Protective relays are devices that detect abnormal conditions in electrical circuits by measuring_____________?

current during abnormal condition

voltage during abnormal condition

constantly the electrical quantities which differ during normal and abnormal conditions

Overheating of relay contacts or contact born out is due to_______________?

slow making and breaking of load circuit contacts

foreign matter on the contact surface

Overfluxing protection is recommended for_____________?

auto-transformer of the power plant

generator transformer of the power plant

auto-transformer of the power plant

station transformer of the power plant

Oil switches are employed for_____________?

high voltages and large currents circuits

Large internal faults are protected by_______________?

merz price percentage differential protection

horn gaps and temperature relays

earth fault and positive sequence relays

Interruption of large currents by relay requires______________?

wide separation of the opened contacts

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?

be of sufficient size and proper shape

In a single bus-bar system there will be complete shut down when____________?

two or more faults occur simultaneously

fault occurs with respect to earthing

If the fault occurs near the impedance relay, the VII ratio will be____________?

higher than that of if fault occurs away from the relay

lower than that of if fault occurs away from the relay

higher than that of if fault occurs away from the relay

For the protection of power station buildings against direct strokes the requirements are___________?

interception, conduction, dissipation and reflection

interception, conduction and dissipation

interception, conduction, dissipation and reflection

Circuit breakers usually operate under______________?

sub-transient state of short-circuit current

transient state of short-circuit current

sub-transient state of short-circuit current

steady state of short-circuit current

after D.C. component has ceased

Circuit breakers are essentially______________?

current carrying contacts called electrodes

transformers to isolate the two systems

Circuit breakers are essentially____________?

current carrying contacts called electrodes

transformers to isolate the two systems

Burden of a protective relay is the power______________?

required to operate the circuit breaker

absorbed by the circuit of relay

Arc in a circuit behaves as_______________?

a resistance increasing with voltage rise across the arc

a resistance decreasing with voltage rise across the arc

An isolator is installed_____________?

to operate the relay of circuit breaker

as a substitute for circuit breaker

always independent of the position of circuit breaker

generally on both sides of a circuit breaker

An efficient and a well designed protective relaying should have_____________?

good selectivity and reliability

A.C. network analyser is used to solve problems of_______________?

load flow, short-circuit and stability

A transmission line is protected by_____________?

time graded and current graded over current protection

A switchgear is device used for_____________?

interrupting an electrical circuit

switching an electrical circuit 111.

switching and controlling an electrical circuit

switching, controlling and protecting the electrical circuit and equipment

104 + Mcqs in Switchgear in Electrical Engineering Questions Page 2 McqOptions

51.	Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________
A.	Restriking voltage
B.	Final arc extinction
C.	Rise of voltage
D.	All of the above
Answer» C. Rise of voltage

Discussion

52.	Protective relays are devices that detect abnormal conditions in electrical circuits by measuring_____________?
A.	current during abnormal condition
B.	voltage during abnormal condition
C.	constantly the electrical quantities which differ during normal and abnormal conditions
D.	none of the above
Answer» D. none of the above

Discussion

53.	Protection by fuses is generally not used beyond__________?
A.	20 A
B.	50 A
C.	100 A
D.	200 A
Answer» D. 200 A

Discussion

54.	Overload relays are of_______________type
A.	induction
B.	solid state
C.	thermal
D.	electromagnetic
E.	all above
Answer» F.

Discussion

55.	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» E.

Discussion

56.	Overfluxing protection is recommended for_____________?
A.	distribution transformer
B.	generator transformer of the power plant
C.	auto-transformer of the power plant
D.	station transformer of the power plant
Answer» C. auto-transformer of the power plant

Discussion

57.	Over voltage protection is recommended for______________?
A.	hydro-electric generators
B.	steam turbine generators
C.	gas turbine generators
D.	all of the above
E.	none of the above
Answer» E. none of the above

Discussion

58.	Oil switches are employed for_____________?
A.	low currents circuits
B.	low voltages circuits
C.	high voltages and large currents circuits
D.	all circuits
Answer» D. all circuits

Discussion

59.	Magnetic circuit breaker has ___________ trip action
A.	delayed
B.	instantaneous
C.	both of the above
D.	none of the above
Answer» C. both of the above

Discussion

60.	Large internal faults are protected by_______________?
A.	merz price percentage differential protection
B.	mho and ohm relays
C.	horn gaps and temperature relays
D.	earth fault and positive sequence relays
Answer» B. mho and ohm relays

Discussion

61.	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
Answer» E.

Discussion

62.	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» E.

Discussion

63.	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» D. 500 mega ohms

Discussion

64.	Induction cup relay is operated due to changes in________________?
A.	current
B.	voltage
C.	impedance
D.	all of the above
Answer» E.

Discussion

65.	In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
A.	have low contact resistance
B.	be clean and smooth
C.	be of sufficient size and proper shape
D.	have all above properties
Answer» E.

