Switchgear and Protection - Electrical Engineering (MCQ) questions and answers

1)   SF6 is which type of gas?

a. Electro positive
b. Electro negative
c. Both (a) and (b)
d. None of these
Answer  Explanation 

ANSWER: Both (a) and (b)

Explanation:
No explanation is available for this question!


2)   For a high speed circuit breaker what will the total clearing time?

a. Few minutes.
b. Few seconds.
c. 1 to 2 cycles.
d. 5 to 20 cycles.
Answer  Explanation 

ANSWER: 1 to 2 cycles.

Explanation:
No explanation is available for this question!


3)   In a circuit breaker the contact space is ionised by what?

a. Field emission from the contact surface.
b. Thermal emission from the contact surface.
c. Thermal ionisation of gas.
d. All of above.
Answer  Explanation 

ANSWER: Thermal ionisation of gas.

Explanation:
No explanation is available for this question!


4)   Which of the following should have low value for the contacts and their material?

a. Thermal capacity.
b. Contact resistance.
c. Thermal conductivity.
d. None of above.
Answer  Explanation 

ANSWER: Contact resistance.

Explanation:
No explanation is available for this question!


5)   How is the initiation of electric arc at the instant of contact separation caused?

a. Thermionic emission of electrons.
b. Field emission of electrons.
c. Both (a) and (b)
d. None of these.
Answer  Explanation 

ANSWER: Both (a) and (b)

Explanation:
No explanation is available for this question!


6)   The arc resistance depends on which among the following factors?

a. Cross section of the arc.
b. Length of the arc.
c. Degree of ionization
d. All of the above.
Answer  Explanation 

ANSWER: All of the above.

Explanation:
No explanation is available for this question!


7)   What is the advantage of HRC fuses over Rewirable fuses?

a. High speed operation
b. High rupturing capacity
c. No ageing effect.
d. All of the above.
Answer  Explanation 

ANSWER: All of the above.

Explanation:
No explanation is available for this question!


8)   A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9A. What will be the radius of the wire that will blow off at a current of 1A?

a. 0.2 mm
b. 0.18 mm
c. 0.28 mm
d. 0.3 mm
Answer  Explanation 

ANSWER: 0.18 mm

Explanation:
No explanation is available for this question!


9)   In the following figure, which component ensures the safety of the line from damage?
V Curves For Synchronous Generator


a. Relay
b. Circuit breaker
c. Bus bar
d. Current transformer
Answer  Explanation 

ANSWER: Relay

Explanation:
No explanation is available for this question!


10)   Which of the following circuit breakers is used for the railway electrification?

a. Air blast circuit breaker
b. SF6 circuit breaker
c. Bulk oil circuit breaker
d. Minimum oil circuit breaker
Answer  Explanation 

ANSWER: Air blast circuit breaker

Explanation:
No explanation is available for this question!


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