on it.

2) For a normal installation in which light is directed upwards on a vertical surface, the amount of light reflected that reaches

an observer, and, therefore, brightness of the surface illuminated, will decrease with the increase of surface uniformity.

3) The necessary illuminance will be influenced by the combination degree between the spectrum of the source of light

used and the colour of the construction material to a certain extent. Favourable solutions are obtained when the colour of

the light is close to that of the illuminated surface. In Chart 2 elaborated bearing in mind those three points, recommended

illuminances for lighting through floodlighting are shown.

Chart 2

Recommended lighting levels are those necessary to create a luminance of 4, 6 or 12 cd/m2 on the facade when the

surroundings are poorly illuminated, well illuminated or with a lot of brightness, respectively. Values are valid for lamps with

RECOMMENDED LIGHTING LEVELSIlluminance in Lux Correction coefficients

Facade material Poor Good Very good M S Clean Dirty

Light-coloured stone 20 30 60 1.0 0.9 3.0 5.0white marbleMedium-coloured stone 40 60 120 1.1 1.0 2.5 5.0CementLight-coloured marbleDark-coloured stone 100 150 300 1.0 1.1 2.0 3.0Grey graniteDark marbleLight yellow brick 35 50 100 1.2 0.9 2.5 5.0Light brown brick 40 60 120 1.2 0.9 2.0 4.0Dark brown brick 55 80 160 1.3 1.0 2.0 4.0Pink graniteRed brick 100 150 300 1.3 1.0 2.0 3.0Dark brick 120 180 360 1.3 1.2 1.5 2.0Architectonic detail 60 100 200 1.3 1.2 1.5 2.0Aluminium coating: 200 300 600 1.2 1.1 1.5 2.0natural finishSaturated lacquer thermicfinish (10%) 120 180 360 1.3 1.1 1.5 2.0red, brown, yellowSaturated lacquer thermicfinish (10%) 120 180 360 1.0 1.3 1.5 2.0blue, greenMedium lacquer thermicfinish (30-40%) 40 60 120 1.2 1.0 2.0 4.0red, brown, yellowMedium lacquer thermicfinish (30-40%) 40 60 120 1.0 1.2 2.0 4.0 blue, greenPastel lacquer thermic 20 30 60 1.1 1.0 3.0 5.0finish (60-70%), red, brown, yellowPastel lacquer thermic 20 30 60 1.0 1.1 3.0 5.0finish (60-70%), blue, green

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a wolfram filament of 2 800 K and clean surfaces of buildings . Correction coefficients shown are multiplying.

11.3.2. Lighting of buildings The convenience that a building is illuminated through floodlighting is determined by several factors, including the shape

and surfaces of the building, its features (which may be difficult to define), its architectural merit, its historical or social

meaning and its surroundings.

The appearance of a surface illuminated through floodlighting depends, among other factors, on its texture. Rough surfaces

reflect some light in all directions and, thus, when it is illuminated, it appears more or less bright independent from the angle

from which it is being observed. Moreover, glasses and other very polished surfaces, reflect all the incident light on them as

a mirror. Due to this reason, they appear as dark and lifeless when illuminated and seen from normal positions (Figs. 5, 6,

7 and 8).

Figure 5. Specular reflection (bright, polished surfaces, etc.).

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Figure 6. Composed reflection (irregular, rough surfaces, etc.).

Figure 7. Mixed reflection (barnished, non- polished surfaces, etc.).

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Figure 8. Diffused reflection (matte surfaces, etc.).

It is obvious that these differences in the reflection properties of the surface of the material makes necessary a different

lighting for each facade to obtain the desired luminosity in each case. Even the amount of dirtiness on the facade is

important; the reflection factor of a clean facade may be more than twice that of the same dirty facade.

The surroundings have a powerful influence in the effect produced by the buildings illuminated through floodlighting. For

example, if there is a lake, river, channel, etc. near the building, this will be highlighted when its reflections are projected in

water.

Cathedrals, churches, castles, public buildings, bridges and old monuments are examples of buildings which generally

respond well to floodlighting; some industrial and commercial buildings may be illuminated through floodlighting as an

advantage for themselves and for their surroundings.

Design basic conditions

Apart from the ideas exposed before in "design general conditions", the following comments are generally applied to lighting

design through floodlighting. The relevant aspects of each comment varies with the type of building and lighting requisites.

a) Lighting contrasts are generally more important than their homogeneity, and shadows are as important as light

reflexes.

b) Lighting through coloured floodlighting allows the highlighting of different planes and the production of

coloured shadows. As a general rule, colour should be used moderately and discreetely.

c) The aspect of a building illuminated through floodlighting and specially that modelled with shadows, differs

quite a lot from its appearance during daylight, mainly because the direction and distribution of light are different.

This also changes with the direction of observation, and especially with the change of angle between the direction

of observation and the direction of the main light flux.

d) As commented before, the visual impact of a building illuminated through floodlighting depends considerably

on the brightness of the surroundings; the darker the background, the more dramatic the effect and the less the

amount of light necessary to highlight the building.

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e) The form of a building illuminated through floodlighting is best highlighted when its contours are visible, its

solidity is emphasized, and the corners are emphasized too, by illuminating the neighbouring walls with a

different luminance. The shape of a building with a non- peaked roof is evidently complete when both, roof and

wall, are illuminated through floodlighting.

f) The “solidity” of towers, domes and column heads is emphasized if illuminated through floodlighting from no

more than three directions in azimuth.

g) A good pronounced modelling is always desirable, but it does not make sense to highlight small details on flat

facades when the building is seen from a certain distance.

h) Height is more pronounced if building lighting is reduced progressively from its base upwards. If the lowest

parts of a building are hidden from observation at a certain distance by the structures of the surroundings, maybe

it will be convenient to reduce brightness in the opposed direction, for example, towards the ground.

Lighting of contemporary design buildings

New materials and building methods have played an important role in the development of a distinctive style of contemporary

buildings. For example, external and internal walls of modern buildings with a steel structure are not load- bearing walls and,

therefore, they may be made of light materials and be pre- manufactured before installation; structures of reinforced

concrete, some with roofs of 40 meters or more in height, are another typical element of the contemporary landscape.

On condition that the structure is adequate, lighting through floodlighting may be used to emphasize social and architectural

meaning of many civilian, commercial and educative buildings recently built. Maybe, it will also be propaganda for the

products of the company which owns or rents the building. For example, in Fig. 9 an office building may be seen. It has a

pre- manufactured reinforced concrete facade which was built for a company which manufactures concrete; lighting through

floodlighting strongly reveals the forms of the material.

Figure 9

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11.3.3. Monuments Monuments should be illuminated through floodlighting in a way that indicates their style, age and their historical meaning

wherever possible.

Floodlights for monument lighting are similar to those for historical buildings in general. The effects of erosion and, if ceilings

and walls have been destroyed or partially destroyed, should be reported. Lighting should be designed to achieve an effect

without and apparent cause (Fig. 10).

Figure 10

Floodlights for lighting of castles in ruins and similar monuments should be designed to emphasize the compact character

of their structures and reveal the shape of their towers and other prominent elements (Fig. 11).

Figure 11

The historical importance of a monument may be indicated by coloured light. For example, blue light may be used to create

a mysterious atmosphere, and red light to indicate the scene of a battle.

The splendour and magnificence of a monument may be manifested to the maximum only by means of a close and

continuous cooperation between the architect of the project, the lighting engineer and, wherever appropriate, the

archeologist, whose main interest is the preservation of the monument. The lighting equipment should not be attached to

the structure of the building unless a special permission has been granted.

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11.3.4. Bridges and viaducts In general, bridges are attractive elements and, when conveniently illuminated, they contribute to improve night- time

landscape (Fig.12). There are too many types of bridges. Discussing lighting of each and every one of them individually is

impossible, but the following criteria are applicable from a general point of view:

Figure 12

- The shape and main elements of the bridge must be visible from a considerable distance. Most of the times it is desirable

for bridges on roads to include accesses in the lighting project so that it is seen as a part of the road and not as an isolated

element of the complex. Amenity lighting luminaires for roadway lighting should be treated as part of the lighting design.

- The convenience for a bridge to be illuminated through floodlighting depends on the surroundings, the main directions and

the observation distances, the importance of the structure and architecture of the bridge, its importance in the night- time

decoration, and the materials with which it has been built.

- Stone and reinforced concrete bridges generally respond well to lighting through floodlighting, but it may be difficult to show

the shape and details in iron and steel bridges this way, due to the low reflectance and the small area projected of the

members of the structure. However, other methods may be used. For example, lighting with ornamental lights, lamps

supported by cables and chain, have been used in some hanging bridges with satisfaction, but an effective maintenance may

be difficult.

- Lighting should not distract attention from traffic (motorized, highway or maritime traffic) which goes under or above the

bridge. If coloured lighting is used, a special care must be taken to avoid confusion with traffic signals.

- Illuminance necessary to show the effective shape of the bridge will mainly depend on the type of bridge, its surroundings

(including district lighting) and reflectance of the building materials. When the lighting system and location of floodlights has

been decided, its type, number and voltage may be estimated using the INDALWIN calculation program. After the lighting

system has been installed, the effects must be valued from a critical point of view, and adjustments must be done in situ.

- The sides of a stone bridge or similar crossing a valley, a clearing or a river may be usually illuminated through mounted

asymmetric rectangular floodlights in one or both banks. If light is directed from one of the sides mainly, the arches, wring

walls, counterforts and balustrades will be emphasized through coherent shadows which will be formed.

However, this system is not likely to be applied if the bridge is very long. Preferably, floodlights should be mounted under the

bridge platform to minimize glare for traffic and pedestrians going over or under the bridge (Fig. 13). Floodlights that,must be

mounted over the bridge height due to practical reasons should be conveniently oriented so that glare is restricted as much

as possible. This type of bridges may be illuminated also through luminaires mounted on the bridge or near it and hidden

from the normal observation angles or by a continuous row of waterproof fluorescent luminaires mounted on the railing.

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The latter system may be applied for the lighting of pedestrian bridge by using luminaires which direct part of the light to

the sidewalk and part to the sides of the bridge. Often, the appearance of an arched bridge is improved if the lower part of

the arches is illuminated, preferably with a different colour of light to the one used on the sides of the bridge. A very dramatic

effect is produced leaving the sides without lighting (in the dark). It is difficult to delineate cables and chains of hanging

bridges except for festive lighting, but their support towers may be generally illuminated by floodlights with a great advantage,

using circular symmetrical floodlights with a narrow beam, mounted in the bridge or next to it and aiming upwards. Lighting

of the zone of the bridge for motorized traffic is normally done with public lighting luminaires.

Figure 13

11.3.5. Lighting of entertaining and leisure areas Night- time lighting of public parks and gardens is essential for security purposes, especially of children, and increases the

time during which leisure elements may be used. Lighting shows the beauty of flowered gardens, trees, bushes and

fountains or lakes. Another objective is that of lighting dark areas.

Trees and bushes: During the day, a tree is generally seen as a silhouette against a bright sky. If the tree is illuminated during

the night, the situation is the opposite: the tree clearly protrudes against the dark sky. This dramatic effect is highlighted if

the sources of light are hidden.

Figure 14

Luminaires may illuminate the foliage from a certain distance or be located next to the trunk lighting its branches from the

ground upwards (Fig. 14). The first technique is appropriated for trees with a dense foliage, whereas the other type of

focusing is appropriate for light foliage trees. Beautiful effects may be achieved using different coloured lights (Fig. 15).

Tree lighting

sideways from below

Asymmetric floodlight Asymmetric floodlight

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Figure 15

If a superior frontal or vertical lighting is not desired or it is not applicable, flowered trees or with naked branches may be

projected against a white or light coloured wall, fence or railing. Another subtle effect more interesting than frontal lighting

from a visual point of vie, may be obtained by illuminating trees and bushes from behind.

But in most cases, floodlights should be placed between the public and the objects to be illuminated. Glare may be avoided

placing screens on floodlights, even though most gardens have many places to hide them, such as bushes, tree trunks or

stumps, rocks, fences, small walls, etc. Alternatively, floodlights may be embedded in the ground (in this case, drainage

possibility must be born in mind).

In general, it is neither economical nor practical to illuminate but a few trees in the park; and due to aesthetical reasons,

uniform lighting of the totality of an area through floodlighting is satisfactory very few times. The trees chosen should be

important and beautiful species and placed in positions where depth and subtlety are given to the scenery.

11.4. Sports lighting

11.4.1. General remarksThe goal of lighting indoor or outdoor sports facilities is to offer an adequate environment to practice and enjoy sport events both on

the part of the spectators and the players. From a logical point of view, needs will vary according to installation types (recreation,

entertainment or competition) and activity level (amateur, professional or television broadcasting).

11.4.1.1. Basic requisitesWhen designing sports facilities ligthing, requisites and comfort of the following users must be taken into account: sportmen

or players, judges or referees, spectators and broadcasting and mass media.

Players and referees

Players (sportmen) and referees (judges) must be able to observe clearly everything that is hapenning on the playfield to

so that the sport event takes place in the best possible circumstances.

Spectators

Spectators must be able to follow the player’s activity and the sport action making the least effort. The surrounding

environment must be comfortable, which means that not only must the playfield or court be seen, but also the immediate

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surroundings. Lighting must help the spectator to enter and exit the sport installation security. This security issue is also very

important for players.

T.V. broadcasting

For T.V. broadcasting, lighting must provide conditions that will secure a good quality colour image (Publication C.I.E. nº 83),

both for general images of the play and close- ups of spectators and players.

Transmission continuity

In order to comply with T.V. transmission continuity, requirements in case of failure of the normal lighting system, a secondary

system is generally installed to provide an “emergency T.V. lighting”.

11.4.1.2. Lighting criteriaThe most important lighting criteria for sports lighting are the following ones.

Horizontal illuminance

The illuminated area where the sport activity is taking place is the main part of the visual field of sportmen and spectators.

Therefore, horizontal plane illuminance at ground level serves the purpose of establishing visual adaptation. Due to this fact,

and also to the playfield area being used as a visual background, it is very important that there is an adequate horizontal

plane illuminancce to achieve the correct contrast against the background.

Horizontal illuminance is also very relevant in circulation areas, like anti- panic ligthing, used in case there is a failure of the

normal lighting system to secure spectators´ movement in and out of the sports field.

Recommended average illuminances in Chart 4 are maintained values. That is to say, they are values that must be reached

during an installation operation period. For the required initial values, maintained values must be multiplied by the inverse

of the maintenance factor (fm).

Vertical Illuminance

Enough contrast must exist for the player´s body to be identified. This is only obtained if vertical planes are well illuminated,

since this kind of illuminance is essential to recognize objects.

Vertical illuminance is characterized by magnitude and direction. For players, a vertical illuminance is important from all

positions. However, for spectators and cameras occupying a certain position, vertical illuminance must only be considered

for such positions. For cameras with different positions, vertical illuminance on the four lateral planes of the field must be

taken into account.

In practice, vertical illuminance required for players and spectators is automatically obtained if horizontal illuminance

requisites are observed. Therefore, from a practical point of view, vertical illuminance which must be measured at a 1.5

metre height over the playfield, is only a design criterion when considering T.V. transmission continuity, since it plays a major

influence on image quality.

Vertical illuminance must guarantee not only a player´s recognition or image quality but also the fact that spectators and

players are easily able to follow a ball, a ring, etc. that are flying over the playfield.

Spectators and tribunes are part of the camera visual medium. Therefore, an adequate vertical illuminance must also be

created for tribunes.

Illuminance uniformity

A good vertical and horizontal illuminance uniformity in horizontal and vertical planes is important. It avoids adaptation

problems for players and spectators and it eliminates the need for continuous adjustment of cameras in different visual

directions. If uniformity is not good enough, there is the possibility (especially with television cameras) that a ball or player

will not clearly be seen in certain positions in the field.

Uniformity may be expressed as the ratio between minimum illuminance and maximum illuminance (U1) or as the ratio

between minimum illuminance and average illuminance (U2).

In order for cameras to obtain the best possible visual conditions, the ratio between average illuminance on the horizontal

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plane and average illuminance on the vertical one must be kept between 0.5 and 2 in general.

Glare

Glare occurs whenever a discomfort bright area approaches or enters the visual field, producing a disturbing effect for players

and spectators.

Glare may be minimised paying careful attention to floodlight or luminaire choice. We must also make sure that they are

carefully focused, taking into account the main visual directions.

Evaluation of glare

The C.I.E. has developed a basis to evaluate the subjective impression of glare in outdoor areas.

Essentially, it includes a glare index in which the lower the reaching is also, the lower the glare. Glare Rating (GR) is obtained

this way:

where:

Lvl = veiling luminance produced by luminaires.

where Eeye,i is the eye illuminance produced by the source of light (lux) i, and i is the angle between the direction of vision

and the direction of incident light from the source of light i (degrees).

Lve = veiling luminance produced by the medium.

Lve may be approached from the horizontal average illuminance where the sports event is taking place, Ehav, using the

following formula:

where p = the area reflectance.

For Lvl the sources of light are luminaires, whereas for Lve the field and luminous surroundings are considered as an infinite

number of small light sources.

It is necessary to calculate GR for the observer´s most critical positions, defined in Fig. 16. for a football playfield.

Lve = 0.035 . Ehav. p

Lvl =Ε eyej

Φi2

LvlLve

GR = 27 + 24 . logEE R 0,9R

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Figure 16

Nowadays, international sport associations are introducing their own GR norms and veiling luminance.

External glare

In past times, glare was only taken into account for players and spectators who were in the illuminated area or very close to

it. Nevertheless, in case of outdoor lighting sports, the disperse light of the installation may bother spectators who are outside

the playfield: for example, for traffic on adjacent roads or for those people who live in the surroudings.

Currently, the C.I.E. is studying a direct parameter to quantify such disturbance, which is directly related to the optical quality

of the floodlights used. This means that in order to avoid this inconvenience, floodlights must be chosen taking into account

the limitation of the disperse light outside the main beam. They must be focused and mounted in an adequate manner.

Recommendations

Although glare ratio, or GR, is not specified in the recommendation sections, it is highly important for all sports lighting

installations. It must coincide with the GR values established in the Publication C.I.E. n 83.

The calculated GR value depends partially on the reflectance area where the sports activity is taking place. For grass courts,

a diffused reflectance of about 0.15 to 0.25 is generally presupposed.

The GR value must be determined for the observer´s positions of such a sport, at a height of 1.5 metres over the area where

the sports activity is taking place. The observer must see all points at ground level. For an outdoor installation, the effect of

disperse light outside the precinct at a distance of 300 metres from the centre of the area must be calculated. This means

that veiling luminance must be calculated at a 1.5 metre height over the ground for the five most extreme positions.

Modelling and shadows

Modulate is the lighting capability to reveal forms and textures. This is particularly important to provide a general vision of sportmen,

300 m.

1

2 8 9

10

3

1/4 B

1/2 B

1B

4

5

6 11

7

300 m. 300 m.

300 m. 300 m.

1/4

A1/

4 A

1/2

A

1A

• 1-11 Observer´s position for GR calculations• Reference positions to calculate veiling luminance

outside the playfield area

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players, ball or other elements and spectators who are in the area where the sports activity is taking place or near it.

The efficacy of modelling depends on directions from which light sources come from as well as on the number and type of sources

used in it. Modelling may be “hard”, produced by means of deep shadows, for example, using floodlights with a narrow and simple

beam; or “soft”, resulting from lighting without shadows from a luminous ceiling, for example. None of these extremes is advisable.

However, for the latter case, it is possible to add some small floodlights to improve modulate.

Good quality television images require a good modulate for lighting. This is the reason why up to 60% of the installed total flux may

come from the side of the main camera, and 40% or even more, from the opposite side, in order to limit length and hardness of

projected shadows for sportment where an asymmetric arrangement of floodlights is used.

Colour appearance and reproduction

A good colour perception is important in most sports, and, although some distortion due to artificial light is accepted, it must

not be so much as to produce colour discrimination problems (between partially distorted colours).

Two important aspects related to colour must be distinguished.

- Light colour appearance: It is the colour impression in all the medium created by the lamp.

- Light colour reproduction: It is the ability of light to reproduce colours of objects.

Both colour appearance and colour reproduction of the light emitted by lamps depend on the distribution of spectral energy

of theemitted light. One indication of the colour appearance of a lamp may be obtained from its colour correlative

temperature, measured in Kelvin (K), which varies between 2 000 and 6 000 K. If colour temperature is lower, light colour

impression will be warmer. The higher colour temperature, the colder or more bluish light colour impression.

Colour reproduction properties of a luminous source may be indicated by the colour reproduction index (R). The maximum

theoretical value of the colour reproduction index is 100, which may be compared with daylight. The visual characteristics

of the surroundings depend on the R. The higher the R, the more comfortable the environment.

11.4.2. Design considerations

11.4.2.1. Luminaire type

Floodlights

Floodlights are classified according to their light distribution:

Circular floodlights (Fig. 17)

There are two types of circular floodlights used in sports floodlighting:

a) With a symmetric beam in a conical shape. They may have a narrow beam or a wide beam.

b) With a slightly asymmetric beam on the vertical plane. They may have a narrow, medium, wide and very wide beam.

Figure 17. Circular floodlights.

Rectangular floodlights (Fig. 18).

There are two types:

a) With asymmetric distribution of light on horizontal and vertical planes. The beam is wide on the horizontal plane, whereas,

it may be wide or narrow on the vertical plane.

b) With symmetric distribution of light on the horizontal plane and asymmetric distribution of light on the vertical plane. The

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horizontal beam is wide.

Figure 18. Rectangular floodlights.

Circular floodlights require the use of a source of light more or less narrow, such as a short discharge tube of a high intensity

discharge lamp. When it is not focused downwards from a vertical point of view, the conical beam emits an elliptical or

almost elliptical light modelling over the field (Fig. 17).

Rectangular floodlights are used together with their linear sources such as tubular discharge lamps and halogene ones. A

fan- shaped beam produces a very trapezoidal model of light on the sports area where the activity is practiced (Fig. 18).

Figure 19. Lateral disposition.

When rectangular floodlights are mounted in a not very separate way on the sides of a sports area (normal disposition for a small

area) two advantages are met if compared to the circular unit: light distribution is more uniform and light loss is less (Fig. 19). However,

the circular floodlight is more efficient than the rectangular unit when used in the four corners, diagonal disposition (Fig. 20), whenever

several units per column are used.

