Latest Cables Interview Questions and Answers List

7/25/2019 Latest Cables Interview Questions and Answers List

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Latest Cables Interview Questions and Answers List

1. The insulating material for a cable

should have

(a) low cost

(b) high dielectric strength

(c) high mechanical strength

(d) all of the above

Ans: D

2. Which of the following protects a

cable against mechanical inur!"

(a) #edding

(b) $heath

(c) Armouring

(d) %one of the above

Ans: &

'. Which of the following insulation

is used in cables"

(a) arnished cambric

(b) ubber

(c) *aper

(d) An! of the above

Ans: D

+. ,mpire tape is

(a) varnished cambric

(b) vulcani-ed rubber

(c) impregnated paper

(d) none of the above

Ans: A

. The thic/ness of the la!er of insulationon the conductor0 in cables0 depends upon

(a) eactive power

(b) *ower factor

(c) oltage

(d) &urrent carr!ing capacit!

Ans: &

. The bedding on a cable consists of

(a) essian cloth

(b) 3ute

(c) An! of the above


Ans: &

4. The insulating material for cables

should

(a) be acid proof

(b) be non5inflammable

(c) be non5h!groscopic

(d) have all above properties

Ans: D

6. 7n a cable immediatel! above

metallic sheath 88888 is provided.

(a) ,arthing connection

(b) #edding(c) Armouring


Ans: #

9. The current carr!ing capacit! of


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cables in D.&. is more that in A.&. mainl!

due to

(a) absence of harmonics

(b) non5eistence of an! stabilit! limit

(c) smaller dielectric loss(d) absence of ripples

(e) none of the above

Ans: c

1;. 7n case of three core fleible cable

the colour of the neutral is

(a) blue

(b) blac/

(c) brown


Ans: a

11 cables are used for 1'2 / lines.

(a) igh tension

(b) $uper tension

(c) ,tra high tension

(d) ,tra super voltage

Ans: d

12. &onduit pipes are normall! used to

protect 88888 cables.

(a) unsheathed cables

(b) armoured

(c) *& sheathed cables


Ans: a

1'. The minimum dielectric stress in a

cable is at

(a) armour

(b) bedding

(c) conductor surface

(d) lead sheath

Ans: d

1+. 7n single core cables armouring isnot done to

(a) avoid ecessive sheath losses

(b) ma/e it fleible

(c) either of the above


Ans: a

1. Dielectric strength of rubber is

around

(a) /


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16. igh tension cables are generall!

used up to

(a) 11/

(b) ''/

(c) /(d) 1'2 /

Ans: a

19. The surge resistance of cable is

(a) ohms

(b) 2; ohms

(c) ; ohms

(d) 1;; ohms

Ans: c

2;. *& stands for

(a) pol!vin!l chloride

(b) post varnish conductor

(c) pressed and varnished cloth

(d) positive voltage conductor


Ans: a

7n the cables0 the location of fault

is usuall! found out b! comparing

(a) the resistance of the conductor

(b) the inductance of conductors

(c) the capacitances of insulated

conductors

(d) all above parameters

Ans: c

22. 7n capacitance grading of cables

we use a 888888 dielectric.

(a) composite

(b) porous

(c) homogeneous

(d) h!groscopic

Ans: a

2'. *ressure cables are generall! notused be!ond

(a) 11 /

(b) '' /

(c) /

(d) 1'2 /

Ans: c

2+. The material for armouring on

cable is usuall!

(a) steel tape

(b) galvanised steel wire

(c) an! of the above


Ans: c

2. &ables0 generall! used be!ond

/ are

(a) oil filled

(b) $.=. t!pe

(c) belted

(d) armoured

Ans: a

2. The relative permittivit! of

rubber is

(a) between 2 and '(b) between and

(c) between 6 and 1;

(d) between 12 and 1+

Ans: a


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24. $olid t!pe cables are considered

unreliable be!ond / because

(a) insulation ma! melt due to higher

temperature

(b) s/in effect dominates on theconductor

(c) of corona loss between conductor

and sheath material

(d) there is a danger of brea/down of

insulation due to the presence of voids

Ans: d

26. 7f the length of a cable is doubled0

its capacitance

(a) becomes one5fourth

(b) becomes one5half

(c) becomes double

(d) remains unchanged

Ans: c

29. 7n cables the charging current

(a) lags the voltage b! 9;>

(b) leads the voltage b! 9;>

(c) lags the voltage b! 16;>

(d) leads the voltage b! 16;>

Ans: b

';. A certain cable has an insulation of

relative permittivit! +. 7f the insulation

is replaced b! one of relative permittivit!

20 the capacitance of the cable willbecome

(a) one half

() double

(c) four times


Ans: a

'1. 7f a cable of homogeneous

insulation has a maimum stress of 1;

/


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minimum at the sheath

(d) -ero at the conductor as well as on

the sheath


Ans: c

'. The brea/down of insulation of the

cable can be avoided economicall! b! the

use of

(a) inter5sheaths

(b) insulating materials with different

dielectric constants

(c) both (a) and (b)


Ans: c

'. The insulation of the cable

decreases with

(a) the increase in length of the

insulation

(b) the decrease in the length of the

insulation

(c) either (a) or (b)


Ans: a

'4. A cable carr!ing alternating

current has

(a) h!steresis losses onl!

(b) h!steresis and lea/age losses onl!

(c) h!steresis0 lea/age and copperlosses onl!

(d) h!steresis0 lea/age0 copper and

friction losses

Ans: b

'6. 7n a cable the voltage stress is

maimum at

(a) sheath

() insulator

(e) surface of the conductor(d) core of the conductor

Ans: d

'9. &apacitance grading of cable

implies

(a) use of dielectrics of different

permeabilities

(b) grading according to capacitance

of cables per /m length

(c) cables using single dielectric in

different concentrations

(d) capacitance re?uired to be

introduced at different lengths to

counter the effect of inductance


Ans: a

+;. @nderground cables are laid at

sufficient depth

(a) to minimise temperature stresses

(b) to avoid being unearthed easil! due

to removal of soil

(c) to minimise the effect of shoc/s

and vibrations due to gassing vehicles0

etc.

(d) for all of the above reasonsAns: c

+1. The advantage of cables over

overhead transmission lines is

(a) eas! maintenance


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(b) low cost

(c) can be used in congested areas

(d) can be used in high voltage circuits

Ans: c

+2. The thic/ness of metallic shielding

on cables is usuall!

(a) ;.;+ mm

(b) ;.2 to ;.+ mm

(e) ' to mm

(d) +; to ; mm

Ans: a

+'. &ables for 22; / lines are

invariabl!

(a) mica insulated

(b) paper insulated

(c) compressed oil or compressed gas

insulated

(d) rubber insulated


Ans: c

++. 7s a cable is to be designed for

use on 1;;; /0 which insulation would !ou

prefer "

(a) *ol!vin!le chloride

(b) ulcanised rubber

(c) 7mpregnated paper

(d) &ompressed $e gas

(e) none of the aboveAns: d

+. 7f a power cable and a

communication cable are to run parallel

the minimum distance between the two0

to avoid interference0 should be

(a) 2 cm

(b) 1; cm

(c) ; cm

(d) +;; cmAns: c

+. &opper as conductor for cables is

used as

(a) annealed

(b) hardened and tempered

(c) hard drawn

(d) allo! with chromium

Ans: a

+4. The insulating material should have

(a) low permittivit!

(b) high resistivit!

(c) high dielectric strength


Ans: d

+6. The advantage of oil filled cables

is

(a) more perfect impregnation

(b) smaller overall si-e

(c) no ionisation0 oidation and

formation of voids


Ans: d

+9. The disadvantage with paper as

insulating material is

(a) it is h!groscopic

() it has high capacitance

(c) it is an organic material


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Ans: a

;. The brea/down voltage of a cable

depends on(a) presence of moisture

(b) wor/ing temperature

(c) time of application of the voltage


Ans: d

1. 7t is difficult to maintain oil filled

cables.

(a) Bes

(b) %o

Ans: a

1. 7n capacitance grading a

homogeneous dielectric is used.

(a) Bes

(b) %o

Ans: b

2. 7n congested areas where

ecavation is epensive and inconvenient

Cdraw in s!stemC of la!ing of underground

cables

is often adopted.

(a) Bes

(b) %o

Ans: a

'. %atural rubber is obtained from

mil/! sap of tropical trees.

(a) Bes

(b) %o

Ans: a

+. ubber is most commonl! used

insulation in cables.

(a) Bes(b) %o

Ans: a

. *ol!eth!lene has ver! poor

dielectric and ageing properties.

(a) Bes

(b) %o

Ans: b

. The metallic sheath ma! be made of

lead or lead allo! or of aluminium.

