Quiznetik

Testing and Commissioning of Electrical Equipment’s | Set 1

1. The main function of a fuse is to

Correct : D. prevent excessive currents

2. On which of the following routine tests are conducted ?

Correct : D. All of the above

3. SF6 gas

Correct : C. is nontoxic

4. The arcing contacts in a circuit breaker are made of

Correct : A. copper tungsten alloy

5. Which of the following medium is employed for extinction of arc in air circuit breaker ?

Correct : C. Air

6. With which of the following, a circuit breaker must be equipped for remote operation ?

Correct : C. Shunt trip

7. Fault diverters are basically

Correct : C. fast switches

8. A thermal protection switch can protect against

Correct : C. overload

9. Arc in a circuit behaves as

Correct : D. a resistance decreasing with voltage rise across the arc

10. Thermal circuit breaker has

Correct : A. delayed trip action

11. Thermal overload relays are used to protect the motor against over current due to

Correct : B. heavy loads

12. Magnetic circuit breaker has ______ trip action.

Correct : B. instantaneous

13. D.C. shunt relays are made of

Correct : C. many turns of thin wire

14. The relay operating speed depends upon

Correct : D. all of the above

15. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should

Correct : D. have all above properties

16. Circuit breakers usually operate under

Correct : A. transient state of short-circuit current

17. Circuit breakers are essentially

Correct : A. current carrying contacts called electrodes

18. The current zero interruption, in oil and air blast circuit breakers, is achieved by

Correct : C. both (A) and (B)

19. Air blast circuit breaker is used for

Correct : D. repeated duty

20. An efficient and a well designed protective relaying should have

Correct : D. all of the above

21. Burden of a protective relay is the power

Correct : B. absorbed by the circuit of relay

22. Directional relays are based on flow of

Correct : A. power

23. A differential relay measures the vector difference between

Correct : C. two or more similar electrical quantities

24. A transmission line is protected by

Correct : D. both (B) and (C)

25. Large internal faults are protected by

Correct : A. merz price percentage differential protection

26. When a transmission line is energized, the wave that propagates on it is

Correct : C. both (A) and (B)

27. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring

Correct : C. constantly the electrical quantities which differ during normal and abnormal conditions

28. The voltage appearing across the contacts after opening of the circuit breaker is called______voltage.

Correct : A. recovery

29. Ionization in circuit breaker is facilitated by

Correct : D. all of the above

30. In a circuit breaker the basic problem is to

Correct : C. transmit large power

31. Overheating of relay contacts or contact born out is due to

Correct : D. all of the above

32. Interruption of large currents by relay requires

Correct : D. all of the above

33. Shunt capacitance is neglected while considering

Correct : A. short transmission line

34. The arc voltage produced in A.C. circuit breaker is always

Correct : A. in phase with the arc current

35. The time of closing the cycle, in modern circuit breakers is

Correct : A. 0.003 sec

36. Insulation resistance of high voltage circuit breakers is more than

Correct : C. 100 mega ohms

37. H.R.C. fuses provide best protection against

Correct : D. short-circuits

38. The ground wire should not be smaller than No ______ copper.

Correct : D. 10

39. The delay fuses are used for the protection of ________.

Correct : A. motors

40. Which of the following is the least expensive protection for overcurrent is low voltage system ?

Correct : A. Rewireable fuse

41. Resistance grounding is used for voltage between

Correct : C. 3.3kVandllkV

42. The contacts of high voltage switches used in power system are submerged in oil. The main purpose of the oil is to

Correct : C. extinguish the arc

43. In Railway applications ______ circuit breaker is used.

Correct : A. SFe

44. To protect most of the electrical equipment handling low power, the types of relays used are

Correct : C. both (A) and (B)