Figure 20. Diagonal disposition.

For all types of symmetric rectangular floodlights, a special shielding device or louver may be used, on condition that the floodlight is

focused towards a direction producing glare. Such floodlights are designed in such a way that their maximum intensity is not

in the centre of the beam, but towards one side. Luminous intensity diminution on each side of the axis beam is placed in

such a way that when it focus a certain point on the surface, a more or less uniform horizontal illuminance is produced.

In order to limit glare, intensities decrease rapidly from a certain light incident angle, making light distribution even more

asymmetric.

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When glare may produce important discomfort to people outside the area where the sports activity is practiced, luminous

intensities outside the current beam must be the lowest possible. For this application, a floodlight that may distribute light

totally under the horizontal plane is recommended.

11.4.2.2. Lighting design

Lighting calculations

In daily practice, it is very common to use computer programs (INDALWIN) to design sports lighting installations. The results

of the program show quantitative values for most of the parameters, such as vertical and horizontal illuminances, uniformity

and glare ratios.

Floodlight orientation and location

Calculations done with the computer assume that small groups of floodlights in a power supply network are located in a

single point, that is to say, in the centre of the group. Such calculations are generally exact enough for general applications.

However, when there are large groups of floodlights and the spacing between the external units is considerable, the

calculation may result inexact in the focusing (Fig. 21). In these cases, a point of reference is determined for each small

group of floodlights.

Figure 21

Calculation matrix

Since the distance between the matrix points is relatively small, the value shown for each point represents the area

surrounding such a point (Fig. 22.). Matrix sizes commonly used are:

- from 1 to 2 m.: For small playing areas.

- from 5 m.: For football, hockey or rugby.

In order to specify horizontal illuminances, the matrix must be at ground level, whereas in order to specify vertical

illuminances, it generally is at 1.5 m. over such a level.

γ

γγA

A ε

Error in the focusing of floodlight S when the same focusingangle is used for very spaced floodlights.

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Figure 22

The positions of the observer and the observation or vision directions used when calculating glare are defined in the matrix.

Camera positions

Camera positions must be known to secure that lighting in such directions is adequate. These are specified as points of

reference in the computer program, and generally speaking, separate calculations are done for a number of points.

11.4.2.3. Football fields

Because of practical reasons, lighting requisites for different activities taking place in different periods of the year

in outdoor football fields, must have floodlighting systems. Therefore, they may be defined in general.

Illuminance

When the events are regularly broadcasted from a stadium or football field, the floodlight lighting project is generally designed

to provide the high illuminance necessary to comply with television requisites. The necessary horizontal illuminance for a

play field depends on:

a) The competition level taking place on it.

b) The speed of the ball (also the rapid movement of players must be taken into account).

c) The maximum distance between players and between any of them and the ball during the game.

If the play field has tiers for spectators and the distance between the centre of the field and the most distant spectator is

greater than the maximum distance existent between a player and the game object, the latter is the one that must be taken

into account as a reference criterion. In Fig. 23, the minimum horizontal illuminance levels recommended for different

distances between spectators and the centre of the field are represented.

1/2 Sx Sx

1/2 Sy

Sy

S =Sx, Sy. matrix spacing=Point on which lighting is calculated.=Calculated value valid for this area (Sx, Sy)

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Figure 23

Vertical illuminance is characterized not only by its magnitude but also by its direction. Vertical illuminance is considered

on a vertical plane in a straight angle with the observer’s line of vision (Fig. 24).

Figure 24. Vertical illuminance planes for different observer’s positions.

An adequate vertical lighting from all directions is very important for players. Nevertheless, if it is checked in the four directions

parallel to the play field exterior lines, it will be the adequate one in the rest of directions. For spectators and cameras occupying

a fixed position, only vertical lighting seen from that place must be verified.

In the charts at the end of the chapter, minimum vertical illuminance levels recommended for T.V. broadcasting are shown.

Position of observer 1 Position of

observer 2

Distance from the spectator to the centre of the playfield

Horizontalilluminance Competition level

Competition

Training

Leisure

Professional/ colour T.V.

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Uniformity ratio

Illuminance uniformity necessary on the field and surrounding courts depends on what is happening. For example, greater

light uniformity is required for television broadcasting than for game development or following of a competition without

broadcasting by the naked eye. A lower uniformity may be accepted for training than for competition. See Chart 3.

Glare

Glare should not be discomforting unless:

a) Floodlights with a precise light control are used and correctly pointed.

b) Floodlights are mounted far from the important observation directions. Mounting angles measured from the centre of the

field should be higher than 20º on the horizontal.

c) The least number of floodlight groups is used or a one- sided disposition. The number of groups in any of the field sides

should not be greater than 4.

d) Illuminance on the field of vision (which includes the field and the areas opposed to spectators) is as high and uniform

as possible, consequent with the avoidance of too much illuminance in the spectators' eyes. In practice, this means that

average illuminance on planes vertical to the height of the spectators’ eyes opposite it should not be greater than half their

average value on the vertical over the field, and preferably not more than 1/3.

If these requisites are met, the size and luminosity of individual sources and the number of floodlights in each group is not

very important with respect to glare. They have a stronger effect on illuminance on the field. Experience has proved that glare

of a correctly planned installation does not increase when illuminance is greater.

Illuminance on vertical planes; modelling

If floodlights are mounted at more than 30º on the horizontal measured from the centre of the field, the expense of towers

is normally unaffordable. The reason for illuminance on vertical or almost vertical planes to that of horizontal ones is lower

than expected, and modelling is not satisfactory.

In general, the best balance between glare degree and illuminance on vertical planes is obtained when floodlights are well

pointed and illuminance at the level of the spectators' eyes in front of it is within the given limits.

The most adequate modelling is obtained with floodlights mounted in 4 towers at the corners (Fig. 28). The effect is lower

with 6 towers, even less with groups of floodlights laterally mounted, and even less with continuous lines close to laterally

mounted floodlights. Moreover, with lateral lighting, illuminance on vertical planes opposed to the band line is higher than

with the systems of towers in corners. The advantages and disadvantages of the various floodlight lighting systems are

discussed later in the chapter.

Floodlight lighting systems

To a great extent, the following descriptions of floodlight lighting systems reflect conditions which are necessary for football

or similar games, but they will be generally satisfactory when other events take place in the stadium.

Lateral lighting systems

A lateral lighting system using 4 groups of floodlights on each side of the field is observed in the upper half of Fig. 25. The

lower half shows the design for 3 groups of floodlights.

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Figure 25

Small training fields may be illuminated from fewer positions and sometimes only from one side. Rectangular symmetric or

asymmetric floodlights (which produce a fan- shaped beam) are used for most lateral lighting projects. The recommended

mounting height is deduced from Fig. 26, the characteristic angles being measured from the longitudinal line of the centre

of the field and the band line.

Figure 26

When three groups of floodlights are used, these should be pointed to obtain an acceptable illuminance uniformity along

the nearby band line. Choosing an appropriate number of floodlights for each tower, illuminances that may be provided go

from adequate low values for training fields, up to high values necessary for colour T.V. broadcasting. Illuminance on vertical

planes on the play area is approximately equal to that of the horizontal planes. Modelling is relatively insignificant and several

shadows may be clearly seen. A careful pointing is necessary to avoid inadequate glare.

Fig. 27 shows the design of lateral floodlight systems where floodlights are mounted in single rows under each side of the

field and provide the necessary high illuminance for colour T.V. Mounting heights of floodlights are defined by the angles

given in Fig. 26. The row of floodlights should be preferably extended beyond the goal lines in order to maintain a reasonable

illuminance uniformity, especially in the areas, and provide light over the players so that they are seen behind the goal posts.

12 m

. min

imum

75° max.45° min.

Objective 25°Maximum 30°Minimum 20°

a

l

l/6

l/8 l/4 l/4 l/4 l/8

l/6l/3 l/3

Design for four poles

Design for three poles

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However, this extension may not be possible in practice. Then, trimmer in illuminance towards the goal lines should be

restricted by a reduction of the space of floodlights towards the end of lines or by the pointing of final floodlights outwards.

As for other systems of lateral lighting, average illuminance on vertical planes on the play area is approximately equal to that

of the horizontal ones and a careful pointing is necessary to avoid excessive glare. Where floodlights are mounted on ceilings

(shelters) of tiers, the compensation distance may not be large enough to provide adequate vertical illuminance on the

closest band line. Then, extra floodlights will be needed and should be mounted under the ceiling (shelter) at the necessary

compensation distance.

Figure 27

Systems of towers in corners

The design used for 4 towers in corners is the one observed in Fig. 28. Recommended heights for the tower are deduced

from Fig. 26. Normally, symmetric circular- shaped floodlights are used giving a symmetric beam. Individual beams may be

joined to fill what is seen as a playing area in a non- rectangular form from the above structure. This allows an adequate

illuminance design to be increased over the field. Angular compensations of 5° and 15° degrees, respectively, from the

centre of the band line and the goal entrance provide adequate locations for the towers. In practice, location of the tower is

ordered more often by the disposition of the place than by the ideal lighting requisites.

Large stadiums, and specially those with courts outside the play field, are difficult to illuminate enough from the 4 corners.

Very high towers would be necessary to comply with the angular requisites in Fig. 26, and glare from the long reach

floodlights which would be necessary, would be probably excessive. Because of these reasons, the 6 tower system seen in

Fig. 29 is preferred. The tower height is defined from the centre of the half of the field and approximately twice as many

grouped floodlights in the central towers as those in the corners. Pointing angles are sharp and glare may be controlled quite

easily. The illuminance ratio between vertical planes and horizontal planes is approximately 0.7.

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Figure 28.

Figure 29

Shadows of tiers

The position of shadows projected in the field by tier ceilings and other obstacles may be obtained from the sketch seen in

Fig. 30. If possible, height and location of the tower must be chosen so that shadows do not fall on the play field. Wherever

this is not possible, additional floodlights should be mounted under the tier ceiling and directed towards the shadowed areas

with the same average angle of the main floodlights.

15°

15°

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Figure 30

Atmospheric absorption losses

Dust and humidity in the air make light to be lost by absorption and dispersion, depending on the amount lost of the stadium

localization, projection length of floodlights and atmospheric conditions at the same time. The UEFA and CIE recommend

that a discount of 30% of light lost should be done in calculations.

Dispersion of light caused by fog, mist or rain produces veiling glare with the consequent reduction of visibility. Very little may

be done about this, but there is evidence and it is that the effect is the least with the tower systems in corners that with the

lateral lighting systems.

h

H

a

D

d

Tow

er

Tower

Tier

Tier

Shad

ow a

rea

a= d Hh-H

D= d hh-H

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HORIZONTAL ILLUMINANCE LEVEL CHARTS

Sport Activity level E (lux) U1 U2 R Tc Group

Archery (indoors)

- shooting zone t/r 100 0.3 0.4 60 2000

ca 500 0.3 0.4 60 2000

cp n.a.

- target t/r 300* n.a. n.a. 60 2000

ca 500* n.a. n.a. 60 2000

cp n.a.

Archery (outdoors)

- shooting zone t/r 50 0.3 0.4 60 2000

ca 100 0.3 0.4 60 2000

cp n.a.

- target t/r 100* n.a. n.a. 60 2000

ca 200* n.a. n.a. 60 2000

cp n.a.

Athletics A

- indoors t/r 200 0.3 0.5 65 2000

ca 300 0.4 0.5 65 4000

cp 500 0.5 0.7 65 4000

- outdoors t/r 100 0.2 0.3 20 2000

ca 200 0.2 0.3 20 2000

cp 400 0.3 0.5 65 4000

Badminton B

t/r 300 0.4 0.6 65 4000

ca 600 0.5 0.7 65 4000

cp 800 0.5 0.7 65 4000

Baseball B

- in the field t/r 150 0.3 0.5 65 4000

ca 300 0.4 0.6 65 4000

cp 750 0.5 0.7 65 4000

- outside the field t/r 100 0.2 0.3 65 4000

ca 200 0.3 0.4 65 4000

cp 500 0.4 0.5 65 4000

Basketball B

- indoors t/r 300 0.4 0.6 65 4000

ca 400 05 0.7 65 4000

cp 600 0.5 0.7 65 4000

- outdoors t/r 100 0.2 0.3 60 2000

ca 200 0.3 0.4 60 2000

cp n.a.

Cycle racing B

- indoors t/r 200 0.3 0.4 65 4000

ca 300 0.4 0.5 65 4000

cp 500 0.4 0.5 65 4000

- outdoors t/r 100 0.2 0.3 20 4000

ca 200 0.4 0.5 65 4000

cp 400 0.4 0.5 65 4000

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HORIZONTAL ILLUMINANCE LEVEL CHARTS

Sport Activity level E (lux) U1 U2 R Tc Group

Billiards Aall 500 0.5 0.7 85 3000

Sleigh Bt/r/ca 150 0.2 0.3 65 4000

cp 300 0.2 0.3 65 4000Bowls- approximations, t/r 200 0.3 0.5 65 3000- greens and rinks

ca 200 0.3 0.5 65 3000cp 400 0.3 0.5 65 3000

- pins t/r 300* n.a. n.a. 65 3000ca 300* n.a. n.a. 65 3000cp 500* n.a. n.a. 65 3000

BoxingSee martial artsCricket C- in the field t/r/ca 750 0.5 0.7 65 4000

cp 1.500 0.7 0.8 65 4000- outside the field t/r/ca 500 0.4 0.5 65 4000

cp 1.000 0.5 0.6 65 4000Curling A- tees/court t/r 100 0.2 0.3 65 4000

ca 200 0.3 0.4 65 4000cp 300 0.4 0.5 65 4000

Darts At/r 300* n.a. n.a. 85 3000ca 500* n.a. n.a. 85 3000cp 1.000* n.a. n.a. 85 3000

Greyhound racing Bt/r/ca 200 0.5 0.7 20 2000

cp 500 0.5 0.7 65 4000Fencing C

t/r 300 0.4 0.6 65 4000Ca 600 0.5 0.7 65 4000cp 800 0.5 0.7 65 4000

Football B- indoors t/r 300 0.4 0.6 65 4000

ca 400 0.5 0.7 65 4000cp 600 0.5 0.7 65 4000

- outdoors t/r 100 0.4 0.6 65 4000ca 200 0.5 0.7 65 4000cp 500 0.5 0.7 65 4000

Golf driving- tee/green t/r 50 0.2 0.3 65 4000

ca 50 0.4 0.5 65 4000cp n.a.

- fairway/range t/r 30* n.a. n.a. 65 4000ca 30* n.a. n.a. 65 4000cp n.a.

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HORIZONTAL ILLUMINANCE LEVEL CHARTS

Sport Activity level E (lux) U1 U2 R Tc Group

Gynastics Bt/r 300 0.4 0.6 65 4000ca 400 0.5 0.7 65 4000cp 600 0.5 0.7 65 4000

Handball B- indoors t/r 300 0.4 0.6 65 4000

ca 400 0.5 0.7 65 4000cp 600 0.5 0.7 65 4000

- outdoors t/r 100 0.4 0.6 65 4000ca 200 0.5 0.7 65 4000cp 500 0.5 0.7 65 4000

Lawn hockey B- indoors t/r 300 0.4 0.6 65 4000

ca 600 0.5 0.7 65 4000cp 800 0.5 0.7 65 4000

- outdoors t/r 100 0.4 0.6 65 4000ca 250 0.5 0.7 65 4000cp 500 0.5 0.7 65 4000

Ice hockey B- indoors t/r 300 0.4 0.6 65 4000

ca 600 0.5 0.7 65 4000cp 800 0.5 0.7 65 4000

- outdoors t/r 100 0.3 0.5 20 2000ca 250 0.4 0.6 65 4000cp n.a.

Equestrian sports A- indoors t/r 300 0.3 0.5 65 4000

ca 400 0.4 0.6 65 4000cp 600 0.4 0.6 65 4000

- outdoors t/r 50 0.2 0.3 20 2000ca 150 0.3 0.5 65 4000cp 300 0.3 0.5 65 4000

Horce racing Bt/r/ca 200 0.5 0.7 20 2000

cp 500 0.5 0.7 65 4000Judo B

t/r 300 0.4 0.6 65 4000ca 400 0.5 0.7 65 4000cp 600 0.5 0.7 65 4000

KarateSee martial artsLacrosse C

t/r 100 0.4 0.6 65 4000ca 200 0.5 0.7 65 4000cp 500 0.5 0.7 65 4000

Martial arts Ct/r 500 0.4 0.6 65 4000ca 1000 0.5 0.7 65 4000cp 2000 0.5 0.7 65 4000

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HORIZONTAL ILLUMINANCE LEVEL CHARTS

Sport Activity level E (lux) U1 U2 R Tc Group

Car racing B- indoors t/r 300 0.3 0.4 65 4000

ca 400 0.4 0.6 65 4000cp 600 0.4 0.6 65 4000

- outdoors t/r 50 0.2 0.3 20 2000ca 100 0.3 0.4 20 4000cp 200 0.3 0.4 65 4000

Tennis Ct/r 250 0.4 0.6 60 2000ca 500 0.4 0.6 65 4000cp 750 0.4 0.6 65 4000

Pelota court Ct/r 250 0.4 0.6 60 2000ca 500 0.4 0.6 65 4000cp 750 0.4 0.6 65 4000

Roller skating Bt/r 100 0.2 0.3 20 2000ca 200 0.4 0.5 65 4000cp 500 0.4 0.5 65 4000

Rugby Bt/r 100 0.4 0.6 65 4000ca 200 0.5 0.7 65 4000cp 500 0.5 0.7 65 4000

Shooting (indoors) A- shooting zone t/r 200 0.3 0.4 60 2000

ca 400 0.3 0.4 60 2000cp n.a.

- target t/r 500* n.a. n.a. 60 2000ca 1.000* n.a. n.a. 60 2000cp n.a.

Shooting (outdoors) A- shooting zone t/r 100 0.3 0.4 60 2000

ca 200 0.3 0.4 60 2000cp n.a.

- target t/r 200* n.a. n.a. 60 2000ca 400* n.a. n.a. 60 2000cp n.a.

Figure skating B- indoors t/r 300 0.3 0.5 65 4000

ca 600 0.4 0.6 65 4000cp 800 0.4 0.6 65 4000

- outdoors t/r 100 0.3 0.5 20 2000ca 250 0.4 0.6 65 4000cp n.a.

Speed skating B- indoors t/r 200 0.3 0.4 65 4000

ca 300 0.4 0.5 65 4000cp 500 0.4 0.5 65 4000

- outdoors t/r 100 0.2 0.3 20 2000ca 200 0.4 0.5 65 4000cp 400 0.4 0.5 65 4000

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HORIZONTAL ILLUMINANCE LEVEL CHART

Sport Activity level E (lux) U1 U2 R Tc Group

Skiing B

t/r 50 0.2 0.3 20 2000

ca 100 0.2 0.3 20 2000

cp 200 0.2 0.3 20 2000

Skiing jump B

- sliding t/r 100 0.4 0.5 60 2000

ca 200 0.4 0.5 60 2000

cp 200 0.4 0.5 60 2000

- winning post t/r 200 0.3 0.5 65 4000

ca 400 0.3 0.5 65 4000

cp 400 0.3 0.5 65 4000

Swimming A

- indoors t/r 200 0.3 0.5 60 3000

ca 300 0.3 0.5 60 3000

cp 500 0.3 0.5 60 3000

- outdoors t/r 100 0.2 0.3 65 4000

ca 200 0.3 0.5 65 4000

cp 400 0.3 0.5 65 4000

Table tennis C

t/r 300 0.4 0.6 60 4000

ca 400 0.5 0.7 60 4000

cp 600 0.5 0.7 60 4000

TaekwondoSee martial arts

Tennis B

- indoor (PPA) t/r 500 0.4 0.6 65 4000

ca 750 0.4 0.6 65 4000

cp 1.000 0.4 0.6 65 4000

- indoor (TPA) t/r 400 0.3 0.5 65 4000

ca 600 0.3 0.5 65 4000

cp 800 0.3 0.5 65 4000

- outdoor (PPA) t/r 250 0.4 0.6 60 2000

ca 500 0.4 0.6 65 4000

cp 750 0.4 0.6 65 4000

- outdoor (TPA) t/r 200 0.3 0.5 60 2000

ca 400 0.3 0.5 65 4000

cp 600 0.3 0.5 65 4000

Diving board A

t/r 300 0.4 0.6 65 4000

ca 400 0.5 0.7 65 4000

cp 600 0.5 0.7 65 4000

Volleyball B

- indoor t/r 300 0.4 0.6 65 4000

ca 400 0.5 0.7 65 4000

cp 600 0.5 0.7 65 4000

- outdoor t/r 100 0.4 0.6 65 4000

ca 200 0.5 0.7 65 4000

cp 500 0.5 0.7 65 4000

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Legend for chart 3:

t: Training (amateur and professional).

r: General recreation.

ca: National competition.

cp: National and international competition without T.V. requisites.

E: Minimum average horizontal illuminance at ground level or, when it is signalled with *, minimum vertical

illuminance.

n.a.: Non applicable.

U1= Illuminance extreme uniformity (Emin/Emax)

U2= Illuminance average uniformity (Emin/Emed)

R: Colour reproduction index.

Tc= Colour temperature (in Kelvin’s degrees).

Chart 4. Recommended lighting for national T.V.

Chart 5. Recommended lighting for international T.V.

(1) An R of 65 is admissible, but 90 is advised.(2) A Tc of 4 000 K is admissible, but 5,500 K is advised.

Group Maximum Illuminance Uniformitydistance Main Secondary Vertical Horizontal R Tc

camera camera U1 U2 U1 U2

A

25 m 700 lux 700 lux 0.4 0.5 0.3 0.5 65(1) 4 000(2)

75 m 1 000 lux 700 lux 0.5 0.6 0.3 0.5 65(1) 4 000(2)

150 m 1 400 lux 1 000 lux 0.5 0.6 0.4 0.6 65(1) 4 000(2)

B

25 m 1 000 lux 700 lux 0.5 0.6 0.3 0.5 65(1) 4 000(2)

75 m 1 400 lux 1 000 lux 0.6 0.7 0.4 0.6 65(1) 4 000(2)

150 m 1 750 lux 1 250 lux 0.6 0.7 0.4 0.6 65(1) 4 000(2)

C

25 m 1 400 lux 1 000 lux 0.6 0.7 0.4 0.6 65(1) 4 000(2)

75 m 1 750 lux 1 250 lux 0.7 0.8 0.5 0.7 65(1) 4 000(2)

150 m n.a. n.a.

