IT_21_Questions_20_November_10.pdf

7/27/2019 IT_21_Questions_20_November_10.pdf

http://slidepdf.com/reader/full/it21questions20november10pdf 1/34

IT 21

Candidate Code No.

For Board Use Only

Result

Date

Int

Result

Date

Int

ELECTRICAL INSPECTOR EXAMINATION

20 November 2010

QUESTION AND ANSWER BOOKLET

Time Allowed: Three hoursINSTRUCTIONS – READ CAREFULLY

You have 10 minutes to read this paper but do not start writing until you are told to doso by the supervisor.

Write your Candidate Code Number in the box provided above. Your namemust NOT appear anywhere in this paper.

Answer all questions.

The pass mark for this examination is 60 marks.

Use a pen for written answers. Do not use pencils or red pens.

Drawing instruments and pencils may be used when diagrams are required. Marks areallocated on the basis of correctness.

Do not use correcting fluid or correcting tape.

Non-programmable calculators may be used.

It is recommended that the reference source for your answers be included in thespace provided if a question can be answered from the Act, Regulations, Standard orCode of Practice. However, just stating a reference only will earn no marks.

For calculation questions all workings, including formulae, must be shown to gain fullmarks.

Warning – You could get 0 marks for any question, or part of a question, if you showanything hazardous or dangerous in your answer.

You may need to use the following documents in this examination:

Electricity Act 1992 reprint dated 2008 and The Electricity Amendment Act 2006

or The Electricity Act 1992 reprint dated 1 April 2010 Electricity (Safety) Regulations 2010 AS/NZS 3000:2007 and Amendment No 1

AS/NZS 3001:2008 Amendment A

AS/NZS 3004.1:2008 AS/NZS 3760:2003 and Amendment No 1; or AS/NZS 3760:2010

AS/NZS 3019:2007 NZECP 34; NZECP 35; and NZECP 51

PLEASE HAND THIS PAPER TO THE SUPERVISOR BEFORE LEAVING THE ROOM

(turn over)



IT21 QUESTIONS – 20 NOVEMBER 2010 2

Question 1

(a) The Electricity (Safety) Regulations sets requirements for electrical safety

when work is carried out on works, installations and appliance. Refer to the

Regulations and state what a person must ensure when doing work in an

electrical installation.(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(b) The Electricity (Safety) Regulations places requirements on a person whodesigns an electrical installation.

Refer to the Regulations and state what outcome the person’s installation

design must achieve.(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(c) While inspecting an electrical installation you discover a hazard that youconsider to be an immediate danger to life. The Electricity (Safety)

Regulations requires you to notify the Secretary of the danger.

State the other person the Electricity (Safety) Regulations requires you tonotify.

(1 mark)

____________________________________________________________

Ref: …………………………………………..

(turn over)




Question 1 continued

(d) A person working under an employer licence has issued a Certificate of

Compliance for prescribed electrical work carried out.

Refer to the Electricity (Safety) Regulations and state:

(i) For how long must a copy of the Certificate of Compliance be retained?

(½ mark)

________________________________________________________

Ref: …………………………………………..

(ii) Who must retain the copy of the Certificate of Compliance?

(½ mark)

________________________________________________________

Ref: …………………………………………..

(e) There are certain circumstances under which a registered electricalinspector cannot inspect prescribed electrical work.

Refer to the Electricity (Safety) Regulations and state whether a registeredelectrical inspector has committed a grade A offence by inspecting work

that that inspector has certified on a certificate of compliance. State a

reason to support your answer.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)





(f) You have carried out an inspection of a new low voltage electrical

installation.

Refer to the Electricity (Safety) Regulations and state the TWO aspects thatthe inspection is required to ensure.

(1 mark)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(g) A person is working on a low voltage electrical installation that is isolated

from the power supply. There is a risk of unintentional connection to the

power supply.

Refer to the Electricity (Safety) Regulations and state the TWO courses of

action the person must take to prevent an unintentional connection of thepower supply.

(1 mark)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

Ref: …………………………………………..

(turn over)





(h) Refer to the Electricity (Safety) Regulations and state who the Secretary

may appoint to provide opinions on disputes over whether or not the

technical requirements of the regulations have been complied with.