Discussion

66.	In a single bus-bar system there will be complete shut down when____________?
A.	fault occurs on the bus itself
B.	fault occurs on neutral line
C.	two or more faults occur simultaneously
D.	fault occurs with respect to earthing
Answer» B. fault occurs on neutral line

Discussion

67.	In a short circuit test on a circuit breaker, the following readings were obtained on single frequency transients a. Time to reach the peak re striking voltage - 50μ sec b. The peak re striking voltage, 100 kV what will be the frequency of oscillations?
A.	100 Hz
B.	1,000 Hz
C.	10,000 Hz
D.	10 Hz
Answer» D. 10 Hz

Discussion

68.	In a HRC fuse what is the time between the cut off and the final current zero called?
A.	Pre - arcing time.
B.	Arcing time.
C.	Total operating time.
D.	None of these.
Answer» C. Total operating time.

Discussion

69.	In a circuit breaker, the active recovery voltage depends upon which among these?
A.	Circuit conditions.
B.	Power factor.
C.	Both (a) and (b)
D.	None of the above
Answer» D. None of the above

Discussion

70.	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» D. emit the ionizing electrons

Discussion

71.	If the fault occurs near the impedance relay, the VII ratio will be____________?
A.	constant for all distances
B.	lower than that of if fault occurs away from the relay
C.	higher than that of if fault occurs away from the relay
D.	none of the above
Answer» C. higher than that of if fault occurs away from the relay

Discussion

72.	H.R.C. fuses provide best protection against________________?
A.	overload
B.	reverse current
C.	open-circuits
D.	short-circuits
Answer» E.

Discussion

73.	H.R.C. fuse, as compared to a rewirable fuse, has_________________?
A.	no ageing effect
B.	high speed of operation
C.	high rupturing capacity
D.	all of the above
Answer» E.

Discussion

74.	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
E.	none of the above
Answer» D. interception, conduction, dissipation and reflection

Discussion

75.	For cost and safety, the outdoor substations are installed for voltages above_________________?
A.	11 kV
B.	33 kV
C.	60kV
D.	110kV
Answer» C. 60kV

Discussion

76.	Fault diverters are basically____________?
A.	fuses
B.	relays
C.	fast switches
D.	circuit breakers
Answer» D. circuit breakers

Discussion

77.	Distance relays are generally_____________?
A.	split-phase relays
B.	reactance relays
C.	impedance relays
D.	none of the above
Answer» E.

Discussion

78.	Directional relays are based on flow of____________?
A.	power
B.	current
C.	voltage wave
D.	all of the above
Answer» B. current

Discussion

79.	D.C. shunt relays are made of_____________?
A.	few turns of thin wire
B.	few turns of thick wire
C.	many turns of thin wire
D.	many turns of thick wire
Answer» D. many turns of thick wire

Discussion

80.	Circuit breakers usually operate under______________?
A.	transient state of short-circuit current
B.	sub-transient state of short-circuit current
C.	steady state of short-circuit current
D.	after D.C. component has ceased
Answer» B. sub-transient state of short-circuit current

Discussion

81.	Circuit breakers are essentially______________?
A.	current carrying contacts called electrodes
B.	arc extinguishers
C.	circuits to break the system
D.	transformers to isolate the two systems
E.	any of the above
Answer» B. arc extinguishers

Discussion

82.	Circuit breakers are essentially____________?
A.	current carrying contacts called electrodes
B.	arc extinguishers
C.	circuits to break the system
D.	transformers to isolate the two systems
E.	any of the above
Answer» B. arc extinguishers

Discussion

83.	Bus coupler is very essential in arrangement______________?
A.	single bus
B.	double bus, double breaker
C.	main and transfer bus
D.	all of the above
Answer» D. all of the above

Discussion

84.	Burden of a protective relay is the power______________?
A.	required to operate the circuit breaker
B.	absorbed by the circuit of relay
C.	developed by the relay circuit
D.	none of the above
Answer» C. developed by the relay circuit

Discussion

85.	Arc in a circuit breaker is interrupted at___________?
A.	zero current
B.	maximum current
C.	minimum voltage
D.	maximum voltage
Answer» B. maximum current

Discussion

86.	Arc in a circuit behaves as_______________?
A.	a capackive 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» E.

Discussion

87.	An isolator is installed_____________?
A.	to operate the relay of circuit breaker
B.	as a substitute for circuit breaker
C.	always independent of the position of circuit breaker
D.	generally on both sides of a circuit breaker
Answer» E.

Discussion

88.	An efficient and a well designed protective relaying should have_____________?
A.	good selectivity and reliability
B.	economy and simplicity
C.	high speed and selectivity
D.	all of the above
Answer» E.

Discussion

89.	Air blast circuit breakers for 400 kV power system are designed to operate in_______________?
A.	100 microsecond
B.	50 millisecond
C.	0.5 sec
D.	0.1 sec
Answer» C. 0.5 sec

Discussion

90.	Air blast circuit breaker is used for_____________?
A.	over currents
B.	short duty
C.	intermittant duty
D.	repeated duty
Answer» E.

