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Electrical Engineering Objective Questions { Power System }

43. Breakdown of insulation of a cable can be avoided economically by the use of
A. insulating material with different dielectric
B. intersheath
C. both (a) and (b) above
D. none of these

44. The dielectric strength of air at 25?C and 76 cm of mercury is
A. 2.11 kV rms/cm
B. 21.1 kV rms/cm
C. 211 kV nns/cm
D. 2110 kV nns/cm

45. Bulk oil circuit breaker is suitable for voltages upto
A. 4 kV
B. 10 kV
C. 25 kV
D. 36 kV

46. For remote operation, circuit breaker must be equipped with
A. shunt trip
B. inverse shunt trip
C. time delay trip
D. both B and C above

47. The following medium is employed for extinction of arc in air break circuit breakers?
A. oil
B. air
C. water
D. none of these

48. Which of the following circuit breakers takes minimum time for installation?
A. bulk oil circuit breaker
B. minimum oil circuit breaker
C. air blast circuit breaker
D. SF6 circuit breaker

49. In oil and air blast circuit breakers, the current zero interruption is attained by
A. lengthening of arc
B. cooling and blast effect
C. deionizing the oil with forced air
D. both A and B above

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