(a) Bes

(b) %o

Ans: b


8/96

Latest Transmission and Distribution

Questions and Answers List

1. #! which of the following s!stems

electric power ma! be transmitted "

(a) verhead s!stem

(b) @nderground s!stem

(c) #oth (a) and (b)

(d) %one of the aboveAns: c

2 are the conductors0 which connect

the consumerCs terminals to the

distribution

(a) Distributors

(b) $ervice mains

(c) eeders


Ans: b

'. The underground s!stem cannot be

operated above

(a) ++;

(b) 11 /

(c) '' /

(d) /Ans: d

+. verhead s!stem can be designed

for operation up to

(a) 11 /

(b) '' /

(c) /

(d) +;; /

Ans: c

. 7f variable part of annual cost onaccount of interest and depreciation on

the capital outla! is e?ual to the annual

cost of electrical energ! wasted in the

conductors0 the total annual cost will be

minimum and the corresponding si-e of

conductor will be most economical. This

statement is /nown as

(a) EelvinCs law

(b) hmCs law

(c) Eirchhoffs law

(d) arada!Cs law


Ans: a

. The wooden poles well impregnated

with creosite oil or an! preservative

compound have life

(a) from 2 to !ears

(b) 1; to 1 !ears

(c) 2 to '; !ears

(d) ; to 4; !ears

Ans: c

4. Which of the following materials is

not used for transmission and distribution

of electrical power "(a) &opper

(b) Aluminium

(c) $teel

(d) Tungsten

Ans: d


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6. Falvanised steel wire is generall!

used as

(a) sta! wire

(b) earth wire(c) structural components


Ans: d

9. The usual spans with .&.&. poles

are

(a) +;G; meters

(b) ;G1;; meters

(c) 6;G1;; meters

(d) ';;G;; meters

Ans: c

1;. The corona is considerabl!

affected b! which of the following "

(a) $i-e of the conductor

(b) $hape of the conductor

(c) $urface condition of the conductor

(d) All of the above

Ans: d

11. Which of the following are the

constants of the transmission lines "

(a) esistance

(b) 7nductance

(c) &apacitance

(d) All of the aboveAns: d

12. '1; /m line is considered as

(a) a long line

(b) a medium line

(c) a short line

(d) an! of the above

Ans: a

1'. The phenomenon ?f rise in voltageat the receiving end of the open5circuited

or lightl! loaded line is called the

(a) $eebac/ effect

(b) erranti effect

(c) aman effect


Ans: b

1+. The s?uare root of the ratio of

line impedance and shunt admittance is

called the

(a) surge impedance of the line

(b) conductance of the line

(c) regulation of the line


Ans: a

1. Which of the following is the

demerit of a Cconstant voltage

transmission s!stemC "

(a) 7ncrease of short5circuit current

of the s!stem

(b) Availabilit! of stead! voltage at all

loads at the line terminals

(c) *ossibilit! of better protection

for the line due to possible use of higherterminal reactants

(d) 7mprovement of power factor at

times of moderate and heav! loads

(e) *ossibilit! of carr!ing increased

power for a given conductor si-e in case


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of long5distance heav! power

transmission

Ans: a

1. =ow voltage cables are meant foruse up to

(a)l.l/

(b)'.'/

(c)./

(d)ll/

Ans: e

14. The operating voltage of high

voltage cables is up to

(a)l.l/

(b)'.'/

(c)./

(d)ll/

Ans: d

16. The operating voltage of

supertension cables is up to

(a) '.' /

(b) . /

(c) 11 /

(d) '' /

Ans: d

19. The operating voltage of etra

high tension cables is upto

(a) . /(b) 11 /

(c) '' /

(d) /

(e) 1'2 /

Ans: d

2;. Which of the following methods is

used for la!ing of underground cables "

(a) Direct la!ing

(b) Draw5in5s!stem(c) $olid s!stem


Ans: d

21. Which of the following is the

source of heat generation in the cables "

(a) Dielectric losses in cable insulation

(b) losses in the conductor

(c) =osses in the metallic sheathings

and armourings


Ans:

22. Due to which of the following

reasons the cables should not be

operated too hot "

(a) The oil ma! loose its viscosit! and

it ma! start drawing off from higher

levels

(b) ,pansion of the oil ma! cause the

sheath to burst

(c) @ne?ual epansion ma! create voids

in the insulation which will lead to

ioni-ation

(d) The thermal instabilit! ma! rise

due to the rapid increase of dielectriclosses with temperature

(e) All of the above

Ans: e

2'. Which of the following D.&.


11/96

distribution s!stem is the simplest and

lowest in first cost "

(a) adial s!stem

(b) ing s!stem

(c) 7nter5connected s!stem(d) %one of the above

Ans: a

2+. A booster is a

(a) series wound generator

(b) shunt wound generator

(c) s!nchronous generator


Ans: a

2. #esides a method of trial and

error0 which of the following methods is

emplo!ed for solution of networ/

problems in interconnected s!stem "

(a) &irculating current method

(b) TheveninCs theorem

(c) $uperposition of currents

(d) Direct application of Eirehhoffs

laws


Ans: e

2. Which of the following faults is

most li/el! to occur in cables "

(a) &ross or short5circuit fault

(b) pen circuit fault(c) #rea/down of cable insulation


Ans:

24. The cause of damage to the lead

sheath of a cable is

(a) cr!stallisation of the lead through

vibration

(b) chemical action on the lead when

buried in the earth(c) mechanical damage


Ans:

26. The voltage of the single phase

suppl! to residential consumers is

(a) 11;

(b) 21;

(c) 2';

(d) +;;

Ans: c

29. Host of the high voltage

transmission lines in 7ndia are

(a) underground

(b) overhead



Ans: b

';. The distributors for residential

areas are

(a) single phase

(b) three5phase three wire

(c) three5phase four wire

(d) none of the aboveAns: c

'1. The conductors of the overhead

lines are

(a) solid


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(b) stranded

(c) both solid and stranded


Ans:

'2. igh voltage transmission lines use

(a) suspension insulators

(b) pin insulators



Ans: a

''. Hulticore cables generall! use

(a) s?uare conductors

(b) circular conductors

(c) rectangular conductors

(d) sector5shaped conductors


Ans: d

'+. Distribution lines in 7ndia

generall! use

(a) wooden poles

(b) .&.&. poles

(c) steel towers


Ans: b

'. The material commonl! used for

insulation in high voltage cables is

(a) lead(b) paper

(c) rubber


Ans: b

'. The loads on distributors s!stems

are generall!

(a) balanced

(b) unbalanced

(c) either of the above(d) none of the above

Ans: b

'4. The power factor of industrial

loads is generall!

(a) unit!

(b) lagging

(c) leading

(d) -ero

Ans: b

'6. verhead lines generall! use

(a) copper conductors

(b) all aluminium conductors

(c) A.&.$.. conductors

(d) none of these

Ans: c

'9. 7n transmission lines the cross5

arms are made of

(a) copper

(b) wood

(c) .&.&.

(d) steel

Ans: d

+;. The material generall! used for

armour of high voltage cables is

(a) aluminium

(b) steel

(c) brass


13/96

(d) copper

Ans: b

+1. Transmission line insulators are

made of(a) glass

(b) porcelain

(c) iron

(d) *..&.

Ans:

+2. The material commonl! used for

sheaths of underground cables is

(a) lead

(b) rubber

(c) copper

(d) iron

Ans: a

+'. The minimum clearance between

the ground and a 22; / line is about

(a) +.' m

(b) . m

(c) 4.; m

(d) 1;. m

Ans: c

++. The spacing between phase

conductors of a 22; / line is

approimatel! e?ual to

(a) 2 m(b) '. m

(c) m

(d) 6. m

Ans: c

+. =arge industrial consumers are

supplied electrical energ! at

(a) +;;

(b) 11 /

(c) /(d) +;; /

Ans: c

+. 7n a D.&. '5wire distribution

s!stem0 balancer fields are cross5

connected in order to

(a) boost the generated voltage

(b) balance loads on both sides of the

neutral

(c) ma/e both machineI run as

unloaded motors

(d) e?uali-e voltages on the positive

and negative outers

Ans:

+4. 7n a D.&. '5wire distributor using

balancers and having une?ual loads on the

two sides

(a) both balancers run as generators

(b) both balancers run as motors

(c) balancer connected to lightl!5 loaded

side runs as a motor

(d) balancer connected to heavil!5 loaded

side runs as a motor

Ans:

+6. Transmitted power remaining the

same0 if suppl! voltage of a D.&. 25wire

feeder is increased 1;; percent0 saving in

copper is

(a) 2 percent


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(b) ; percent

(c) 4 percent

(d) 1;; percent

Ans: b

+9. A uniforml!5loaded D.&.

distributor is fed at both ends with e?ual

voltages. As compared to a similar

distributor fed at one end onl!0 the drop

at the middle point is

(a) one5fourth

(b) one5third

(c) one5half

(d) twice


Ans: a

;. As compared to a 25wire D.&.

distributor0 a '5wire distributor with

same maimum voltage to earth uses onl!