Group Maximum Illuminance Uniformitydistance Main Secondary Vertical Horizontal R Tc

camera camera U1 U2 U1 U2

A

25 m 500 lux 500 lux 0.4 0.5 0.3 0.5 65 4 000

75 m 700 lux 500 lux 0.4 0.5 0.3 0.5 65 4 000

150 m 1 000 lux 700 lux 0.5 0.6 0.4 0.6 65 4 000

B

25 m 700 lux 500 lux 0.5 0.6 0.3 0.5 65 4 000

75 m 1 000 lux 700 lux 0.5 0.6 0.3 0.6 65 4 000

150 m 1 400 lux 1 000 lux 0.6 0.7 0.4 0.6 65 4 000

C

25 m 1 000 lux 700 lux 0.5 0.6 0.4 0.6 65 4 000

75 m 1 400 lux 1 000 lux 0.6 0.7 0.4 0.6 65 4 000

150 m n.a. n.a.

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201LIGHTING ENGINEERING 2002

Chapter 12.

ROAD LIGHTING

12.1 Decision making criteria on road lighting . . . . . . . . . . . . . . . . . . . . . . 203

12.2 Project situations, types of lighting systems and lighting levels . . . . . . . 205

12.3 Lighting engineering calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

12.4 Lighting systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216

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12.1. Decision making criteria on road lighting

12.1.1. ObjectivesThe fundamental objective of road lighting is to allow a secure and comfortable vision during the night. Such qualities may

protect, ease and improve motor traffic. An adequate use of public lighting as an operative instrument provides economic and

social benefits like:

a) Reduction in accidents at night- time, including human endangered lives and economic losses.

b) Help to police protection and safety of population.

c) Easier traffic.

d) Promotion of transport and travelling at night.

The aim of public lighting is to provide the driver with the necessary visibility to distinguish obstacles and road layout with

enough time to maneuver in order to guarante security, apart from providing the automobilist with visual comfort while driving.

12.1.2. Night- time driving and users’ visual capacityThe visual environment of an automobilist driving at night is basically formed by the roadway. Visibility of an obstacle located

on the roadway, will depend on the luminance difference between the obstacle and the background, constituted by the

roadway on which it may be seen. In the case of a light- coloured object on a dark background, its contrast is positive. However,

an object darker than its background is seen as a silhouette and its contrast is negative. Road lighting generally produces

negative contrasts for dark objects or obstacles or those with low reflectance.

Night- time driving implies a mesopic or twilight vision comprised in the interval between 10-3 and 3 or 4 cd/m2. It is

characterized by a reduction in visual sharpness and a diminution in contrast differential sensitivity. A high luminance contrast

threshold is necessary for obstacle visibility. Likewise, this kind of vision in night- time driving implies an important alteration in

distance judging (deficient binocular vision), a limited perception of lateral obstacles and, finally, rare and unusual chromatic

vision.

It must be taken into account that vehicle headlights only illuminate a limited area ahead of them, while public lighting provides

light to the road and its surroundings, opening the field of vision to the driver. This results in an approach to day- time light

conditions, which may be important in certain traffic or environmental circumstances.

On the other hand, differential sensitiveness to contrast for any same driver is more than three times higher in a road provided

with lighting (2 cd/m2), when compared with that provided by a vehicle traffic beam (0.2 to 0.3 cd/m2). Visual sharpness

during night- time driving evolves in such a way that for a driver on a road provided with lighting, visual sharpness becomes

two and a half times higher than for the same driver using only the vehicle dipped headlights. For night driving with a vehicle

dipped headlights (0.2-0.3 cd/m2), the efficacy of binocular vision is reduced to one third (1/3) of that reached during the

day. Consequently, distance perception and judgment decreases considerably, implying a higher risk of accidents.

12.1.3. Decision making criteria for the need of road lightingA selection of possible road segments must be conducted in order to determine which should be provided with public lighting.

There is a need, then, for establishing factors and criteria which will determine the introduction of such installations.

Factors influencing lighting

Some factors to take into account when implementing public lighting are the following:

1. Road type (motorways, dual carriageways, express roads or conventional roads), its location and its layout.

2. Conflict areas, such as crossroads, complicated crossings and special parts.

3. Traffic intensity and composition.

Lighting installation criteria in road segments recommend to bear in mind factors influencing the need for lighting, as well as

considering situations in which due to traffic intensity, only the car dipped headlights can be used for a long period of time.

In conventional roads, changes from full lights to dipped lights in order to avoid glares must be done at an approximate

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204 LIGHTING ENGINEERING 2002

distance of 500 m. between vehicles circulating in opposite directions. Therefore, the maximum number of vehicles driving

with full headlights per hour, at an average speed of 75 Km/h., is that of 150. This number is equivalent to a total of 300

vehicles per hour during the night on a straight stretch.

Chart 1 offers guiding criteria by indicating values for traffic daily average intensity (IMD) that may be adopted to take into

account the possibility of road lighting.

Likewise, in order to avoid the so-called "black hole" effect, it would be convenient to consider lighting stretches between

merging areas whose distance is inferior to 6 Km. in separate carriageway roads, and to 2 Km. in single carriageway roads.

Besides, it would be advisable to bear in mind those road stretches where there exists a considerable percentage of accidents

during the night when compared to daytime conditions.

Chart 1. IMD limit values recommended for lighting.

Road type Minimum IMD to illuminate (Veh/hour)

Conventional roads 12 000

Motorways and dual carriageways 22 000

Intersections 4 000

Merging areas 7 000

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12.2. Project situations, types of lighting systems and lighting levels

12.2.1. Project situation classificationRegarding present recommendations, the following situations compiled in Chart 2 must be considered.

Chart 2

12.2.2. Lighting class selectionOnce the project situation has been established according to Chart 2, lighting class is chosen. It must satisfy the illumination

needs required for the mentioned project situation.

The following lighting classes ME series are defined for roads on dry conditions: ME1, ME2, ME3 (a, b) and ME4 (a, b). These

are established from greater to lesser need of lighting levels.

Each ME series lighting class comprises the following lighting levels:

- Road surface average luminance.

- Luminance overall uniformity.

- Luminance longitudinal uniformity.

- Disability glare (increase in threshold contrast).

- Environmental ratio (lighting of roadway adjacent areas).

Chart 3 includes lighting classes corresponding to A project situations.

Chart 4 comprises a total of 4 lighting classes ordered from greater to lesser lighting engineering need, expressing the levels

as minimum values in service. This means with maintenance of installation, except for the threshold increment TI which is

maximum initial value. In turn, ME3 and ME4 lighting classes are divided into a and b, whose difference lies in their longitudinal

uniformity.

Roads with separate carriageways, flyovers and access control

(motorways, expresss roads). A1Two- way circulation road and access control (express roads) M

Urban traffic routes with no separation for walkways or cycle paths. 0 A2

Access roads and by- passes. Restricted urban traffic routes. 0 0 0 A3

Types of users ProjectsituationsM

Road type

PROJECT SITUATION CLASSIFICATION

TYPES OF USERS

Main user M Motor traffic

Other permited users S Slow moving vehicles

Excluded users C Bicyclists

P Pedestrians

0

S C P

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206 LIGHTING ENGINEERING 2002

Chart 3

Luminance is expressed in cd/m2, whereas uniformities, understood as a ratio between luminances, lacks a unit. Disability glare

appears as a percentage, and again, the environmental ratio also lacks units because it is a quotient between luminances.

From the point of view of lighting engineering, the most interesting project situations are the ones belonging to group A-1.

Situations for A-2 and A-3 lighting class are treated in a more general way.

For A1 project situation, Chart 3 summarizes the specific kind of lighting to be adopted, depending only on traffic intensity and

road layout complexity.

For the rest of project situations A2 and A3 there are several options to choose the kind of lighting. In each case, it is selected

according to traffic intensity and road layout complexity, traffic control and separation of different kinds of users, as well as

dominant specific parameters, specified below:

A2 project situation. Dominant parameters:

- Crossroad type (merging areas, intersections).

- Number of junctions.

A3 project situation. Dominant parameters:

- Roadway separation.

- Crossroad type (merging areas, intersections).

- Number of junctions.

12.2.2.1. Lighting engineering requirements for project situations

In Chart 4, lighting levels corresponding to each ME series lighting class are detailed.

PROJECT TYPES OF USER LIGHTINGSITUATIONS CLASS*

LIGHTING CLASSES FOR TRAFFIC ROADS

A1

A2

A3

* For all project situations (A1-A2 and A3), whenever nearby areas are light (light backgrounds), all traffic roads will increase their exigencies to that of

their immediately above lighting class.

– Roads with separate carriageways, crossings at grade and access control (highways,motorways):

• Traffic density and complexity of road layout:

High (IMD) > 25,000Medium (IMD) – Between 15,000 and 25,000Low (IMD) < 15,000

– Two- way circulation roads and access control (high speed roads):

• Traffic density and complexity of road layout:

High (IMD) > 15,000Medium and low (IMD) < 15,000

– Urban traffic routes with no separation for walkways or cycle paths.

• Traffic density and complexity of road layout.• Traffic control and separation of different user types.• Specific parameters.

– Distributor roads and by- passes.– Intercity roads with no access control.

• Traffic density and complexity of road layout.• Traffic control and separation of different user types.• Specific parameters.

ME 1ME 2ME 3a

ME 1ME 2

ME 1

ME 2ME 3aME 4a

ME 1ME 2

ME 3bME 4aME 4b

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Chart 4

12.2.2.2. Road lighting for wet conditions

In the particular case of wet roadways, the surface reflects light in a more specular or directed way than in a diffuse

one (same luminance in all directions in space). Roadway luminance uniformity is lessened negatively affecting

obstacle visibility on the road.

In those geographic areas where rain intensity and persistence provokes the roadway surface to be wet during a

significant part of night- time hours, criteria shown in Chart 5 will be taken into account. For these recommendations,

as an orientation, areas with an average higher than 100 rainy days in a year fall within this category. In these cases,

calculation of luminances overall uniformity will be done according to the method described in the publication CIE

nº 47 (1979), bearing in mind the photometric features of normalized pavements in that case.

Chart 5

LIGHTING CLASS

ROADWAY SURFACE LUMINANCE IN DRY AND WET CONDITIONS

DRY ROADWAYWET

ROADWAY

Average luminance

Lm (cd/m2)

Overalluniformity

U0

Overalluniformity

U0

Longitudinaluniformity

U1*

DISTURBINGGLARE

ThresholdincreaseTI (%)

SURROUNDINGSLIGHTING

SurroundingratioSR

LIGHTING CLASSES MEW SERIES

* This criterion is not restrictive but may be applied, for example, to motorways, dual carriageways, two- way traffic single carriageways with access control.

MEW1 2.00 0.40 0.60 0.15 10 0.50

MEW2 1.50 0.40 0.60 0.15 10 0.50

MEW3 1.00 0.40 0.60 0.15 15 0.50

MEW4 0.75 0.40 — 0.15 15 0.50

LIGHTING CLASS*

ROADWAY SURFACE LUMINANCE IN DRYCONDITIONS

Average luminance

Lm (cd/m2)

Overalluniformity

U0

Longitudinaluniformity

U1*

DISTURBINGGLARE

ThresholdincreaseTI (%)**

SURROUNDINGSLIGHTING

Surroundingratio

SR***

LIGTHING CLASSES ME SERIES

*The levels for the chart are minimum values in service with maintenance of the lighting installation, except for TI, which are maximum initial values. In order

maintain such service levels, a depreciation factor not greater than 0.8 must be considered, depending on luminaire type and degree of pollution in the air.

** When low luminance level sources of light are used (fluorescent tubes and low pressure sodium), a 5% threshold increase (TI) is allowed.

*** The surround ratio SR must be applied to those traffic roadways where there are not other adjacent areas to the roadway with their own requisites.

ME1 2.00 0.40 0.70 10 0.50ME2 1.50 0.40 0.70 10 0.50

ME3a

1.00 0.400.70

15 0.50b 0.60

ME4a

0.75 0.400.60

15 0.50b 0.50

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12.2.2.3. Conflict areas

Conflict areas may be defined as such due to the complexity of vision and maneuver problems that vehicles

circulating on it have. Some examples are:

- Junctions (merging areas and intersections), and traffic circles.

- Areas where the number of lanes is reduced or the roadway width is decreased.

- Areas where new lanes are merging.

- Underpasses.

- Overhead crossings.

Likewise, conflict areas are those sectors with great difficulty because of a high presence of pedestrians, cyclists or

other users of the roadway or lanes.

Lighting installation must reveal or stress the conflict area, as well as all its characteristics, such as position of kerbs,

pavement markings, different delineations, traffic directions, etc. Following the same policy, the presence of

pedestrians, cyclists, obstacles, other vehicles and their movement in the surroundings of the conflict area must be

made evident.

a) Luminance criterion

Whenever possible, luminance criteria, overall and longitudinal uniformities, disability glare and environmental ratios

defined for different lighting classes, will be applied to conflict areas. In all cases, lighting class defined for the conflict

area will be one degree higher than the degree of the roadway to which such a conflict area corresponds. For

example, if a road is to be provided with an ME4 lighting class, a conflict area included in its route will need an ME3a

lighting class. If several lanes meet in a conflict area, as it may happen with crossroads, the lighting class will be a

degree higer than the degree of the roadway that has the highest lighting class.

b) Illuminance criterion

Only when luminance criteria cannot be applied, will illuminance criteria be used. This situation may take place when

the sight distance is lower than 60 m. (minimum value used for luminance calculation), and whenever the observer

may not be properly located due to convolution and complexity of road layout.

In such situations, lighting criteria will be applied by means of average illuminance and its uniformity, which

correspond to the CE series lighting classes (Chart 6). Limitations of glare or lighting pollution control, represented

by G series intensity classes (Chart 7), will also be observed.

Chart 6

HORIZONTAL ILLUMINANCE LIGHTINGCLASS*

Average IlluminanceEm (lux)

Average UniformityUm

LIGHTING CLASS CE SERIES

* The levels of the chart are minimum values in service with lighting installation maintenance. In order to keep

such service levels, a depreciation factor not lower than 0.8, depending on luminaire type and air pollution

degree, must be considered.

CEO 50 0.40

CE1 30 0.40

CE2 20 0.40

CE3 15 0.40

CE4 10 0.40

CE5 7.5 0.40

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According to Chart 8, ME and CE lighting classes, with identical numbers (for example CE3 and ME3), have a similar

lighting level. When the illuminance criterion is used, lighting class defined for the conflict area will be one degree

higher than that of the corresponding conflict area road. For example, if a road is attributed an ME2 lighting class, a

CE1 lighting class would correspond to a conflict area included in it.

Supposing there is a conflict area in which there is an ME1 lighting class road merging, the conflict area will continue

also as an ME1 lighting class or its equivalent, CE1. When this conflict area offers special complexity and a high risk

of accidents, in the worst situation and circumstances, a CE0 (50 lux) lighting class will correspond to such an area

or its similar luminance level of 3.3 cd/m2. For intermediate situations, lighting classes ranging between the CE1 and

CE0 interval may be adopted, corresponding to illuminance levels of 35, 40 and 45 lux or their similar values of 2.3,

2.7 and 3 cd/m2, respectively.

Conflict areas whose sidewalks or shoulders are not provided with a specific lighting, this will be considered as a

lighting level of, at least, 50% of that foreseen for the roadway.

Chart 7

When an exhaustive requirement on glare limitation or light pollution control is needed, intensity classes G1, G2 and

G3 may be adopted. Supposing the conflict area typology, due to its configuration, complexity and potential

dangerousness, requires a greater glare limitation or light pollution control, only G4 and G5 intensity classes can be

chosen. Only under extreme circumstances, will G6 intensity class be mandatory.

12.2.2.4. Layout losses

Nowadays, there are no methods to quantify visual guidance provided by the installation of lighting on motor traffic

roads. Nevertheless, there are certain practical considerations which may be helpful when there are layout losses.

It is obvious that for safe driving, road layout, edges, possible crossroads and any other conflict area must be perfectly

visible. Lighting must contribute to achieve this goal, and so, the following points must be carefully considered:

- Lighting must increase road visibility with regard to adjacent areas and visibility of vertical, horizontal signaling and

beacons.

- Disposition of aiming points (luminaires) must allow detection of road layout, crossroads and other conflict areas

beofre reaching them, marking the route.

- Change in the source of light of a different colour compared to the colour of the traffic road at junctions,

intersections, traffic circles, by-passes and conflict areas where the ratio between night- time and day- time accidents

is high. This helps visual guidance.

Regarding vision of horizontal signalling, and pavement markings, to be exact, the essential point is to secure good

visibility at night, as well as for wet roadway conditions. In this case, rows of luminaires, retro reflective post mounted

INTENSITY CLASS

MAXIMUM INTENSITY(cd/Klm)** OTHER REQUIREMENTS

At 70° * At 80° * At 90° *

INTENSITY CLASSES G SERIES

** Any direction formed by the specified angle from the vertical downwards, with the luminance installed for its working.

** All intensities are proportional to lamp flux for 1 000 lm.

NOTE: Intensity classes G1, G2 and G3 coresspond to «semi cut-off» and «cut-off» photometric representations, concepts traditionally used for lighting

requirements defined in section 7.5.2. Intensity classes G4, G5 and G6 designate luminaires with very strong «cut-off» distribution, like for example,

luminaires with glass flat closing, in any position near the horizontal of the opening or the horizontal position strictly.

G1 — 200 50 None.G2 — 150 30 None.G3 — 100 20 None.G4 500 100 10 Intensities above 95° must equal zero.G5 350 100 10 Intensities above 95° must equal zero.G6 350 100 0 Intensities above 95° must equal zero.

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210 LIGHTING ENGINEERING 2002

delineators and contrasting pavement markings, being over the roadway water film caused by rain, maintain visibility

provided by road lighting and vehicle own headlights, preserving visual guidance and road security.

12.2.3. Reference areaDefined as part of the public working area, under consideration or study, several assumptions must be made according to

project situation groups specified below.

A project situation groups

The reference area will be constituted by the totality of the motor traffic roadway width, between its edges. For double

carriageway roads, the reference area will be formed by the total width of both roadways including the central reservation

between the two of them, unless their width is such that each roadway may be considered separately. The width of their

adjacent bands for the SR surrounding ratio, will be equal, at least, to the width of a traffic lane, 5 m width if possible. A specific

requirement will be the application of such ratio around the roadway adjacent bands, according to the ME series lighting classes

(Chart 4), MEW series (Chart 5) or CE series (Chart 6).

If there are parallel roads next to the motor traffic road, there are two alternatives:

1) Consider the total area

The reference area will be formed by the width of the motor traffic roadway, including parallel roads between their extreme

edges.

2) Consider the roadway and the parallel roads separately

The reference area of the motor traffic road will be exclusively the width of the roadway.

The reference area of the parallel road will be only its width. For cycle paths and pedestrian areas, the reference area, apart

from the width of such roads or lanes, must include 2 m. on each side.

12.2.3.1. Lighting classes with similar lighting levels

For all project situations or A traffic roads, lighting engineering levels must be specified for each reference area. The

difference between two adjacent areas should not be greater than two comparable lighting classes or those of a

similar lighting level, as established in Chart 8.

Once lighting levels of the ME, MEW and CE lighting classes series have been detailed, Chart 8 establishes lighting

classes with similar lighting level for such series.

Chart 8

COMPARABLE BY COLUMNS

CE 0

ME 1MEW 1CE 1

ME 2MEW 2CE 2

ME 3MEW 3CE 3

ME 4MEW 4CE 4

ME 5MEW 5CE 5

ME 6

LIGHTING CLASSES WITH SIMILAR LIGHTING LEVEL

For ME/MEW classes r-chart C 2 roadway surface reflectance (Publication CIE nº 66)

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12.2.4. Lighting class temporal variations In order to save energy in all project situations, lighting class may be momentarily changed to another one with an inferior level

of lighting engineering at certain hours at night during which traffic intensity is fundamentally lower. This can be done by means

of the corresponding regulation of the lighting level system. Lighting class temporal variations should not be done in conflict

areas . When lighting level is reduced, that is to say, it is changed from one lighting class to another at a certain hour, (midnight

lights out), changes will be such that, if average luminance is reduced to a lower class (for example, go from M2 to M3), glare

and luminance uniformity criteria established in Chart 4 must be observed.

12.2.5. High mounting support lightingThis name is given to lighting through aiming points whose mounting height is higher than 16 m., and whose maintenance

cannot be performed with a vehicle provided with a hydraulic basket.

This system is used each time the use of lighting conventional solutions is not satisfactory, due to the handling of supports

and to the difficulty of their installation in their corresponding location.

Lighting by means of high mounting supports is related to lighting of large surfaces, and is usually applied, in the following

situations, among others:

- Complex motorways, dual carriageways or road junctions.

- Traffic circles.

- Toll areas.

Lighting installation by means of high mounting supports is a solution when the installation of classic shafts or columns

originates problems in the surroundings, such as:

- Loss of perspective and level separation between supports (crossroads of motor traffic roads at different levels).

- Dimensioning problems (large areas), or aesthetics and visual guidance confusion (multiplicity of supports).

For this type of lighting the most frequent installation heights are 30 and 35 m. supports, even though in concrete situations

like complex crossroads, they may be higher than 40 m. The number of lighting sources will be reduced as much as possible,

by using discharge lamps with high lighting efficacy and potency. Luminaires provided with a conventional, adjustable or

specific optical system as well as floodlights may be installed, always paying attention to convenient solutions to achieve the

established goals.

In order to perform maintenance operations, accessibility to luminaires, control gears and lamps will be done by means of

fixed scales attached to the supports, up to a height of 20 m. For higher columns, the installation of an impeller system is

convenient.

In order to decrease glare, the tilt angle of floodlight maximum intensity will amount to 65%, limiting, as far as possible,

intensity values above this angle. Besides, the installation of grids or other antiglare devices may also be contemplated.