(1 mark)

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(i) Refer to AS/NZS 3000 and state whether a combined protective earthing

and neutral (PEN) conductor can be switched. Include a reference to

support your answer.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(j) Refer to AS/NZS 3000 and state the prohibition relating to installing

systems under wall linings or roofing material.(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)





(k) A 230V isolated supply feeds three 10A socket outlets.

Refer to AS/NZS 3000 and state TWO requirements relating to the earthing

terminal of the socket outlets.(1 mark)

(1) ________________________________________________________

________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(l) Refer to AS/NZS 3000 and state the requirement for overcurrent protectionin an extra-low voltage electrical installation where the supply is earthed at

the point of supply.

(1 mark)

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(m) Refer to AS/NZS 3000 and state the requirements relating to the minimum

resistance of the protective earthing conductor of a final subcircuit in a

low voltage electrical installation.(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)





(n) State the main reason for testing the three-phase socket outlets in a new

electrical installation with a phase sequence indicator?

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(o) (i) What typical applications are “gG” type HRC fuse cartridges used for?

(½ mark)

________________________________________________________

(ii) What is a typical fusing factor (utilisation category) of a “gG” HRC fuse

cartridge?

(½ mark)

________________________________________________________

(p) (i) What typical applications are “gM” type HRC fuse cartridges used for?

(½ mark)

________________________________________________________

(ii) What is a typical fusing factor (utilisation category) of a “gM” HRC fuse

cartridge?(½ mark)

________________________________________________________

(turn over)





(q) An earth loop impedance test on a single phase 230V 10A socket outlet is

measured at 0.45Ω in a commercial office. A Class I electrical appliance

plugged into the socket outlet has a protective earthing conductor

resistance of 0.76Ω.

A short circuit of negligible impedance has occurred between the phase and

frame of the appliance. Calculate the prospective short circuit current

flowing in the protective earthing conductor.(1 mark)

(r) Briefly explain the basic principle of operation of an RCD tester.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

(s) A 100kVA, 400V, three-phase transformer has a 5% impedance and

develops a fault current level of 2MVA.

Determine the prospective short circuit current that would flow if a short

circuit of negligible impedance occurs across the transformer output

terminals.(1 mark)

(turn over)





(t) (i) If an RCD is being used for personal protection, what is the

permitted:

Type?

Maximum a.c. rated residual current?(½ mark)

________________________________________________________

(ii) If an RCD is being used for the protection of property, what is the

permitted:

Type? Maximum a.c. rated residual current?

(½ mark)

________________________________________________________

(turn over)




Question 2

A homeowner has installed the wiring for a new extension to their existing home.

The homeowner has requested that you test, inspect, certify and connect all of

the work in accordance with the Electricity (Safety) Regulations.

(a) (i) In accordance with which document must the homeowner have carriedout this work?

(1 mark)

________________________________________________________

Ref: …………………………………………..

(ii) The homeowner has run new TPS twin and earth final subcircuits (but

not connected them) back to the existing switchboard position.

What is the minimum size cable must the home owner use for:

(2 marks)

The lighting circuits. _______________________

The socket outlet circuits _______________________

The permanently connected 3kW hot water cylinder _____________

The permanently connected room heater __________________

Ref: …………………………………………..

(iii) The homeowner has installed light fittings that are connected to the

fixed wiring by ceiling roses in the new bedrooms.

What is the minimum size and type of flexible cord the homeowner

must use between a ceiling rose and a light fitting?

(1 mark)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(turn over)





(iv) The homeowner has installed an isolating switch to control the new hotwater cylinder.

What is the minimum rating for the isolating switch the homeownermust install?(½ mark)

________________________________________________________

Ref: …………………………………………..

(b) (i) Refer to the Electricity (Safety) Regulations and state the documentthat details the checking and testing you are required to carry out onthe homeowners work.

(1 mark)

________________________________________________________

Ref: …………………………………………..

(ii) Refer to the document you have stated for (b)(i) and stateTHREE tests using test instruments you will carry out on the finalsubcircuits installed by the homeowner before they are connected atthe switchboard.

(1½ marks)

(1) ____________________________________________________

(2) ____________________________________________________

(3) ____________________________________________________

Ref: …………………………………………..