(a) '1.2 percent of copper

(b) ''.' percent of copper

(c) .4 percent of copper

(d) 12 percent of copper

Ans: a

1. Which of the following is usuall!

not the generating voltage "

(a) . /

(b) 6.6 /

(c) 11 /(d) 1'.2 /

Ans: b

2. or an overhead line0 the surge

impedance is ta/en as

(a) 2;5'; ohms

(b) 4;G6; ohms

(c) 1;;G2;; ohms

(d) ;;G1;;; ohms

(e) none of the aboveAns: c

'. The presence of o-one due to

corona is harmful because it

(a) reduces power factor

(b) corrodes the material

(c) gives odour

(d) transfer energ! to the ground


Ans: b

+. A feeder0 in a transmission

s!stem0 feeds power to

(a) distributors

(b) generating stations

(c) service mains


Ans: a

. The power transmitted will be

maimum when

(a) corona losses are minimum

(b) reactance is high

(c) sending end voltage is more

(d) receiving end voltage is more

Ans: c

. A '5phase + wire s!stem is

commonl! used on

(a) primar! transmission

(b) secondar! transmission


15/96

(c) primar! distribution

(d) secondar! distribution

Ans: d

4. Which of the following materials isused for overhead transmission lines "

(a) $teel cored aluminium

(b) Falvanised steel

(c) &admium copper


Ans: d

6. Which of the following is not a

constituent for ma/ing porcelain

insulators "

(a) Juart-

(b) Eaolin

(c) elspar

(d) $ilica

Ans: d

9. There is a greater possibilit! of

occurence of corona during

(a) dr! weather

(b) winter

(c) summer heat

(d) humid weather


Ans: d

;. Which of the following rela!s isused on long transmission lines "

(a) 7mpedance rela!

(b) HhoCs rela!

(c) eactance rela!


Ans: b

1. The steel used in steel cored

conductors is usuall!

(a) allo! steel(b) stainless steel

(c) mild steel

(d) high speed steel

(e) all of the above

Ans: c

2. Which of the following

distribution s!stems is more reliable "

(a) adial s!stem

(b) Tree s!stem

(c) ing main s!stem

(d) All are e?uall! reliable

Ans: c

'. Which of the following

characteristics should the line supports

for transmission lines possess "

(a) =ow cost

(b) igh mechanical strength

(c) =onger life


Ans: d

+. Transmission voltage of ll / is

normall! used for distances upto

(a) 2;G2 /m(b) +;G; /m

(c) ;G4; /m

(d) 6;G1;; /m

Ans: a


16/96

. Which of the following regulations

is considered best"

(a) ;K

(b) 2;K

(c) 1;K(d) 2K

Ans: d

. $/in effect is proportional to

(a) (conductor diameter)

(b) (conductor diameter)

(c) (conductor diameter)

(d) (conductor diameter)


Ans: c

4. A conductor0 due to sag between

two supports0 ta/es the form of

(a) semi5circle

(b) triangle

(c) ellipse

(d) catenar!

Ans: d

6. 7n A&.$.. conductors0 the

insulation between aluminium and steel

conductors is

(a) insulin

(b) bitumen

(c) varnish

(d) no insulation is re?uiredAns: d

9. Which of the following bus5bar

schemes has the lowest cost "

(a) ing bus5bar scheme

(b) $ingle bus5bar scheme

(c) #rea/er and a half scheme

(d) Hain and transfer scheme

Ans: b

4;. wing to s/in effect

(a) current flows through the half cross5

section of the conductor

(b) portion of the conductor near the

surface carries more current and core of

the conductor carries less current

(c) portion of the conductor near the

surface carries less current and core of

the conductor carries more curLrent



Ans: b

41. #! which of the following

methods string efficienc! can be

improved "

(a) @sing a guard ring

(b) Frading the insulator

(c) @sing long cross arm


(e) %one of the above

Ans: d

42. 7n aluminium conductors0 steel

core is provided to

(a) compensate for s/in effect(b) neutralise proimit! effect

(c) reduce line inductance

(d) increase the tensile strength

Ans: d


17/96

4'. #! which of the following a bus5

bar is rated "

(a) &urrent onl!

(b) &urrent and voltage

(c) &urrent0 voltage and fre?uenc!(d) &urrent0 voltage0 fre?uenc! and

short time current

Ans: d

4+. A circuit is disconnected b!

isolators when

(a) line is energi-ed

(b) there is no current in the line

(c) line is on full load

(d) circuit brea/er is not open

Ans: b

4. or which of the following

e?uipment current rating is not necessar!

"

(a) &ircuit brea/ers

(b) 7solators

(c) =oad brea/ switch

(d) &ircuit brea/ers and load brea/

switches

Ans: b

4. 7n a substation the following

e?uipment is not installed

(a) eciters

(b) series capacitors(c) shunt reactors

(d) voltatre transformers

Ans: a

44. &orona usuall! occurs when the

electrostatic stress in air around the

conductor eceeds

(a) . / (r.m.s. value)


18/96

(a) 1 /

(b) 11 /

(c) 22 /

(d) '' /

Ans: d

62. Aluminium has a specific gravit! of

(a) 1.

(b) 2.4

(c) +.2

(d) 4.6

Ans: b

6'. or transmission of power over a

distance of 2;; /m0 the transmission

voltage should be

(a) 1'2 /

(b) /

(c) '' /

(d) 11 /

Ans: a

6+. or aluminium0 as compared to

copper0 all the following factors have

higher values ecept

(a) specific volume

() electrical conductivit!

(c) co5efficient of linear epansion

(d) resistance per unit length for same

cross5section

Ans: b

6. Which of the following e?uipment0

for regulating the voltage in distribution

feeder0 will be most economical "

(a) $tatic condenser

(b) $!nchronous condenser

(c) Tap changing transformer

(d) #ooster transformer

Ans: d

6. 7n a tap changing transformer0 the

tappings are provided on

(a) primar! winding

(b) secondar! winding

(c) high voltage winding


Ans: b

64. &onstant voltage transmission

entails the following disadvantage

(a) large conductor area is re?uired

for same power transmission

(b) short5circuit current of the

s!stem is increased



Ans: b

66. n which of the following factors

s/in effect depends "

(a) re?uenc! of the current

(b) $i-e of the conductor

(c) esistivit! of the conductor

material


Ans: d

69. The effect of corona can be

detected b!

(a) presence of o-one detected b!

odour


19/96

(b) hissing sound

(c) faint luminous glow of bluish colour


Ans: d

9;. or transmission of power over a

distance of ;; /m0 the transmission

voltage should be in the range

(a) 1; to 22; /

(b) 1;; to 12; /

(c) ; to 1;; /

(d) 2; to ; /

Ans: a

91. 7n the anal!sis of which of the

following lines shunt capacitance is

neglected "

(a) $hort transmission lines

(b) Hedium transmission lines

(c) =ong transmission lines

(d) Hedium as well as long

transmission lines

Ans: a

92. When the interconnector between

two stations has large reactance

(a) the transfer of power will ta/e place

with voltage fluctuation and noise

(b) the transfer of power will ta/e place

with least loss

(c) the stations will fall out of stepbeLcause of large angular displacement

between the stations


Ans: c

9'. The fre?uenc! of voltage generated0

in case of generators0 can be increased

b!

(a) using reactors

(b) increasing the load(c) adusting the governor

(d) reducing the terminal voltage


Ans: c

9+. When an alternator connected to

the bus5bar is shut down the bus5bar

voltage will

(a) fall

(b) rise

(c) remain unchanged


Ans: c

9. The angular displacement between

two interconnected stations is mainl! due

to

(a) armature reactance of both

alternators

(b) reactance of the interconnector

(c) s!nchronous reactance of both the

alternators


Ans: a

9. ,lectro5mechanical voltageregulators are generall! used in

(a) reactors

(b) generators

(c) transformers



20/96

Ans: b

94. $eries capacitors on transmission

lines are of little use when the load A

re?uirement is(a) large

(b) small

(b) fluctuating


Ans: b

96. The voltage regulation in magnetic

amplifier t!pe voltage regulator is

effected b!

(a) electromagnetic induction

(b) var!ing the resistance

(c) var!ing the reactance

(d) variable transformer

Ans: c

99. When a conductor carries more

current on the surface as compared to

core0 it is due to

(a) permeabilit! variation

(b) corona

(c) s/in effect

(d) uns!mmetrical fault


Ans: c

1;;. The following s!stem is notgenerall! used

(a) 15phase ' wire

(b) 15phase + wire

(c) '5phase ' wire

(d) '5phase + wire

Ans: a

1;1. The s/in effect of a conductor will

reduce as the

(a) resistivit! of conductor materialincreases

(b) permeabilit! of conductor material

increases

(c) diameter increases

(d) fre?uenc! increases

Ans: a

1;2. When a live conductor of public

electric suppl! brea/s down and touches

the earth which of the following will

happen "

(a) &urrent will flow to earth

(b) $uppl! voltage will drop

(c) $uppl! voltage will increase

(d) %o current will flow in the

conductor


Ans: a

Latest Transformers Interview


1. Which of the following does not

change in a transformer "


21/96

(a) &urrent

(b) oltage

(c) re?uenc!