Chart 9

Very complex crossings with high traffic density and complex road layout and field of vision

CE 0

Complex crossings, traffic circles CE 0CE 1

Toll areas CE 2

NOTE: In lighting situations corresponding to very complex crossings with high traffic density and complex road

layout and field of vision, in some special cases, luminance average uniformity will be 0.5.

LIGHTING WITH HIGH SUPPORTS. LIGHTING CLASSES

DESCRIPTION OF ROAD TYPELIGHTINGCLASSES

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12.3. Lighting engineering calculations

12.3.1. Luminance calculation of lighting installation

12.3.1.1. Method

Luminance at a point of the roadway is calculated using the following formula:

where the sum () comprises, in theory, all luminaires in the installation. Luminous intensity values (I(c,)) and

reduced luminance coefficient (r(, tg)) are obtained by square interpolation of the luminaire intensity matrix and

the pavement reflection chart. Lastly, variable h is the luminaire maximum height (Fig. 1).

Figure 1. Luminance at a point.

Calculated luminance values are influenced by the maintenance factor as decreasing, which takes into account the

lamp luminous depreciation caused by dirtiness. In all calculations, a value lower or equal to 0.8 will be adopted,

depending on luminaire type and local degree of atmospheric pollution.

12.3.1.2. Hypothesis

The following sections are applicable to straight roadway stretches or large radius curves (radius >= 300 m.). In

another kind of configuration, each case will be studied separately, applying certain criteria for special situations.

Moreover, as it has already been indicated, calculations are established for pavement in dry conditions.

12.3.1.3. Selection of calculation lattice

The lattice calculation is the set of points in which luminance values will be calculated. In a longitudinal sense, the

lattice will cover the stretch of roadway between two consecutive luminaires in the same side.

In a transversal sense, it must comprise the width defined for the reference area.

Calculation points will be distributed as shown in Fig. 2 and their number will be:

- From a longitudinal point of view: 10 points for separations between luminaires lower than 50 m., or the least

h

P

β

γ

δ

α

T

Q

s

Observer

L = E (cm/m2)Ι (c, γ) · r (β, tgγ)

h2 R

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number of points that will provide distances equal or inferior to 5 m. between them, for separations between

luminaires higher than 50 m.

- From a transversal point of view: 5 points per lane, one of them located in its center. The two most external points

will remain inside the roadway, with respect to its edge, at 1/6 of the lane width.

Figure 2. Calculation lattice.

12.3.1.4. Observer’s position

a) Height: 1.5 m. over the roadway surface.

b) Longitudinal situation: At 60 m. from the first transversal line of calculation points.

c) Transversal situation:

- For the calculation of average luminance and overall uniformity, the situation will be at 1/4 of the roadway total

width, measured from the right edge of the roadway.

- For the calculation of longitudinal uniformity, for roads with traffic in two directions, the situation will be in the center

of each of the lanes of the direction under study.

12.3.1.5. Number of luminaires

The number of luminaires that contribute to luminance of a calculation point must be restricted to those previously

located at five times their mounting height, and at twelve times their mounting height, in the circulation sense.

Likewise, as for luminaires placed in a transversal way to the direction of circulation, only those which are at 5 times

less than their mounting height will be taken into account.

12.3.1.6. Calculations

- Average luminance: luminance average value calculated in the lattice points.

- Overall uniformity: quotient between the minimum luminance calculated in a lattice point and its average

luminance.

- Longitudinal uniformity: for each of the lanes, it is obtained by dividing minimum and maximum exact luminance

calculated on the axis of the lane.

a

a/2

a/6

Luminaire

: Lattice point

Luminaire

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214 LIGHTING ENGINEERING 2002

12.3.2. Calculation of horizontal illuminances

12.3.2.1. Method

Horizontal illuminance at a point of the roadway is calculated using the following formula:

γ being the angle formed by the direction of incidence at the point with the vertical (Fig. 3). The sum (∑) comprises,

in theory, all luminaires in the installation.

Figure 3. Illuminance at a point

Illuminance calculations, as that of luminances, will be affected by a maintenance factor lower or equal to 0.8,

depending on the type of luminaire and the local degree of atmospheric pollution.

12.3.2.2. Selection of calculation lattice

The same as described in section 12.3.1.3 will be used.

12.3.2.3. Number of luminaires

Illuminances produced by luminaires will accumulate in the lattice points little by little, evolving from the closest to

the furthest ones, up to a point in which a luminaire will not produce a level higher than 1% of the accumulated

value in any of the lattice points.

12.3.2.4. Calculations

- Average illuminance: average value of illuminances calculated in the lattice points.

- Average uniformity: quotient between minimum illuminance calculated at a point of the lattice and average

illuminance.

- Extreme uniformity: quotient between minimum and maximum illuminances calculated at a point of the lattice.

12.3.3. Disability glare calculation

12.3.3.1. Method

It is based on the calculation of veiling luminance:

h

a

γP

I

C

E =dφ

dS

E = E (lux)Ι (c, γ) · cos3 γ

h2 R

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where Eg (lux) is the illuminance produced by the eye in a plane perpendicular to the line of vision, and θ (rad) is

the angle between the direction of light inciding in the eye and the observation direction. The sum () is extended,

in principle, to all luminaires of the installation (see 12.3.3.4.).

The increase of the perception threshold is calculated according to the following formula:

which is a valid formula for roadway average luminances (Lm) between 0.05 and 5 cd/m2.

12.3.3.2. Shielding angle

For disability glare calculation purposes, luminaires whose observation direction forms an angle greater than 20° with

the vision line will not be considered, since they are shielded by the roof of the vehicle.

12.3.3.3. Observer’s position

a) Height: 1.5 m. over the roadway surface.

b) Longitudinal situation: in such a way that the closest luminaire to be considered in the calculation will formed

exactly a 20° angle with the vision line. For staggered dispositions, two different calculations will be done (with the

first luminaire on each side at 20°). The highest value of the two will be the result provided.

c) Transversal situation: at 1/4 of the roadway total width, measured from its right edge.

d) Observation point: The observer always looks at a point on the roadway placed at 90 m. in front of him, in the

same transversal situation in which he finds himself.

Figure 4. Observer’s position.

α=1ºθ

20º

W

O

P

1/4W

Shie

ldin

gpla

ne

Ig

TI = 65 · Lv

... (in %)(Lm)0.8

Lv = 3 · 10-3 · Σ (Eg

) (cd/m2)θ2

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12.3.3.4. Number of luminaires

All luminaires placed at less than 500 m. from the observer are considered to contribute to disability glare.

12.3.3.5. Calculations

- Veiling luminance: for each row of luminaires, the closest one is first considered, progressively driving away and

accumulating veiling luminances produced by each of them until their individual contribution is lower than 2% of the

accumulated one. The maximum is up to luminaires located at 500 m. from the observer. Finally, veiling luminance

of all rows of luminaires will be summed.

- Increase in perception threshold: it will be calculated with veiling luminance values obtained according to 12.3.3.1.

and with average luminance according to 12.3.1.6.

12.4. Lighting systems

12.4.1. Distribution of aiming points in crossroads, traffic rounds and curvesIn crossroads and intersections lighting levels will be those established for conflict areas and, at least, from a 10 to 20% higher

than those corresponding to the road class whose lighting level is higher between those that merge in the same point.

Consequently, the situation of aiming points will be ideal in order to achieve such mentioned levels. By way of an example,

ground plan dispositions are indicated in Figs. 5 and 6.

Figure 5

Figure 6

H mounting height of aiming points (Figs. 7 and 8) must be equal to that of the points of the main road that merges in the

traffic round to be illuminated. In case the central area of the traffic round lacks lighting higher or equal to 1.5 times the main

roadway average illuminance, supplementary lighting will be required.

Wal

kway

Walkway

Wal

kway

Walkway

Roadway

Wal

kway

Wal

kway

Walkway Walkway

Walkway

Roadway

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Figure 7

Figure 8

If the central part of the traffic round has a diameter lower than 18 m., a special aiming point in a column or multiple arm

shaft will be installed in its center (Fig. 7). If its diameter is greater than 18 m. or it has trees in the center, aiming lights will

be placed in the prolongation of the circulation axis (Fig. 8).

With regard to installation of aiming points in curves and in relation to lighting, curve stretches are considered those whose

radius is inferior to 300 m. When their radius is greater than such a figure, they will be considered as straight stretches.

If the width A of the traffic road is lower than 1.5 times its mounting height H, aiming points must be installed in the outer

part of the curve, locating an aiming point in the prolongation of the circulation axis (Figs. 9 and 10). Separation between

aiming points will be inversely proportional to the radius of the curve, varying between 3/4 and 1/2 of the calculated average

separation of a straight stretch of such a traffic road.

For traffic roads whose width is greater than 1.5 times their mounting height H, the installation of aiming points must be two-

sided coupled. In any case staggered distribution must be avoided.

Figure 9

Walkway

Roadway

Roadway

Walkway

Walkw

ayW

alkw

ay

Roadway Roadway

Road

way

Walkway

Walkw

ayW

alkw

ay

Roadway Roadway

Road

way

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Figure 10

12.4.2. Installation of aiming points in straight stretchesFor traffic roads in straight stretches, five basic types of distribution of aiming points will be considered.

12.4.2.1. One- sided

When aiming points are situated in a single side of the traffic road (Fig. 11). It will generally be used when the A

width of the roadway is equal or inferior to the mounting height H of the luminaires.

Figure 11. One- sided installation.

12.4.2.2. Two- sided staggered

When aiming points are located in both sides of the traffic road staggered or alternate (Fig. 12). It will generally be

used when the A width of the roadway is 1 to 1.5 times the mounting height H of the luminaires. The 1 to 1.3 H

interval is ideal.

Figure 12. Two- sided staggered installation.

12.4.2.3. Two- sided coupled

When aiming points are located in both sides of the traffic road, one opposing the other (Fig. 13). It will generally be

used when the A width of the road is greater than 1.5 times the mounting height H of the luminaires. It is more

adequate to use it when the width is greater than 1.3 times the height H.

Walkway

Walkway

Roadway A

S

A

H

Walkway

Walkway

Roadway A

S

A

H

Roadway

Walkw

ay

Walkw

ay

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Figure 13. Two- sided coupled installation.

12.4.2.4. Central or double row

In traffic roads with a central reservation between the two directions of traffic, aiming points will be installed in double-

armed columns or shafts, located in the central reservation, when its width ranges between 1 and 3 m. (Fig. 14).

Figure 14. Installation for values 1 < b < 3 m.

For central reservations, wider than 3 m., double-armed shafts will not be used. In any case, their disposition will be

studied as if we were talking of two separate and independent roadways, giving rise to the installation of the following

figures. Fig. 15 is recommended over Fig. 16, since drivers are incited to circulate always on the traffic lane nearest

to the central reservation (left lane).

Figure 15. Installation for any b value.

b

Walkway

Walkway

Roadway

Roadway

Direction of traffic

Direction of traffic

Central reservation

b

Walkway

Walkway

Roadway

Roadway

Direction of traffic

Direction of traffic

Central reservation

Walkway

Walkway

Roadway A

S

A

H

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220 LIGHTING ENGINEERING 2002

Figure 16. Installation for values b > 3m.

12.4.2.5. Catenary

Aiming points are fixed axially to the catenary longitudinal cables, lying between two solid supports installed in the

central reservation and located at a great distance one from the other, at about 50 to 100 m. (Fig. 17).

Figure 17. Catenary installation.

This type of distribution has a very serious inconvenience which is that aiming points are easily moved by the action

of the wind, losing some of their effectiveness.

b

Walkway

Walkway

Roadway

Roadway

Direction of traffic

Direction of traffic

Central reservation

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12.4.2.6. Combined groupings

Different combinations of the five basic dispositions (one- sided, staggered, two- sided, central and catenary) may

be used. For example, in two roadway roads with a central reservation, it is usuall to combine central and two- sided

installations in opposition (Figs.18 and 19).

Figure 18. Combined grouping.

Figure 19. Combined grouping.

Slow moving traffic roadway

Slow moving traffic roadway

Direction of traffic

Central reservation

Central reservation

Walkway

Walkway

Fast moving traffic roadway

Direction of traffic

Direction of traffic

Direction of traffic

Walkway

Slow moving traffic roadway (2 lanes)

Slow moving traffic roadway (2 lanes)

Fast moving traffic roadway (3 lanes)

Fast moving traffic roadway (3 lanes) RoadwayDirection of traffic

Direction of traffic

Direction of traffic

Central reservation

Central reservation

Central reservation

Walkway

Direction of traffic

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222 LIGHTING ENGINEERING 2002

12.4.3. Disposition of aiming points in elevationFor disposition of aiming points in elevation, the height adopted will be mounting height H chosen in lighting engineering

calculations. However, there are special instances in which mounting height must be fixed according to other concepts, as it

happens with traffic roadways with trees near the edges.

If trees have an enormous size, they can be cleared up to a height of 8 or 10 metres. Luminaires will be placed at such height

(Fig. 20).

Figure 20. Elevation of enormous trees.

If trees have a small size, luminaires will be placed at a height of 12 to 15 metres (Fig. 21). In any case, it is convenient to

give trees an adequate pruning periodically.

Figure 21. Elevation of small trees.

12 - 15 mts.

8 - 10 mts.

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12.4.4. Disposition of aiming points in intersections

12.4.4.1. Intersections in right angle with two illuminated roadways

Two cases must be distinguished for this type of intersections: whenever motor traffic on roadways is not canalized

(Figs. 22 to 25), and whenever motor traffic on only one of the roadways is canalized by means of small directional

traffic islands (Fig. 26).

When motor traffic on roadways is not canalized, the problem must be tackled by combining installations

recommended for each type of lighting (one- sided, staggered, double row, two- sided, etc.), as represented in Figs.

22 to 25.

Aiming points drawn in intersections in white serve as the basis for installing the rest.

Figure 22

Figure 23

e = normal separation

Right angle intersection: Recommended installation on two roadways with staggered lighting

e' = reduced separation

e ee' < e

e1e1

e1' <

e1

e = normal separation

Right angle intersection: Recommended installation on two roadways with one- sided lighting

e' = reduced separation

e ee' < e

e1e1

e1' <

e1

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224 LIGHTING ENGINEERING 2002

Figure 24

Figure 25

In the second case, when motor traffic in one of the roadways is canalized by means of small directional traffic islands

whereas, traffic is not in the other, (Fig. 26), the installation of aiming points must begin with the roadway provided

with traffic islands, which will be studied separately. The installation of aiming points will begin from the intersection,

reducing the separation between these and continuing with the roadway with canalized traffic, adopting any of the

adequate installation systems (one- sided, staggered, double row, two- sided, etc.).

The origin of locating aiming points for roadway lighting wherever traffic is not canalized by means of traffic islands

will be also tackled at the intersection, adjusting aiming points as established for the other roadway, and continuing

with an adequate placing of aiming points bearing in mind the roadway characteristics (one- sided, staggered, double

e = normal separation

Right angle intersection: Recommended installation on roadwayswith staggered and two- sided lighting

e' = reduced separation

e ee' < e

e1e1

e1' <

e1

e = normal separation

Right angle intersection: Recommended installation on two roadways with one- sided and two- sided lighting

e' = reduced separation

e ee' < e

e1e1

e1' <

e1

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row, two- sided, etc.).

Eventually, lighting in the center of the intersection may be reinforced by installing more powerful aiming points, by

adopting more powerful lamps or installing two luminaires in every aiming point or support.

Figure 26

12.4.4.2. "T"- shaped intersections between two illuminated and partially canalized roadways

This type of intersections (Fig. 27) establishes an installation of aiming points recommended so that users who arrive

from the merging roadway are able to see an illuminated background ahead of them.

This is not the only possible solution, though. Depending on local conditions, it may be possible to reduce the

number of aiming points, using others of a higher potency and height installation (Fig. 28).

Figure 27

"T"- shaped intersection: Installation example. Double lined areasrepresent the visual guidance effect that must be provided by lighting.It may turn useful to provide circled aiming points with more power.

"X"- shaped intersection: It may turn useful to provide circled aiming points with more power

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226 LIGHTING ENGINEERING 2002

Figure 28

12.4.4.3. "Y" or "T"- shaped intersections between two roadways totally canalized

In the proximity of such intersections, generally both traffic directions for vehicles are separated by large directional

traffic islands, along which the layout of aiming points is one- sided (Fig. 29).

Likewise, more powerful and aiming points of a greater height may be placed (Fig. 30).

Figure 29

"Y" or "T"- shaped intersection: Example of a one- sided installation on two important roadways totally canalized by means of traffic islands

"T"- shaped intersection: Installation example with aiming points of more power and of height supports than those of figure 13.27. Aiming point of 18 m.with 4 luminaires. Aiming point of 18 m. with 2 luminaires. Aiming point of 12 m. with 1 luminaire. Aiming point of 12 m. with 2 luminaires

60 m.

Chapter 12. ROAD LIGHTING

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Figure 30

12.4.5. VegetationUnderstanding and cooperation between vegetation and lighting is required so that neither interferes with the job or function

performed by the other.

Figure 31

luminaire

A

D

M

Pruning line

Mou

ntin

g he

ight

70°75°80°

M = 0.36 DM = 0.26 DM = 0.17 D

Pruning line angle "A"

Tree pruningheight

"Y" or "T"- shaped intersection: Example of a one- sided installation with aiming points of more power and height than those of figure 13.29

50 m.50 m.

50 m.50 m.

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228 LIGHTING ENGINEERING 2002

The selection of the type of shrub or tree must be based on those which leave enough free space for lighting with minimum

interference between both of them. These selections may include trees with stylized, spherical or normal forms. In most cases,

a good pruning service may solve any problem between trees and road lighting.

It must be highlighted that even in installations with a great mounting height, it is not necessary to prune all trees up to the

luminaire height. It is only necessary to prude those branches which fall below the useful luminous beam (Fig. 31). Leafiness

of trees located between the luminaire and the objects, may serve the purpose of trimming and distinguishing silhouettes in

an intentioned way. At the same time, it helps to reduce luminaire direct glare on possible observers or drivers. This advantage

is particularly important in roads with local traffic and residential areas, where relatively high inter- distances, together with high

potencies and angles approaching the horizontal are required.

12.4.5.1. Criteria and design compromises

To minimize lighting interferences with trees, there are certain types of compromises which may be applied to lighting

systems. Regarding this respect, possible variations that may happen in inter-distance, mounting height, and

transverse situation of aiming points must be born in mind. Such variations generally produce, in turn, changes in the

luminous distribution of the lighting installation.

12.4.5.2. Design modifications

As a modification example, mention the fact that all luminaires may be mounted on long arms. This usually increases

the installation expenses, but improves lighting effectiveness, avoiding or palliating interference with vegetation.

Figure 32

Another possible design modification may be luminaire suspension by means of catenary systems over the center

of the roadway. In this case, the problem is the extra expenses implied by the utilization of two supports per

luminaire. An added disadvantage to this system is the loss of lighting efficacy which takes place when luminaires

are under the action of the wind, given that the wind modifies their orientation and, therefore, also their photometric

distribution.

Another possible design variation consists in reducing the luminaire installation height under vegetation, in such a

way that also lamp potency is reduced. The problem is also that of extra expenses, since the interdistance between

luminaires has to be reduced. Therefore, the number of luminaires must be increased and advantages disappear.

One last design alteration may be performed, which consists in increasing lamp potency to compensate for light lost

on its way towards roadway and sidewalks. However, this presupposes a clear inconvenience since the luminaire

RoadwayWalkway

0 2 4 6

02

46

810

1214

Luminaire projection mts.

lum

inai

re m

ount

ing

heig

ht m

ts.

Cylin

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l type

Sphe

rical

type

Ova

ltyp

e Wid

e py

ram

idal

type

Nar

row

pyr

amid

al ty

pe

Chapter 12. ROAD LIGHTING

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direct glare increases and, above all, energetic cost is also higher without resulting in a clear improvement of luminous

uniformity.

12.4.5.3. Design fundamentals

When variations in the longitudinal inter- distance of aiming points is performed so that they do not interfere with

trees, deviations of ±10% of the previous calculated separation may be assumed. Such variations do not imply great

differences as far as results are concerned.

Maximum differences of about 20% of the interdistance may be tolerated, provided it does not happen in two

consecutive aiming points. Such variation, anyway, may be proved through calculations which will indicate whether

all exigencies established beforehand are verified or not for those areas affected by modification. When separation

of two or more consecutive luminaires is altered, it must be confirmed by means of variation of other parameters,

like transverse location of aiming points or their installation height.

Luminaire alingment over the roadway is a basic factor with respect to visibility and installation aspect or appearance.

Only when it is not possible in any other way, a luminaire will be installed outside the line of the others.

The height of columns or shafts which support luminaires will be selected in such a way that it will be adequate to

each installation in particular. The higher these supports are, the fewer problems will be encountered with leafiness

of vegetation, but it is also true that expenses will probably grow in a considerable way.

12.4.5.4. Design data

Figs. 32 and 33 aim at being a practical guide when this kind of difficulties between lighting and tree leafiness appear.

For example, a luminaire transverse situation for different heights and vegetation types.

Figure 33

Although roadway lighting usually produces interferences with vegetation, lighting of walkways of other lateral areas

of the roadway must not be forgotten. This aspect is sometimes even more important than roadway lighting itself in

certain residential or pedestrian areas.

Wal

kway

sid

eRo

dway

sid

e

Dist. from luminaire to vegetation

Lum

inai

re p

roje

ctio

n in

mts

.

1

2

3

4

5

Spherical type

Wide

pyramidaltype

Cylindricaltype

Narrowpyram

idaltype

Sphe

rical typ

eW

id

e pyramidal type

Cylin

drical type

Nar

ro

wpyramidal type

229LIGHTING ENGINEERING 2002

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230 LIGHTING ENGINEERING 2002

In order to solve this problem three factors may be changed, namely:

- Luminaire installation location and height.

- Correct and regular pruning.

- Addition of an aiming point exclusively for the lighting of these areas, at a lower height than road conventional

lighting.

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231LIGHTING ENGINEERING 2002

Chapter 13.