(c) The switchboard has the necessary RCCBs and MCBs to which the new

circuits can be connected.

State the minimum electrical protection that is required for:(3 marks)

The lighting circuits. _______________________

The socket outlet circuits _______________________

The permanently connected hot water cylinder __________________

The permanently connected room heater __________________




(turn over)




Question 3

A small commercial factory is to be connected to a three-phase 400V MEN power

supply and has the following loads:

10kW of electric heating 12 - 250W metal halide light fittings with a power factor of 0.8 lag.

Several lightly loaded machines with a total load of 20kW and an overall

power factor of 0.5 lag

You have been requested to recommend a suitable size transformer that can

supply this installation. You need to allow for a one-third increase in load.

Determine by calculation the most suitable size transformer.

(10 marks)

(There is additional room for your calculations over the page)

(turn over)





(turn over)




Question 4

As an electrical inspector you have been asked to provide advice relating to theinstallation of apparatus and accessories in an existing commercial building thatoperates at standard low voltage.

Most of the apparatus and accessories will be supplied at 230V, single-phase.However some apparatus and accessories will be supplied at 12V, SELV.

(a) (i) Refer to the Electricity (Safety) Regulations and state the standard to

which the 230V socket outlets must comply.(½ mark)

________________________________________________________

Ref: …………………………………………..

(ii) State the main reason why it is only the 230V socket outlets in this

installation that can comply with the standard pin arrangementdetailed in the Standard you have stated in (a)(i).

(1½ marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(b) A 230V motor driven machine is supplied by a multi-core flexible cable that incorporates 12V conductors. The 12V conductors are part of a control

circuit that allows the machine to be controlled remotely.

Refer to AS/NZS 3000 and state the requirement relating to the insulationof the conductors of the multi-core flexible cable.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)





(c) Within the installation some SELV cables will be installed in a trunking

system with 230V cables.

Refer to AS/NZS 3000 and state TWO methods, either of which that willpermit SELV cables and 230V to be enclosed in the same wiring system.

(2 marks)

(1) ________________________________________________________

________________________________________________________

(2) ________________________________________________________

________________________________________________________

Ref: …………………………………………..

(d) The installation will also incorporate switched standard socket outlets,

switched pendant socket outlets and switched floor socket outlets.

(i) Refer to AS/NZS 3000 and state the requirement relating to the

polarity (polarisation) of the standard socket outlets.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(ii) The switched pendant socket outlets will be supplied via a flexible

cord.

Refer to AS/NZS 3000 and state the requirements relating to the

switch in the pendant socket outlet.(1 mark)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(turn over)





(e) The installation will incorporate SELV socket outlets.

Refer to AS/NZS 3000 and state:

(i) The requirements relating to the marking of the SELV socket outlets.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(ii) The requirements relating to the plugs for the SELV apparatus.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(f) The installation incorporates recessed luminaires, for which there are no

manufacturer’s instructions.

Refer to AS/NZS 3000 and state ONE method that can used to install the

recessed luminaries.

(1 mark)

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)




Question 5

A small three-phase 400V/230V low rise development comprises six 230Vdomestic electrical installations combined with communal areas. The intention isthat the load be spread evenly, as much as is possible, over the three phases.

The installation comprises:

Domestic installation Group 1. Three single-phase installations.

Domestic installation Group 2. Three single-phase installations.

Communal Group.

Refer to AS/NZS 3000 calculate the maximum demand in amps of the highestloaded phase.

(10 marks)

(a) Domestic installation Group 1. Three single-phase installations have the

following loads:

15 Lighting points 1 Electric oven – 2.5kW4 Double socket outlets (10A) 1 Storage water heater – 2kW6 Single socket outlets (10A) 1 Air-conditioning unit – 3kW

Load Group Calculation Load (A)

Group

Group

Group

Group

Group

Maximum demand

(turn over)





(b) Domestic installation Group 2. Three single-phase installations have the

following loads:

15 Lighting points 1 Electric range – 5kW4 Double socket outlets (10A) 1 Instantaneous water heater –

3kW

6 Single socket outlets (10A) 1 Sauna – 6kW


Group

Group

Group

Group

Group

Maximum demand

(turn over)





(c) Communal Group. The communal areas incorporate the following single

phase loads:

30 Lights – 100W each3 Clothes dryers – 4 kW each

3 Air-conditioning unit, each rated at:

6kW – winter setting3kW – summer setting


Group

Group

Group

Maximum demand

(d) Maximum demand of the heaviest loaded phase.

