Unit2 Transmission Line

7/30/2019 Unit2 Transmission Line

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Stesan

Kuasa

Penghantaran

Pengagihan

PenggunaUnit 2: TRANSMISSION


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Introduction

Penghantaran Pengagihan

TRANSMISSION DISTRIBUTION

Transmit from power plant

to distribution substationsDistribute from distribution

substations to end users.


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Transmission line

R L C


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What is Transmission line?

A transmission line is the material mediumor structure that forms all or part of a path

from one place to another for directing the

transmission of energy, such as

electromagnetic waves as well as electric

power transmission.

Components of transmission lines include

wires, coaxial cables, dielectricslabs,

optical fibres, electric power lines, and

waveguides.
http://en.wikipedia.org/wiki/Transmission_mediumhttp://en.wikipedia.org/wiki/Pathhttp://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Wirehttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Optical_fibrehttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Waveguidehttp://en.wikipedia.org/wiki/Optical_fibrehttp://en.wikipedia.org/wiki/Dielectrichttp://en.wikipedia.org/wiki/Coaxial_cablehttp://en.wikipedia.org/wiki/Wirehttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Electromagnetic_wavehttp://en.wikipedia.org/wiki/Transmission_%28telecommunications%29http://en.wikipedia.org/wiki/Pathhttp://en.wikipedia.org/wiki/Transmission_medium


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TransmissionSystem

Losses

4 type of power lines


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4 type of power lines:

1- Low Voltage (< 600 V)

2- Medium Voltage ( 2.4 kV to 69 kV)

3 -High Voltage (< 230kV)

4 - Extra High Voltage (800 kV, 1000

km)


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Losses

Some of the power that is fed into atransmission line is lost because of itsresistance.

This effect is called ohmicorresistiveloss(see ohmic heating). At high frequencies, another effect called

dielectric lossbecomes significant, addingto the losses caused by resistance.

Dielectric loss is caused when the insulatingmaterial inside the transmission lineabsorbs energy from the alternating electricfield and converts it to heat (see dielectricheating).
http://en.wikipedia.org/wiki/Ohmic_heatinghttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Dielectric_heatinghttp://en.wikipedia.org/wiki/Heathttp://en.wikipedia.org/wiki/Ohmic_heating


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Losses (cont)

In an alternating current circuit, the inductance andcapacitance of the phase conductors can besignificant.

The currents that flow in these components of the

circuit impedance constitute reactive power, whichtransmits no energy to the load.

Reactive current flow causes extra losses in thetransmission circuit.

The ratio of real power (transmitted to the load) toapparent power is the power factor.

As reactive current increases, the reactive powerincreases and the power factor decreases.

For systems with low power factors, losses are higherthan for systems with high power factors.

http://en.wikipedia.org/wiki/Electric_power_transmission#Losses
http://en.wikipedia.org/wiki/Inductancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Reactive_powerhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Reactive_powerhttp://en.wikipedia.org/wiki/Electrical_impedancehttp://en.wikipedia.org/wiki/Capacitancehttp://en.wikipedia.org/wiki/Inductance


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R,L,C in transmission line.

There are several term involves intransmission line such as resistance,capacitance and inductance calledparameter.

This parameters are not the samealong the lines and may effect the

efficiency of power transmissions. The effect may vary by length of

transmission lines.


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Component of a

transmission line

Schematic

representation of

the elementary

component of atransmission line.


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Component of a

transmission line (cont..)

The distributed resistance Rof the conductors is represented by aseries resistor (expressed in ohms per unit length).

The distributed inductance L (due to the magnetic field around thewires, self-inductance, etc.) is represented by a series inductor(henries per unit length).

The capacitance Cbetween the two conductors is represented by ashuntcapacitorC (farads per unit length). The conductance Gof the dielectric material separating the two

conductors is represented by a conductance G shunted betweenthe signal wire and the return wire (siemens per unit length).

*** The model consists of an infinite seriesof the elements shown in

the figure, and that the values of the components are specified perunit lengthso the picture of the component can be misleading. R, L,C, and Gmay also be functions of frequency. An alternativenotation is to use R', L', C' and G' to emphasize that the values arederivatives with respect to length.
http://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Shunt_(electrical)http://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Shunt_(electrical)http://en.wikipedia.org/wiki/Inductorhttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Self-inductancehttp://en.wikipedia.org/wiki/Magnetic_field


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Telegrapher's equations

The Telegrapher's Equations (or justTelegraph Equations) are a pair of

linear differential equations whichdescribe the voltage and current on

an electrical transmission line with

distance and time. They were

developed by Oliver Heaviside whocreated the transmission line model,and are based on Maxwell's

Equations.
http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Oliver_Heavisidehttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Maxwell%27s_Equationshttp://en.wikipedia.org/wiki/Oliver_Heavisidehttp://en.wikipedia.org/wiki/Electric_currenthttp://en.wikipedia.org/wiki/Voltage


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Classification oftransmission lines


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Classification of transmissionlines

Transmission lines are classifiedas short, medium and long.

