Latest Switchgear Protections Multiple choice Questions and Answers pdf

31.    Ionization in circuit breaker is facilitated by
(a)     high temperature
(b)     increase of mean free path
(c)    increasing field strength
(d)    all of the above
Ans: d

32.    In a circuit breaker the basic problem is to
(a)     maintain the arc
(b)     extinguish the arc
(c)    transmit large power
(d)    emit the ionizing electrons
Ans: c

33.    Overheating of relay contacts or contact born out is due to
(a)    slow making and breaking of load circuit contacts
(b)    foreign matter on the contact surface
(c)    too low contact pressure
(d)    all of the above
Ans: d

34.    Interruption of large currents by relay requires
(a)    arc suppressing blow out coils
(b)    wide separation of the opened contacts
(c)    high speed opening of contacts
(d)    all of the above
Ans: d

35.    Shunt capacitance is neglected while considering
(a)     short transmission line
(b)    medium transmission line
(c)    long transmission line
(d)    medium and long transmission lines
Ans: a

36.    The arc voltage produced in A.C. circuit breaker is always
(a)     in phase with the arc current
(b)     lagging the arc current by 90"
(c)    leading the arc current by 90°
(d)    none of the above
Ans: a

37.    The time of closing the cycle, in modern circuit breakers is
(a) 0.003 sec
(b) 0.001 sec
(c) 0.01 sec
(d) 0.10 sec
(e) none of the above
Ans: a

38.    Insulation resistance of high voltage circuit breakers is more than
(a) 1 mega ohms 
(b) 10 mega ohms
(c) 100 mega ohms
(d) 500 mega ohms
Ans: c

39.    H.R.C. fuses provide best protection against
(a) overload
(b) reverse current
(c) open-circuits  
(d) short-circuits
Ans: d

40.   The ground wire should not be smaller than No ______ copper.
(a) 2
(b) 4
(c) 6
(d) 10
Ans: d

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