switchgear and protection MCQs – Page 4

Practise focused switchgear and protection questions with marked answers for exam preparation and subject revision.

switchgear and protection Mcqs

61. Oil switches are employed for_____________?
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A. low currents circuits

B. all circuits

C. low voltages circuits

D. high voltages and large currents circuits

62. Protection by fuses is generally not used beyond__________?
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A. 20 A

B. 100 A

C. 50 A

D. 200 A

63. The reflection co-efficient at the open circuited end of a transmission line___________?
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A. infinity

B. none of the above

C. zero

D. unity

64. Insulation resistance of high voltage circuit breakers is more than________________?
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A. 100 mega ohms

B. 500 mega ohms

C. 1 mega ohms

D. 10 mega ohms

65. Which of the following statements is incorrect ?
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A. Lightning arrestors are used before the switchgear

B. The peak short current is (1.8 xV2) times the A.C. component

C. Shunt reactors are used as compensation reactors

D. The MVA at fault is equal to base MVA divided by per unit equivalent fault reactance

66. The short circuit in any winding of the transformer is the result of______________?
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A. mechanical vibration

B. loose connection

C. impulse voltage

D. insulation failure

67. The inductive interference between power and communication line can be minimized by__________?
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A. transposition of the power line

B. transposition of the communication line

C. both (A) and (B)

D. increasing the distance between the conductors

68. For which of the following ratings of the transformer differential protection is recommended ?
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A. none of the above

B. above 30 kVA.

C. equal to and above 5 MVA

D. equal to and above 25 MVA

69. Which of the following circuit breakers has high reliability and minimum maintenance ?
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A. Vacuum circuit breakers

B. Air blast circuit breakers

C. Circuit breaker with SF6 gas

D. Oil circuit breakers

70. A.C. network analyser is used to solve problems of_______________?
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A. load flow, short-circuit and stability

B. none of the above

C. load flow

D. load flow and short-circuit

E. load flow and stability

71. To reduce short circuit fault currents are used_____________?
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A. none of the above

B. capacitors

C. resistors

D. reactors

72. Which of the following devices will receive voltage surge first travelling on the transmission line ?
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A. Relays

B. Switchgear

C. Step-down transformer

D. Lightning arresters

73. Induction cup relay is operated due to changes in________________?
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A. impedance

B. voltage

C. current

D. all of the above

74. Distance relays are generally_____________?
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A. split-phase relays

B. none of the above

C. reactance relays

D. impedance relays

75. The short circuit in any winding of the transformer is the result of_______________?
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A. loose connection

B. mechanical vibration

C. insulation failure

D. impulse voltage

76. Arc in a circuit behaves as_______________?
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A. a resistance decreasing with voltage rise across the arc

B. a resistance increasing with voltage rise across the arc

C. an inductive reactance

D. a capackive reactance

77. On which of the following routine tests are conducted ?
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A. All of the above

B. Oil circuit breakers

C. Air blast circuit breakers

D. Minimum oil circuit breakers

78. Circuit breakers usually operate under______________?
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A. sub-transient state of short-circuit current

B. after D.C. component has ceased

C. steady state of short-circuit current

D. transient state of short-circuit current

79. Circuit breakers are essentially____________?
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A. circuits to break the system

B. current carrying contacts called electrodes

C. any of the above

D. transformers to isolate the two systems

E. arc extinguishers

80. Short-circuit currents are due to_______________?
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A. three phase faults

B. single phase to ground faults

C. two phase to ground faults

D. phase to phase faults

E. any of these

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