Switchgear Protections

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

1. transmission line
2. motor
3. generator
4. feeder

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

1. zero
2. infinity
3. unity
4. none of the above

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73. The relay operating speed depends upon

1. the spring tension
2. the rate of flux built up
3. armature core air gap
4. all of the above

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74. The relay with inverse time characteristic will operate within

1. 1.5 sec
2. 5 to 10 sec
3. 5 to 20 sec
4. 20 to 30 sec

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

1. mechanical vibration
2. insulation failure
3. loose connection
4. impulse voltage

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

1. single phase motors only
2. two phase motors only
3. two single phase motors running in parallel
4. three phase motors

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

1. connecting lines in parallel
2. connecting lines in series
3. using machines of high impedance
4. reducing the excitation of machines

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

1. 0.003 sec
2. 0.001 sec
3. 0.01 sec
4. 0.10 sec
5. none of the above

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

1. inversely proportional to the current
2. inversely proportional to the square of the current
3. proportional to the current
4. proportional to square of the current

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80. The under voltage relay can be used for

1. generators
2. busbars
3. transformers
4. motors
5. all of the above

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