Switchgear and Protection MCQs | Switchgear and Protection Short Questions and Answers

Questions
41 The main function of a fuse is to
A protect the line
B open the circuit
C protect the appliance
D prevent excessive currents

Answer: prevent excessive currents
42 Arc in a circuit behaves as
A a capacitive reactance
B an inductive reactance
C a resistance increasing with voltage rise across the arc
D a resistance decreasing with voltage rise across the arc

Answer: a resistance decreasing with voltage rise across the arc
43 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

Answer: 0.003 sec
44 Wave trap is used to trap waves of
A power frequencies
B higher frequencies entering generator or transformer units
C either of the above
D none of the above

Answer: higher frequencies entering generator or transformer units
45 Bus coupler is very essential in arrangement
A single bus
B double bus, double breaker
C main and transfer bus
D None Of The Above

Answer: main and transfer bus
46 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

Answer: 5 to 10 sec
47 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

Answer: Circuit breaker with SF6 gas
48 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

Answer: transmit large power
49 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

Answer: All Of The Above
50 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

Answer: all of the above
51 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

Answer: in phase with the arc current
52 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

Answer: 100 mega ohms
53 H.R.C. fuses provide best protection against
A overload
B reverse current
C open-circuits
D short-circuits

Answer: short-circuits
54 The delay fuses are used for the protection of ________ .
A motors
B power outlet circuits
C fluorescent lamps
D None Of The Above

Answer: motors
55 Resistance grounding is used for voltage between
A 33kVto66kV
B HkVto33kV
C 3.3kVandllkV
D none of the above

Answer: 3.3kVandllkV
56 Wave trap is used to trap waves of
A power frequencies
B higher frequencies entering generator or transformer units
C either of the above
D all of the above

Answer: higher frequencies entering generator or transformer units
57 Ungrounded neutral transmission system is not recommended because of system
A insulation being overstressed due to over voltages
B insulation overstress may lead to failure and subsequent phase to phase faults
C being inadequately protected against ground fault
D all of the above

Answer: all of the above
58 For the protection of power station buildings against direct strokes the requirements are
A interception
B interception and conduction
C interception, conduction and dissipation
D interception, conduction, dissipation and reflection

Answer: interception, conduction and dissipation
59 The interaction between a transmission line and communication line is minimized by
A transposing transmission as well as communication lines
B increasing the height of the trans-mission line tower
C increasing the distance between the two lines
D all of the above

Answer: all of the above
60 Which of the following statements is incorrect?
A Station batteries are used to operate relay only
B The lightning arresters are basically surge diverters
C An impedance relay has maximum fault current when fault occurs near the relay
D A high speed relay has an operation of 1 to 2 cycles

Answer: Station batteries are used to operate relay only
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