1) Refer to the following facts to answer the question
A 50 Hz, 11 kV, 3 phase alternator with earthed neutral having a reactance of 3 ohms per phase and is connected to a bus bar through a circuit breaker, if the distributed capacitance upto CB between the phase and neutral is 0.01 μ F.
What is the peak re striking voltage?
a. 18.36 kV
b. 17.96 kV
c. 15.96 kV
d. 12.65 kV
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Answer
Explanation
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ANSWER: 17.96 kV
Explanation:
No explanation is available for this question!
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2) What is / are the main disadvantage / s of using oil as the quenching medium in the circuit breakers?
a. Need periodical replacement.
b. Risk of formation of explosive mixture with air.
c. Possibility of causing fire hazards.
d. All of the above.
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Answer
Explanation
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ANSWER: All of the above.
Explanation:
No explanation is available for this question!
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3) What is the major cause of the failure of the circuit breaker?
a. Trip circuit open
b. Trip latch defective
c. Spring defective
d. All of these
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Answer
Explanation
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ANSWER: All of these
Explanation:
No explanation is available for this question!
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4) 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.
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Answer
Explanation
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ANSWER: 1 to 2 cycles.
Explanation:
No explanation is available for this question!
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5) What is switchgear?
a. An apparatus used for switching, controlling and protecting the electrical circuits and equipments.
b. It detects the faults only.
c. It corrects the faults only.
d. All of the above.
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Answer
Explanation
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ANSWER: All of the above.
Explanation:
No explanation is available for this question!
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6) Circuit breakers usually operate under
a. Steady short circuit current
b. Sub transient state of short circuit current
c. Transient state of short circuit current
d. None of these
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Answer
Explanation
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ANSWER: Sub transient state of short circuit current
Explanation:
No explanation is available for this question!
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7) What should be the value of fusing factor?
a. Equal to zero
b. Equal to one
c. Less than one
d. More than one
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Answer
Explanation
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ANSWER: Less than one
Explanation:
No explanation is available for this question!
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8) SF6 is which type of gas?
a. Electro positive
b. Electro negative
c. Both (a) and (b)
d. None of these
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Answer
Explanation
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ANSWER: Both (a) and (b)
Explanation:
No explanation is available for this question!
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9) What is the purpose of back up protection?
a. To increase the speed
b. To increase the reach
c. To leave no blind spot
d. To guard against failure of primary
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Answer
Explanation
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ANSWER: To guard against failure of primary
Explanation:
No explanation is available for this question!
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10) 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.
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Answer
Explanation
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ANSWER: Thermal ionisation of gas.
Explanation:
No explanation is available for this question!
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