When the length of the line is lessthan about 60km the effect ofshunt capacitance andconductance is neglected and the

line is designated as a shorttransmission line.

For these lines the operatingvoltage is less than 20KV.


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Short transmission line model

Vsn = Vm+ IR kos R + IX sin R.


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Short transmission line model(cont)

Vsn - Voltan pada penghujung

penghantaran

Vm - Voltan hujung penerima I - Arus beban pada R mengekor

R - Rintangan gelung ()

X - Kearuhan gelung ()


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S

RR

S

V

IRkosV

OC

OFkos


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Sebenarnya daripada rajah vektor ini bukan sahaja kita

dapat menentukan nilai VS dan faktor kuasa,

tapi kita juga dapat menentukan peratus pengaturan bagi

sebuah talian pendek dengan merujuk kepada parameter-parameter yang diberikan. Peratus pengaturan voltan

merujuk kepada Rajah 2.3 boleh ditulis sebagai.

Peratus Pengaturan =100

sinx

V

IXkosIR

S

RR


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Short Transmission Line

Short Transmission LineThe equivalent circuit and vector diagram of a shorttransmission line are shown in the figure given below.

In the equivalent circuit short transmission line is

represented by the lumped parameters R and L. R isthe resistance (per phase) L is the inductance (perphase) of the entire transmission line.

The effect of shunt capacitance and conductance isnot considered in the equivalent circuit.

The line is shown to have two ends : sending end(designated by the subscript S) at the generator, andthe receiving end (designated R) at the load.


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Performance of Transmission Lines

The performance of a power system ismainly dependent on the performance ofthe transmission lines in the system.

It is necessary to calculate the voltage,current and power at any point on atransmission line provided the values at onepoint are known.

The transmission line performance is

governed by its four parameters - seriesresistance and inductance, shuntcapacitance and conductance.


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Performance of TransmissionLines (CONT.)

All these parameters are distributed over the length ofthe line.

The insulation of a line is seldom perfect and leakagecurrents flow over the surface of insulators especially

during bad weather. This leakage is simulated by shunt conductance.

The shunt conductance is in parallel with the systemcapacitance.

Generally the leakage currents are small and the shuntconductance is ignored in calculations.


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Performance of transmission lines is meant thedetermination of efficiency and regulation of lines.

The efficiency of transmission lines is defined as:
http://bp1.blogger.com/_v2T5FtcWTMk/Rujkpq8BC-I/AAAAAAAABLQ/uNYICGUKG9Y/s1600-h/tr+effic.bmp


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The end of the line where load is connected is called thereceiving end and where source of supply is connected iscalled the sending end.

The Regulation of a line is defined as the change in thereceiving end voltage, expressed in percent of full loadvoltage, from no load to full load, keeping the sendingend voltage and frequency constant.


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Classification oftransmission lines (cont)

Formedium transmission lines the length of the line isin between 60km - 150km and the operating linevoltage wil be in between 21KV-100KV.

In this case the shunt capacitance can be assumed to

be lumped at the middle of the line or half of the shuntcapacitance may be considered to be lumped eachend of the line.

The two representations of medium length lines aretermed as nominal-T and nominal- respectively.


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2. Medium transmission line

Vsn = Vm + Isn (R + jX).


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Lines more than 150km long and line

voltage above 100KV require calculations in

terms of distributed parameters.

Such lines are known as long transmission

lines.

This classification on the basis of length is

more or less arbitrary and the real criterionis the degree of accuracy required.

Classification oftransmission lines (cont)


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3. Long transmission line

Electronic Model of a Transmission Line


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Capacitance and inductance are associated with thephysical devices called capacitors and inductors used incircuits to create various types of filters.

Capacitance and inductance are also encounteredwhenever electricity is flowing in conductors. In this

situation, they are effectsrather than physical circuitelements.

Resistance, capacitance, and inductance are distributeduniformly along the length of a transmission line.

Capacitance is a parallel effect, inductance is a series effect,and resistance is both a series and parallel effect. The

parallel capacitance and resistance are called shuntcapacitanceand shunt resistance. All these characteristic effects are expressed on a per

distance basis, for example, farads per mile for shuntcapacitance.


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Talian terdiri dari beberapa parameter malar ialaiturintangan, kearuhan, kemuatan dan kealiran yang wujuddisepanjang pengagihan talian penghantaran yang panjang.

Rintangan (R) dan regangan beraruhan (X) merupakanelement siri dalam talian

pengehantaran. Rentetan kemuatan (B) dan kealiran bocor (G) merupankan

element pirau, kealiran bocor juga menyebabkankehilangan kuasa dalam talian. Ia berpunca daripadakebocoran penebatan atau kesan korona pada pengalir.