45. Wave trap is used to trap waves of

Correct : B. higher frequencies entering generator or transformer units

46. Ungrounded neutral transmission system is not recommended because of system

Correct : D. all of the above

47. The reflection co-efficient at the open circuited end of a transmission line.

Correct : C. unity

48. For the protection of power station buildings against direct strokes the requirements are

Correct : C. interception, conduction and dissipation

49. The interaction between a transmission line and communication line is minimized by

Correct : D. all of the above

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

Correct : D. sending and other end

51. Which of the following statements is incorrect?

Correct : A. Station batteries are used to operate relay only

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

Correct : C. slow

53. Induction cup relay is operated due to changes in

Correct : D. all of the above

54. A.C. network analyser is used to solve problems of

Correct : D. load flow, short-circuit and stability

55. Which of the following statements is incorrect ?

Correct : A. Lightning arrestors are used before the switchgear

56. To reduce short circuit fault currents are used.

Correct : A. reactors

57. Bus coupler is very essential in arrangement

Correct : C. main and transfer bus

58. For cost and safety, the outdoor substations are installed for voltages above

Correct : B. 33 kV

59. The short circuit in any winding of the transformer is the result of

Correct : D. impulse voltage

60. relays are used for phase faults on long line.

Correct : A. Impedance

61. For which of the following protection from negative sequence currents is provided ?

Correct : A. Generators

62. relay is preferred for phase fault on short transmission line.

Correct : B. Reactance

63. Distance relays are generally

Correct : B. reactance relays

64. For which of the following ratings of the transformer differential protection is recommended ?

Correct : D. none of the above

65. A _______ is used to measure the stator % winding temperature of the generator.

Correct : C. resistance thermometer

66. The relay with inverse time characteristic will operate within

Correct : B. 5 to 10 sec

67. The single phasing relays are used for the protection of

Correct : D. three phase motors

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

Correct : A. Lightning arresters

69. Which of the following parameter can be neglected for a short line ?

Correct : B. Capacitance

70. Series reactors should have

Correct : A. low resistance

71. Which of the following circuit breakers has high reliability and minimum maintenance ?

Correct : B. Circuit breaker with SF6 gas

72. Arc in a circuit breaker is interrupted at

Correct : A. zero current

73. transmission line has reflection coefficient as one.

Correct : A. Open circuit

74. What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?

Correct : A. Zero

75. The inverse definite mean time relays are used for over current and earth fault protection of transformer against

Correct : B. internal short-circuits

76. Over voltage protection is recommended for

Correct : D. all of the above

77. Air blast circuit breakers for 400 kV power system are designed to operate in

Correct : B. 50 millisecond

78. Overfluxing protection is recommended for

Correct : B. generator transformer of the power plant

79. Series capacitors are used to

Correct : A. compensate for line inductive reactance

80. Admittance relay is _______ relay.

Correct : B. directional

81. The material used for fuse must have

Correct : A. low melting point and high specific resistance

82. If the fault occurs near the impedance relay, the VII ratio will be

Correct : B. lower than that of if fault occurs away from the relay

83. The torque produced in induction type relay (shaded pole structure) is

Correct : B. inversely proportional to the square of the current

84. The steady state stability of the power system can be increased by

Correct : A. connecting lines in parallel

85. The inductive interference between power and communication line can be minimized by

Correct : C. both (A) and (B)

86. The power loss is an important factor for the design of

Correct : A. transmission line

87. A fuse is connected

Correct : A. in series with circuit

88. H.R.C. fuse, as compared to a rewirable fuse, has

Correct : D. all of the above

89. The fuse rating is expressed in terms of

Correct : A. current

90. The fuse blows off by

Correct : C. melting

91. On which of the following effects of electric current a fuse operates ?

Correct : C. Heating effect

92. An isolator is installed

Correct : D. generally on both sides of a circuit breaker

93. A fuse in a motor circuit provides protection against

Correct : B. short-circuit and overload

94. Protection by fuses is generally not used beyond

Correct : C. 100 A

95. A fuse is never inserted in

Correct : A. neutral wire

96. Which of the following circuit breakers is used for the railway electrification?

Correct : A. Air blast circuit breaker

97. The stability of arc in vacuum depends on _________.

Correct : D. Both (b) and (c)

98. SF6 is which type of gas?

Correct : C. Both (a) and (b)

99. What is the average rate of rise of restriking voltage upto the first peak?

Correct : B. 453 * 103kV / sec

100. Circuit breakers usually operate under

Correct : B. Sub transient state of short circuit current