electrical

Switchgear and Protection MCQ Objective Questions and Answers Page - 6

1.

To protect the power transformer  (Y – Y with neutral grounded)  against fault, what type of connection do the CTs have  ?

Answer/ Hint      

Answer : B

Explanation :

2.

In Merz-Price percentage differential protection of a    transformer, the CT secondaries connection in the primary and secondary winding of the transformer would be in the form of

Answer/ Hint      

Answer : B

Explanation :

3.

To prevent mal operation of differentially connected relay while energising a transformer, the relay restraining coil is biased with

Answer/ Hint      

Answer : A

Explanation :

4.

The inrush current of a transformer at no load is maximum if the supply voltage is switched on

Answer/ Hint      

Answer : B

Explanation :

5.

Magnetising inrush phenomena occur in

Answer/ Hint      

Answer : A

Explanation :

6.

In case of power transformer  :

Answer/ Hint      

Answer : A

Explanation :

7.

For the protection of transformers, harmonic restraint is used to guard against

Answer/ Hint      

Answer : A

Explanation :

8.

The connections of  CTs  are opposite to that of transformer windings so that current in the pilot wires of two  are/have

Answer/ Hint      

Answer : A

Explanation :

9.

For preventing the maloperation of Merz-Price protection scheme on inrush of magnetizing current

Answer/ Hint      

Answer : A

Explanation :

10.

Problems associated with differential protection  is/are

Answer/ Hint      

Answer : D

Explanation :

11.

Which of the following sections can be employed for bus-bars  ?

Answer/ Hint      

Answer : D

Explanation :

12.

The material used for bus-bars should have

Answer/ Hint      

Answer : D

Explanation :

13.

A bus-bar is rated by

Answer/ Hint      

Answer : D

Explanation :

14.

Single bus-bar arrangement

Answer/ Hint      

Answer : D

Explanation :

15.

Double bus-bar arrangement makes use of two identical bus-bars and has the advantage(s) that

Answer/ Hint      

Answer : D

Explanation :

16.

A bus coupler circuit breaker is utilised in a substation for

Answer/ Hint      

Answer : B

Explanation :

17.

Zero-sequence impedance of the transmission line is

Answer/ Hint      

Answer : B

Explanation :

18.

Which is the pilotless protection method for feeder line  ?

Answer/ Hint      

Answer : B

Explanation :

19.

In the case of transmission line protection, overcurrent used is  :

Answer/ Hint      

Answer : C

Explanation :

20.

Which is the main relay for protecting up to  90%  of the transmission line-length in the forward direction  ?

Answer/ Hint      

Answer : B

Explanation :

21.

For complete protection of a 3-phase line

Answer/ Hint      

Answer : D

Explanation :

22.

How many relay are used to detect interphase fault of a three-line system  ?

Answer/ Hint      

Answer : C

Explanation :

23.

The transmission line distance production relay having the property of being inherently directional is

Answer/ Hint      

Answer : B

Explanation :

24.

Time graded protection of a radial feeder can be achieved by using

Answer/ Hint      

Answer : C

Explanation :

25.

For protection of parallel feeders fed from one end, the relays required are

Answer/ Hint      

Answer : A

Explanation :

26.

Pilot-wire protection scheme is most economical and provides high speed relaying for

Answer/ Hint      

Answer : A

Explanation :

27.

Adjustable resistors are connected in the pilot wires in order to

Answer/ Hint      

Answer : B

Explanation :

28.

Signal mixing transformers are used for

Answer/ Hint      

Answer : C

Explanation :

29.

In a balanced voltage pilot-wire protection scheme, if the pilot-circuit gets short-circuited, the relay will

Answer/ Hint      

Answer : C

Explanation :

30.

The frequency of carrier in the carrier current pilot scheme is in the range of

Answer/ Hint      

Answer : D

Explanation :

31.

The frequency of carrier transmitted by microwave pilot is in the range of

Answer/ Hint      

Answer : C

Explanation :

32.

In carrier current protection the purpose of the wave-trap is for

Answer/ Hint      

Answer : B

Explanation :

33.

A line trap in carrier current relaying tuned to carrier frequency presents

Answer/ Hint      

Answer : A

Explanation :

34.

A line trap in a long transmission line is used to

Answer/ Hint      

Answer : C

Explanation :

35.

Distance protection scheme is preferred over graded time-lag over-current protection in HV and EHV lines because

Answer/ Hint      

Answer : A

Explanation :

36.

Three step time-distance characteristic of distance relay can be had by

Answer/ Hint      

Answer : D

Explanation :

37.

Lightning is a huge spark caused by electrical discharge taking place between

Answer/ Hint      

Answer : D

Explanation :

38.

Switching over-voltages are more hazardous than lightning surges in case of

Answer/ Hint      

Answer : C

Explanation :

39.

The over-voltage surges in power system may be caused by

Answer/ Hint      

Answer : D

Explanation :

40.

Requirements of protection power station buildings against direct stokes are

Answer/ Hint      

Answer : D

Explanation :

41.

The line insulation is _____________ the insulation level of the station equipment

Answer/ Hint      

Answer : D

Explanation :

42.

When a wave propagates on a transmission line, it suffers reflection several times at

Answer/ Hint      

Answer : D

Explanation :

43.

Which of the following statements is incorrect?

Answer/ Hint      

Answer : A

Explanation :

44.

Discrimination between main and back up protection is provided by the use of relays which are

Answer/ Hint      

Answer : C

Explanation :

45.

Induction cup relay is operated due to changes in

Answer/ Hint      

Answer : D

Explanation :

46.

AC network analyser is used to solve problems of

Answer/ Hint      

Answer : D

Explanation :

47.

Which of the following statements is incorrect?

Answer/ Hint      

Answer : A

Explanation :

48.

Short-circuit currents are due to

Answer/ Hint      

Answer : D

Explanation :

49.

To reduce short circuit fault currents ______________  are used.

Answer/ Hint      

Answer : A

Explanation :

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