Arus bocor yang mengalir melalui lepasan pirau adalah

maksima pada hujung penghantaran talian penghantarandan berkurangan secara berterusan ketika menuju kehujung penerima dan akhirnya menjadi sifar setelah tiba kehujung talian penerima.


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Kesan-Kesan Voltanke atas Kecekapan

Penghantaran.


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ASSIGNMENT #1(B)

Terangkan:

Adakah peningkatan voltan dapat

meningkatkan kecekapan penghantaranbekalan kepada pengguna?

Adakah peningkatan voltan dapat

menjimatkan kos penghantaran bekalan

kepada pengguna?

Unit2/19


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Corona


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Corona discharge

Corona discharge is the creation ofions in afluid (such as air) by the presence of astrong electric field.

Electrons are torn from un-ionized air, andeither the positive ions or else the electronsare attracted to the conductor, whilst thecharged particles drift.

This effect can cause considerable power

loss, create audible and radio-frequencyinterference, generate toxic compoundssuch as oxides of nitrogen and ozone, andlead to arcing.
http://en.wikipedia.org/wiki/Corona_dischargehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electronhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Earth%27s_atmospherehttp://en.wikipedia.org/wiki/Fluidhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Corona_discharge


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Both AC and DC transmission lines can

generate coronas, in the former case in the

form of oscillating particles, in the latter a

constant wind.

Due to the space charge formed around the

conductors, an HVDC system may have

about half the loss per unit length of a high

voltage AC system carrying the same

amount of power.
http://en.wikipedia.org/wiki/Space_chargehttp://en.wikipedia.org/wiki/Space_charge


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Corona is the physical manifestation ofenergy loss, and can transform dischargeenergy into very small amounts of sound,radio noise, heat, and chemical reactions ofthe air components.

Because power loss is uneconomical andnoise is undesirable, corona on

transmission lines has been studied byengineers since the early part of thiscentury.


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Factors influence the

corona.

Several factors, including:

voltage,

shape and diameter of conductor, and surface irregularities such as

scratches, nicks, dust, or water drops

can affect a conductors electricalsurface gradient and its corona

performance.


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CORONA AND INDUCED

CURRENT EFFECTS

Effects include:

audible noise,

radio, television and computer monitorinterference

gaseous effluents, shock potential.


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Overcome the corona

i). increase the conductor diameter

(example; by using ACSR).

ii). Use more than one conductor(bundle conductor)

iii). Increase the distance of

conductors, so the effect of magnetic

field will be reduced.

ALUMINIUM CONDUCTORS STEEL


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ALUMINIUM CONDUCTORS STEELREINFORCED (ACSR)

Available in a wide

range of steel

varying from as low

as 6% to as high as40%...


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http://encyclopedia2.thefreedictionary.com/Energy+transmission

Transmission lines use ACSR (aluminum cable, steelreinforced) and ACAR (aluminum cable, alloy reinforced)conductors.

In an ACSR conductor, a stranded steel core carries themechanical load, and layers of stranded aluminum surrounding

the core carry the current. An ACAR conductor is a stranded cable made of an aluminum

alloy with low resistance and high mechanical strength. ACSRconductors are usually used for high-voltage lines, and ACARconductors for subtransmission and distribution lines.

Ultrahigh-voltage (UHV) and extrahigh-voltage (EHV) lines usebundle conductors. Each phase of the line is built with two,

three, or four conductors connected in parallel and separated byabout 1.5 ft (0.5 m). Bundle conductors reduce coronadischarge

ALUMINIUM CONDUCTORS STEEL REINFORCED (ACSR)

ALUMINIUM CONDUCTORS


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ALUMINIUM CONDUCTORS

STEEL REINFORCED

This conductor consists of a solid or stranded steel coresurrounded by strands of aluminium (E.C. GRADE). ACSRconductor is available in a wide range of steel varying fromas low as 6% to as high as 40 %.

The higher strength ACSR conductors are used for river

crossings, overhead ground wires, installations involvingextra long spans etc. against any given resistance ofconductor, ACSR conductor may be manufactured forhaving a wide range of tensile strength as per requirement.

The principal advantage of these conductors are high tensilestrength and light weight with longer spans as well as withlesser supports. Due to the greater diameter of ACSRconductors a much higher corona limit can be obtainedcausing big advantages on high as well as extra highvoltage overhead lines.


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Recap


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Recap

Menakrifkan talian pendek, melakar rajah litar satu talian

pendek dan melabelkannya.

Menakrifkan talian sederhana, melakar rajah litar satu talian


Menakrifkan talian panjang, melakar rajah litar satu talian


Mentakrifkan pengaturan voltan.

Menakrifkan kecekapan penghantaran.

Date post:	04-Apr-2018
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Unit2 Transmission Line

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