Interview Questions Answers in Electrical Engineering

Question { 4818 }

how to caculate no load loss, load losses & impedance
percentage in power or distribution transformers

Answer

we can calculate no load loss of TR, but you need to know impedance of TR

Is This Answer Correct ?

0 Yes

0 No

Question { 5117 }

what is difference between earth fault& restricted earth
fault.

Answer

EF/SEF/50N/51N/51G can be detected by core balance CT or by vector summation of line CT(residual)
64REF is by comparing current flowing at TR neutral CT with residual CT at line CT,

Is This Answer Correct ?

0 Yes

0 No

Question { 17495 }

formula for incomer breaker size calculation of powerfactor
correction unit

Answer

you need to consider of breaking capacity too

Is This Answer Correct ?

2 Yes

0 No

Question { 2559 }

what is resonance in electrical circuit and its effect?
where we get high resonance and low resonance?

Answer

resonance mean when XC is equal to XL,

Is This Answer Correct ?

0 Yes

0 No

Question { 4509 }

why the undervoltage relay's interlock is used in
earthswitch closing operation of the 400kV line scheme?

Answer

to make sure ES can be closed only if line is dead, besides that in common practice, CB status is needed also as interlock Earthing switch

Is This Answer Correct ?

0 Yes

0 No

Question { 5323 }

what is the basis for selection of Protection CT class ?
How anyone can decide whether to go for 5P10 or 5P20 ?

Answer

it depends on Vkp requirement

Is This Answer Correct ?

0 Yes

0 No

Question { ABB, 2703 }

what is meant by distance protection ? how distance
protection relay function ?

Answer

by comparing actual impedance with setting impedance of relay

Is This Answer Correct ?

0 Yes

0 No

Question { 3523 }

In protection core of a C.T. why Knee pont voltage is
greater than SLV and in metering its viceversa?

Answer

knee point voltage should higher than required Vkp by relay to avoid CT saturated when fault happen

Is This Answer Correct ?

0 Yes

0 No

Question { 4256 }

Which is the best protection in case of shortcircut fuses or mccb ?

Answer

it depends on voltage rating, current rating, and application, for motor, it is better to use fuse, why?. because we can select arcing current and arcing time.MCCB does not have. MCCB suitable only for static load

Is This Answer Correct ?

1 Yes

1 No

Question { ABB, 2765 }

When we synchronize the Generator BKR with TIE BKR then Gen
BKR is hold but TIE BKR is Tripped on Non directional over
current but when TIE BKR is Syn. with Gen. BKR then no fault
occur so what is the problem

Answer

i guess the protection setting relay at breaker is wrong

Is This Answer Correct ?

1 Yes

0 No

Question { 2528 }

why protection meter is always connect to star

Answer

if you connect in delta, you can not detect 50N/51N

Is This Answer Correct ?

0 Yes

0 No

Question { Jindal, 4059 }

Is 3 phase induction motor can work as a generator?? if so
why & how??

Answer

in other word, if the motor loss of synchro with the supply

Is This Answer Correct ?

0 Yes

0 No

Question { 3660 }

In directional earth fault protection for generator, one
core balance CT is for residual current, what other CT is
for, which is placed on neutral?

Answer

I guess to CT is used for 50G or 64REF

Is This Answer Correct ?

0 Yes

0 No

Question { 4088 }

What is the purpose of reactor.why we used in over head line?

Answer

to compensate capacitive coupling between line to ground

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0 Yes

0 No

Question { GVK, 2946 }

what is the difference beteen differential protection and over
current protection of an alternator

Answer

differential/87G-need two sets of CTs, coverage are protection is only area between CT,
overcurrent/50,51--only need 1set CTs, Relay trip CB regardless fault location

Is This Answer Correct ?

0 Yes

0 No

nur asidik