881. The current zero interruption, in oil and air blast circuit breakers, is achieved by____________?
A. lengthening of the gap
B. cooling and blast effect
C. both (A) and (B)
D. deionizing the oil with forced air
E. none of the above
882. Burden of a protective relay is the power______________?
A. required to operate the circuit breaker
B. absorbed by the circuit of relay
C. developed by the relay circuit
D. none of the above
883. When a transmission line is energized, the wave that propagates on it is____________?
A. current wave only
B. voltage wave only
C. Both (A) and (B)
D. power factor wave only
884. A transmission line is protected by_____________?
A. inrush protection
B. distance protection
C. time graded and current graded over current protection
D. both (B) and (C)
E. none of the above
885. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
A. have low contact resistance
B. be clean and smooth
C. be of sufficient size and proper shape
D. have all above properties
886. Circuit breakers are essentially______________?
A. current carrying contacts called electrodes
B. arc extinguishers
C. circuits to break the system
D. transformers to isolate the two systems
E. any of the above
887. D.C. shunt relays are made of_____________?
A. few turns of thin wire
B. few turns of thick wire
C. many turns of thin wire
D. many turns of thick wire
888. Circuit breakers usually operate under______________?
A. transient state of short-circuit current
B. sub-transient state of short-circuit current
C. steady state of short-circuit current
D. after D.C. component has ceased
889. Air blast circuit breaker is used for_____________?
A. over currents
B. short duty
C. intermittant duty
D. repeated duty
890. Directional relays are based on flow of____________?
A. power
B. current
C. voltage wave
D. all of the above
NOTE
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