Ans: c

2. 7n a transformer the energ! is

conve!ed from primar! to secondar!

(a) through cooling coil

(b) through air

(c) b! the flu


Ans: c

'. A transformer core is laminated to

(a) reduce h!steresis loss

(b) reduce edd! current losses

(c) reduce copper losses

(d) reduce all above losses

Ans: b

+. The degree of mechanical vibrations

produced b! the laminations of a

transformer depends on

(a) tightness of clamping

(b) gauge of laminations

(c) si-e of laminations


Ans: d

. The no5load current drawn b!transformer is usuall! what per cent of

the full5load current "

(a) ;.2 to ;. per cent

(b) 2 to per cent

(c) 12 to 1 per cent

(d) 2; to '; per cent

Ans: b

. The path of a magnetic flu in a

transformer should have(a) high resistance

(b) high reluctance

(c) low resistance

(d) low reluctance

Ans: d

4. %o5load on a transformer is carried out

to determine

(a) copper loss

(b) magnetising current

(c) magnetising current and loss

(d) efficienc! of the transformer

Ans: c

6. The dielectric strength of transformer

oil is epected to be

(a) l/

(b) '' /

(c) 1;; /

(d) ''; /

Ans: b

9. $umpnerCs test is conducted on

trans5formers to determine

(a) temperature

(b) stra! losses(c) all5da! efficienc!


Ans: a

1;. The permissible flu densit! in case


22/96

of cold rolled grain oriented steel is

around

(a) 1.4 Wb


23/96

change of flu is -ero


Ans: c

19. *rimar! winding of a transformer(a) is alwa!s a low voltage winding

(b) is alwa!s a high voltage winding

(c) could either be a low voltage or high

voltage winding


Ans: c

2;. Which winding in a transformer has

more number of turns "

(a) =ow voltage winding

(b) igh voltage winding

(c) *rimar! winding

(d) $econdar! winding

Ans: b

21. ,fficienc! of a power transformer is

of the order of

(a) 1;; per cent

(b) 96 per cent

(c) ; per cent

(d) 2 per cent

Ans: b

22. 7n a given transformer for given

applied voltage0 losses which remain

constant irrespective of load changes are(a) friction and windage losses

(b) copper losses

(c) h!steresis and edd! current losses


Ans: c

2'. A common method of cooling a power

transformer is

(a) natural air cooling

(b) air blast cooling(c) oil cooling


Ans: c

2+. The no load current in a transformer

lags behind the applied voltage b! an

angle of about

(a) 16;>

(b) 12;N

(c) 9;>

(d) 4>

Ans: d

2. 7n a transformer routine efficienc!

depends upon

(a) suppl! fre?uenc!

(b) load current

(c) power factor of load

(d) both (b) and (c)

Ans: d

2. 7n the transformer the function of a

conservator is to

(a) provide fresh air for cooling the

transformer

(b) suppl! cooling oil to transformer intime of need

(c) protect the transformer from damage

when oil epends due to heating


Ans: c


24/96

24. %atural oil cooling is used for

transformers up to a rating of

(a) ';;; /A

(b) 1;;; /A(c) ;; /A

(d) 2; /A

Ans: a

26. *ower transformers are designed to

have maimum efficienc! at

(a) nearl! full load

(b) 4;K full load

(c) ;K full load

(d) no load

Ans: a

29. The maimum efficienc! of a

distribution transformer is

(a) at no load

(b) at ;K full load

(c) at 6;K full load

(d) at full load

Ans: b

';. Transformer breaths in when

(a) load on it increases

(b) load on it decreases

(c) load remains constant


Ans: b

'1. %o5load current of a transformer has

(a) has high magnitude and low power

factor

(b) has high magnitude and high power

factor

(c) has small magnitude and high power

factor

(d) has small magnitude and low power

factorAns: d

'2. $pacers are provided between

adacent coils

(a) to provide free passage to the

cooling oil

(b) to insulate the coils from each

other



Ans: a

''. Freater the secondar! lea/age flu

(a) less will be the secondar! induced

e.m.f.

(b) less will be the primar! induced e.m.f.

(c) less will be the primar! terminal

voltage


Ans: a

'+. The purpose of providing iron core in

a step5up transformer is

(a) to provide coupling between primar!

and secondar!

(b) to increase the magnitude of mutualflu

(c) to decrease the magnitude of mag5

neti-ing current

(d) to provide all above features

Ans: c


25/96

'. The power transformer is a constant

(a) voltage device

(b) current device

(c) power device(d) main flu device

Ans: d

'. Two transformers operating in

parallel will share the load depending upon

their

(a) lea/age reactance

(b) per unit impedance

(c) efficiencies

(d) ratings

Ans: b

'4. 7f 2 is the resistance of secondar!

winding of the transformer and E is the

transformation ratio then the e?uivalent

secondar! resistance referred to primar!

will be

(a) 2


26/96

transformer should have the ?ualit! of

(a) ioni-ing air

(b) absorbing moisture

(c) cleansing the transformer oil

(d) cooling the transformer oil.Ans: b

+'. The chemical used in breather is

(a) asbestos fiber

(b) silica sand

(c) sodium chloride

(d) silica gel

Ans: d

++. An ideal transformer has infinite

values of primar! and secondar!

inductances. The statement is

(a) true

(b) false

Ans: b

+. The transformer ratings are usuall!

epressed in terms of

(a) volts

(b) amperes

(c) /W

(d) /A

Ans: d

+. The noise resulting from vibrations of

laminations set b! magnetic forces0 istermed as

(a) magnetostrication

(b) boo

(c) hum

(d) -oom

Ans: c

+4. !steresis loss in a transformer

varies as ma M maimum flu densit!)

(a) #ma(b) #ma15

(&) #ma156'

(d) # ma

Ans: b

+6. Haterial used for construction of

transformer core is usuall!

(a) wood

(b) copper

(c) aluminium

(d) silicon steel

Ans: d

+9. The thic/ness of laminations used in a

transformer is usuall!

(a) ;.+ mm to ;. mm

(b) + mm to mm

(c) 1+ mm to 1 mm

(d) 2 mm to +; mm

Ans: a

;. The function of conservator in a

transformer is

(a) to proect againstCinternal fault

(b) to reduce copper as well as core

losses(c) to cool the transformer oil

(d) to ta/e care of the epansion and

contraction of transformer oil due to

variation of temperature of sur5roundings

Ans: d


27/96

1. The highest voltage for transmitting

electrical power in 7ndia is

(a) '' /.

() /(c) 1'2 /

(d) +;; /

Ans: d

2. 7n a transformer the resistance

between its primar! and secondar! is

(a) -ero

(b) 1 ohm

(c) 1;;; ohms

(d) infinite

Ans: d

'. A transformer oil must be free from

(a) sludge

(b) odour

(c) gases

(d) moisture

Ans: d

+. A #uchhol- rela! can be installed on

(a) auto5transformers

(b) air5cooled transformers

(c) welding transformers

(d) oil cooled transformers

Ans: d

. Fas is usuall! not liberated due to

dissociation of transformer oil unless the

oil temperature eceeds

(a) ;>&

(b) 6;>&

(c) 1;;>&

(d) 1;>&

Ans: d

. The main reason for generation ofharmonics in a transformer could be

(a) fluctuating load

(b) poor insulation

(c) mechanical vibrations

(d) saturation of core

Ans: d

4. Distribution transformers are

generall! designed for maimum

efficienc! around

(a) 9;K load

(b) -ero load

(c) 2K load

(d) ;K load

Ans: d

6. Which of the following propert! is

not necessaril! desirable in the material

for transformer core "

(a) Hechanical strength

() =ow h!steresis loss

(c) igh thermal conductivit!

(d) igh permeabilit!

Ans: c

9. $tar


28/96


Ans: b

;. Delta


29/96

6. Which of the following is not a

routine test on transformers "

(a) &ore insulation voltage test

(b) 7mpedance test

(c) adio interference test(d) *olarit! test

Ans: c

9. A transformer can have -ero voltage

regulation at

(a) leading power factor

(b) lagging power factor

(c) unit! power factor

(d) -ero power factor

Ans: a

4;. elical coils can be used on

(a) low voltage side of high /A

transformers

(b) high fre?uenc! transformers

(c) high voltage side of small capacit!

transformers

(d) high voltage side of high /A rating

transformers

Ans: a

41. armonics in transformer result in

(a) increased core losses

(b) increased 72 losses

(c) magnetic interference with

communication circuits(d) all of the above

Ans: d

42. The core used in high fre?uenc!

transformer is usuall!

