Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on External earth

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on
External earth fault REF relay trips along with earth fault
relay.The REF relay has no complant as we tested relay.Why is
it happening?

Question Posted / manu

3 Answers
5264 Views
KSEB, I also Faced
E-Mail Answers

Answers were Sorted based on User's Feedback

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on External earth fault REF relay trip..

Answer / shariff

REF relay shold not operate otherthan its zone of operation
i.e 11kV REFR zone is from 11kV trf busings to 11kV CT
(incomer) and some times PT also if PT is before CT. It is
a mal function only and it can be any of the following.
1) Check the 11kV NCT wiring it may be loose/ got cut in
the NCT wiring box in the yard.
2) The 11kV incomer CT wiring may be loose/ got cut etc.
3) Check the 11kV PT primary resistance it may notbe equal.

Is This Answer Correct ?

3 Yes

0 No

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on External earth fault REF relay trip..

Answer / k.prakashchandra

The NCT is responsible..The ungrounded lead from The NCT may
be grounded.

Is This Answer Correct ?

1 Yes

0 No

Sir We have a REF relay connected to 10MVA(Y-Y) Transformer.on External earth fault REF relay trip..

Answer / k.prakashchandra

Also may be due to 1 .reverse connection of NCT leads ( Unbalanced current of lines and NCT current add to each other ). 2. Low saturation point of NCT as Kv of bushing NCT is usually less than that of line CTs

Is This Answer Correct ?

0 Yes

0 No

Post New Answer

More Electrical Engineering Interview Questions

How to check the efficiency of the generator , air compressors.

1 Answers CIL,

HOW TO CALCULATE EACH PHASE CURRENT WHILE A MOTOR CONNECTED TO STAR- DELTA STARTER?

3 Answers

What happens when the power factor is leading and its disadvantages.

1 Answers

UPS battery Back time = no.of Batteries * Ah of the Battery / output KVA * 130 ? what is the 130 means ? can any one help? because all are using this formula how its came 130?

2 Answers

at present how many EHVAC lines are there in India?

8 Answers HCL, L&T,

How test for Ddo vector group test condition?

0 Answers

why zero sequence impedance measurement is not applicable for single phase GT

0 Answers

What is the RMS Value. Please discribe in detail

14 Answers Bhel,

WHAT IS THE DIFFERENE IN ACTION OF MCB,MCCB,RCCB

0 Answers IBM,

What is the difference between "Earthing" and "Neutral"?

10 Answers Power Grid,

1.what is electricity 2.what is electronice 3.how many modules 4.five electrical component with symbol 5.five electronice componene with symbol 6.how convert 220v.A/C to 24v/DC 7.220V.WAIRING DIAGRAM OF AMMETER/VOLTMETER/OHMMETEER

1 Answers Hatsun,

can anyone show me how the 3 phase power is supplied to socket outlets?

0 Answers Bhel,

For more Electrical Engineering Interview Questions Click Here