Quiznetik

Switch Gear and Protection | 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. Relays can be designed to respond to changes in

Correct : D. all above

12. Overload relays are of…… type.

Correct : D. all above

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

Correct : B. heavy loads

14. Magnetic circuit breaker has ______ trip action.

Correct : B. instantaneous

15. D.C. shunt relays are made of

Correct : C. many turns of thin wire

16. The relay operating speed depends upon

Correct : D. all of the above

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

Correct : D. have all above properties

18. Circuit breakers usually operate under

Correct : A. transient state of short-circuit current

19. Circuit breakers are essentially

Correct : A. current carrying contacts called electrodes

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

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

21. Air blast circuit breaker is used for

Correct : D. repeated duty

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

Correct : D. all of the above

23. Burden of a protective relay is the power

Correct : B. absorbed by the circuit of relay

24. Directional relays are based on flow of

Correct : A. power

25. A differential relay measures the vector difference between

Correct : C. two or more similar electrical quantities

26. A transmission line is protected by

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

27. Large internal faults are protected by

Correct : A. merz price percentage differential protection

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

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

29. 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

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

Correct : A. recovery

31. Ionization in circuit breaker is facilitated by

Correct : D. all of the above

32. In a circuit breaker the basic problem is to

Correct : C. transmit large power

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

Correct : D. all of the above

34. Interruption of large currents by relay requires

Correct : D. all of the above

35. Shunt capacitance is neglected while considering

Correct : A. short transmission line

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

Correct : A. in phase with the arc current

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

Correct : A. 0.003 sec

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

Correct : C. 100 mega ohms

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

Correct : D. short-circuits

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

Correct : D. 10

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

Correct : A. motors

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

Correct : A. Rewireable fuse

43. Resistance grounding is used for voltage between

Correct : C. 3.3kVandllkV

44. 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

45. In Railway applications ______ circuit breaker is used.

Correct : D. air break

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

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

47. Wave trap is used to trap waves of

Correct : B. higher frequencies entering generator or transformer units

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

Correct : D. all of the above

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

Correct : C. unity

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

Correct : C. interception, conduction and dissipation

51. The line insulation is the insulation level of the station equipment.

Correct : D. not directly related with

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

Correct : D. all of the above

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

Correct : D. sending and other end

54. Which of the following statements is incorrect?

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

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

Correct : C. slow

56. Induction cup relay is operated due to changes in

Correct : D. all of the above

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

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

58. Which of the following statements is incorrect ?

Correct : A. Lightning arrestors are used before the switchgear

59. Short-circuit currents are due to

Correct : D. any of these

60. To reduce short circuit fault currents are used.

Correct : A. reactors

61. Bus coupler is very essential in arrangement

Correct : C. main and transfer bus

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

Correct : B. 33 kV

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

Correct : D. impulse voltage

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

Correct : A. Impedance

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

Correct : A. Generators

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

Correct : B. Reactance

67. Distance relays are generally

Correct : D. none of the above

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

Correct : B. equal to and above 5 MVA

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

Correct : C. resistance thermometer

70. The under voltage relay can be used for

Correct : D. all of the above

71. The relay with inverse time characteristic will operate within

Correct : B. 5 to 10 sec

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

Correct : D. three phase motors

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

Correct : A. Lightning arresters

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

Correct : B. Capacitance

75. Series reactors should have

Correct : A. low resistance

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

Correct : B. Circuit breaker with SF6 gas

77. Arc in a circuit breaker is interrupted at

Correct : A. zero current

78. transmission line has reflection coefficient as one.

Correct : A. Open circuit

79. 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

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

Correct : B. internal short-circuits

81. Over voltage protection is recommended for

Correct : D. all of the above

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

Correct : B. 50 millisecond

83. Overfluxing protection is recommended for

Correct : A. distribution transformer

84. Series capacitors are used to

Correct : A. compensate for line inductive reactance

85. Admittance relay is _______ relay.

Correct : B. directional

86. The material used for fuse must have

Correct : A. low melting point and high specific resistance

87. 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

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

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

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

Correct : A. connecting lines in parallel

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

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

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

Correct : A. transmission line

92. A fuse is connected

Correct : A. in series with circuit

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

Correct : D. all of the above

94. The fuse rating is expressed in terms of

Correct : A. current

95. The fuse blows off by

Correct : C. melting

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

Correct : C. Heating effect

97. An isolator is installed

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

98. A fuse in a motor circuit provides protection against

Correct : B. short-circuit and overload

99. Protection by fuses is generally not used beyond

Correct : C. 100 A

100. A fuse is never inserted in

Correct : A. neutral wire