Discussion

91.	Admittance relay is __________ relay?
A.	impedance
B.	directional
C.	non-directional
D.	none of the above
Answer» C. non-directional

Discussion

92.	A.C. network analyser is used to solve problems of_______________?
A.	load flow
B.	load flow and short-circuit
C.	load flow and stability
D.	load flow, short-circuit and stability
E.	none of the above
Answer» E. none of the above

Discussion

93.	A transmission line is protected by_____________?
A.	inrush protection
B.	distance protection
C.	time graded and current graded over current protection
D.	both (B) and (C)
E.	none of the above
Answer» E. none of the above

Discussion

94.	A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?
A.	35 kA
B.	49 kA
C.	70 kA
D.	89 kA
Answer» E.

Discussion

95.	A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current?
A.	1200 A
B.	3600 A
C.	35 kA
D.	104.8 kA
Answer» D. 104.8 kA

Discussion

96.	A thermal protection switch can protect against_____________?
A.	short-circuit
B.	temperature
C.	overload
D.	over voltage
Answer» D. over voltage

Discussion

97.	A switchgear is device used for_____________?
A.	interrupting an electrical circuit
B.	switching an electrical circuit 111.
C.	switching and controlling an electrical circuit
D.	switching, controlling and protecting the electrical circuit and equipment
Answer» E.

Discussion

98.	A short-circuit is identified by_____________?
A.	no current flow
B.	heavy current flow
C.	voltage drop
D.	voltage rise
Answer» C. voltage drop

Discussion

99.	A _________ is used to measure the stator % winding temperature of the generator?
A.	thermocouple
B.	pyrometer
C.	resistance thermometer
D.	thermometer
Answer» D. thermometer

Discussion

100.	A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9A. What will be the radius of the wire that will blow off at a current of 1A?
A.	0.2 mm
B.	0.18 mm
C.	0.28 mm
D.	0.3 mm
Answer» C. 0.28 mm

Discussion

Explore topic-wise MCQs in Electrical Engineering Questions.

Recovery voltage is the value of rms voltage that reappears across the poles of a circuit breaker before_______________

Protective relays are devices that detect abnormal conditions in electrical circuits by measuring_____________?

Protection by fuses is generally not used beyond__________?

Overload relays are of_______________type

Overheating of relay contacts or contact born out is due to_______________?

Overfluxing protection is recommended for_____________?

Over voltage protection is recommended for______________?

Oil switches are employed for_____________?

Magnetic circuit breaker has ___________ trip action

Large internal faults are protected by_______________?

Ionization in circuit breaker is facilitated by___________?

Interruption of large currents by relay requires______________?

Insulation resistance of high voltage circuit breakers is more than________________?

Induction cup relay is operated due to changes in________________?

In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?

In a single bus-bar system there will be complete shut down when____________?

In a short circuit test on a circuit breaker, the following readings were obtained on single frequency transients a. Time to reach the peak re striking voltage - 50μ sec b. The peak re striking voltage, 100 kV what will be the frequency of oscillations?

In a HRC fuse what is the time between the cut off and the final current zero called?

In a circuit breaker, the active recovery voltage depends upon which among these?

In a circuit breaker the basic problem is to________________?

If the fault occurs near the impedance relay, the VII ratio will be____________?

H.R.C. fuses provide best protection against________________?

H.R.C. fuse, as compared to a rewirable fuse, has_________________?

For the protection of power station buildings against direct strokes the requirements are___________?

For cost and safety, the outdoor substations are installed for voltages above_________________?

Fault diverters are basically____________?

Distance relays are generally_____________?

Directional relays are based on flow of____________?

D.C. shunt relays are made of_____________?

Circuit breakers usually operate under______________?

Circuit breakers are essentially______________?

Circuit breakers are essentially____________?

Bus coupler is very essential in arrangement______________?

Burden of a protective relay is the power______________?

Arc in a circuit breaker is interrupted at___________?

Arc in a circuit behaves as_______________?

An isolator is installed_____________?

An efficient and a well designed protective relaying should have_____________?

Air blast circuit breakers for 400 kV power system are designed to operate in_______________?

Air blast circuit breaker is used for_____________?

Admittance relay is __________ relay?

A.C. network analyser is used to solve problems of_______________?

A transmission line is protected by_____________?

A three phase circuit breaker is rated 2000 MVA, 33 kV. What will be its making current?

A three phase, 33 kV oil circuit breaker is rated 1200 A, 2000 MVA, 3s. What is its symmetrical breaking current?

A thermal protection switch can protect against_____________?

A switchgear is device used for_____________?

A short-circuit is identified by_____________?

A _________ is used to measure the stator % winding temperature of the generator?

A fuse wire of circular cross section has a radius of 0.8mm. The wire blows off at a current of 9A. What will be the radius of the wire that will blow off at a current of 1A?