Ref: …………………………………………..

(turn over)




Question 6

(a) You have been requested to connect a new three-phase low voltage

electrical installation to the electricity supply.

You have not been involved in any way with doing prescribed electricalwork on the installation.

You have sighted a Certificate of Compliance that has been completed and

signed by the electrician who certified the work and the electrical inspectorwho inspected the work.

Refer to the Electricity (Safety) Regulations and state:

(i) The connection of the installation can only proceed if the Certificate of

Compliance has been issued within a specific time-frame. What is that

time-frame?

(½ mark)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(ii) FOUR matters any or all of which could be confirmed on the Certificate

of Compliance you have sighted.(2 marks)

(1) ____________________________________________________

____________________________________________________

(2) ____________________________________________________

____________________________________________________

(3) ____________________________________________________

____________________________________________________

(4) ____________________________________________________

____________________________________________________

Ref: …………………………………………..

(turn over)





(iii) State the action you must take in relation to the new meters.

(1 mark)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(iv) What must be contained in the document you have sighted relating to

the testing of the installation.(2 marks)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(v) Who must sign the documentation you have sighted in (a)(iv).

(1 mark)

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(b) You have been requested to reconnect an existing electrical installation thathas been disconnected for 10 months. No prescribed electrical work has

been carried out in the time the installation has been disconnected.

You have not been involved in any way with testing or checking the

installation.

You have sighted a certificate before reconnecting the installation. Refer tothe Electricity (Safety) Regulations and state:

(i) The Standard under which the certificate is issued.

(½ mark)

________________________________________________________

Ref: …………………………………………..

(turn over)





(ii) The name of that certificate.

(½ mark)

________________________________________________________

Ref: …………………………………………..

(iii) The matters that must be confirmed on the certificate that you havesighted.

(1½ marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(iv) Refer to the Standard you have stated in (b)(i) and state the

requirement relating to the adequacy of the overcurrent protectivedevices in the installation.

(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(turn over)




Question 7

(a) Final subcircuits are generally required to have overcurrent protection.

(i) Refer to AS/NZS 3000 and state the overcurrent protection

requirements for the active conductors of a final subcircuit supplying astandard socket outlet.

(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(ii) Refer to AS/NZS 3001 and state the overcurrent protectionrequirements for the active conductors of a final subcircuit supplying a

socket outlet for a caravan in a caravan park.(1 mark)

________________________________________________________

________________________________________________________

________________________________________________________

Ref: …………………………………………..

(turn over)





(b) TWO types of single-phase socket outlets can be installed on a servicepillar in a caravan park for the supply of electricity to caravans. Eachtype is required to have specific characteristics

Refer to AS/NZS 3001 and for each type of socket outlet state:

The configuration The applicable Standard The minimum current rating.

(3 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(c) TWO types of single-phase socket outlets can be installed on a servicepillar in areas other than a caravan park for the supply of electricityconnectable installations. Each type is required to have specificcharacteristics

Refer to AS/NZS 3001 and for each type of socket outlet state:

The configuration The applicable Standard The minimum current rating.

(3 marks) ____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)





(d) Refer to AS/NZS 3001 and state the overcurrent protection requirements

within a caravan for the incoming supply.

(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

Ref: …………………………………………..

(turn over)




Question 8

The figure below represents a new low voltage single-phase supply to a domestic

installation. The installation is live and there maybe a phase/neutral

transposition between the distribution supply system and the MEN

switchboard.

(a) You are going to carry out testing using a multi-meter that has the requiredfunctions (scales) to verify whether a mains phase/neutral transposition has

taken place.

(i) State the function (scale) you would select on the multi-meter.

