In a Kelvin's Double Bridge, two sets of readings are taken when measuring a low resistance, one with the current in one direction and the other with direction of current reversed. This is done to eliminate the effect of

1.  contact-resistance

2.  resistance of leads

3.  changes in battery voltage

4.  thermo-electric emfs

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4
Correct Answer :

thermo-electric emfs


Explanation :
No Explanation available for this question

A transformer er is rated at 11 kV/0.4 kV, 500 kVa, 5% reactance. What is ,the short. circuit MVA of the transformer when connected to an infinite bus

1.  20 MVA

2.  10 MVA

3.  15 MVA

4.   5 MVA

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4
Correct Answer :

10 MVA


Explanation :
No Explanation available for this question

When a potentiometer is used for measurement of voltage of an unknown source, the power consume in the circuit of the unknown source under null conditions is

1.  very high

2.  high

3.  small

4.  ideally zero

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4
Correct Answer :

ideally zero


Explanation :
No Explanation available for this question

Standardization of potentiometers is done in order that, they become

1.  accurate

2.  Precise

3.  accurate and direct reading

4.  accurate and precise

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4
Correct Answer :

accurate and direct reading


Explanation :
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Two 11 kV, 20 MVA, three phase, star connected generators operate in parallel. The positive negative and zero sequence reactance of each having j 0.18, j 0.15, j 0.10 p.u. Assume that the grounded generator is solidly grounded. What is the voltage of the healthy phase for a double line to ground fault at terminals of the generator Assume (solid fault Zf= 0)

1.  0.45

2.  0.969

3.  0.251

4.   0.85

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4
Correct Answer :

0.969


Explanation :
No Explanation available for this question

Two generating stations having short circuit capacities of 1200 MVA and 800 KVA respectively and operating at 11 kV are, linked by an interconnected cable having a reactance of 0.5Ω per phase The short circuit current of each station will be

1.  1600 MVA, 1800 MVA

2.  1200 MVA, 200 MVA

3.  1009 MVA, 1200 MVA

4.  1386 MVA, 1001 MVA

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4
Correct Answer :

1386 MVA, 1001 MVA


Explanation :
No Explanation available for this question

A Buchholz relay is used for

1.  protection of a transformer againts all internal faults

2.  protection of a transformer against external faults

3.  protection of a transformer against both internal and external faluts

4.   protection of induction motors

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4
Correct Answer :

protection of a transformer againts all internal faults


Explanation :
No Explanation available for this question

Resistance switching in normally employed in

1.  all breakers

2.  bulk oil breakers

3.  minimum oil breakers

4.  air blast circuit breakers

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4
Correct Answer :

air blast circuit breakers


Explanation :
No Explanation available for this question

If the fault current is 2000 A, the relay setting is 50 % and CT ratio is 400: 5, then plug setting multiplier will be

1.  25A

2.  15A

3.  50A

4.  10A

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4
Correct Answer :

10A


Explanation :
No Explanation available for this question

Reactance relay is normally preferred for protection against

1.  earth faults

2.  phase faults

3.  open corciut faults

4.  none of these

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4
Correct Answer :

open corciut faults


Explanation :
No Explanation available for this question
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