switchgear and protection Mcqs
101. The arc voltage produced in A.C. circuit breaker is always_____________?
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A. none of the above

B. in phase with the arc current

C. lagging the arc current by 90?

D. leading the arc current by 90

102. A differential relay measures the vector difference between_________________?
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A. two currents

B. two or more similar electrical quantities

C. two voltages

D. none of the above

103. Wave trap is used to trap waves of__________________?
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A. power frequencies

B. higher frequencies entering generator or transformer units

C. either of the above

D. none of the above

104. The time of closing the cycle, in modern circuit breakers is_____________?
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A. 0.10 sec

B. none of the above

C. 0.003 sec

D. 0.01 sec

E. 0.001 sec

105. The torque produced in induction type relay (shaded pole structure) is_____________?
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A. inversely proportional to the current

B. proportional to the current

C. proportional to square of the current

D. inversely proportional to the square of the current
106. An isolator is installed_____________?
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A. to operate the relay of circuit breaker

B. as a substitute for circuit breaker

C. always independent of the position of circuit breaker

D. generally on both sides of a circuit breaker