Objective Type Question or MCQ of Power System Protection page-4

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31. Plug setting of a relay can be altered by varying

a) Air gap of magnetic path
b) Number of ampere-turns
c) Adjustable back up stop
d) None of these

Ans: (b)

32. If the operation of a relay does not involve any change in air gap, then the ratio of rest to pick up is usually

a) Low
b) Medium
c) High
d) Independent of the change in air gap

Ans: (c)

33. Drop out to cutoff ratio for most relays is of the order of

a) 0.2 to 0.3
b) 0.3 to 0.4
c) 0.4 to 0.6
d) 0.6 to 1.0

Ans: (d)

34. Basic quantity measured in a distance relay is

a) Impedance
b) Current difference
c) Voltage difference
d) None of these

Ans: (a)

35. Which of following are the desirable qualities of protective relays?

a) Stability, reliability
b) Speed sensitivity
c) Selectivity, adequacy
d) None of these

Ans: (d)

36. Protective relays are devices which detect abnormal conditions in electrical circuit by measuring

a) Current during abnormal condition
b) Voltage during abnormal condition
c) Both (a) and (b) simultaneously
d) Constantly the electrical quantities which differ during normal and abnormal conditions

Ans: (d)

37. Resistance offered by series reactor is usually

a) Low
b) High
c) Medium
d) Very high

Ans: (a)

38. Time interval from instant of contact separation to time of arc extinction is called

a) Arcing time
b) Opening time
c) Closing time
d) None of these

Ans: (b)

39. A distance relay measures

a) Current difference
b) Voltage difference
c) Impedance difference
d) Distance between two CT’s

Ans: (c)

40. Maximum short circuit current occurs due to

a) Line-to-line fault
b) Line-to-line circuit
c) Dead short circuit
d) Both (a) and (b) occurring simultaneously

Ans: (d)

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Objective Type Question or MCQ of Power System Protection page-4

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