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Objective Switchgear Protections Questions and Answers pdf

71.    The relay with inverse time characteristic will operate within
(a) 1.5 sec 
(b) 5 to 10 sec
(c) 5 to 20 sec 
(d) 20 to 30 sec
(e) none of the above
Ans: b

72.    The single phasing relays are used for the protection of
(a)    single phase motors only
(b)    two phase motors only
(c)    two single phase motors running in parallel
(d)    three phase motors
Ans: d

73.    Which of the following devices will receive voltage surge first travelling on the transmission line ?
(a)    Lightning arresters
(b)    Relays
(c)    Step-down transformer
(d)    Switchgear
Ans: a

74.    Which of the following parameter can be neglected for a short line ?
(a) Inductance 
(b) Capacitance
(c) Resistance 
(d) Reactance
Ans: b

75.    Series reactors should have
(a) low resistance
(b) high resistance
(c) low impedance
(d) high impedance
Ans: a

76.    Which of the following circuit breakers has high reliability and minimum maintenance ?
(a)     Air blast circuit breakers
(b)     Circuit breaker with SF6 gas
(c)    Vacuum circuit breakers
(d)    Oil circuit breakers
Ans: b

77.    Arc in a circuit breaker is interrupted at
(a)     zero current
(b)    maximum current
(c)    minimum voltage
(d)    maximum voltage
Ans: a

78    transmission line has reflection coefficient as one.
(a) Open circuit   
(b) Short-circuit
(e) Long
(d) None of the above
Ans: a

79.    What will be the reflection co-efficient of the wave of load connected to transmission line if surge impedance of the line is equal to load ?
(a)     Zero 
(b)     Unity
(c)    Infinity
(d)    None of the above
Ans: a

80.    The inverse definite mean time relays are used for over current and earth fault protection of transformer against
(a)     heavy loads
(b)     internal short-circuits
(c)    external short-circuits
(d)    all of the above
Ans: b
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