Objective Type Question or MCQ of Power System Protection page-6

51. For an arc length of 1 metres carrying fault current of I amperes, the arc resistance in ohms is

a) (2.9×10³ ɭ)/I^1.4
b) (2.9×10⁴ ɭ)/I^1.4
c) (2.9×10⁴ ɭ)/I²
d) (2.9×10⁴ ɭ)/I

Ans: (a)

52. Which of the following are the requirements of protection of power station building against direct strokes?

a) Interception alone
b) Interception, conduction and dissipation
c) Interception and conduction
d) Conduction and dissipation

Ans: (b)

53. Generator internal fault protection is usually based the principle of

a) Differential protection
b) Cross-differential protection
c) Negative sequence protection
d) All of these

Ans: (a)

54. A relay is said to be high speed relay if it operation time is

a) 1 to 2 cycles
b) 3 to 5 cycles
c) 2 to 3 cycles
d) 5 to 7 cycles

Ans: (a)

55. The phase comparison relay has merit that

a) Its operation does not depend upon the direction of power flow
b) Correct relay action can be obtained by using series capacitors on the line
c) It can operate even for low value of fault current
d) None of these

Ans: (c)

56. Maximum demand of consumer is 2kW and his daily energy consumption is 20 units. His load factor will be

a) 10%
b) 25%
c) 41.6%
d) None of above

Ans: (c)

57. The advantage of grounding a power system is that

a) Earth fault current can be used to operate relays
b) “Arcing ground” phenomenon is avoided
c) It provides symmetry to the line impedances
d) Both (a) and (b)above

Ans: (c)

58. Advantage of hydro-electric power station is

a) Low operating cost
b) Free from pollution problems
c) No fuel transportation problems
d) All of the above.

Ans: (d)

59. Pilot wire protection is basically used for the protection of

a) Transmission lines
b) Alternators
c) Switch gears
d) Transformers

Ans: (d)

60. A sodium graphite reactor uses

a) Sodium as moderator and graphite as coolant
b) Sodium as coolant and graphite as moderator
c) A mixture of sodium and graphite as coolant
d) A mixture of sodium and graphite as moderator.

Ans: (b)

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Objective Type Question or MCQ of Power System Protection page-6

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