(½ mark)

________________________________________________________

(ii) State the range you would select on the multi-meter.(½ mark)

________________________________________________________

(iii) State additional equipment you would use with the multi-meter.(1 mark)

________________________________________________________

________________________________________________________

(turn over)

Neutral bar

Main switch Earth bar

Single-phase consumer

Meter box





(b) On the figure on the previous page, use the instrument and equipment you

have stated in (a) to show how testing for a mains phase/neutraltransposition is carried out.

(2 marks)

(c) For the tests you have carried out in (b) state:

(i) The readings you would get on the multi-meter if phase/neutral

transposition has not taken place.(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(ii) The readings you would get on the multi-meter if a phase/neutral

transposition has taken place.(2 marks)

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

(d) The low voltage installation is protected on the distribution supply system

by a 60A rewireable pole fuse.

State the main reason why a phase and neutral transposition on the mains

will not operate (“blow”) the pole fuse.(2 marks)

____________________________________________________________

____________________________________________________________

____________________________________________________________

____________________________________________________________

(turn over)




Question 9

(a) A 230V PVC insulated two-core copper TPS cable is required to be installed

to supply a 230V, single phase switchboard on a farm.

Calculate the minimum size of cable that will meet the load, voltage dropand environmental conditions by using the following information and

information in the tables on pages 30, 31 and 32.

The cable route between the point of supply and switchboard is 300

metres:

The cable will be buried direct. The only load in the switchboard is a 10A socket outlet.

The ambient temperature is that set under the Electricity (Safety)

Regulations.

The maximum conductor temperature permitted is 75 oC. The maximum allowable voltage drop is that stated in AS/NZS 3000

(6 marks)

(turn over)





(b) A PVC insulated three-core copper cable is to be used to supply a 70 kW,

three-phase, 400 V furnace in a foundry.

Calculate the minimum size of cable that will meet the load, voltage dropand environmental conditions by using the following information andinformation in the tables on pages 30, 31 and 32.

The cable is to be clipped direct (touching). The protective earthing conductor is to be run adjacent to the cable

The ambient air temperature is 35 oC.

The distance between the switchboard and the furnace is 5 metres The cable is to be protected by HRC fuses.

The maximum conductor temperature permitted is 75 oC.

. (4 marks)

(turn over)





The following are extracts from AS/NZS 3008.1.2.

Table 9

Current Carrying Capacities of Two-Core O.6/1 kV Insulated andSheathed (including Neutral Screened) Cables with or without Earth

Conductor, Armoured or Non-Armoured Cables

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Current carrying capacity A

Unenclosed Enclosed BuriedDirect

Undergroundnon-metallicwiringenclosureCon

ductorsize

Spaced Touching Non-metallicwiringenclosures

in air –roundcable

Non-metallicwiringenclosures

in air – flatcable

In non-metallicwiringenclosures

orunenclosedpartiallysurroundedby thermalinsulation

Completelysurroundedby thermalinsulation

mm2 Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al

1 17 -- 16 -- 13 10 15 11 11 9 8 - 24 - 19 -1.5 22 - 21 - 16 13 19 15 15 11 10 - 31 - 24 -2.5 31 - 30 - 23 17 25 19 21 16 15 - 44 - 34 -

4 42 - 39 - 30 23 33 25 27 22 19 - 57 - 44 -6 52 - 50 - 39 30 42 32 35 27 25 - 72 - 56 -10 73 - 68 - 54 41 57 43 49 38 34 - 96 - 75 -

16 97 75 91 71 72 55 75 57 65 50 46 35 127 97 97 7525 131 100 120 95 100 76 101 76 90 71 60 47 160 127 127 9835 160 125 148 114 120 89 120 89 105 82 74 58 198 154 154 121

Note: The ratings are based on 300C ambient air temperature and 150C ambient soil temperature

(turn over)





Table 12

Current Carrying Capacities of Three-Core And Four-Core O.6/1 kV

Insulated and Sheathed (including Neutral Screened) Cables with orwithout Earth Conductor, Armoured or Non-Armoured Cables

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Current carrying capacity A

Unenclosed Enclosed BuriedDirect

Undergroundnon-metallicwiringenclosureCon

ductorsize

Spaced Touching Non-metallicwiringenclosuresin air –roundcable

Non-metallicwiringenclosuresin air – flatcable

In non-metallicwiringenclosuresorunenclosedpartiallysurroundedby thermalinsulation