TUNNEL LIGHTING

13.1 General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233

13.2 Long tunnel lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242

13.3 Lighting of short tunnels and underpasses . . . . . . . . . . . . . . . . . . . . . 251

13.4 Emergency lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254

13.5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.6 Ignition control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.7 Night- time lighting (tunnel exterior zone) . . . . . . . . . . . . . . . . . . . . . 255

13.8 Tunnel lighting design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255

13.9 Visual guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257

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232 LIGHTING ENGINEERING 2002

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13.1. General remarks

Vehicle driving through tunnels during day- time hours gives rise to a totally different problem when compared to night- time outdoor

driving, which is basically reduced to differences existing between high outdoor luminance levels and low luminance levels in the

interior of tunnels.

The fundamental visual problem in tunnels is that of adaptation of the human eye from high outdoor luminances during the day, to

low luminances (virtually null) in the interior of a tunnel. It must also be born in mind that, for a certain luminance distribution, an

obstacle cannot be seen if its luminance is much lower than the distribution luminance. All this provokes what is called "the black hole

effect" which prevents drivers from seeing the interior of the tunnel during the day, when they are at a certain distance from its mouth.

All this considering that for the majority of tunnels, day- time natural light only enters, depending on their orientation, some distance

of about one to three times their longest transversal dimension. Beyond such a distance, existent luminous conditions are not enough

to secure visibility of eventual obstacles, or for an adequate guidance of drivers.

From the point of view of lighting engineering, the following zones may be differentiated in tunnels: access, entrance constituted by

the zones of threshold and transition, interior and finally, exit (see Fig. 4). Due to economic reasons, it is not possible to establish

lighting conditions identical to those existing during the day in the outside (access zone) in the tunnel entrance zone, which may reach

values of up to 100 000 lux.

In the threshold zone located just at the entrance of the tunnel, with an approximate length equal to the security distance, lighting

during the day must be measured in such a way that it will secure enough vision of eventual obstacles on the roadway. Although a

first brusque reduction of lighting levels existent outside (access zone) takes place, it is acceptable. In the second part of the threshold

zone, lighting levels progressively diminish.

13.1.1. Visual problems in tunnelsVisual problems in tunnels comprises induction and adaptation effects, as well as the influence of veiling luminances. All this

requires to bear security distance in mind depending on tunnel traffic speed.

13.1.1.1. Induction effect

Human eye sensitivity depends on the distribution of luminances in the field of vision. Sensitivity is also influenced

by two phenomena called induction and adaptation.

Regarding induction, it is the effect produced by the influence of adjacent parts of the retina to that in which the

image of the object being seen is formed. If the driver’s eyes are in a state of adaptation to a certain distribution of

luminances, this person can only see those objects whose luminance is close to the mentioned distribution.

Due to the eye adaptation of a driver who is approaching a tunnel to high daytime exterior luminances, when the

driver observes the mouth or entrance of the tunnel, the part of the retina receiving the image from outside

influences the other part receiving the image of the tunnel entrance, thus, creating an effect of induction. Hence, the

tunnel entrance appears as a “black hole” in which not a single detail can be seen. The induction effect makes that

with a given distribution of luminances (natural daytime road lighting), an object cannot be seen if its luminance is

much lower than the distribution one (virtually null lighting at the tunnel entrance), no matter how long such an

object is contemplated.

13.1.1.2. Adaptation effect

It allows the adjustment of the human eye sensitivity to a change in the distribution of luminances in the field of

vision. The time required for the adaptation of the human eye sensitivity to a change in the distribution of luminances,

is known as adaptation time.

The adaptation of the eye sensitivity to quick changes in the distribution of luminances in the field vision is not

instantaneous. For a certain amount of time, visual capacity decreases, giving rise to a momentaneous blindness in

case of a brusk change in the distribution of luminances. That is to say, in some situations like the case of tunnel

entrances, the problem may be serious and visual function may not be possible.

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234 LIGHTING ENGINEERING 2002

13.1.1.3. Influence of veiling luminances

Parasite light present on the drivers’ eyes (foveal veiling luminance or Fry’s), the atmospheric situation (atmospheric

luminance) and reflexes on the vehicle winshield (windshield luminance), are combined to form a luminous veiling

that reduces visibility of obstacles at the entrance of tunnels.

The main reason for tunnel lighting is to secure visibility of obstacles at any time, which requires to perceive a

difference between luminance of the obstacle and luminance of the background or tunnel roadway and walls.

By definition, contrast is expressed in the following way:

where:

L0 = Luminance of the obstacle.

Lf = Luminance of the background.

Contrast C may be positive or negative:

If L0 > Lf C > 0 Positive contrast (obstacle lighter than background)

If L0 < Lf C < 0 Negative contrast (obstacle darker than background)

In the case of tunnels, two types of contrast must be distinguished: the so- called intrinsic or physic Cint measured

next to the obstacle and the retina contrast CR measured from the vehicle driver’s eye.

In Fig. 1, it may be checked that intrinsic contrast Cint is measured next to the obstacle in (1), while retina contrast

CR is evaluated from the observer’s eye in (4). Between both contrasts, a set of veiling luminances called atmospheric

Latm, of windshield Lpb and foveal or Fry’s Lv, respectively, which give rise to veiling glare which discomforts vision in

the driver’s eyes.

The layers of air in the atmosphere containing particles illuminated by sunlight give rise to atmospheric luminance

Latm due to the refraction of light in such air layers of the atmosphere. This type of luminance depends on

atmospheric conditions and the position of the sun.

Luminance of the windshield Lpb is produced as a result of the existence of windshields in vehicles, which provokes

difraction or reflection effects depending on the position of the sun in the visual field and the state, curvature and

inclination of the windshield itself.

Foveal veiling luminance or Fry’s Lv is caused by the discomfort in vision provoked by a luminance not belonging to

the visual task to be perfomed. This also difficulties the perception of images of such a visual task, due to the

luminous veil produced in the driver’s eye as a result of the difraction of light in the aqueous humor of the eye globe.

Atmospheric windshield and foveal or Fry’s veiling luminances produced between the obstacle and the driver, as

shown in Fig. 1, reduce the intrinsic contrast Cin of the obstacle (CR < Cint) without changing the sign of the contrast,

decreasing visibility of obstacles at the entrance of tunnels.

Such a reduction in the intrinsic contrast may cause that visibility of obstacles at the entrance of tunnels is not

secured, above all in the case of strong veiling luminances, which may oblige to duplicate luminance values to be

reached in the tunnel threshold zone by means of artificial lighting. The aim is to soften reduction of the mentioned

contrast. Consequently, a decrease of the visibility of obstacles on the part of the driver may take place. Thus, the

effect produced by veiling luminances is taken into account when establishing lighting levels at the entrance of

tunnels.

Parasite or veiling luminances which characterise the effects of the surroundings of the tunnel, the windshield and

the atmosphere and bother the driver’s vision are variable according to the region and zone where the tunnel is

located. They also depend on its orientation, season, climate, hour of the day, etc.

C = L0 – Lf

Lf

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Figure 1

13.1.1.4. Security distance

Security distance (DS) is defined as the necessary distance for the driver of a vehicle circulating at a certain speed

to stop before an obstacle on the roadway is reached. Such a distance consists of two addends: the vehicle travel

from the moment in which the driver sees the obstacle until this person brakes, and the breaking distance as such.

Security distance may be calculated according to the following formula:

where:

DS = Security distance (m.).

V0 = Design speed (Km/h.).

RT = Perception- reaction time (s).

f1(v) = Friction coefficient (longitudinal) dependent on v.

g = Gravity acceleration (9.81 m/s2).

h = Slope or gradient inclination of the road (%).

Applying the formula, the following examples of stopping distance “DS” on flat roads for retardations from 3.5 to 5

m/s2 are obtained:

Chart 1

When a vehicle is close to a tunnel, the induction and adaptation effects and the influence of veiling luminances are

intimately related to the distance at which the driver of the vehicle is at the entrance of such a tunnel, in the so-called

access zone with an approximate length equal to the security distance (DS, Fig. 4).

The higher the speed of a vehicle, the higher the security distance (DS). This is the reason why some considerations

must be taken into account:

- Perception of an obstacle is proportional to the inverse of the square of the security distance (DS-2), supposing

contrast is constant.

- Atmospheric veiling luminance Latm is proportional to the security distance (DS). Atmospheric transmission is

Tatm = 10-k·DS.

- Visual adaptation speed is related to the vehicle approximation speed.

Design speed (Km/h) Ret 120 100 80 70 60 50

DS (wet road) m. 3.5 230 160 105 90 70 50

DS (dry road) m. 5 150 110 75 65 55 40

DS = RT · V0 +

1

3.6 3.62 · g

vdv

f1 (v) + h· !

AtmosphereWindshield

Foveal or Fry's veil

2

4

3

1

Atmospheric parasite veils Latm of windshield Lpb and of foveal veil or Fry's Lv

CR = LOR - LfR

LfRCint. = LO - Lf

Lf

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236 LIGHTING ENGINEERING 2002

For a driver in the access zone, the higher the speed of the vehicle, the longer the distance from the entrance of the

tunnel towards the interior in which the driver has to see inside the tunnel. This presupposes greater length of the

threshold zone to be illuminated.

Likewise, the greater the distances, an obstacle located in the interior of the tunnel requires a smaller angle in the

driver’s eye and, thus, it is less visible. Besides, the air layer between the driver located in the access zone and the

entrance of the tunnel is greater, which means greater atmospheric luminance Latm, reduction of intrinsic contrast Cint

and, consequently, decrease of visibility of obstacles. All this requires higher lighting levels in the threshold zone of

the tunnel.

In short, higher speeds require longer security distances (DS), which means greater length of the threshold zone of

the tunnel to be provided with lighting, as well as higher lighting levels in such a zone. Therefore, due to both reasons,

higher costs come along.

13.1.2. Lighting systemsLighting systems in tunnels may be divided into two families: symmetrical and asymmetrical, which, at the same time,

comprises a lighting system with flux opposite to vehicle circulation directions. This also receives the name of “counterflux”.

The lighting system favoring the flux lacks practical utility and, therefore, is not considered.

Lighting of tunnels is characterized by the contrast quality parameter P, also known as contrast development coefficient qc

whose formula is the following:

where:

L = Roadway luminance in cd/m2.

Ev = Obstacle vertical illuminance in lux at the roadway level in the direction of traffic. That is to say, average

illuminance on a vertical surface perpendicular to the axis of the tunnel, and oriented towards the entrance.

13.1.2.1. Symmetrical lighting system

The symmetrical lighting system is that in which luminaires have a distribution of luminous intensity which is

symmetrical in relation to the plane C 90º/270º. To a plane perpendicular to the axis of the tunnel, as represented in

Fig. 2.

Contrasts of obstacles may be negative or positive, depending on the reflection properties of their surface.

Nevertheless, this system strives to secure vision on a positive contrast: obstacles will be seen as light against the

dark background of the tunnel roadway and walls.

The symmetrical lighting system is used in all cases in the interior zone of tunnels with luminaires provided with

conventional and compact fluorescent lamps, high and low pressure sodium lamps or discharge by induction lamps.

The installation of such a system is possible in the entrance zone of such tunnels which have established a low

limitation in the approximation speed of vehicles.

This system allows good visibility of obstacles and lack of glare. From a photometric point of view, it is advisable that

the roadway pavement and the tunnel walls are diffusing surfaces (low specular factor S1) and light (high average

luminance coefficient Q0). Therefore, it is convenient that pavement belongs to the R1, R2 or C1 Class, following

recommendations of the C.I.E., with a high degree of brightness or luminosity (Q0 is the highest possible).

P = qc = L

Ev....

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Figure 2

The measuring of tunnel lighting, by means of a symmetrical system in the entrance zone leads to lighting levels

difficult to achieve for approximation speed of vehicles higher than 90 Km/h with weak or average veiling luminances

in the access zone, or higher than 70 Km/h with strong veiling luminances. When levels higher than 200 cd/m2 are

to be achieved, very complicated to reach in practice with the symmetrical system, it is necessary to find other

alternatives in such situations, either limitation of the speed of vehicles or installation of a lighting system at

counterflux in the entrance zone.

13.1.2.2. Counterflux lighting system

The counterflux lighting system is a system in which luminaires have a distribution of asymmetric luminous intensity,

directed against the direction of traffic, as represented in Fig. 3.

This lighting system favours seeing obstacles by negative contrast. Obstacles are highlighted as dark against the

roadway light background and tunnel walls, due to the fact that vertical illuminance in planes facing approaching

drivers is low. This vision in negative contrast is achieved reducing the obstacle luminance (L0), slightly limiting its

vertical illuminance (Ev), and increasing roadway luminance.

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238 LIGHTING ENGINEERING 2002

Figure 3

The counterflux lighting system is only used in the tunnel entrance zones. It is recommended in this zone where the

limitation of the vehicle speed is high, that is to say, from approximately 90 Km/h, given economic advantages found

in these situations. Luminaires are to be installed over traffic lanes and are normally equipped with high pressure

sodium lamps. It must be stressed that counterflux lighting is never installed in the interior zone of tunnels.

Due to the own structure of the system, its installation must be avoided in two- way tunnels (bidirectional), because

in this case, what is counterflux for one determined direction of traffic would be favourable for the opposite one, thus,

modifying drivers’ visual conditions.

The counterflux lighting system usually creates more contrast between the obstacle and the background, but it can

also produce a certain increase in the “black hole” effect, reducing drivers’ visual comfort. Likewise, such a counterflux

system may not be appropriate for the entrance of tunnels with high daytime light, and it is even less effective when

traffic intensities are very high or a high percentage of slow moving vehicles is foreseen.

In this lighting system which provides good visibility of obstacles, glare must be limited controlling luminous intensity

emited by luminaires. The use of specular pavement (high specular factor S1) and light is advisable, from a

photometric point of view. That is to say, with a high average luminance coefficient Q0, pavement class R3, R4 or C2,

according to recommendations of the C.I.E., with a high degree of brightness or luminosity (Q0 is the highest

possible). Besides, a high luminance must be limited in tunnel walls, at least, up to a 1 m. level, with the aim of

reducing obstacle vertical illuminance (Ev).

13.1.2.3. Contrast development coefficient

The adopted lighting system either symmetrical or counterflux is characterized by certain contrast development

coefficients qc, whose values are included in Chart 2.

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Chart 2

The value of the contrast development coefficient qc = L/Ev is slightly linked to the intrinsic characteristics of the

tunnel lighting system, to the installation of luminaires and the reflective characteristics of the pavement, as well as

to the photometric contribution of the tunnel walls.

These values of Chart 2 characterize the lighting system of tunnels only in night- time measures, that is to say, without

influence of day- time light, which alters values of the contrast development coefficient qc.

In measurements during the day in the entrance zone of tunnels and for the symmetrical lighting system, qc reaches

figures higher than 0.2, whereas for the counterflux system, qc values are lower than 0.6. Especially, due to this

variation in the contrast development coefficient qc = L/Ev during a day- time measurement respect to a night- time

measurement, contrast changes sign going from negative to positive contrasts and viceversa. This gives rise to

situations in which obstacles are not perceived.

13.1.2.4. Natural lighting system with daytime light

Besides artificial lighting systems and counterflux ones, there is another alternative for tunnel entrance lighting by

means of an adequate use of shielded daytime light provided by paralumens or screens. This type of natural lighting

must satisfy the same luminous levels than those of artificial lighting. Factor k values (coefficient by which luminance

of the tunnel access zone must be multiplied L20 in order to obtain luminance of the threshold zone of the tunnel

Lth, that is to say, Lth = k L20), are identical to those of the symmetrical lighting system. Likewise, the contrast

development coefficient qc for natural lighting will be determined in the same way as for artificial lighting, included

also, in the calculation to the interreflected light contribution.

13.1.3. Tunnel classificationThe parameter that allows a classification of tunnels is that of their geometric conditions and, their length, in particular. Lighting

exigencies for long and short tunnels differ according to the degree in which the driver of an approaching vehicle may see

through the tunnel. The capacity to see through the tunnel essentially depends on its length, but also on other design

parameters (width, height, horizontal and vertical curvatures, etc.).

13.1.3.1. Classification of long tunnels

As far as lighting is concerned, long tunnels are classified according to traffic intensity, speed and composition, visual

guidance and driving comfort.

13.1.3.1.1. Ponderation factors according to traffic intensity

There is a certain ratio, but not a linear one, between traffic intensity and the risk of accidents which

may be counteracted, increasing the lighting level of the tunnel to a certain extent.

The second factor to bear in mind is that high speed requires better visibility and, this is the main reason

why a higher luminance level on the roadway is necessary.

As soon as it has been decided that a tunnel should be provided with lighting, speed has a considerable

importance, due to its influence in visibility requisites. The higher the speed, the longer security distance

(DS), which obliges to higher luminances in the threshold zone of the tunnel.

When a tunnel is going to be illuminated, traffic intensity is defined as hourly intensity, that is to say, as

the number of vehicles circulating on a road lane at a certain hour. Ponderation factors depend on traffic

intensity they are detailed in Chart 3.

Symmetrical ≤ 0.2

Counterflux ≥ 0.6

Contrast development coefficient qc = LIEv

Lighting systems

CONTRAST DEVELOPMENT COEFFICIENT

Note: Lighting systems whose values for contrast development coefficient is between 0.2 and0.6 have not been taken into account.

239LIGHTING ENGINEERING 2002

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240 LIGHTING ENGINEERING 2002

Chart 3

13.1.3.1.2. Ponderation factors according to traffic composition

As it has been indicated, the degree of dificulty of the task of driving a vehicle on a road is generally

influenced by traffic speed and intensity, not to mention traffic composition and road layout and

surrounding areas.

Traffic composition also influences lighting design of tunnels in several aspects:

- Percentage of lorries.

- Presence/ ausence of motorbikes and/ or bicyclists.

- Presence/ ausence of limitation to allow the transit of dangerous cargo.

Lighting design in tunnels must be adapted to previous circumstances. Higher luminous levels or better

lighting of walls or roadways is required when conditions are more difficult or more dangerous.

Ponderation factors depending on traffic composition are the following:

Chart 4

13.1.3.1.3. Ponderation factors according to visual guidance

The driver of a vehicle must have adequate information to drive along the tunnel. This may be achieved

dividing the longitudinal surface of the tunnel into several contrast surfaces, like for example, using a

light wall and a dark ceiling. Visual guidance is of special importance:

- When the user is approaching the tunnel.

- Specially if the tunnel entrance contour is low.

Ponderation factors according to visual guidance are the following:

Chart 5

Good visual guidance 0

Poor visual guidance 2

PONDERATION FACTORVISUAL GUIDANCE

PONDERATION FACTORS ACCORDING TO VISUAL GUIDANCE

Motorized traffic 0

Motorized traffic (trucks percentage > 15%) 1

Mixed traffic 2

PONDERATION FACTOR TRAFFIC COMPOSITION

PONDERATION FACTORS ACCORDING TO TRAFFIC COMPOSITION

< 60 < 30 0

60-100 30-60 1

100-180 60-100 2

180-350 100-180 3

350-650 180-350 4

650-1200 35-650 5

> 1200 650-1200 6

> 1200 7

BidirectionalUnidirectionalPONDERATION FACTOR

TRAFFIC INTENSITY (Vehicles/hour per lane)

PONDERATION FACTORS ACCORDING TO TRAFFIC INTENSITY

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Visual guidance provided by tunnel lighting allows an increase in the visibility of the roadway and vertical

and horizontal marking, especially the latter, installing, in turn, marking (rows of luminaires, post

mounted delineators, etc.) both on the roadway and on the tunnel walls in order to improve visual

guidance.

In this sense, when establishing ponderation factors depending on visual guidance (Chart 5), additional

installation of retroreflecting dispositives on the walls and surface of the roadway, especially for tunnels

corresponding to 5, 6 and 7 lighting classes (Chart 7), will be taken into account.

13.1.3.1.4. Ponderation factors according to driving comfort

Driving comfort of vehicles in tunnels must be taken into account for their lighting purposes, understood

as easiness and a minimum effort on the part of users, due to complete information received and lack

of complexity of the visual field.

Ponderation factors according to comfort when driving are the following:

Chart 6

13.1.3.2. Lighting classes for long tunnels

Once ponderation factors have been established according to traffic intensity and composition (Charts 3 and 4), as

well as the corresponding factors depending on visual guidance and driving comfort (Charts 5 and 6), lighting classes

for long tunnels are defined:

Chart 7

13.2. Lighting of long tunnels

The main photometric characteristics necessary to establish lighting quality for a tunnel are the ones listed below:

- Luminance level of the roadway.

- Luminance level of the walls, especially up to a height of 2 m.

- Luminance distribution uniformity in roadway and walls.

- Limitation of glare.

- Control of Flicker’s effect.

In Fig. 4, a cross- sectional representation of an intercity unidirectional long tunnel, is giving a detailed account of lengths and luminance

0-3 1

4-5 2

6-7 3

8-9 4

10-11 5

12-13 6

14-15 7

PONDERATION FACTOR SUMPONDERATION FACTOR

LIGHTING CLASSES FOR LONG TUNNELS

Low comfort needed 0

Intermediate comfort needed 2

High comfort needed 4

PONDERATION FACTORDRIVING COMFORT

PONDERATION FACTORS DEPENDING ON DRIVING COMFORT

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levels of the different zones. Nomenclature and a corresponding definition of such lighting engineering levels is established below:

L20 = Luminance in access zone.

Lth = Luminance in the threshold zone.

Ltr = Luminance in the transition zone.

Ln = Luminance in the interior zone.

Lex = Luminance in the exit zone.

Figure 4

13.2.1. Luminance in the access zoneThe access zone is the part of the road in the open air, situated immediately before the entrance or tunnel portal. It covers

the distance at which a driver approaching the tunnel must be able to see its interior. The length of the access zone is equal

to the security distance (DS), as it has been stated in Fig. 4.

The luminance value necessary at the beginning of the threshold zone must be based on the luminance value in the access

zone L20 at a separation in front of the tunnel equal to the security distance (DS). Under identical daytime light conditions,

tunnels with different approximation zones and surroundings (different relief, surroundings, etc.) will have considerably

different luminance values in the access zone L20.

In order to design and project the lighting installation in a tunnel, it is necessary to know the L20 maximum value which takes

place with enough frequency during the entire year, at a separation in front of the tunnel equal to the security distance (DS).

