electrical

Switchgear and Protection MCQ Objective Questions and Answers Page - 1

1.

Short-circuit currents are due to

Answer/ Hint      

Answer : D

Explanation :

2.

The most serious consequence of a major uncleared short-circuit fault could be

Answer/ Hint      

Answer : B

Explanation :

3.

Which of the following results in a symmetrical fault  ?

Answer/ Hint      

Answer : C

Explanation :

4.

Which portion of the transmission system is more prone to faults  ?

Answer/ Hint      

Answer : C

Explanation :

5.

Which portion of the power system is least prone to faults  ?

Answer/ Hint      

Answer : A

Explanation :

6.

The magnitude of fault current depends upon

Answer/ Hint      

Answer : D

Explanation :

7.

The most common type of fault is

Answer/ Hint      

Answer : A

Explanation :

8.

The maximum short-circuit current occurs in the case of  :

Answer/ Hint      

Answer : A

Explanation :

9.

For a fault at the terminals of synchronous generator, the fault current is maximum for a

Answer/ Hint      

Answer : C

Explanation :

10.

A 25 MVA, 33 kV transformer has a pu impedance of 0.9 . the per unit impedance at a new base  50 MVA at 11 kV would be

Answer/ Hint      

Answer : D

Explanation :

11.

The per unit value of a  4 Ω  resistor at  100 MVA  base and  10 kV base voltage is

Answer/ Hint      

Answer : B

Explanation :

12.

A  10 kVA, 400  V/200 V  single-phase transformer with  10% impedance, draws a steady short-circuit current of

Answer/ Hint      

Answer : C

Explanation :

13.

A transformer rated for  500 kVA.  1 =1kV/0.4 kV has an impedance of  10%  and is connected to an infinite bus. The fault level of the transformer is

Answer/ Hint      

Answer : C

Explanation :

14.

In the above system, the three-phase fault MVA at the bus 3 is

Answer/ Hint      

Answer : D

Explanation :

15.

The per-unit impedance of an alternator corresponding to base values  13.2 kV  and  30 MVA  is  0.2 p.u. value of the impedance for base values of  13.8 kV  and  50 MVA  in pu will be

Answer/ Hint      

Answer : C

Explanation :

16.

Four alternators, each rated at  5 MVA, 11 kV, with 20% reactance are working in parallel. The short-circuit level at bus-bars is

Answer/ Hint      

Answer : D

Explanation :

17.

The post fault voltages at buses  1 and 3  in per unit respectively are

Answer/ Hint      

Answer : D

Explanation :

18.

The instant (t0) of the fault will be

Answer/ Hint      

Answer : A

Explanation :

19.

The  rms  value of the ac component of fault current (Ix) will be

Answer/ Hint      

Answer : A

Explanation :

20.

Instead of the three phase fault, if a single line-to ground fault occurs on phase  ‘a’  point  ‘F’  with zero fault impedance, then the rms of the ac component of fault current (Ix) for phase  ‘’  will be

Answer/ Hint      

Answer : C

Explanation :

21.

Series reactors are used to

Answer/ Hint      

Answer : D

Explanation :

22.

Current limiting reactors may be

Answer/ Hint      

Answer : D

Explanation :

23.

Symmetrical  components are used in power system for the analysis of

Answer/ Hint      

Answer : B

Explanation :

24.

In a star-connected system without neutral grounding, zero sequence currents are

Answer/ Hint      

Answer : A

Explanation :

25.

A balanced 3-phase system consists of

Answer/ Hint      

Answer : B

Explanation :

26.

The Positive sequence current of a transmission line is  :

Answer/ Hint      

Answer : C

Explanation :

27.

For a fully transposed transmission line

Answer/ Hint      

Answer : B

Explanation :

28.

In case of an unbalanced star-connected load supplied from an unbalanced 3-phase, 3-wire system, load currents will consist of

Answer/ Hint      

Answer : D

Explanation :

29.

For an unbalanced fault, with paths for zero-sequence currents, at the point of fault

Answer/ Hint      

Answer : B

Explanation :

30.

In case of single line to ground fault

Answer/ Hint      

Answer : B

Explanation :

31.

When a line-to-ground fault occurs, the current, the current in the faulted phase is  100 A. the zero-sequence current in this case will be  :

Answer/ Hint      

Answer : B

Explanation :

32.

Zero sequence fault current is absent when fault is

Answer/ Hint      

Answer : D

Explanation :

33.

The current of a single-phase load drawn from a 3-phase system has  :

Answer/ Hint      

Answer : C

Explanation :

34.

If the positive, negative – and zero-sequence reactances of an element of a power system are 0.3, 0.3 and 0.8 pu respectively, then the element would be a

Answer/ Hint      

Answer : D

Explanation :

35.

If all the sequence voltages at the fault point in a power system are equal, then the fault is a

Answer/ Hint      

Answer : D

Explanation :

36.

The three sequence voltages at the point of fault in a power system are found to be equal. The nature of the fault is

Answer/ Hint      

Answer : D

Explanation :

37.

The zero-sequence current of a generator for line-to ground fault is j2.4 pu. Then the current through the neutral during the fault is

Answer/ Hint      

Answer : C

Explanation :

38.

One current transformer (CT) is mounted over a 3-phase, 3-core cable with its sheath and armour removed from the portion covered by the CT. an ammeter placed in the CT secondary would measure

Answer/ Hint      

Answer : D

Explanation :

39.

The positive sequence driving point reactance at the bus is

Answer/ Hint      

Answer : D

Explanation :

40.

The zero sequence driving point reactance at the bus is

Answer/ Hint      

Answer : B

Explanation :

Switchgear and Protection MCQ Objective Questions and Answers Page - 1
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