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Multiple Choice Question (MCQ) of C. Power System Protection page-5


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41. For L – G fault, all networks are in

a) Series
b) Parallel
c) Star
d) Delta

Ans: (a)

42. Negative sequence component of a voltage is equal to

a) Zero sequence component
b) Positive sequence component
c) Complex conjugate of the positive sequence component
d) Complex conjugate of the zero sequence component

Ans: (c)

43. 3ɸ, short circuit current will be

a) Infinity at infinite time
b) Maximum at infinite time
c) Zero at infinite time
d) 10 mA at infinite time

Ans: (c)

44. In a generator, 3ɸ, short circuit current is limited by

a) Transient reactance
b) Synchronous reactance
c) Sub-tranisent reactance
d) All of these

Ans: (b)

45. Reactance used in case of generator is

a) Synchronous reactance
b) Transient reactance
c) Sub-tranisent reactance
d) All of these

Ans: (d)

46. Power system uses

a) Suppression coils
b) Current limiting resistors
c) Compensation reactors
d) All of these

Ans: (d)

47.Surge impedance of 400 W implies

a) Open circuit impedance of 400 Ω
b) Line can be theoretically loaded upto 400 Ω
c) Line can be practically loaded upto 400 Ω
d) Short circuit impedance of 400 Ω

Ans: (b)

48. System frequency and system voltage respectively control

a) Active power, reactive power
b) Active power, active power
c) Reactive power, reactive power
d) Reactive power, active power

Ans: (a)

49. Impedance relays can be used for

a) Phase faults only
b) Earth fault only
c) Both phase and earth faults
d) None of these

Ans: (c)

50. A large-size alternator is protected against overloads by providing

a) Overcurrent relays.
b) Temperature sensitive relays.
c) A combination of (a) and (b).
d) A combination of (b) and (c).

Ans: (b)

51. Most suitable C.B. for short line fault without switching resistor is

a) Air blast C.B.
b) M.O.C.B.
c) SF6 Breaker
d) None of the above

Ans: (c)

52. If a combination of HRC fuse and circuit breaker is used, the C.B. operates for

a) Low overload currents.
b) Short circuit current.
c) Under all abnormal current.
d) The combination is never used in practice.

Ans: (a)


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