As in most cases, this value L20 depends on seasonal conditions and weather. Two simplified empirical methods for the

evaluation of L20 are used. Next, two methods to calculate luminance in the access zone are exposed.

Approximation method

As indicated by its name, this method only provides an approximate indication, and must only be used when there is a lack

of information enough detailed about the immediate surroundings of the entrance mounth of the tunnel. This method consists

in choosing the luminance of the access zone with the help of Chart 8 expressed in Kcd/m2 (103 cd/m2).

Tunnel length

Interior zone

DS= Security distance

Direction of traffic

Lin

Transitionzone

Threshold zone

Access zone

Entrance zone

Lum

inan

ce

DSDS DS

Exit zone

Entr

ance

Exit

L20Lth

Ltr

Lex

Entrance ExitDirection of traffic

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Chart 8

Exact method

Luminance of the access zone L20 is the average luminance contained in a conical field of vision represented by an angle of

20%, with its vertex in the position of the driver’s eye. It is located at a distance before the tunnel equal to the stopping

distance, and the cone oriented towards the tunnel portal on a point situated at a height of 1/4 of the tunnel mouth.

Determining luminance for the access zone L20 is extremely relevant since it predetermines the level to be obtained by means

of lighting in the threshold zone. Such luminance of the access zone depends on the atmospheric conditions of the place

where the tunnel is located. The calculation of the luminance of the access zone L20 is obtained from a sketch of the

surroundings of the tunnel zone. The formula below is used:

L20 = a * Lc + b * LR + c * LE + d * Lth

where:

a = % of the sky.

Lc = Sky luminance.

b = % of the road.

LR = Road luminance.

c = % of the surroundings.

LE = Surrounding luminance.

d = % tunnel entrance.

Lth = Threshold zone luminance.

with: a + b + c + d = 1

The unknown factor to be determined in the formula is the value of the luminance in the threshold zone (Lth). When stopping

distances higher than 100 m. are faced, the mouth entrance percentage of tunnels is low (< at 10%) and since Lth also has

ROAD TYPES

SKY PERCENTAGE (%) IN CONICAL VISUAL FIELDS AT 20°

REGULAR SNOW

0%

CHART AAVERAGE LUMINANCE OF THE ACCESS ZONE L20 (Kcd/m2)

Brightness situation in the visual field

Security distance 60 m

Security distance 100 to 160 m

Being:

1) Effect fundamentally depends on tunnel orientation:«B»: Low; In the north hemisphere: «southern entrance».«A»: High; In the north hemisphere: «northern entrance».For eastern and western entrances intermediate values between low and high must be chosen.

2) Effect fundamentally depends on brightness of surroundings:«B»: Low; Low reflectances of surroundings.«A»: High; High reflectances of surroundings.

3) Effect fundamentally depends on tunnel orientation:«B»: Low; In the north hemisphere: «northern entrance».«A»: High; In the north hemisphere: «southern entrance».For eastern and western entrances intermediate values between low and high must be chosen.

4) For a stopping distance of 60 m, in practice, there are no sky percentages of 35$.

Notes: «northern entrance» means the entrance for drivers circulating southwards. «southern entrance» refers to the entrance for drivers circulating northwards.

(1)

(4)

4 6 4 6 4 6 4 6 3 4.5 3 5 2.5 5 2.5 5

(4) 4 5 4 5 2.5 3.5 3 3.5 1.5 3 1.5 4

(1) (1) (1) (2) (3) (2) (3)

B AB A

REGULAR SNOW

10%

B AB A

REGULAR SNOW

25%

B AB A

REGULAR SNOW

35%

B AB A

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244 LIGHTING ENGINEERING 2002

a low value with respect to other luminance values, the contribution of Lth may be disregarded.

For a stopping distance of 60 m., the norm establishes that:

L20 = (a * Lc + b * LR + c * LE) / (1 / K)

Because K never exceeds 0.1, the result is:

L20 = a * Lc + b * LR + c * LE

being a + b + c < 1.

If the data to know exactly the value for “a, b, c and d” are not available, the ones defined in the following charts will be used.

If surrounding values are not available, the following are used:

Chart 9

In this chart, the value for “L” is known. In order to define the percentage of the sky which contributes to the value L20 in the

installation under study, Fig. 5 is used.

N 8 3 3 8 15 (M, H) 2

E - O 12 4 2 6 10 (M) 2

15 (H)

S 16 5 1 4 5 (M) 2

15 (H)

Driving

direction

Sky

(Lc)

Kcd/m2

Road

(LR)

Kcd/m2

Surroundings

(LE)

Rocks Edifices

Kcd/m2

Snow Grass

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Figure 5

13.2.2. Luminance in the entrance zoneAs Fig. 4 shows, tunnel entrance consists of two consecutive stretches: the threshold zone, which is the nearest to the

Security distance 160 m. Sky 35% Security distance 100 m. Sky 27%

Security distance 60 m. Sky 14% Security distance 100 m. Sky 18%

Security distance 160 m. Sky 14% Security distance 100 m. Sky 3%

Security distance 100 m. Sky 18% Security distance 100 m. Sky 4%

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tunnel mouth and the transition zone.

13.2.2.1. Lighting levels for threshold zone

The threshold zone is the first part of the tunnel located directly after the portal, thus, beginning at its entrance. The

luminance level Lth (average luminance in service of the roadway surface with maintenance of the installation), which

must be provided by lighting during the day at the beginning of the threshold zone, is a percentage of the luminance

of the access zone L20; thus, it is verified:

Lth = k · L20

Factor k is established in Chart 10 taking into account the lighting system adopted (counterflux or symmetrical),

security distance (DS) and lighting class defined in Chart 7, depending on ponderation factors (traffic intensity and

composition, visual guidance and vehicle driving comfort).

Chart 10

13.2.2.2. Threshold zone length

Length of the threshold zone must be, at least, equal to the security distance (DS). For the first half of such distance

(DS), luminance on the roadway will be equal to Lth, that is to say, the value at the beginning of the threshold zone.

Half of the security distance (DS) onwards, luminance of the roadway may gradually and linearly decrease down to

a value, at the end of the threshold zone, equal to 0.4 Lth (Fig. 6). The gradual reduction in the second half of the

threshold zone may take place in a staged way, so that ratio between stages does not exceed the ratio 3:1 and

luminance does not go under those values corresponding to linear gradual decrease.

13.2.2.3. Luminance of walls

Wall average luminance in the threshold zone, up to a height of 2 m., must be similar to average luminance of the

roadway surface.

13.2.2.4. Luminance and length of the transition zone

The transition zone is that part of the tunnel following the threshold zone, as indicated in Fig. 4. Therefore, it begins

at the end of the threshold zone and finishes at the beginning of the interior zone.

1 10 15 30 15 20 35

2 15 20 40 20 25 40

3 20 30 45 25 35 45

4 25 35 50 30 40 50

5 30 40 55 35 50 65

6 35 45 60 40 55 80

7 40 50 70 50 60 100

Notes: For security or stopping distances (DS) ranging between (60-100 and 160 m), values for factor (k) are obtained by linear interpolation between thefigures established in the chart. Values for factor (k) for the lighting system at counterflux have been determined to guarantee, in most situations, a degreeof security and comfort, at least, comparable to that achieved with the symmetric lighting system.Security or stopping distances for 60, 100 and 160 m are respectively equivalent to design speeds of the tunnel of 60, 80 and 100 km/h.

LIGHTING

SYSTEM

Lighting

class

Security distance (DS)

60 m 100 m 160 m

Security distance (DS)

COUNTERFLUX SYMMETRIC

60 m 100 m 160 m

VALUES FOR k · 103 FOR THE THRESHOLD ZONE

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Figure 6

According to Fig. 6, the length of the transition zone is the distance a vehicle must travel to go from the level of

luminance at the end of the threshold zone, up to the luminance value at the beginning of the interior zone, visual

adaptation supposed. Consequently, for each speed of the vehicle, the allowed reduction of luminance in the

transition zone Ltr, depends on the distance travelled in the mentioned zone.

Average luminance in service of the roadway with maintenance of the installation of the transition zone Ltr decreases

gradually, from the luminance of the threshold zone down to the luminance of the interior zone. In any position in

the transition zone, luminance of the roadway surface must be equal or exceed luminance established in Fig. 6.

The curve of Fig. 6 is the result of numerous experimental tests depending on eye adaptation, from high luminance

levels to very low values which have given rise to a mathematical approximation corresponding to the following

formula:

Ltr = Lth · (1.9 + t)-1.428

being: t = time in seconds.

In practice, a decrease in the luminance in the transition zone may take place through a series of stages which must

be lower than the ratio 3:1. Luminance cannot reach values lower than those of the curve in Fig. 6. The end of the

transition zone is reached when its luminance is equal to three times the level of the interior zone of the tunnel.

It is compulsory that wall average luminance of the tunnel up to a 2 m. height, in any specific position of the transition

zone, must not be lower than average luminance of the roadway in such a place.

13.2.3. Lighting of the interior zoneThe interior zone is that part of the tunnel following the transition zone directly. Its length is given by the distance existing

between the end of the transition zone and the beginning of the exit zone. Luminance levels Lin of the interior zone of the

tunnel, constant along such a zone, since eye adaptation is finished from the high luminous values in the exterior, are

L %10080

0.5 DS

Lth

60

40

20

108

6

4

2

10 2 4 6 8

100 m.

100 m.

100 m.

100 m. 200 m. 300 m. 400 m. 500 m. 600 m.

200 m. 300 m. 400 m. 500 m.

200 m. 300 m. 400 m.

200 m. 300 m.60 Km./h

80 Km./h

100 Km./h

120 Km./h

10 12 14 16 18 20

t. sec.

Threshold zone Transition zone

Security distance(DS)

Ltr = Lth(1.9 + t)-1-428

Ltr = Lth(1.9 + t)-1-428

with Lth = 100% and t = time in seconds

SCHEMATIC REPRESENTATION OF THE LIGHTING LEVEL OF DIFFERENT ZONES

Minimum luminance in entrance zone. The 100% value correspondsto the first half of the threshold zone

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248 LIGHTING ENGINEERING 2002

established in Chart 11 depending on the security distance (DS) and the lighting class defined in Chart 7.

Up to a height of 2 m., the walls of the tunnel must have an average luminance similar to the roadway average luminance in

service with maintenance of the installation Lin.

The luminance level in the interior zone of the tunnel must allow to reach the following objectives:

- Visibility of any eventual obstacle on the roadway at a distance, at least, equal to the security distance, bearing in

mind opacity of the atmosphere of the tunnel due to vehicle toxic fumes.

- Guidance of vehicles without ambiguities.

- Good quality of the luminous environment, whose psychological effect above all is important in very long tunnels.

It must be stated that levels of the interior zone are achieved in all the length of the tunnel. Also, in the so- called lighting

reinforcement zones (entrance zone and, exit ones, too), where this lighting is called basic lighting.

Chart 11

13.2.4. Lighting of the exit zoneThe exit zone is the part of the tunnel in which, during the day, the driver’s vision is predominantly influenced by the exterior

high luminance of the tunnel. The exit zone begins at the end of the interior zone and finishes at the mouth of the tunnel exit.

In the exit zone of the tunnel a luminance level Lex on the roadway must be established to illuminate vehicles directly. This

must be done in such a way that the smallest are visible in the exit zone of the tunnel, given that, they would remain hidden

behind big vehicles without lighting reinforcement above the levels of the interior zone Lin. The reason being glare originated

by daytime light of the tunnel exit.

Likewise, such roadway average luminance in service with maintenance of the installation Lex of the exit zone of the tunnel

allows drivers of vehicles leaving the tunnel to have enough vision through rear- view mirrors of the rear part of the vehicle.

This happens particularly when the distance between vehicles is short (high intensity of traffic).

All this, even bearing in mind that to go from a weak interior luminance Lin from a high luminance in the exterior of the tunnel,

the adaptation of the driver’s eye is very fast. In general, this does not constitute a problem for the user.

However, in long unidirectional tunnels whose lighting class is 6 and 7, according to Chart 7, luminance in the exit zone Lex

must increase linearly along a length, at least, equal to the security distance (DS) from the luminance of the interior zone, to

a level 5 times higher than that of the interior zone (Lex = 5 · Lin) at a distance of 20 m. This must happen before reaching

the entrance or portal of the exit of the tunnel. The linear increase of the luminance may be done in stages, in such a way

that the ratio between stages does not exceed the ratio 3:1 in one length, at least, equal to the security distance (DS).

In cases of unidirectional tunnels whose lighting classes are 1 to 5 both included, the exit zone will have the same luminance

than the interior zone of the tunnel (Lex = Lin). Additional lighting to the one foreseen for the interior zone is not required.

Nevertheless, independently from the lighting class which corresponds to the tunnel, in certain particular cases of unidirectional

tunnels, there are serious risks of discomfort and glare at the exit. This is due to tunnel orientation, for example, or to

inconveniences produced at sunrise and sunset, thus, lighting of the tunnel exit zone must be reinforced in the conditions

1 0.5 2 3

2 1,5 2 4

3 2,5 3 5

4 2,5 3 6

5 2,5 4 6

6 3,5 5 8

7 3,5 6 10

LIGHTING

SYSTEM

SECURITY DISTANCE (DS)

60 m 100 m 160 m

LUMINANCES IN cd/m2 IN THE INTERIOR ZONE

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established for lighting classes 6 and 7.

13.2.5. Uniformity of the roadway luminanceIn tunnels, the roadway and walls behave as limits or visual guides for motor traffic. Thus, a good uniformity must be achieved

on the roadway and walls of tunnels up to a height of 2 m.

In chart 12, minimum values are established in service with maintenance of the installation of luminance overall and

longitudinal uniformity on tunnel roadways, in all zones. That is to say, in their total length and complete width of the roadway,

depending on their lighting class.

Chart 12

13.2.6. Glare limitationGiven that glare reduces visibility, it is very important to minimize it in tunnel lighting. Disturbing glare, defined as the increase

of the contrast threshold (TΙ) necessary to see an obstacle when there is glare, is specified by the following expressions:

in % for 0.05 [ Lm [ 5 cd/m2

in % for Lm > 5 cd/m2

where:

TI = Threshold increase corresponding to disturbing glare.

Lv = Total veiling luminance in cd/m2.

Lm = Average luminance on the roadway in cd/m2.

The threshold increase (TI) must be lower than 15% for threshold, transition and interior zones during the day, and for all

zones during the night. For the exit zone during the day, there is no limit in the disturbing glare.

13.2.7. Control of Flicker’s effectThe feeling of flickering or Flicker’s effect is the bothering and uncomfortable feeling caused by periodical variations of the

luminance in the field of vision. Such feelings are experimented when a vehicle is driven through luminance spatial periodical

changes, like the ones produced by luminaires installed in walls or ceilings of tunnels when there exists an inadequate

separation between them, with a high speed of change in the distribution of luminous intensity.

Visual discomfort experimented by the driver due to flickering or Flicker’s effect depends fundamentally on the following

factors:

- Number of changes of the luminance per second (flickering frequency or Flicker).

- Total duration of Flicker’s effect.

- Speed of change from light to dark, in a single cycle.

- Ratio of peak- light to valley- darkness, within each period (luminance modelling depth).

Influence of the three first points depends on the speed of the vehicle and the separation between luminaires; the last point

depends on the photometric characteristics, (luminous intensity distribution) and interdistance between luminaires, too.

When the distance between the extremes of adjacent luminaires is lower than the length of a single luminaire, the third point

TI = 95 · LV

· (Lm) 1.05

TI = 65 · LV

· (Lm) 0.8

1-2-3 0.3 0.5

4-5-6-7 0.4 0.6

LIGHTING

CLASS

UNIFORMITY

Overall U0 Longitudinal U1

LUMINANCE UNIFORMITIES ON THE ROADWAY SURFACE

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250 LIGHTING ENGINEERING 2002

related to speed of change from light to dark is minimized, the flickering or Flicker’s effect perceived becomes insignificant,

due to the fact that the lighting installation may be similar to a continuous line.

In order to calculate the flickering frequency or Flicker in a zone of the tunnel, speed of traffic is divided in metres/ second by

the separation between luminaires in metres.

Example:

v = 60 Km/h. = 16.6 m/s.

Luminaire separation = 4 m.

Flickering frequency or Flicker = 16.6 / 4 4.2 Hz.

Flickering frequencies or Flicker (luminance variation) ranging between 2.5 Hz. and 15 Hz. at driving speed for more than 20

seconds must be avoided, given the fact that the flickering effect may be disregarded for frequencies under 2.5 Hz. and above

15 Hz.

13.2.8. Night- time lightingIf the tunnel is on an illuminated stretch of road, night- time lighting of the tunnel must be, at least, equal to that of the access

road. It is recommended to have 1.5 to 2 times the values of the exterior stretch, as far as luminance level of the roadway

surface is concerned. Luminance uniformities at night must satisfy the same exigencies than in the case of day- time lighting,

thus, following minimum values established in Chart 12. All this will be equally applied to tunnels of 100 m. in length which

are not illuminated during the day.

In the case of tunnels located on a stretch of the road that is not illuminated, besides installing lighting in the tunnel according

to what has been established in the previous paragraph, the rear way of the tunnel exit must be illuminated in a length equal

to 2 times security distance (DS), at least in a 200 m. distance, with an average luminance higher than 1/3 of the roadway

luminance in the exit zone of the tunnel.

Night- time lighting will be equal to the one in the zone of the interior of the tunnel for stretches with paralumens or screens

for daytime light in the entrance zone and/ or exit of the tunnel. Supposing that an invigilance system for motor traffic is

installed and works through television cameras because of security reasons, the minimum night- time level will be of 1 cd/m2.

For general night- time lighting of all zones of the tunnel, the minimum value in service with maintenance of the installation

of the roadway average luminance will be established in Chart 13.

Chart 13

LUMINANCES OF NIGHT TIME LIGHTING IN cd/m2

LIGHTING CLASS AVERAGE LUMINANCE CD/M2

1-2 0.5

3-4-5-6-7 1

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13.3. Lighting of short tunnels and underpassesShort tunnels and underpasses present the dilemma of providing them with day- time lighting or not. Once the dilemma has been

solved in favour of requiring such an installation, the type of day- time lighting to be installed must be decided either limited, completed

or with the same characteristics than that of long tunnels.

The critical factor for establishing day- time lighting is determined by the certainty or not that drivers of vehicles approaching the tunnel

at a distance equal to the security distance (DS), see vehicles and, also, pedestrians crossing it.

Likewise, the need of artificial day- time lighting is related to the extent to which the short tunnel exit or underpass is visible for a driver

located in front of the entrance, at the security distance (DS). That is to say, vision through the tunnel depends on the following factors:

- Tunnel length.

- Existence of curves in the interior.

- Presence of slopes or ramps in the tunnel.

Figure 7. View of a short tunnel with a frame or dark background.

Short tunnels and underpasses shorter than 25 metres in length, normally do not require installation of day- time lighting. When the

short tunnel length is slightly higher than 25 metres, the dark background formed by the walls and ceiling of the tunnel, as well as by

the roadway itself, may hamper the vision of vehicles and, in turn, of pedestrians crossing it (see Fig. 7), difficulting perception. In this

case day- time lighting must be installed in the tunnel or underpass.

13.3.1. Guiding diagrams for short tunnelsWith the aim of providing a guide that will allow to make decisions of installing day- time lighting or not in short tunnels and

underpasses, as well as opting for the type of day- time lighting to be installed, a classification of four types of short tunnels

must be established. A guiding diagram is explained for each one.

Short tunnels A type – Chart 14.

Tunneles located in urban surroundings or by- passes on traffic roads (motorways and dual carriageways excluded), frequently

provided with public lighting and whose driving speed is limited between 40 and 60 Km/h.

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252 LIGHTING ENGINEERING 2002

Chart 14

Short tunnels B type – Chart 15.

Bidirectional intercity tunnels, considering a dense amount of traffic when daily average intensity of vehicles is higher than 5

000 (IMD > 5 000).

Chart 15

Short tunnels C type – Chart 16.

One- way intercity tunnels (motorways and dual carriageways), estimating a dense amount of traffic when daily average

intensity of vehicles is higher than 10 000 (IMD > 10 000).

Chart 16

Short tunnels D type – Chart 17.

Intercity tunnels with low speed traffic (speed limit considerably lower than 80 Km/h.), and a traffic density notably lower than

a daily average intensity of 5 000 vehicles (IMD < 5 000).

Chart 17

Length (m)

Visible exit?

0 to 100 101 to 150 151 to 200 > 200

— YES NO YES NO —

Lightingrequired

Day- time lightingis not required

Limitedday- time lighting

Complete day- timelighting

Long tunnel lighting

Day- time lighting for type D tunnels, intercity, short with low speed traffic (lower than 80 Km/h) and traffic density lower than5 000 vehicles in a day (IMD < 5 000).

Length (m)

Visible exit? —

YES

YES

NO

Light Dense Light Dense

YES

NO —

NO YES NO —

Speed ≤ 80 Km/h

Traffic volume

Lighting required Day- time lighting is not required Limited day- timelighting

Long tunnel lightingComplete day- timelighting

0 to 100 100 to 150 151 to 200 > 200

Day-time lighting for type C short urban unidirectional tunnels for highways and motorways (dense traffic when IMD > 10 000).

Length (m)

Visible exit? —

YES

YES

NO

Light Dense Light Dense

YES

NO —

NO YES NO —

Speed ≤ 80 Km/h

Traffic density

Lightingrequired

Day-time lighting is not required Limited day-timelighting

Long tunnel lightingComplete day-time lighting

0 to 80 81 to 120 121 to 150 > 150

Day-time lighting for type B short, urban, bidirectional tunnels (dense traffic when IMD > 5 000).

Length (m)

Visible exit?

< 25 25 to 75 75 to 125 > 125

— YES NO YES NO —

Lightingrequired

Daytime lightingis not required

Limiteddaytime lighting

Long tunnellighting

Daytime lighting for A type tunnels, short or urban tunnels or by- passes (highways and dual carriageways excluded), with limitedcirculating speed between 40 and 60 km/h.

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For each type of short tunnel in guiding diagrams and in their left part, the following four questions are posed: length, exit

visibility, speed and traffic density.

- Length (m): Four sorts of length are established for each guiding diagram for short tunnels or underpasses,

expressed in metres.