(a) copper core

(b) cost iron core

(c) air core

(d) mild steel core

Ans: c

4'. The full5load copper loss of a

transLformer is 1;; W. At half5load0

the copper loss will be

(a) +;; W

(b) 1;; W

(c) 6;; W

(d) +;; W

Ans: d

1.4+. The value of flu involved m the

e.m.f. e?uation of a transformer is

(a) average value

(b) r.m.s. value

(c) maimum value

(d) instantaneous value

Ans: c

=.4. $ilicon steel used in laminations

mainl! reduces

(a) h!steresis loss

(b) edd! current losses

(c) copper losses


Ans: a

4. Which winding of the transformer

has less cross5sectional area "

(a) *rimar! winding

(b) $econdar! winding

(c) =ow voltage winding


30/96

(d) igh voltage winding

Ans: d

44. *ower transformers are generall!

designed to have maimum efficienc!around

(a) no5load

(b) half5load

(c) near full5load

(d) 1;K overload

Ans: c

.46. Which of the following is the main

advantage of an auto5transformer over a

two winding transformer "

(a) !steresis losses are reduced

(b) $aving in winding material

(c) &opper losses are negligible

(d) ,dd! losses are totall! eliminated

Ans: b

49. During short circuit test iron losses

are negligible because

(a) the current on secondar! side is

negligible

(b) the voltage on secondar! side does

not var!

(c) the voltage applied on primar! side is

low

(d) full5load current is not supplied to the

transformerAns: c

6;. Two transformers are connected in

parallel. These transformers do not have

e?ual percentage impedance. This is li/el!

to result in

(a) short5circuiting of the secondaries

(b) power factor of one of the

transformers is leading while that of the

other lagging(c) transformers having higher copper

losses will have negligible core losses

(d) loading of the transformers not in

proportion to their /A ratings

Ans: d

61. The changes in volume of transformer

cooling oil due to variation of atmospheric

temperature during da! and

night is ta/en care of b! which part of

transformer

(a) &onservator

(b) #reather

(c) #ushings

(d) #uchhol- rela!

Ans: a

62. An ideal transformer is one which has

(a) no losses and magnetic lea/age

(b) interleaved primar! and secondar!

windings

(c) a common core for its primar! and

secondar! windings

(d) core of stainless steel and winding of

pure copper metal

(e) none of the aboveAns: a

6'. When a given transformer is run at

its rated voltage but reduced fre?uenc!0

its


31/96

(a) flu densit! remains unaffected

(b) iron losses are reduced

(c) core flu densit! is reduced

(d) core flu densit! is increased

Ans: d

6+. 7n an actual transformer the iron loss

remains practicall! constant from noload

to fullload because

(a) value of transformation ratio

remains constant

(b) permeabilit! of transformer core

remains constant

(c) core flu remains practicall! constant

(d) primar! voltage remains constant

(c) secondar! voltage remains constant

Ans: c

6. An ideal transformer will have

maimum efficienc! at a load such that

(a) copper loss M iron loss

(b) copper loss P iron loss

(c) copper loss Q iron loss


Ans: a

6. 7f the suppl! fre?uenc! to the

transformer is increased0Nthe iron loss

will

(a) not change

(b) decrease(c) increase


Ans: c

64. %egative voltage regulation is

indicative that the load is

(a) capacitive onl!

(b) inductive onl!

(c) inductive or resistive

(d) none of the aboveAns: a

66. 7ron loss of a transformer can be

measured b!

(a) low power factor wattmeter

(b) unit! power factor wattmeter

(c) fre?uenc! meter

(d) an! t!pe of wattmeter

Ans: a

69. When secondar! of a current

transformer is open5circuited its iron

core will be

(a) hot because of heav! iron losses

ta/ing place in it due to high flu densit!

(b) hot because primar! will carr! heav!

current

(c) cool as there is no secondar! current

(d) none of above will happen

Ans: a

9;. The transformer laminations are

insulated from each other b!

(a) mica strip

() thin coat of varnish

(c) paper(d) an! of the above

Ans: b

91. Which t!pe of winding is used in

'phase shell5t!pe transformer "


32/96

(a) &ircular t!pe

(b) $andwich t!pe

(c) &!lindrical t!pe

(d) ectangular t!pe

Ans: b

92. During open circuit test of a

transformer

(a) primar! is supplied rated voltage

(b) primar! is supplied full5load current

(c) primar! is supplied current at reduced

voltage

(d) primar! is supplied rated /A

Ans: a

9'. pen circuit test on transformers is

conducted to determine

(a) h!steresis losses

(b) copper losses

(c) core losses

(d) edd! current losses

Ans: c

9+. $hort circuit test on transformers is

conducted to determine

(a) h!steresis losses

(b) copper losses

(c) core losses

(d) edd! current losses

Ans: b

9. or the parallel operation of single

phase transformers it is necessar! that

the! should have

(a) same efficienc!

(b) same polarit!

(c) same /A rating

(d) same number of turns on the

secondar! side.

Ans: b

9. The transformer oil should have

88888 volatilit! and 88888 viscosit!.

(a) low0low

(b) high0high

(c) low0high

(d) high0low

Ans: a

94. The function of breather in a

transformer is

(a) to provide o!gen inside the tan/

(b) to cool the coils during reduced load

(c) to cool the transformer oil

(d) to arrest flow of moisture when

outside air enters the transformer

Ans: d

96. The secondar! winding of which of

the following transformers is alwa!s /ept

closed "

(a) $tep5up transformer

(b) $tep5down transformer

(c) *otential transformer

(d) &urrent transformer

Ans: d

99. The si-e of a transformer core will

depend on

(a) fre?uenc!

(b) area of the core

(c) flu densit! of the core material


33/96

(d) (a) and (b) both

Ans: d

1;;. % atural air coo ling is generall!

restricted for transformers up to(a) 1. HA

(b) HA

(c) 1 HA

(d) ; HA

Ans: a

1;1. A shell5t!pe transformer has

(a) high edd! current losses

(b) reduced magnetic lea/age

(c) negligibl! h!steresis losses


Ans: b

1;2. A transformer can have regulation

closer to -ero

(a) on full5load

(b) on overload

(c) on leading power factor

(d) on -ero power factor

Ans: c

1;'. A transformer transforms

(a) voltage

(b) current

(c) current and voltage

(d) powerAns: d

1;+. Which of the following is not the

standard voltage for power suppl! in

7ndia "

(a) ll/

(b) ''/

(c) /

(d) 122 /

Ans: d

1;. eduction in core losses and increase

in permeabilit! are obtained with

transformer emplo!ing

(a) core built5up of laminations of cold

rolled grain oriented steel

(b) core built5up of laminations of hot

rolled sheet



Ans: a

1;. 7n a power or distribution

transformer about 1; per cent end turns

are heavil! insulated

(a) to withstand the high voltage drop due

to line surge produced b! the shunting

capacitance of the end turns

(b) to absorb the line surge voltage and

save the winding of transformer from

damage

(c) to reflect the line surge and save

the winding of a transformer from

damage


Ans: a

1;4. or given applied voltage0 with the

increase in fre?uenc! of the applied

voltage

(a) edd! current loss will decrease


34/96

(b) edd! current loss will increase

(c) edd! current loss will remain

unchanged


Ans: c

1;6. =osses which occur in rotating

electric machines and do not occur in

trans formers are

(a) friction and windage losses

(b) magnetic losses

(c) h!steresis and edd! current losses

(d) copper losses

Ans: a

1;9. 7n a given transformer for a given

applied voltage0 losses which remain

constant irrespective of load changes are

(a) h!steresis and edd! current losses

(b) friction and windage losses

(c) copper losses


Ans: a

11;. Which of the following statements

regarding an idel single5phase

transformer having a turn ratio of 1 : 2

and

drawing a current of 1; A from 2;;

A.&. suppl! is incorrect "

(a) 7ts secondar! current is A(b) 7ts secondar! voltage is +;;

(c) 7ts rating is 2 /A

(d) 7ts secondar! current is 2; A

(e) 7t is a step5up transformer

Ans: d

111. The secondar! of a current

transformer is alwa!s short5circuited

under operating conditions because it

(a) avoids core saturation and highvoltage induction

(b) is safe to human beings

(c) protects the primar! circuit


Ans: a

112. 7n a transformer the resistance

between its primar! and secondar! should

be

(a) -ero

(b) 1; J

(c) 1;;; J

(d) infinit!

