Objective Questions & Answers of Circuit Breaker page-2

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

A) Air
B) Oil
C) SF₆
D) Water.

Ans : (A)

12. Which of the following circuit breakers is preferred for EHT application

A) Air blast circuit breakers
B) Minimum oil circuit breakers
C) SF₆ oil circuit breakers
D) Bulk oil circuit breakers.

Ans : (C)

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

A) Tank type oil circuit breaker
B) Air blast circuit breaker
C) Vacuum circuit breaker
D) Miniature circuit breaker.

Ans : (B)

14. In a vacuum circuit breaker, the vacuum is of the order of

A) 10 mm Hg
B) 10^-2 mm Hg
C) 10^-6 mm Hg
D) 10^-9 mm Hg

Ans : (D)

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

A) 0.01 sec
B) 0.1 sec
C) 3 seconds
D) 30 seconds.

Ans : (C)

16. Which of the following is not type of the contactor for circuit breakers ?

A) Vacuum
B) Pneumatic
C) Electro-pneumatic
D) Electromagnetic.

Ans : (A)

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

A) 0.001 sec
B) 0.015 sec
C) 0.003 sec
D) 0.03 sec.

Ans : (D)

18. In a HRC fuse the time between cut-off and final current zero, is known as

A) total operating time
B) arcing time
C) pre-arcing time
D) any of the above.

Ans : (B)

19. Interrupting medium in a contactor may be

A) air
B) oil
C) SF₆ gas
D) any of the above

Ans : (D)

20. In air blast circuit breakers, the pressure of air is of the order of

A) 100 mm Hg
B) 1 kg/cm²
C) 20 to 30 kg/cm²
D) 200 to 300 kg/cm².

Ans : (C)

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