Interview Questions Answers in Electrical Engineering, Power Plant Engineering

Question { HCL, 3917 }

how to get more than 1000 ohms between 2 earth pits ?

Answer

Fill the earth pit with dry saw dust with bottom resting on
an insulated block

Is This Answer Correct ?

4 Yes

0 No

Question { KOC, 4159 }

HOW MUCH MAXIMUM CURRENT TAKEN BY NEAUTRAL IN 125 KVA DG SET

Answer

20% of the rated current as the EFR is at 20%. Neutral
current should be avoided as far as possible .

Is This Answer Correct ?

2 Yes

0 No

Question { Jayaswal Neco Industries, 10395 }

explain the f=np/120 this equ.how to come 120

Answer

In other words , 2 poles make one cycle ,P/2 cycles for one
revolution . Rpm ( N) /60 = rps ( rev per second )

Is This Answer Correct ?

2 Yes

0 No

Question { 1754 }

I have lowered a submersible pump having 100 LPM discharge &
130 Mts. Head, 15 HP rating on borewell. After lowering 108
Meters, It is taking 39 amps & blowing the fuse. Can someone
put light what is the cause behind it ?

Answer

I think water level is high . Reduce the discharge as the motor is overloaded . Provide a valve on the delivery pipe to control the discharge

Is This Answer Correct ?

0 Yes

0 No

Question { Neucel, 2006 }

Please let me know when replacing electromechanical
Relays for protection of generators with sr489 multilin
Relay, then there is no need to use 86 master trip relay
Too. I am wondering this multilin relay has no contact to
Stop breaker reclosing as 86 does

Answer

The electronic relays do not have heavy duty contacts and they are usually self reset. Tripping relay is required to take high trip currents and they are to be reset . Otherwise the contacts of e- relays will burn out and breaker may close without clearing fault . In addition , a back up EM relay may be required

Is This Answer Correct ?

0 Yes

0 No

Question { 4895 }

If the kvar rating of capacitor bank is
600 kvar at 525V then what it's rating at
415v.

Answer

[( 415 / 525 )^2 ] x 600 k var

Is This Answer Correct ?

2 Yes

0 No

Question { Electro Tech, 4108 }

what is the reason for using 110
volt and 60 hertz ac supply for
using power distribution in America?

Answer

Power dist was first introduced in America with 110 v 60 hz.
Now if they want to switch over to 220 v ,all the present
appliances are to be replaced .

Is This Answer Correct ?

4 Yes

2 No

Question { Orange, 4832 }

How to calculate 33 kv panther conductor line losses.

Answer

The resistance of Panther conductor is 0.14 ohm / km .I^2 R
is the loss in watt .

Is This Answer Correct ?

4 Yes

1 No

Question { NEEC, 3507 }

i want to measure voltage difference between neutral and
earth so i just simply use voltmeter.
my question is that may i use this measure continuosly.or
there are some electricity board restrication on that? or it
creat some problem on my measuring device..?

Answer

You can measure after the metering . Do not use service wire
or meter terminal

Is This Answer Correct ?

1 Yes

0 No

Question { IOCL, 7322 }

What is differance between alternator and generator?

Answer

The output of alternator is AC only and that of generator
could be either AC or DC

Is This Answer Correct ?

13 Yes

2 No

Question { MSETCL Maharashtra State Electricity Transmission Co Ltd, 3038 }

IT IS SAID THAT THE OLTC OPERATION SHOULD NOT BE PERFORMED
WHEN THE TRANSFORMER IS GENERATION TRANSFOREMR/STEP UP MODE.
WHY IS IT SO?

Answer

With OLTC ,voltage variation is in increments which may not
be the requirement or may affect unit diff relay . When
the required voltage can be obtained by varying excitation
,OLTC is not needed .

Is This Answer Correct ?

4 Yes

1 No

Question { BS, 2990 }

There is 15 KVA UPS using for single phase load.And 30
batteries of 12 V, 100 Ah are connected in series. Load is
taking 15 A current.What will be the back up power for this
UPS on same load?

Answer

Is it correct that batteries are connected in series ? The stored energy in each battery is 12 x 100 = 1200 Wh. Total = 36000Wh . The load in watts = 230 x 15 = 3500W ( app ) . Back up = 36000/ 3500 = 10 hr(app)

Is This Answer Correct ?

2 Yes

0 No

Question { UPPCL, 4991 }

What will happen if the field of synchronous generator is
removed when it is in operation with no load?

Answer

If it is connected to network ( grid ) with the prime mover
still running ,it may work as induction generator . If not
, there will be a small output voltage due to residual
magnetism

Is This Answer Correct ?

5 Yes

2 No

Question { DS Sugars, 10911 }

What is df/dt protection?, How to calculate setting range
of 30 MW steam generator???

Answer

This relay is usually employed in sub-station to avert sharp drop in frequency due to sudden additional load or drop in generating capacity . The setting may 0.3 Hz / sec. Under such condition ,this relay will open selected outgoing feeders to reduce the load

Is This Answer Correct ?

9 Yes

1 No

Question { Hofincons, 4309 }

anti pumping relay function

Answer

The relay allows one closing command for one closing operation

Is This Answer Correct ?

0 Yes

3 No

k.prakashchandra