- Visible exit?: In each guiding diagram it is considered, whether the exit of the tunnel or underpass is visible or not

when the driver of the vehicle approaches the tunnel and finds himself, at least, at a distance equal to that of

security distance (DS) before the tunnel entrance.

- Speed [80 Km/h: In guiding diagrams 2 and 3, corresponding to tunnels of the B and C type, the speed of the

tunnel or underpass design is thought to be higher or lower than 80 Km/h. The design speed is very important in

relation to security distance (DS), as well as regarding risk of accidents and their severity.

- Traffic density: In guiding diagrams 2 and 3, it is born in mind and it may be classified as light and dense.

In diagram 2 corresponding to short tunnels of the B type (two- way intercity), a dense amount of traffic is valued when daily

average intensity of vehicles is higher than 5 000 (IMD > 5 000).

In diagram 3, which makes reference to short tunnels of the C type (one- way intercity of motorways and dual carriageways),

a dense amount of traffic is estimated when daily average intensity of vehicles in higher than 10 000 (IMD > 10 000).

Four diagrams are established constituting a guide of an orientative nature. They also provide help to decide whether the short

tunnel or underpass needs day- time lighting or not. If necessary, the type of lighting to be adopted is also detailed.

For example, the case of a short tunnel of 120 metres in length, located on an intercity road with slow moving traffic (v < 60

Km/h.) and a daily average intensity of IMD < 3 000. It is necessary to decide whether day- time lighting must be provided

and, in case it is required, to determine the type of lighting to be installed. The working system is the one described below:

Following guiding diagram n. 4, the tunnel is located within the corresponding interval of lengths. That is to say, between 101

and 150 metres.

The second question, visible exit?, is answered. For an affirmative answer, day- time lighting is not required according to

diagram 4. For a negative answer, due to the existence of curves or slopes in the interior of the tunnel, limited day- time lighting

is installed.

Supposing the same short tunnel but with a length of 170 metres, according to diagram 4, the only two alternatives are, in

case the tunnel exit is not visible, the installation of limited day- time or complete day- time lighting respectively.

Diagrams constitute a practical guide that, for each concrete situation, will be adapted to the type of road bearing in mind:

- The real structure of the tunnel, its access and exit roads.

- Traffic density and composition, either motorized or mixed, including slow and fast moving vehicles, bicyclists,

pedestrians, etc.

Guiding diagrams may be considered to be orientative for the design, working and maintenance of short tunnels and

underpasses lighting. The following technical and economic considerations will be taken into account:

- Performance of a detailed analysis of the risk of accidents and security in relation to lighting (quality and quantity).

- Study of convenient marking at the entrance of the tunnel, especially regarding the limit speed, turn- on of vehicle

headlights, etc.

- Performance a meticulous exam of installation costs and annual exploitation of lighting, including working,

maintenance and repairing costs in relation to security and comfort provided by such an installation (costs/ benefits

binomial).

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13.3.2. Lighting types in short tunnels

As it has been established in the four guiding diagrams, besides night- time lighting, situations that may be present for day-

time lighting in short tunnels are the following:

- Lighting not required.

- Limited day- time lighting.

- Complete day- time lighting.

13.3.2.1. Day- time lighting not required

When lighting for short tunnels is not important and, thus, day- time lighting is not required.

13.3.2.2. Limited day- time lighting

It is so called, since it is only working during some part of the time. That is to say, day- time lighting is only working

during periods in which daytime sunlight does not provide a high enough luminance background to allow the

silhouette effect to take place. Such conditions may occur after dusk, before dawn and in cloudy days.

For limited day- time lighting, average luminance in servicie of the roadway with maintenance of the installation will

be three times the luminance of the interior zone of the tunnel (3.Lin), according to the limits established in Chart

11, or 15 cd/m2. The highest figure of the two must be adopted.

In the morning, limited day- time lighting must be turned on half an hour after sunrise and turned off when luminance

in the access zone L20 exceeds 150 cd/m2 (L20 > 150 cd/m2). In the evening, it will be turned on when luminance

of the access zone L20 goes under 150 cd/m2 (L20 < 150 cd/m2) and turn off will be done half an hour before

sunset.

13.3.2.3. Complete day- time lighting

Complete day- time lighting is working during the total period of day- time. Basically, short tunnels similar to long

tunnels must be illuminated like the latter. Consequently, complete day- time lighting will be maintained along all the

length of the tunnel. Levels of luminance required in the threshold zone of long tunnels will be taken away from

factor k established in Chart 10, according to their corresponding lighting class (Chart 7).

13.3.2.4. Night- time lighting

For short tunnels or underpasses longer than 25 m., in which approximation roads are illuminated, installation of

night- time lighting is required. The level of average luminance in service of the roadway with maintenance of the

installation will be, at least equal, but not higher than two times the luminance of the approximation road.

13.4. Emergency lightingRegarding this type of lighting, the norm establishes that when a tunnel suffers from a failure of power supply, an emergency power

supply system and an emergency lighting system must be at hand.

Emergency lighting must cover the total length of the tunnel and the level of luminance must be, at least, less than 10% of the interior

luminance or 0.2 cd/m2 (the highest is chosen).

In tunnels of the 3 ÷ 7 lighting class, a lighting system for fire- prevention emergency guidance is required (whenever at least one exit

is not visible from any position).

The positioning of these luminaires will be on a wall at a height of 0.50 m of the roadway and with a separation lower than 50 m.

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13.5. MaintenanceThe maintenance factor used in lighting studies normally covers luminaire depreciation (dirtiness) and lamp (loss of luminous flux).

In the case of tunnels which are installations with a high degree of atmospheric pollution, it is very important to have a maintenance

program (cleaning of walls and luminaires) defining the cleaning cycles which will allow to comply with the factor established in the

study.

The norm recommends to use a maintenance factor of 0.7 to define the value of the average level of the luminance of the roadway

and 0.5 for the walls.

Relamping will be performed when the average level is under the one established or the lack of uniformity is unacceptable.

13.6. Ignition controlIt is very important to have an automatically controlled system in this kind of installations, taking into account that levels of the threshold

and transition zones are established according to the luminance of the access zone.

When exterior conditions vary (daytime ones), it is necessary to modify levels of these zones to maintain the quality of the design

criteria used in the study of lighting.

13.7. Night- time lighting (exterior zone of the tunnel)For the exit zone of the tunnel, the exterior roadway must be illuminated in a length equal to two times the stopping distance (not

higher than 200 m.), with an average level higher than 1/3 of the tunnel exit zone. In the tunnel under study, for design to be a bit

more conservative, tunnel access zones will extend from 200 to 250 m.

In the access zone, luminaires of the example under study with a 250W high pressure sodium lamp, in 12 m. high posts in a one-

sided disposition at an interdistance between luminaires of 30 m. must be installed.

When there are sunscreens in the entrance or exit zones of the tunnel, the lighting level will be equal to the one in the interior zone

of the tunnel.

13.8. Tunnel lighting designRegarding guiding charts for short tunnels specified in section 13.3. of the present chapter, they constitute only a guide that must be

adapted to the concrete type of tunnel and access and exit roads.

Underpasses under roads or railways shorter than 25 m. in length, constitute the minimum stretches of covered road that are habitually

present. Given the short length, the installation of lighting during the day is not normally necessary. In order to ease entrance of day-

time sunlight in the interior of the short tunnel or underpass, it is convenient to perform the following measures when possible:

- Build a higher mouth of the tunnel.

- Cover the tunnel walls of white color (specular covering).

- Install skylights on the tunnel ceiling.

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Chart 18

If lighting is foreseen on the road, this will be installed in such a way that an adequate penetration of lighting inside the short tunnel

or underpass is guaranteed.

The content of guiding diagrams for short tunnels and underpasses detailed in section 13.3. are summarized in the previous chart.

A high reflectance of walls is important to increase brightness of the background against which objects may be seen. In short tunnels,

where the exit is not visible from the security distance (DS) in front of the tunnel entrance, reflectance of walls is particularly important.

The reason is that reflectance of high walls will secure that a great amount of day- time lighting, entering through the exit mouth, is

reflected towards drivers. Walls with a diffused reflectance in service higher than 40% are known as HIGH, and walls with less than

40% of reflectance, are called LOW (the depreciation or maintenance factor must be considered).

In any tunnel, walls must have a white covering of up to 2 m. in height, with a flat surface and a high specular reflectance in service

or maintained. The low part down to 0.50 m. and lateral sidewalks may be blackened or painted black, basically when the roadway

covering is light or white, due to vehicle driving needs with a good maintained contrast, in order to improve total perception. When

reflectance of the walls is classified as LOW, length signalled in each of the four guiding diagrams must be reduced in a 20%.

The degree of day- time light entering the exit is also important. Thus, a tunnel with a big transverse section, for example, of three lanes

or wider, and a flat exit or with a downward slope and facing south, will admit a maximum of day- time light and will contribute

considerably to visibility in the tunnel. Moreover, day- time light may be poor when the tunnel has two or fewer lanes, in case the exit

is located in a cut or is surrounded by high buildings. Also when the road has an upward slope from the exit or in case the exit faces

north. The importance of day-time light near the exit decreases with the length of the tunnel. When day- time light is GOOD, the length

indicated for each of the four guiding diagrams must be increased up to a 20%.

As far as tunnel geometry and access roads are concerned, lighting design of the tunnel must follow the most conservative route for

each guiding diagram. The same attitude must be considered when:

- The tunnel has a slope first and a ramp later (changes in vertical curvature).

- There are geometrical discontinuities or singularities.

In case the tunnel presents a bad total perception, lighting design must follow a conservative path for each of the four guiding diagrams.

A specific analysis is needed when transportation of dangerous cargo is frequent. In this case, lighting design in the tunnel must be

performed following the most conservative path for each of the guiding diagrams.

Length < 25 < 80 < 100 < 10025 to 75 80 to 120 100 to 150 100 to 15075 to 125 120 to 150 150 to 200 150 to 200

> 125 > 150 > 200 > 200

Visible exit? YES YES YES YES

NO NO NO NO

Speed YES YES< 80 km/h NO NO

Traffic density LIGHT LIGHT

DENSE DENSE

* In type B tunnels, traffic density is high when IMD > 5 000.** In type C tunnels, traffic density is high when IMD > 10 000.

TYPES OF

TUNNELS

TYPE A

DIAGRAM-1

TYPE B

DIAGRAM-2

TYPE C

DIAGRAM-3

TYPE D

DIAGRAM-4

SHORT TUNNELS

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13.9. Visual guidance

When driving in the interior of a tunnel, a vehicle’s driver must have adequate information. This may be achieved dividing the

longitudinal surface of the tunnel into several contrast surfaces, like for example, leaving light tunnel walls and dark celings. Visual

guidance is extremely important when the user is driving the vehicle and he approaches the tunnel, particularly, if the luminous level

of the entrance zone is low. In Chart 4 ponderation factors have been established for a poor or good visual guidance.

13.9.1. Visual guidance for long tunnels

In tunnels with lighting classes 2, 3, 4, 5, 6 and 7 (Chart 7), independently from vertical marking, horizontal marking must be

carefully attended.

In the evaluation of ponderation factors according to visual guidance (Chart 5), installation of additional retro reflective

dispositives will be considered (beaconing, rows of luminaires, post mounted delineators, etc.) on the tunnel walls as well as

on the roadway surface, especially in the case of tunnels corresponding to lighting classes 5, 6 and 7 (Chart 7).

13.9.1.1. Visual guidance in the entrance zone for tunnels. Lighting class 1

In the entrance zone of tunnels with a lighting class 1 (Chart 7), in the first 75 m., at least five luminaires must be

installed whose luminous intensities towards the driver will be adjusted to what has been established in Chart 19. It

may be necessary to tilt luminaires, in order to achieve the luminous intensities specified in Chart 19.

Chart 19

In order to secure an adequate visual guidance, the separation between luminaires will not be higher than 25 m. In

curved tunnels, at least four luminaires will be visible. Regarding separation between luminaires this could be

reduced.

13.9.1.2. Visual guidance in the interior zone for tunnels. Lighting class 1

In the interior zone of tunnels, lighting class 1 (Chart 19), the luminaires installed will have luminous intensities

towards the driver that will comply with what has been established in Chart 20.

During the day 300 800 — 400

During the night 8 50 — 25

ANGLE

TIME

80° < γ < 87.5°

INTENSITY (cd) INTENSITY (cd)

MIN. MAX. MIN. MAX.

γ = 87.5°

CHART ILUMINOUS INTENSITIES IN TUNNEL ENTRANCE ZONE

LIGHTING CLASS 1

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258 LIGHTING ENGINEERING 2002

Chart 20

13.9.2. Visual guidance for short tunnels

Short tunnels or underpasses which lack a lighting installation, require a good marking, both vertical and horizontal. The

following dispositions may be used for visual guidance:

- Retroreflective marking on the roadway.

- Retroreflective beaconing system (rows of luminaires, post mounted delineators, etc.) on the roadway.

- Retroreflective marking and beaconing on the walls.

- Light- emitter diodes.

Day and night 8 50 — 25

ANGLE

TIME

80° < γ < 87.5°

INTENSITY (cd) INTENSITY (cd)

MIN. MAX. MIN. MAX.

γ = 87.5°

CHART IILUMINOUS INTENSITIES IN TUNNEL INTERIORS

LIGHTING CLASS 1

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259LIGHTING ENGINEERING 2002

Chapter14.

LIGHT POLLUTION

14.1 General remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

14.2 Lighting and security levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261

14.3 Contrast vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262

14.4 Zoning system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

14.5 Lamp selection criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263

14.6 Upper hemisphere flux limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

14.7 Other characteristics of luminaires . . . . . . . . . . . . . . . . . . . . . . . . . . . 264

14.8 Distances between zones and point of reference . . . . . . . . . . . . . . . . 265

14.9 Pavement photometric characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 265

14.10 Lighting level temporal variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265

14.11 Recommendations to reduce lighting pollution . . . . . . . . . . . . . . . . . . 266

14.12 Appendix: “Recommendable orientative values to limit disturbing light

coming from exterior lighting installations . . . . . . . . . . . . . . . . . . . . . . 268

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14.1. General remarks

Since the beginning of history, humankind has always worried about the origin and destiny of our planet, as well as about the existence

of life on the Earth. The study of the firmament has always been linked to this worry. From the beginnings of the 20th century and for

the first time in our History, night- time vision of our firmament is under attack, without our realizing about it, because of the anarchic

lighting of urban settlements. Light pollution in the sky of our villages and cities is preventing us from contemplating one of the most

beautiful wonders. The sky has been and still is a source of inspiration for humankind. However, its contemplation is more and more

difficult; even for young generations, it is beginning to belong to the unknown.

Due to this reason, the "Comité Español de Iluminación" (the Spanish Commission on Illumination), has developed a Guide for the

Reduction of Night- time Luminous Glow. It is a kind of technical report we pretend to outline below.

Light pollution is defined as night- time luminous brightness or glow in the sky, produced by the diffusion and reflection of artificial

light in gases and particles suspended in the atmosphere. Such glow, generally produced partly by sources of light installed in external

areas, make brightness of the natural sky background to increase, progressively reducing the value of observation magnitude of

astronomical objects and making observation more difficult.

We must distinguish natural brightness, attributable to the radiation of the celestial sources or objects and to the luminescence of the

atmosphere upper layers, from luminous glow due to artificial sources of light installed in external areas. In the latter case, upwards

direct emissions of several sources of artificial light, as well as radiation reflected by surfaces illuminated by such sources of light must

be considered.

In order to reduce light pollution imputable to artificial sources of light action must be taken. On the one hand, on devices or luminaires

themselves which emit light and. On the other hand, on lighting installation implementing only the minimum number of aiming points

which will allow to reach the required lighting levels without overcoming them. This action will also mean that, as far as road lighting

is concerned, certain recommendations on the type of pavements to be used on roadways must be established.

Likewise, temporal variation or diminution of lighting levels at certain hours at night must be considered, (during these periods of time,

traffic intensity decreases substantially), provided users’ security is guaranteed on such roads.

Moreover, lamp selection criteria must be carefully considered, specially in the immediacy of astronomical observatories of international

category or "E 1" zone, where the installation of only high pressure and low pressure sodium lamps is recommended. Low pressure

sodium lamps should be preferably installed, since they do not emit within the ultraviolet area (far reaching waves with great energy),

there are no interferences with telemetric and spectrographic equipment of astronomical observatories.

Also, other alternatives directed to lessening light pollution or luminous glow in the sky must be considered, in relation to advertising

and amenity lighting.

It must also be pinpointed that light pollution or brightness attributable to sources of artificial light, does not exclusively come from the

design or lighting installation layout. but It is dependant, too, on atmospheric conditions (humidity, clouds, fog, aerosols, atmospheric

pollution, etc.).

In sum, light pollution is determined by two main factors, namely:

- Emission of light coming from luminaires for public lighting, either by direct emission (light not controlled in the luminaire upper

hemisphere) or by indirect emission (reflection of light on walls, roadways or surfaces to be illuminated).

- Sources of light used for external lighting, since their different emission spectra may be more or less dangerous.

14.2. Lighting and security levels

Within the European Union, there is a considerable amount of traffic circulating at night, with an average of about 25%. Likewise, the

ratio of night-time fatal accidents ranges between 25% and 59%, with an average of approximately 48.5%. In Spain, night- time motor

traffic is about 24.3%, and the number of casualties due to night- time accidents amounts to 43%.

The main reason for such high rates in night- time accidents is darkness itself, since drivers’ visual capacities (acuity and visual field,

distance judging, contrast vision, chromatic perception and glare tolerance) are negatively altered due to null or no-existent luminous

levels. Consequently, visibility is exceedingly reduced during night- time.

According to some studies conducted by the C.I.E., it has been proved that lighting of road traffic reduces the total number of accidents

in about 30% during the night.

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262 LIGHTING ENGINEERING 2002

Visual task and pedestrians’ needs differ from drivers’ in many aspects. The speed of movement is lower, and the perception of objects

surrounding pedestrians is more important than seeing objects that are further away. Therefore, quality criteria of pedestrian lighting

cannot be equal to those of road traffic. In urban areas, perception of their immediate environment is more important for pedestrians,

in order to avoid any type of crime (thefts, vandalism, sexual harassment, terrorist acts, etc.).

The decision whether lighting for a public road in a certain area or place must be provided or not must be taken based on a detailed

study. Once the decision to service a lighting installation has been made, design criteria and lighting levels will be adjusted, avoiding

exceeding the criteria established in the following C.I.E. publications:

- Publication C.I.E. 47: 1979 Road Lighting for Wet Conditions.

- Publication C.I.E. 66: 1984 Road Pavement and Lighting.

- Publication C.I.E. 92: 1992 Guide to the Lighting of Urban Areas.

- Publication C.I.E. 115: 1995 Recommendations for the Lighting of Roads for Motor and Pedestrian Traffic.

- Publication C.I.E. 126: 1997 Guidelines for Minimizing Sky Glow.

Nevertheless, lighting levels established in the publications above may be exceeded up to a 20%, except for cases correctly justified

in which it would be possible to exceed such percentage.

As far as those elements which constitute the installation, LIGHTING ENGINEERING calculations, measurements, maintenance, etc.

whatever is established in the following C.I.E. publications will be observed:

- Publication C.I.E. 30.2: 1982 Calculation and Measurement of Luminance and Illuminance in Road Lighting.

- Publication C.I.E. 31: 1976 Glare and Uniformity in Road Lighting Conditions.

- Publication C.I.E. 32/AB: 1977 Lighting in Situations Requiring Special Treatment (in Road Lighting).

- Publication C.I.E. 33: 1977 Depreciation of Installations and their Maintenance.

- Publication C.I.E. 34: 1977 Road Lighting Lantern and Installation Data.Photometrics, Classification and Performance.

- Publication C.I.E. 121: 1996 The Photometry and Goniophotometry of Luminaires

14.3. Contrast vision

Visibility of an object located on a background, depends on luminance differences between an object and its background. For a light

coloured object over a dark background, its contrast will be positive (values between 0 and infinitum). However, an object darker than

its background will be seen as a silhouette and its contrast will be negative, varying between 0 and (–1).

By definition, contrast is expressed as shown below:

Being:

L0= Object luminance.

Lf= Background luminance.

Contrast C may be either positive or negative:

If L0 >Lf C > 0 positive contrast (the object is lighter than its background).

If L0 <Lf C < 0 negative contrast (the object is darker than its background).

Contrast C may acquire the following values:

Positive contrast (light object) 0 < C < ∞Negative contrast (dark object) -1 < C < 0

Light pollution or night- time luminous glare in the sky produces a veil in the observation field which has its own luminance Lv. At the

same time, this luminance is added to the luminance of the object and its background. Thus, the new contrast C’ is the following:

C = L0 – Lf

Lf

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It is always verified that C’ < C, given that the dividend is the same and the divisor is always greater.

When veiling luminance Lv increases, the observed object may disappear from the field of vision, specially in the case of astronomic

observations when a star or celestial object with a very weak luminance L0 is under study.

14.4. Zoning system

Potential contradictions between photometric exigencies related to night- time human activity, security for vehicle and pedestrian traffic,

quality of life, integrity of environment, properties, goods, etc. and light pollution or night- time luminous glow in the sky which makes

astronomic observations of celestial objects difficult, must be approached to adopt solutions.

As far as environment is concerned, when a polluting activity cannot be totally controlled, the basic idea consists in avoiding that

environmental consequences due to pollution damage equally all areas or situations. The zoning system does not stop environmental

pollution, but it is valid as a reference frame for environmental friendly legislation and regulation.

In order to limit interferences produced by light pollution to astronomical observatories known as "point of reference", the introduction

of the zoning system answers two goals. On the one hand, it allows to establish lighting requisites in an area where the "point of

reference" is located. On the other hand, it eases the task of stipulating lighting requirements in other areas, adjacent or not, to the

particular area where the "point of reference” is located.

Chart 1. Description of zoning system.

National parks and areas with a special natural beauty will receive the same treatment as the "E 1" zone, as far as installed upper

hemisphere flux limitations go, as established in Chart 2. Distance regime shown in Chart 4 is not applied to the rest of the zones.