Completelysurroundedby thermalinsulation

mm2 Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al Cu Al

1 15 -- 14 -- 11 9 14 10 11 8 7 - 21 - 17 -1.5 18 - 17 - 15 11 17 13 14 11 9 - 26 - 21 -2.5 26 - 25 - 21 16 23 17 19 15 13 - 37 - 29 -

4 35 - 33 - 27 21 30 23 25 19 17 - 48 - 37 -6 46 - 42 - 35 27 39 30 33 25 22 - 61 - 47 -10 52 - 58 - 48 38 52 40 44 34 29 - 81 - 63 -

16 82 64 78 60 64 49 68 52 59 46 39 30 106 83 81 6425 111 86 104 81 90 68 95 72 82 64 52 40 138 107 106 8335 137 106 125 99 105 80 105 80 96 74 64 49 165 127 127 100

Note: The ratings are based on 300C ambient air temperature and 150C ambient soil temperature

Table 27(1)

Rating Factors for Variations in Ambient Temperature for Cables in Air

or Heated Concrete Slabs and for Cables Buried Direct in the Ground or

in Underground Wiring Enclosures – Air And Concrete Slab

Temperatures

1 2 3 4 5 6 7 8 9 10 11

Rating Factor

Ambient temperature

Conductortemperature0

C 15 20 25 30 35 40 45 50 55 60150 1.07 1.05 1.03 1.00 0.98 0.96 0.94 0.91 0.89 0.87110 1.08 1.06 1.03 1.00 0.97 0.93 0.90 0.87 0.83 0.7990 1.15 1.09 1.05 1.00 0.95 0.91 0.85 0.80 0.74 0.66

80 1.17 1.12 1.06 1.00 0.95 0.89 0.82 0.75 0.68 0.5975 1.18 1.12 1.06 1.00 0.94 0.88 0.80 0.72 0.63 0.53

(turn over)





Table 27(2)

Rating Factors for Variations in Ambient Temperature for Cables in Air

or Heated Concrete Slabs and for Cables Buried Direct in the Ground orin Underground Wiring Enclosures – Soil Temperatures

1 2 3 4 5 6 7 8

Rating Factor

Ambient temperature

Conductortemperature0C 10 15 20 25 30 35 40

110 1.02 1.00 0.97 0.94 0.92 0.89 0.8690 1.04 1.00 0.96 0.93 0.91 0.87 0.8380 1.04 1.00 0.95 0.92 0.88 0.83 0.78

75 1.04 1.00 0.95 0.91 0.86 0.81 0.75

Table 42

Three-Phase Voltage Drop at 50Hz of Multicore Cables with Circular Copper

Conductors

Three-phase voltage drop at 50 Hz, mV/A.m

Conductor temperature, 0CConductor size 45 60 75 90 110

mm2 Max. 0.8p.f.

Max. 0.8p.f.

Max. 0.8p.f.

Max. 0.8p.f.

Max. 0.8p.f.

1 40.3 - 42.5 - 44.7 - 46.8 - 49.7 -1.5 25.9 - 27.3 - 28.6 - 30.0 - 31.9 -2.5 14.1 - 14.9 - 15.6 - 16.4 - 17.4 -

4 8.77 - 9.24 - 9.71 - 10.2 - 10.8 -6 5.86 - 6.18 - 6.49 - 6.80 - 7.22 -10 3.49 - 3.67 - 3.86 - 4.05 - 4.29 -

16 2.19 - 2.31 - 2.43 - 2.55 - 2.70 -25 1.39 - 1.47 - 1.54 - 1.61 - 1.71 -35 1.01 - 1.06 - 1.11 - 1.17 - 1.24 -

Note: To convert to single-phase values multiply the three-phase value by 1.155

(turn over)



For Candidate’s Use For Examiner’s Use OnlyQuestions

Answered

Marks

1

2

3

4

In the box, write thenumber of EXTRA

sheets you have

used. Write NIL if you have not used

any

5

6

7

8

9

TOTAL

Date post:	14-Apr-2018
Category:	Documents
Upload:	muthoot2008
View:	216 times
Download:	0 times

IT_21_Questions_20_November_10.pdf

Documents