Ans: d

11'. A good voltage regulation of a

transformer means

(a) output voltage fluctuation from no

load to full load is least

(b) output voltage fluctuation with power

factor is least

(c) difference between primar! and

secondar! voltage is least

(d) difference between primar! and

secondar! voltage is maimum

Ans: a

11+. or a transformer0 operating at

constant load current0 maimum

efficienc! will occur at

(a) ;.6 leading power factor


35/96

(b) ;.6 lagging power factor

(c) -ero power factor

(d) unit! power factor

Ans: d

11. Which of the following protection is

normall! not provided on small

distribution transformers "

(a) verfluing protection

(b) #uchhol- rela!

(c) vercurrent protection


Ans: b

11. Which of the following acts as a

protection against high voltage surges

due to lightning and switching "

(a) orn gaps

(b) Thermal overload rela!s

(c) #reather

(d) &onservator

Ans: a

114. The efficienc! of two identical

transformers under load conditions can

be determined b!

(a) short5circuit test

(b) bac/5to5bac/ test

(c) open circuit test


Ans: b

116. Which of the following insulating

materials can withstand the highest

temperature safel! "

(a) &ellulose

(b) Asbestos

(c) Hica

(d) Flass fibre

Ans: c

119. Which of the following parts of a

transformer is visible from outside "

(a) #ushings

(b) &ore

(c) *rimar! winding

(d) $econdar! winding

Ans: a

12;. The noise produced b! a transformer

is termed as

(a) -oom

(b) hum

(c) ringing

(d) bu--

Ans: b

121. Which of the following loss in a

transformer is -ero even at full load "

(a) &ore loss

(b) riction loss

(c) ,dd! current loss

(d) !steresis loss

Ans: b

122. Which of the following is the most

li/el! source of harmonics in atransformer "

(a) poor insulation

(b) verload

(c) loose connections

(d) &ore saturation


36/96

Ans: d

12'. 7f a transformer is continuousl!

operated the maimum temperature rise

will occur in(a) core

(b) windings

(c) tan/


Ans: b

12+. The hum in a transformer is mainl!

attributed to

(a) load changes

(b) oil in the transformer

(c) magnetostriction

(d) mechanical vibrations

Ans: c

12. The maimum load that a power

transformer can carr! is limited b! its

(a) temperature rise

(b) dielectric strength of oil

(c) voltage ratio

(d) copper loss

Ans: c

12. The efficienc! of a transformer0

under heav! loads0 is comparativel! low

because

(a) copper loss becomes high inproportion to the output

(b) iron loss is increased considerabl!

(c) voltage drop both in primar! and

secondar! becomes large

(d) secondar! output is much less as

compared to primar! input

Ans: a

124. An open5circuit test on a

transformer is conducted primaril! tomeasure

(a) insulation resistance

(b) copper loss

(c) core loss

(d) total loss

(e) efficienc!

(f) none of the above

Ans: c

126. A no5load test is performed on a

transformer to determine

(a) core loss

(b) copper loss

(c) efficienc!

(d) magnetising current

(e) magnetising current and loss

Ans: e

129. The voltage transformation ratio of

a transformer is e?ual to the ratio of

(a) primar! turns to secondar! turns

(b) secondar! current to primar! current

(c) secondar! induced e.m.f. to primar!

induced e.m.f.

(d) secondar! terminal voltage to primar!

applied voltageAns: c

1';. *art of the transformer which is

most subect to damage from overheating

is


37/96

(a) iron core

(b) copper winding

(c) winding insulation

(d) frame or case

(e) transformer tan/Ans: c

1'1. 7f a transformer is switched on to a

voltage more than the rated voltage

(a) its power factor will deteriorate

(b) its power factor will increase

(c) its power factor will remain

unaffected

(d) its power factor will be -ero

Ans: a

1'2. Auto5transformer ma/es effective

saving on copper and copper losses0 when

its transformation ratio is

(a) approimatel! e?ual to one

(b) less than one

(c) great than one


Ans: a

1''. Hinimum voltage regulation occurs

when the power factor of the load is

(a) unit!

(b) lagging

(c) leading

(d) -eroAns: c

1'+. 7n a step5down transformer0 there is

a change of 1 A in the load current. This

results in change of suppl! current of

(a) less than 1 A

(b) more than 1 A

(c) 1 A


Ans: a

1'. The efficiencies of transformers

compared with that of electric motors of

the same power are

(a) about the same

() much smaller

(c) much higher

(d) somewhat smaller


Ans: c

Latest Switchgear Protections


1. The main function of a fuse is to

(a) protect the line

(b) open the circuit

(c) protect the appliance

(d) prevent ecessive currents


Ans: d

2. n which of the following routinetests are conducted "

(a) il circuit brea/ers

(b) Air blast circuit brea/ers

(c) Hinimum oil circuit brea/ers


Ans: d


38/96

'. $ gas

(a) is !ellow in colour

(b) is lighter than air

(c) is nontoic(d) has pungent small


Ans: c

+. The arcing contacts in a circuit

brea/er are made of

(a) copper tungsten allo!

(b) porcelain

(c) electrol!tic copper

(d) aluminium allo!

Ans: a

. Which of the following medium is

emplo!ed for etinction of arc in air

circuit brea/er "

(a) Water

(b) il

(c) Air

(d) $

Ans: c

. With which of the following0 a circuit

brea/er must be e?uipped for remote

operation "

(a) 7nverse time trip

(b) Time5dela! trip(c) $hunt trip



Ans: c

4. ault diverters are basicall!

(a) fuses

(b) rela!s

(c) fast switches

(d) circuit brea/ersAns: c

6. A thermal protection switch can

protect against

(a) short5circuit

(b) temperature

(c) overload

(d) over voltage

Ans: c

9. Arc in a circuit behaves as

(a) a capac/ive reactance

(b) an inductive reactance

(c) a resistance increasing with

voltage rise across the arc

(d) a resistance decreasing with

voltage rise across the arc

Ans: d

1;. Thermal circuit brea/er has

(a) dela!ed trip action

(b) instantaneous trip action

(c) both of the above


Ans: a

11. ela!s can be designed to respond

to changes in

(a) resistance0 reactance or impedance

(b) voltage and current

(c) light intensit!


39/96

(d) temperature

(e) all above

Ans: e

12. verload rela!s are of...... t!pe.(a) induction

(b) solid state

(c) thermal

(d) electromagnetic

(e) all above

Ans: e

1'. Thermal overload rela!s are used

to protect the motor against over current

due to

(a) short5circuits

(b) heav! loads

(c) grounds


Ans: b

1+. Hagnetic circuit brea/er has

888888 trip action.

(a) dela!ed

(b) instantaneous

(c) both of the above


Ans: b

1. D.&. shunt rela!s are made of

(a) few turns of thin wire(b) few turns of thic/ wire

(c) man! turns of thin wire

(d) man! turns of thic/ wire

Ans: c

1. The rela! operating speed depends

upon

(a) the spring tension

(b) the rate of flu built up

(c) armature core air gap(d) all of the above

Ans: d

14. 7n order that current should flow

without causing ecessive heating or

voltage drop0 the rela! contacts should

(a) have low contact resistance

(b) be clean and smooth

(c) be of sufficient si-e and proper shape

(d) have all above properties

Ans: d

16. &ircuit brea/ers usuall! operate

under

(a) transient state of short5circuit

current

(b) sub5transient state of short5circuit

current

(c) stead! state of short5circuit

current

(d) after D.&. component has ceased

Ans: a

19. &ircuit brea/ers are essentiall!

(a) current carr!ing contacts called

electrodes(b) arc etinguishers

(c) circuits to brea/ the s!stem

(d) transformers to isolate the two

s!stems

(e) an! of the above


40/96

Ans: a

The current -ero interruption0 in

oil and air blast circuit brea/ers0 is

achieved b!(a) lengthening of the gap

(b) cooling and blast effect


(d) deioni-ing the oil with forced air


Ans: c

21. Air blast circuit brea/er is used

for

(a) over currents

(b) short dut!

(c) intermittant dut!

(d) repeated dut!

Ans: d

22. An efficient and a well designed

protective rela!ing should have

(a) good selectivit! and reliabilit!

(b) econom! and simplicit!

(c) high speed and selectivit!


Ans: d

2'. #urden of a protective rela! is the

power

(a) re?uired to operate the circuitbrea/er

(b) absorbed b! the circuit of rela!

(c) developed b! the rela! circuit


Ans: b

2+. Directional rela!s are based on

flow of

(a) power

(b) current(c) voltage wave


Ans: a

2. A differential rela! measures the

vector difference between

(a) two currents

(b) two voltages

(c) two or more similar electrical

?uantities


Ans: c

2. A transmission line is protected b!

(a) inrush protection

(b) distance protection

(c) time graded and current graded

over current protection

(d) both (b) and (c)


Ans: d

24. =arge internal faults are

protected b!

(a) mer- price percentage differential

protection(b) mho and ohm rela!s

(c) horn gaps and temperature rela!s

(d) earth fault and positive se?uence

rela!s

Ans: a


41/96

26. When a transmission line is

energi-ed0 the wave that propagates on it

is

(a) current wave onl!(b) voltage wave onl!


