Circuit Breakers MCQs

51. In a circuit breaker……..

1. The current chopping is associated with low inductive current
2. The current chopping is associated with the low inductive current before its natural zero
3. The current chopping gives rise to low voltage
4. The current chopping gives rise to high voltage cause the restriking of arc

52. In a circuit breaker

1. Both restriking and recovery voltages are transient in nature
2. Both restriking and recovery voltages are RMS in nature
3. Restriking voltage is transient while recovery voltage is RMS in nature
4. Recovery voltage is transient while restriking voltage is RMS in nature

53. The rate of rise of restriking voltage in a circuit breaker depends upon the

1. Both on the inductance and capacitance of the system
2. Type of circuit breaker
3. Inductance of the system only
4. Capacitance of the system only

54. Temperature of the generated heat in the maximum oil circuit breaker is

1. 550 °C
2. 2500 °C
3. 5000 °C
4. 10000 °C

55. When using air blast circuit breaker, current chopping is a phenomenon which is observed, when

1. a long overhead line is Switched off.
2. a bank of capacitors is switched off.
3. a transformer on no load is switched off.
4. a heavy load is switched off.

56. In a Circuit breaker, the re-striking voltage is measured in ……….

1. RMS value
2. Peak value
3. Instantaneous value
4. Average value

57. There will be voltage across the gap in circuit breakers when ……….

1. R = ∞
2. R = 0
3. $R<\frac{1}{2}\sqrt{\frac{L}{C}}$
4. $R=\frac{1}{2}\sqrt{\frac{L}{C}}$

58. For extra high voltage lines, which circuit breaker is used?

1. Bulk oil circuit breaker
2. Vacuum circuit breaker
3. Minimum oil circuit breaker
4. SF₆ circuit breaker

59. For average values of load current, current chopping occurs more frequently in

1. ACB’s
2. SF₆ CB’s
3. VCB’s
4. OCB’s

60. An isolator is used in series with Air blast Circuit Breaker employed at UHV lines because

1. gap between CB contacts is small so an isolator is used to switch off voltage
2. gap between CB poles the use of isolator
3. CB life is enhanced with the use of isolator
4. current to be interrupted will be large.