14.5. Lamp selection criteria

Discharge lamp types are recommended. For motor traffic roads and urban areas, high pressure sodium lamps will be preferably used,

due to their high luminous efficacy (lm/W) and better colour performance than low pressure sodium lamps. These are recommended

in roads in the open, rural areas and areas requiring safety lighting. Likewise, in landscaped areas, old quarters, etc. high pressure

mercury lamps, metal halide, etc., may be used.

In "E 1" zones where the "point of reference" is located, (astronomical observatories of international category), it is recommended to

install low and high pressure sodium lamps, preferably using the latter.

14.6. Upper hemisphere flux limitations

Installed FHSinst upper hemisphere flux emitted by a luminaire is defined as the one directed over the horizontal plane. Such a plane

corresponds to the angle γ = 90° in the (C,γ) representation system. The hemisphere flux is expressed in a percentage of the total flux

emitted by the luminaire.

In Chart 2, upper hemisphere flux maximum limits or installed values FHSinst are established for each of the areas.

ZONE CLASSIFICATION DESCRIPTION

E 1 DARK SURROUNDING AREAS: International category astronomic observatories

E 2 LOW BRIGHTNESS AREAS: Rural areas

E 3 AVERAGE BRIGHTNESS AREAS: Residential urban areas

E 4 HIGH BRIGHTNESS AREAS: High night- time activity in urban centers

C’ = (L0 + Lv) – (Lf + Lv)

= L0 – Lf

(Lf – LV) Lf – LV

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Chart 2. Limit values for the installed upper hemisphere flux.

As a way of an example, Chart 3 contains the type of astronomic observations possible for each zone.

Chart 3. Astronomic activities possible for each zone.

Nevertheless, in the case of lighting of highways and dual carriageways, important urban routes, by-passes, etc. it is recommended to

install luminaires with an Installed FHSinst 5% upper hemisphere flux.

In the case of pedestrian lighting, as well as artistic with lanterns, historic devices, etc., an FHSinst 25% is suggested

When the life of lighting installations is exhausted, or renovation is needed for any reason, it is recommended to install luminaires with

the upper hemisphere flux limitations shown above in this section.

It is advisable to have a replacement program of existent luminaires whose installed upper hemisphere flux is greater than 25%

(FHSinst/25%), installing luminaires which comply with the values recommended in this section.

14.7. Other characteristics of luminaires

Considering that the performance of a luminaire is the ratio between the flux emitted by the luminaire and the flux produced by the

lamp, for lighting installations of traffic motor roads, it is suggested to install preferably luminaires with a performance equal or above

70% (clear tubular lamp) or 60% (opal ovoid lamp).

Likewise, it is suggested that luminaires used in the lighting of pedestrian areas, artistic lanterns, historic devices, etc. will be provided

with an optical block, both to control light emission for the upper hemisphere and to increase the utilization factor for the lower

hemisphere.

In all examples, luminaire photometric distribution will be considered to be the most adequate one to obtain the maximum energetic

efficiency of the installation.

14.8. Distances between zones and point of reference

Light pollution or night- time luminous glow in the sky of a specific zone, for example, the particular area where the "point of reference"

is located (international category astronomic observatories), is due to the dimensions of such a zone and to its own lighting, as well

as lighting of the neighboring or adjacent areas. Thus, lighting of those areas around that which contains the "point of reference" must

be considered.

Lighting influence of those neighboring or adjacent areas over the total light pollution in the "point of reference", depends on distances

between the borders of the zones and the "point of reference".

In Chart 4, distances in Km. recommended between limits for each zone (E 1, E 2, E 3, E 4) and the "point of reference" are

established.

ZONE CLASSIFICATION ASTRONOMIC ACTIVITIES

E 1 International Category Observatories

E 2 Academic and Postgraduate Studies Observatories

E 3 Amateur Observatories

E 4 Sporadic Observations

ZONE CLASSIFICATION INSTALLED FHSinst UPPER HEMISPHERE FLUX (%)

E 1 0

E 2 0-5

E 3 0-15

E 4 0-25

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Chart 4. Minimum distances in Km. between limits for each zone.

For the correct use of Chart 4, the zone where the "point of reference" is located must be first selected. Afterwards, in Chart 4, the

minimum distance in Km. is obtained, where the following zone begins, and so on for the rest of adjacent areas.

Values recorded in Chart 4 have been deduced from practical experience, even when the number of cases under study has been

limited.

14.9. Pavement photometric characteristics

Whenever constructive characteristics, composition and execution systems are ideal with respect to texture, slip- resistance, flatness,

surface drainage, etc., it is advisable to use pavements whose characteristics and reflexive properties are adequate for public lighting

installations. The aim is to achieve the maximum luminance and uniformity to an equal illuminance, thus, reaching, a greater separation

between aiming points in roadways.

Pavement luminosity of a roadway is directly linked to its photometric properties, and to the pavement average luminance coefficient

Q0, to be exact. Hence, given identical illuminance, the higher such a coefficient is, so will roadway luminance be. TI disability glare will

be lower. The specular factor S1 determines to what extent characteristics of the pavement, respect to reflection of incident light,

separate from those of a surface which secures a perfect diffused reflection. This happens in such a way that, illuminance being equal,

the lower the S1 specular factor is the greater luminance uniformities.

From all this, it may be deduced that, whenever possible in roadways, it is convenient to use pavements with an average luminance

coefficient or degree of luminosity Q0 as high as possible, and whose S1 specular factor is low.

14.10. Lighting level temporal variations

In traffic routes, pedestrian areas, cycle paths, etc., luminous levels may be reduced during certain hours at night, whenever users’

security is guaranteed.

In concrete places, with high percentages of night- time accidents, pedestrian areas with a considerable risk of criminality, etc., it is

recommended not to perform temporal variations in lighting levels, due to security reasons.

Under any circumstances will reductions go under the advisable lighting level for traffic security and pedestrian movement.

Reduction of lighting levels by means of aiming points turn off is not advisable. Supposing that such a procedure is used, minimum

uniformities established in C.I.E. publications must be maintained.

Reduction through regulation systems is considered to be the most adequate procedure because it avoids shadowy areas and light

walls which make vision difficult; at the same time, uniformities are maintained.

REFERENCE POINT DISTANCE BETWEEN LIMITS IN ZONES

ZONE E 1 - E 2 E 2 - E 3 E 3 - E 4

E 1 1 10 100

E 2 1 10

E 3 1

E 4 WITHOUT LIMITS

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14.11. Recommendations to reduce light pollution

Possible alternatives to reduce light pollution or night- time lighting glow in the sky are the following:

- to switch off advertising and decorative lighting from a certain hour onwards.

- to direct light downwards and not upwards whenever possible, especially lighting for edifices and monuments (Fig. 1).

Figure 1

- If there is no possibility to direct lighting downwards and not upwards, use screens and paralumens to avoid dispersion of

light beam (Fig. 2).

Figure 2

- To install lighting equipments which will reduce the dispersion of light on the horizontal plane of the luminaire, with

minimum values or even none over such plane (Figs. 3 and 4).

Figure 3

NO YES

NO YES YES

YESYESNO

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Figure 4

- For glare to be minimum, direct light ray beams downwards keeping them under 70°. If mounting height is increased, light

ray beams shoud be lowered. In places with low environmental light, glare may be very disturbing. Due to this reason,

positioning, aiming or orientation of luminaires may be carefully attended (Fig. 5).

Figure 5

- When possible, it is recommended to install luminaires with an asymmetric reflector which will permit to maintain their

front closing parallel or almost parallel to the surface that needs to be illuminated (Fig. 6).

Figure 6

- In order to avoid installing excess of light, recommendations which fix levels to light different tasks with tolerances permited

must be observed.

- In the case of small safety lighting installations and house lighting, there are two solutions:

- • Passive detectors of infrared rays may be effectively used if correctly installed and lined. In general, a 150 W. halogene

lamp is more than enough. 300/500 W. lamps provide too much lighting, greater glare and darker and more emphasized

shadows.

YESNO

NO

90°70° <70°

YES O.K.

NO

YES

267LIGHTING ENGINEERING 2002

Chapter 14. LIGHT POLLUTION

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268 LIGHTING ENGINEERING 2002

- • Permanent illuminations with low brightness during all night. are equally acceptable. In the case of a porch in a house, a

compact fluorescent lamp of 9 W. (600 lm.) is adequate for most cases.

- For motor traffic lighting, flux emitted above the horizontal plane must be reduced and close light must be restricted.

14.12. Apendix: "Recommended orientative values for limiting bothering lightcoming from exterior lighting installations"

Division 5 of the C.I.E. elaborated a roughdraft of a technical report "Guide on the limitation of the effects of bothering light coming

from exterior lighting installations" through its Technical Committee TC 5-12, at the end of 1995 .

Given its empirical nature and subject to modifications resulting from observing parameters included in the mentioned Guide, the

most adequate attitude seems to be including such parameters as a way of orientation and not as obligatory values to be applied.

This way, their incorporation has been performed by means of limitation charts like an appendix and not as part of the present

chapter. The intention being that consignated valued will be compared with our own experience in our country.

Five types of specific effects produced by bothering lighting coming from exterior lighting installations may be considered. These are

the following:

Effects on astronomical observations

Lighting engineering parameters implied are:

- Night- time lighting of the sky by dispersion of light coming from exterior lighting installations (night- time luminous glow). It depends

on the (FHSinst) installed upper hemisphere flux as well as on the reflected flux.

- Spectral characteristics of night- time luminous glow. It is equivalent to speaking about wavelengths coming from luminous

emissions (types of lamps).

- Direct light on the astronomical observatory itself.

Effects on residents

Lighting engineering parameters to be considered are the following:

- Vertical illuminance (EV) on face surfaces, for example, bedroom windows.

-Luminance (L) of luminaires, given the fact that their direct vision may be disturbing. Due to the difficulty in predetermining such

luminance, this parameter is substituted by luminous intensity (Ι) of the source of light in the potential direction of the bothering

source of light.

Effects on citizens

Lighting engineering parameters to bear in mind when talking about the effects of lighting on citizens in general (passers-by, tourists,

etc.) are the following:

- Average luminance (Lm) of surfaces of vertical faces in edifices. Sometimes, as a consequence of excessive lighting, they may be

bothering instead of highlighting decorative or ornamental aspects.

Effects on users of transportation systems

Significative lighting engineering parameters are the following:

- Increase of threshold contrast (TI) which expresses limitation of disturbing glare in the lighting of motor roads. This also constitutes

the measurement through which a loss of sight caused by such glare is quantified.

- Visual caos originated by signalling observation against bright backgrounds produced by intense luminous sources.

Effects on transportation signalling systems

Significative lighting engineering parameters are the following:

- Disturbing glare represented by an increase in the threshold area (ΤΙ), defined as the amount of extra contrast, with regards to the

original contrast, necessary to see the object again when there is glare.

- In case transportation systems work near lighting installations, as in the case of maritime transport, aviation, etc., relevant authorities

will establish adequate norms.

According to the classification of zones established in Chart 1, recommendations as a way of orientation for limiting bothering or

discomforting light coming from exterior lighting installations, are expressed as maximum values in the following chart:

Chapter 14. LIGHT POLLUTION

Page 258: 38 Lighting Handbook

Chart 5. Limitations of bothering light coming from exterior lighting installations.

FHSinst Maximum permited percentage of installed upper hemisphere flux in percentage.

EV Vertical illuminance in lux.

Ι Luminous intensity in Kilocandelas (Kcd.).

Lm Average luminance in cd/m2.

TΙ Contrast threshold increase in percentage.

* Acceptable only for lighting installations of motor traffic roads.

** Applicable to each source of light in the potential direction of the bother.

*** In order to avoid excessive lighting, luminance is limited in edifices. It must coincide with the general luminosity of the

area.

ZONE

CLASSIFICATION

NIGHT- TIME

LUMINOUS

GLOW

IN THE SKY

FHSinst %

LIGHT IN WINDOWS

EV (lux)

Before

lighting

time

After

lighting

time

Before **

reduced

time

After

reduced

time

After reduced

time

INTENSITY OF SOURCELuminance in

edifices***

Lm (cd/m2)Disturbing

glare

ΤΙ %

E 1 0 2 1* 0 0 0 10

E 2 5 5 1 50 0.5 5 10

E 3 15 10 5 100 1.0 10 15

E 4 25 25 10 100 2.5 25 15

269LIGHTING ENGINEERING 2002

Chapter 14. LIGHT POLLUTION

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270 LIGHTING ENGINEERING 2002

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BIBLIOGRAPHY

• IES Lighting Guide: The Outdoor Environment.

• IES Lighting Guide: Sports.

• IES Code for Interior Lighting.

• IDAE: Eficiencia energética y medioambiental en iluminación.

• ADAE: Guía sobre la iluminación de interiores.

• Fördergemeinschaft Gutes Licht: Good Lighting for Schools and Educational Establishments.

• Fördergemeinschaft Gutes Licht: Good Lighting for Safety on Roads, Paths and Squares.

• Fördergemeinschaft Gutes Licht: Good Lighting for Offices and Office Buildings.

• Fördergemeinschaft Gutes Licht: Good Lighting for Trade and Industry.

• Fördergemeinschaft Gutes Licht: Good Lighting for Sports Facilities.

• Fördergemeinschaft Gutes Licht: Prestige Lighting.

• Castejón – Santamaría: Tecnología eléctrica. Ed: McGraw Hill.

• Física. Paul A. Tipler. Ed. Reverté, S.A. 3ª edición.

• Electricidad y Magnetismo. Francis W. Sears. Ed. Aguilar.

• Equipos auxiliares para lámparas de descarga. Antonio Vela Sánchez, Juan José Garrido Vázquez.

• Sistema eléctrico para lámparas de descarga. Antonio Vela Sánchez, Juan José Garrido Vázquez.

• Recomendaciones para la iluminación de carreteras y túneles. Ministerio de Fomento.

• J.I. Urraca Piñeiro: Tratado de alumbrado público. Ed: Donostiarra, S.A.

• Julio Arias – Alfonso Ramos: Luminotecnia Práctica. Indalux Iluminación Técnica, S.L. (1990).

• Jesús Feijó Muñoz: Instalaciones de iluminación en la arquitectura. Ed: Secretariado de publicaciones, Universidad de Valladolid.

• Manual de Iluminación. Philips Iluminación (1997).

• J.A. Taboada. Manual de Luminotecnia. Ed. Dossat, S.A. (4ª edición).

• Catálogo General de Lámparas y Equipos, 1998/1999/2000. Philips.

• Catálogo de Lámparas. Sylvania.

• Catálogo General de Luz, 1998/1999/2000. Osram.

• Spectrum. Catálogo General de lámparas. General Electric Company.

• Catálogo Descarga y Fluorescencia ELT.

• Catálogo General ETI.

• Catálogo 2001 SLUZ.

• Catálogo General 2002. Indalux Iluminación Técnica, S.L.

• Publication CIE nº 18.2 (1983): The Basis of Physical Photometry.

271LIGHTING ENGINEERING 2002

BIBLIOGRAPHY

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272 LIGHTING ENGINEERING 2002

• Publication CIE nº 19/2.1 (1981): An Analytic Model for Describing the Influence of Lighting Parameters upon Visual Performance.

• Publication CIE nº 19/2.2 (1981): An Analytic Model for Describing the Influence of Lighting Parameters upon Visual Performance.

• Publication CIE nº 20 (1972): Recommendations for the Integrated Irradiance and the Spectral Distribution of Simulated Solar

Radiation for Testing Purposes.

• Publication CIE nº 24 (1973): Photometry of Indoor Type Luminaires with Tubular Fluorescent Lamps.

• Publication CIE nº 27 (1973): Photometry of Luminaires for Street Lighting.

• Publicaciòn CIE nº 29.2 (1986): Guía de iluminación interior.

• Publication CIE nº 30.2 (1982): Calculation and Measurement of Luminance and Illuminance in Road Lighting.

• Publication CIE nº 31 (1976): Glare and Uniformity in Road Lighting Installations.

• Publication CIE nº 33 (1977): Depreciation of Installations and their Maintenance.

• Publication CIE nº 34 (1977): Road Lighting Lantern and Installation Data-photometrics, Classification and Performance.

• Publication CIE nº 38 (1977): Radiometric and Photometric Characteristics of Materials and their Measurement.

• Publication CIE nº 42 (1978): Lighting for Tennis.

• Publication CIE nº 43 (1979): Photometry of Floodlights.

• Publication CIE nº 44 (1979): Absolute Methods for Reflection Measurements.

• Publication CIE nº 45 (1979): Lighting for Ice Sports.

• Publication CIE nº 46 (1979): A Review of Publications on Properties and Reflection Values of Material Reflection Standards.

• Publication CIE nº 47 (1979): Road Lighting for Wet Conditions.

• Publication CIE nº 49 (1981): Guide on the Emergency Lighting of Building Interiors.

• Publicación CIE nº 52 (1982): Cálculos para iluminación interior.

• Publication CIE nº 53 (1982): Methods of Characterizing the Performance of Radiometers and Photometers.

• Publication CIE nº 55 (1983): Discomfort Glare in the Interior Working Environment.

• Publication CIE nº 57 (1983): Lighting for Football.

• Publication CIE nº 58 (1983): Lighting for Sports Halls.

• Publication CIE nº 60 (1984): Vision and the Visual Display Unit Work Station.

• Publication CIE nº 61 (1984): Tunnel Entrance Lighting.

• Publication CIE nº 62 (1984): Lighting for Swimming Pools.

• Publication CIE nº 67 (1986): Guide for the Photometric Specification and Measurement of Sports Lighting Installations.

• Publication CIE nº 84 (1989): The Measurement of Luminous Flux.

• Publication CIE nº 85 (1989): Solar Spectral Irradiance.

• Publication CIE nº 92 (1992): Guide to the Lighting of Urban Areas.

• Publication CIE nº 93 (1992): Road Lighting as an Accident Countermeasure.

• Publication CIE nº 95 (1992): Contrast and Visibility.

BIBLIOGRAPHY

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• Publicación CIE nº 96 (1992): Fuentes de luz eléctrica. Estado del arte-1991.

• Publication CIE nº 97 (1992): Maintenance of Indoor Electric Lighting Systems.

• Publication CIE nº 98 (1992): Personal Dosimetry of UV Radiation.

• Publication CIE nº 99 (1992): Lighting Education.

• Publication CIE nº 100 (1992): Fundamentals of the Visual Task of Night Driving.

• Publication CIE nº 102 (1993): Recommended File Format for Electronic Transfer of Luminaire Photometric Data.

• Publication CIE nº 109 (1994): A Method of Predicting Corresponding Colours under Different Chromatic and Illuminance

Adaptations.

• Publication CIE nº 110 (1994): Spatial Distribution of Daylight.

• Publication CIE nº 112 (1994): Glare Evaluation System for Use within Outdoor Sports and Area Lighting.

• Publication CIE nº 114 (1994): CIE COLLECTION in Photometry and Radiometry.

• Publicación CIE nº 115 (1995): Recomendaciones para el alumbrado de calzadas de tráfico motorizado y peatonal.

• Publication CIE nº 117 (1995): Discomfort Glare in Interior Lighting.

• Publication CIE nº 118 (1995): CIE COLLECTION in Colour and Vision.

• Publication CIE nº 129 (1998): Guide for Lighting Exterior Work Areas.

• Publication CIE nº 130 (1998): Practical Methods for the Measurement of Reflectance and Transmittance.

• Publication CIE nº 132 (1999): Desing Methods for Lighting of Roads

• Reglamento Electrotécnico para Baja tensión. Ed: Paraninfo.

• AFE: Recommandations relatives à l’éclairage des installations sportives. (1992).

• Área de I+D, Departamento de proyectos de alumbrado. Indalux Iluminación Técnica, S.L. (Abril-96).

• Norma UNE 20056: Lámparas de filamento de tungsteno para iluminación general.

• Norma UNE 20064 (1973): Lámparas tubulares de fluorescencia para iluminación general.

• Norma UNE-EN 60927 (1990): Aparatos arrancadores y cebadores (excepto los de efluvios).

• Norma UNE 20152 (1981): Balastos para lámparas fluorescentes.

• Norma UNE 72150 (1984): Niveles de iluminación/Definiciones.

• Norma UNE 72151 (1985): Niveles de iluminación/Especificación.

• Norma UNE 72152 (1985): Niveles de iluminación/Clasificación y designación.

• Norma UNE 72153 (1985): Niveles de iluminación/Asignación a tareas visuales.

• Norma UNE 72160 (1984): Niveles de iluminación/Definiciones.

• Norma UNE 72161 (1985): Niveles de iluminación/Especificación.

• Norma UNE 72162 (1985): Niveles de iluminación/Clasificación y designación.

• Norma UNE 72163 (1984): Niveles de iluminación/Asignación a tareas visuales.

• Norma UNE-EN 60598-1 (1996): Luminarias. Parte 1. –Requisitos generales y ensayos.

273LIGHTING ENGINEERING 2002

BIBLIOGRAPHY

Page 263: 38 Lighting Handbook

274 LIGHTING ENGINEERING 2002

• Norma UNE-EN 60598-2-01 (1993): Luminarias. Parte 2. –Requisitos particulares y ensayos. Sección 1: Luminarias fijas de uso

general.

• Norma UNE-EN 60598-2-02 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 2: Luminarias empotradas.

• Norma UNE-EN 60598-2-03 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 3: Luminarias para alumbrado público.

• Norma UNE-EN 60598-2-04 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 4: Luminarias portátiles de uso general.

• Norma UNE-EN 60598-2-05 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 5: Proyectores.

• Norma UNE-EN 60598-2-06 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 6: Luminarias con transformador integrado

para lámparas de filamento de wolframio.

• Norma UNE-EN 60598-2-08 (1993): Luminarias. Parte 2. –Reglas particulares. Sección 8: Luminarias portátiles.

• Curso básico de Ergonomía. Santiago González Gallego. Colegio Oficial de Peritos e Ingenieros Técnicos Industriales de Valladolid.

• Documentos Técnicos: La Iluminación en los Lugares de Trabajo. Instituto Nacional de Seguridad e Higiene en el Trabajo. Ministerio

de Trabajo y Seguridad Social.

• Guía Técnica: Lugares de Trabajo (interpretación y aplicación del R.D. 486/1997 de 14 de Abril). Instituto Nacional de Seguridad e

Higiene en el Trabajo. Ministerio de Trabajo y Seguridad Social.

BIBLIOGRAPHY


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