(d) power factor wave onl!

Ans: c

29. *rotective rela!s are devices that

detect abnormal conditions in electrical

circuits b! measuring

(a) current during abnormal condition

(b) voltage during abnormal condition

(c) constantl! the electrical ?uantities

which differ during normal and abnormal

conditions


Ans: c

';. The voltage appearing across the

contacts after opening of the circuit

brea/er is called888888voltage.

(a) recover!

(b) surge

(c) operating

(d) arc


Ans: a

'1. 7oni-ation in circuit brea/er is

facilitated b!

(a) high temperature

(b) increase of mean free path

(c) increasing field strength


Ans: d

'2. 7n a circuit brea/er the basic

problem is to(a) maintain the arc

(b) etinguish the arc

(c) transmit large power

(d) emit the ioni-ing electrons

Ans: c

''. verheating of rela! contacts or

contact born out is due to

(a) slow ma/ing and brea/ing of load

circuit contacts

(b) foreign matter on the contact

surface

(c) too low contact pressure


Ans: d

'+. 7nterruption of large currents b!

rela! re?uires

(a) arc suppressing blow out coils

(b) wide separation of the opened

contacts

(c) high speed opening of contacts


Ans: d

'. $hunt capacitance is neglectedwhile considering

(a) short transmission line

(b) medium transmission line

(c) long transmission line

(d) medium and long transmission lines


42/96

Ans: a

'. The arc voltage produced in A.&.

circuit brea/er is alwa!s

(a) in phase with the arc current(b) lagging the arc current b! 9;N

(c) leading the arc current b! 9;>


Ans: a

'4. The time of closing the c!cle0 in

modern circuit brea/ers is

(a) ;.;;' sec

(b) ;.;;1 sec

(c) ;.;1 sec

(d) ;.1; sec


Ans: a

'6. 7nsulation resistance of high

voltage circuit brea/ers is more than

(a) 1 mega ohms

(b) 1; mega ohms

(c) 1;; mega ohms

(d) ;; mega ohms

Ans: c

'9. ..&. fuses provide best

protection against

(a) overload

(b) reverse current(c) open5circuits

(d) short5circuits

Ans: d

+;. The ground wire should not be

smaller than %o 888888 copper.

(a) 2

(b) +

(c)

(d) 1;Ans: d

+1. The dela! fuses are used for the

protection of 88888888 .

(a) motors

(b) power outlet circuits

(c) fluorescent lamps

(d) light circuits

Ans: a

+2. Which of the following is the least

epensive protection for overcurrent is

low voltage s!stem "

(a) ewireable fuse

(b) 7solator

(c) il circuit brea/er

(d) Air brea/ circuit brea/er


Ans: a

+'. esistance grounding is used for

voltage between

(a) ''/to/

(b) /to''/

(c) '.'/andll/


++. The contacts of high voltage

switches used in power s!stem are

submerged in oil. The main purpose of the


43/96

oil is to

(a) lubricate the contacts

(b) insulate the contacts from switch

bod!

(c) etinguish the arc(d) all of the above


Ans: c

+. 7n ailwa! applications 888888

circuit brea/er is used.

(a) $e

(b) bul/ oil

(c) minimum oil

(d) air brea/

Ans:

+. To protect most of the electrical

e?uipment handling low power0 the t!pes

of rela!s used are

(a) thermocouple

(b) electronic and bimetallic



Ans: c

+4. Wave trap is used to trap waves of

(a) power fre?uencies

(b) higher fre?uencies entering

generator or transformer units

(c) either of the above(d) none of the above

Ans: b

+6. @ngrounded neutral transmission

s!stem is not recommended because of

s!stem

(a) insulation being overstressed due to

over voltages

(b) insulation overstress ma! lead to

failure and subse?uent phase to phasefaults

(c) being inade?uatel! protected

against ground fault


Ans: d

+9. The reflection co5efficient at the

open circuited end of a transmission line.

(a) -ero

(b) infinit!

(c) unit!


Ans: c

;. or the protection of power

station buildings against direct stro/es

the re?uirements are

(a) interception

(b) interception and conduction

(c) interception0 conduction and

dissipation

(d) interception0 conduction0

dissipation and reflection


Ans: c

1. The line insulation is the insulation

level of the station e?uipment.

(a) less than

(b) same as

(c) more than


44/96

(d) proportional to

(e) not directl! related with

Ans: e

2. The interaction between atransmission line and communication line

is minimi-ed b!

(a) transposing transmission as well as

communication lines

(b) increasing the height of the trans5

mission line tower

(c) increasing the distance between

the two lines


Ans: d

'. When a wave propagates on a

transmission line0 it suffers reflection

several times at

(a) tapping

(b) load end

(c) sending end

(d) sending and other end

(e) all of the above

Ans: d

+. Which of the following statements

is incorrect"

(a) $tation batteries are used to

operate rela! onl!

(b) The lightning arresters arebasicall! surge diverters

(c) An impedance rela! has maimum

fault current when fault occurs near the

rela!

(d) A high speed rela! has an

operation of 1 to 2 c!cles

Ans: a

. Discrimination between main and

bac/ up protection is provided b! the useof rela!s which are

(a) fact

(b) sensitive

(c) slow


Ans: c

. 7nduction cup rela! is operated

due to changes in

(a) current

(b) voltage

(c) impedance


Ans: d

4. A.&. networ/ anal!ser is used to

solve problems of

(a) load flow

(b) load flow and short5circuit

(c) load flow and stabilit!

(d) load flow0 short5circuit and stabilit!


Ans: d

6. Which of the following statements

is incorrect "(a) =ightning arrestors are used

before the switchgear

(b) $hunt reactors are used as

compensation reactors

(c) The pea/ short current is (1.6


45/96

2) times the A.&. component

(d) The HA at fault is e?ual to base

HA divided b! per unit e?uivalent fault

reactance

Ans: a

9. $hort5circuit currents are due to

(a) single phase to ground faults

(b) phase to phase faults

(c) two phase to ground faults

(d) three phase faults

(e) an! of these

Ans: e

;. To reduce short circuit fault

currents are used.

(a) reactors

(b) resistors

(c) capacitors


Ans: a

1. #us coupler is ver! essential in

arrangement

(a) single bus

(b) double bus0 double brea/er

(c) main and transfer bus


Ans: c

2. or cost and safet!0 the outdoorsubstations are installed for voltages

above

(a) 11 /

(b) '' /

(c) ;/

(d) 11;/

Ans: b

'. The short circuit in an! winding of

the transformer is the result of(a) mechanical vibration

(b) insulation failure

(c) loose connection

(d) impulse voltage

Ans: d

+ rela!s are used for phase faults on

long line.

(a) 7mpedance

(b) eactance

(c) ,ither of the above


Ans: a

. or which of the following

protection from negative se?uence

currents is provided "

(a) Fenerators

(b) Hotors

(c) Transmission line

(d) Transformers

Ans: a

rela! is preferred for phase fault

on short transmission line.

(a) 7nduction t!pe(b) eactance

(c) 7mpedance


Ans: b


46/96

4. Distance rela!s are generall!

(a) split5phase rela!s

(b) reactance rela!s

(c) impedance rela!s

(d) none of the aboveAns: d

6. or which of the following ratings

of the transformer differential

protection is recommended "

(a) above '; /A.

(b) e?ual to and above HA

(c) e?ual to and above 2 HA


Ans: b

9. A 8888888 is used to measure the

stator K winding temperature of the

generator.

(a) thermocouple

(b) p!rometer

(c) resistance thermometer

(d) thermometer

Ans: c

4;. The under voltage rela! can be

used for

(a) generators

(b) busbars

(c) transformers

(d) motors(e) all of the above

Ans: e

41. The rela! with inverse time

characteristic will operate within

(a) 1. sec

(b) to 1; sec

(c) to 2; sec

(d) 2; to '; sec

(e) none of the aboveAns: b

42. The single phasing rela!s are used

for the protection of

(a) single phase motors onl!

(b) two phase motors onl!

(c) two single phase motors running in

parallel

(d) three phase motors

Ans: d

4'. Which of the following devices will

receive voltage surge first travelling on

the transmission line "

(a) =ightning arresters

(b) ela!s

(c) $tep5down transformer

(d) $witchgear

Ans: a

4+. Which of the following parameter

can be neglected for a short line "

(a) 7nductance

(b) &apacitance

(c) esistance

(d) eactanceAns: b

4. $eries reactors should have

(a) low resistance

(b) high resistance


47/96

(c) low impedance

(d) high impedance

Ans: a

4. Which of the following circuitbrea/ers has high reliabilit! and minimum

maintenance "

(a) Air blast circuit brea/ers

(b) &ircuit brea/er with $ gas

(c) acuum circuit brea/ers

(d) il circuit brea/ers

Ans: b

44. Arc in a circuit brea/er is

interrupted at

(a) -ero current

(b) maimum current

(c) minimum voltage

(d) maimum voltage

Ans: a

46 transmission line has reflection

coefficient as one.

