Circuit Breakers MCQs

1. A circuit breaker is

  1. power factor correcting device
  2. a device to neutralize the effect of transients
  3. a waveform correcting device
  4. a current interrupting device

Answer. d

2. Low voltage circuit breakers have rated voltage of less than

  1. 220 V
  2. 400V
  3. 1000 V
  4. 10,000 V

Answer. c

3. The medium employed for the extinction of arc in air circuit breaker is

  1. SF6
  2. Oil
  3. Air
  4. Water

Answer. c

4. For high voltage, ac circuit breakers, the rated short circuit current is passed for

  1. 0.01 sec
  2. 0.1 sec
  3. 3 sec
  4. 30 sec

Answer. c

5. Interrupting medium in a contactor may be

  1. air
  2. oil
  3. SF6 gas
  4. any of the above

Answer. d

6. SF6 gas is

  1. sulphur fluoride
  2. sulphur difluoride
  3. sulphur hexafluoride
  4. sulphur hexafluoride

Answer. d

7. SF6 gas

  1. is lighter than hydrogen
  2. is lighter than air
  3. has density 2-times as compared to that of air
  4. has density 5-times as compared to that of air

Answer. d

8. While selecting a gas for circuit breaker, the property of gas that should be considered is

  1. high dielectric strength
  2. non-inflammability
  3. non-toxicity
  4. all of the above

Answer. d

9. Which of the following circuit breaker can be installed on 400 kV line

  1. Tank type oil circuit breaker
  2. Miniature circuit breaker
  3. Vacuum circuit breaker
  4. Air blast circuit breaker

Answer. d

10. In modern EHV circuit breakers, the operating time between the instant of receiving trip signal and final contact separation is, of the order of

  1. 0.001 sec
  2. 0.015 sec
  3. 0.003 sec
  4. 0.03 sec

Answer. d

11. In Extra voltage lines which of the following Circuit breakers are most suitable?

  1. SF6 circuit breakers
  2. Air circuit breakers
  3. Oil circuit breakers
  4. Vacuum circuit breakers

Answer. a

12. _______ is not a method of high resistance interruption of arc extinction

  1. Blast effect
  2. Arc lengthening
  3. Arc constraining
  4. Arc cooling

Answer. a

13. _______ does not have any repairable component

  1. Air Blast CB
  2. MCB
  3. OCB
  4. Air Break CB

Answer. b

14. Resisting capacity of Vaccum circuit breaker is:

  1. Zero
  2. Moderate
  3. Lower as compared to others
  4. High

Answer. d

15. Air Blast Circuit breaker is employed among which of the following?

i. Arc furnace duty

ii. Traction system

  1. only i
  2. only ii
  3. i and ii both
  4. neither i nor ii

Answer. b

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