(a) pen circuit

(b) $hort5circuit

(e) =ong


Ans: a

49. What will be the reflection co5

efficient of the wave of load connectedto transmission line if surge impedance of

the line is e?ual to load "

(a) Rero

(b) @nit!

(c) 7nfinit!


Ans: a

6;. The inverse definite mean time

rela!s are used for over current andearth fault protection of transformer

against

(a) heav! loads

(b) internal short5circuits

(c) eternal short5circuits


Ans: b

61. ver voltage protection is

recommended for

(a) h!dro5electric generators

(b) steam turbine generators

(c) gas turbine generators



Ans: d

62. Air blast circuit brea/ers for +;;

/ power s!stem are designed to operate

in

(a) 1;; microsecond

(b) ; millisecond

(c) ;. sec

(d) ;.1 sec

Ans: b

6'. verfluing protection is

recommended for

(a) distribution transformer

(b) generator transformer of the power

plant


48/96

(c) auto5transformer of the power plant

(d) station transformer of the power

plant

Ans: b

6+. $eries capacitors are used to

(a) compensate for line inductive

reactance

(b) compensate for line capacitive

reactance

(c) improve line voltage


Ans: a

6. Admittance rela! is 8888888

rela!.

(a) impedance

(b) directional

(c) non5directional


Ans: b

6. The material used for fuse must

have

(a) low melting point and high specific

resistance

(b) low melting point and 5low specific

resistance

(c) high melting point and low specific

resistance

(d) low melting point and an! specificresistance

Ans: a

64. 7f the fault occurs near the

impedance rela!0 the 77 ratio will be

(a) constant for all distances

(b) lower than that of if fault occurs

awa! from the rela!

(c) higher than that of if fault occurs

awa! from the rela!(d) none of the above

Ans: b

66. The tor?ue produced in induction

t!pe rela! (shaded pole structure) is

(a) inversel! proportional to the

current

(b) inversel! proportional to the s?uare

of the current

(c) proportional to the current

(d) proportional to s?uare of the

current

Ans: b

69. The stead! state stabilit! of the

power s!stem can be increased b!

(a) connecting lines in parallel

(b) connecting lines in series

(e) using machines of high impedance

(d) reducing the ecitation of

machines


Ans: a

9;. The inductive interference

between power and communication linecan be minimi-ed b!

(a) transposition of the power line

(b) transposition of the communication

line



49/96

(d) increasing the distance between the

conductors

Ans: c

91. The power loss is an importantfactor for the design of

(a) transmission line

(b) motor

(c) generator

(d) feeder

Ans: a

92. A fuse is connected

(a) in series with circuit

(b) in parallel with circuit

(c) either in series or in parallel with

circuit


Ans: a

9'. ..&. fuse0 as compared to a

rewirable fuse0 has

(a) no ageing effect

(b) high speed of operation

(c) high rupturing capacit!


Ans: d

9+. The fuse rating is epressed in

terms of

(a) current(b) voltage

(c) A

(d) /A

Ans: a

9. The fuse blows off b!

(a) burning

(b) arcing

(c) melting


9. n which of the following effects

of electric current a fuse operates "

(a) *hotoelectric effect

(b) ,lectrostatic effect

(c) eating effect

(d) Hagnetic effect

Ans: c

94. An isolator is installed

(a) to operate the rela! of circuit

brea/er

(b) as a substitute for circuit brea/er

(c) alwa!s independent of the position

of circuit brea/er

(d) generall! on both sides of a circuit

brea/er

Ans: d

96. A fuse in a motor circuit provides

protection against

(a) overload

(b) short5circuit and overload

(c) open circuit0 short5circuit and

overload(d) none of the above

Ans: b

99. *rotection b! fuses is generall!

not used be!ond


50/96

(a) 2; A

(b) ; A

(c) 1;; A

(d) 2;; A

Ans: c

1;;. A fuse is never inserted in

(a) neutral wire

(b) negative of D.&. circuit

(c) positive of D.&. circuit

(d) phase dine

Ans: a

1;1. il switches are emplo!ed for

(a) low currents circuits

(b) low voltages circuits

(c) high voltages and large currents

circuits

(d) all circuits

Ans: c

1;2. A switchgear is device used for

(a) interrupting an electrical circuit

(b) switching an electrical circuit

111.

(c) switching and controlling an

electrical circuit

(d) switching0 controlling and

protecting the electrical circuit and

e?uipment

Ans: d

1;'. The fuse wire0 in D.&. circuits0 is

inserted in

(a) negative circuit onl!

(b) positive circuit onl!


(d) either (a) or (b)

Ans: c

1;+. #! which of the following methodsmaor portion of the heat generated in a

..&. fuse is dissipated "

(a) adiation

(b) &onvection

(c) &onduction


Ans: c

1;. A short5circuit is identified b!

(a) no current flow

(b) heav! current flow

(c) voltage drop

(d) voltage rise

Ans: b

1;. The information to the circuit

brea/er under fault conditions is

provided b!

(a) rela!

(b) rewirable fuse

(c) ..&. onl!


Ans: a

1;4. To limit short5circuit current in a

power s!stem are used.(a) earth wires

(b) isolators

(c) ..&. fuses

(d) reactors

Ans: d


51/96

1;6. A balanced '5phase s!stem

consists of

(a) -ero se?uence currents onl!

(b) positive se?uence currents onl!(c) negative and -ero se?uence

currents

(d) -ero0 negative and positive

se?uence currents

Ans: b

1;9. 7n a single bus5bar s!stem there

will be complete shut down when

(a) fault occurs on the bus itself

(b) fault occurs on neutral line

(c) two or more faults occur

simultaneousl!

(d) fault occurs with respect to

earthing

Ans: a

Latest Current Electricity Questions

and Answers List

1. The $.7. unit of power is

(a) enr!

(b) coulomb

(c) watt

(d) watt5hour

Ans: c

2. ,lectric pressure is also called

(a) resistance

(b) power

(c) voltage

(d) energ!

Ans: c

'. The substances which have a large

number of free electrons and offer a low

resistance are called

(a) insulators(b) inductors

(c) semi5conductors

(d) conductors

Ans: d

+. ut of the following which is not a poor

conductor "

(a) &ast iron

(b) &opper

(c) &arbon

(d) Tungsten

Ans: b

. ut of the following which is an

insulating material "

(a) &opper

(b) Fold

(c) $ilver

(d) *aper

Ans: d

. The propert! of a conductor due to

which it passes current is called

(a) resistance

(b) reluctance

(c) conductance(d) inductance

Ans: c

4. &onductance is reciprocal of

(a) resistance


52/96

(b) inductance

(c) reluctance

(d) capacitance

Ans: a

6. The resistance of a conductor varies

inversel! as

(a) length

() area of cross5section

(c) temperature

(d) resistivit!

Ans: b

9. With rise in temperature the

resistance of pure metals

(a) increases

(b) decreases

(c) first increases and then decreases

(d) remains constant

Ans: a

1;. With rise in temperature the

resistance of semi5conductors

(a) decreases

(b) increases

(c) first increases and then decreases

(d) remains constant

Ans: a

11. The resistance of a copper wire 2;; m

long is 21 J. 7f its thic/ness (diameter) is;.++ mm0 its specific resistance is around

(a) 1.2 1;S6 J5m

(b) 1.+ 1;S6 J5m

(c) 1. 1;NN6 J5m

(d) 1.6 1;N6 J5m

Ans: c

12. Three resistances of 1; ohms0 1

ohms and '; ohms are connected in

parallel.The total resistance of the combination is

(a) ohms

(b) 1; ohms

(c) 1 ohms

(d) ohms

Ans:

1'. An instrument which detects electric

current is /nown as

(a) voltmeter

(b) rheostat

(c) wattmeter

(d) galvanometer

Ans: d

1+. 7n a circuit a '' J resistor carries a

current of 2 A. The voltage across the

resistor is

(a) ''

(b) v

(c) 6;

(d) 1'2

Ans: b

1. A light bulb draws ';; mA when the

voltage across it is 2+; . The resistanceof the light bulb is

(a) +;; J

(b) ;; J

(c) 6;; J

(d) 1;;; J


53/96

Ans: c

1. The resistance of a parallel circuit

consisting of two branches is 12 ohms. 7f

the resistance of one branch is 16 ohms0what is the resistance of the other "

(a) 16 J

(b) ' J

(c) +6 J

(d) + J

Ans: b

14. our wires of same material0 the same

cross5sectional area and the same length

when connected in parallel give a

resistance of ;.2 J. 7f the same four

wires are co

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