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switchgear and protection MCQs

Practise focused switchgear and protection questions with marked answers for exam preparation and subject revision.

switchgear and protection Mcqs
1. With which of the following, a circuit breaker must be equipped for remote operation ?
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A. None of the above

B. Shunt trip

C. Time-delay trip

D. All of the above

E. Inverse time trip

2. The single phasing relays are used for the protection of_____________?
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A. two single phase motors running in parallel

B. three phase motors

C. single phase motors only

D. two phase motors only

3. 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 ?
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A. Infinity

B. None of the above

C. Zero

D. Unity

4. Which of the following parameter can be neglected for a short line ?
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A. Resistance

B. Capacitance

C. Inductance

D. Reactance

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

B. thermocouple

C. resistance thermometer

D. pyrometer

6. On which of the following effects of electric current a fuse operates ?
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A. Heating effect

B. Electrostatic effect

C. Photoelectric effect

D. Magnetic effect

7. In order that current should flow without causing excessive heating or voltage drop, the relay contacts should_________________?
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A. be of sufficient size and proper shape

B. be clean and smooth

C. have all above properties

D. have low contact resistance

8. When a transmission line is energized, the wave that propagates on it is____________?
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A. current wave only

B. voltage wave only

C. Both (A) and (B)

D. power factor wave only

9. The main function of a fuse is to_____________?
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A. none of the above

B. protect the line

C. prevent excessive currents

D. protect the appliance

E. open the circuit

10. An efficient and a well designed protective relaying should have_____________?
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A. high speed and selectivity

B. good selectivity and reliability

C. all of the above

D. economy and simplicity

11. Series capacitors are used to_________________?
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A. improve line voltage

B. none of the above

C. compensate for line inductive reactance

D. compensate for line capacitive reactance

12. The arcing contacts in a circuit breaker are made of______________?
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A. aluminium alloy

B. copper tungsten alloy

C. porcelain

D. electrolytic copper

13. The inverse definite mean time relays are used for over current and earth fault protection of transformer against_________________?
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A. heavy loads

B. internal short-circuits

C. all of the above

D. external short-circuits

14. Relays can be designed to respond to changes in________________?
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A. light intensity

B. all above

C. resistance, reactance or impedance

D. voltage and current

E. temperature

15. The fuse blows off by___________?
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A. burning

B. none of the above

C. arcing

D. melting
16. For the protection of power station buildings against direct strokes the requirements are___________?
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A. interception, conduction, dissipation and reflection

B. interception, conduction and dissipation

C. none of the above

D. interception

E. interception and conduction

17. Shunt capacitance is neglected while considering______________?
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A. short transmission line

B. long transmission line

C. medium transmission line

D. medium and long transmission lines

18. Admittance relay is __________ relay?
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A. impedance

B. directional

C. none of the above

D. non-directional

19. In a circuit breaker the basic problem is to________________?
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A. extinguish the arc

B. emit the ionizing electrons

C. transmit large power

D. maintain the arc

20. Air blast circuit breakers for 400 kV power system are designed to operate in_______________?
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A. 100 microsecond

B. 50 millisecond

C. 0.5 sec

D. 0.1 sec

21. In a single bus-bar system there will be complete shut down when____________?
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A. fault occurs on the bus itself

B. fault occurs on neutral line

C. fault occurs with respect to earthing

D. two or more faults occur simultaneously

22. Which of the following is the least expensive protection for overcurrent is low voltage system ?
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A. Isolator

B. Air break circuit breaker

C. None of the above

D. Rewireable fuse

E. Oil circuit breaker

23. D.C. shunt relays are made of_____________?
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A. many turns of thin wire

B. few turns of thick wire

C. many turns of thick wire

D. few turns of thin wire

24. Which of the following medium is employed for extinction of arc in air circuit breaker?
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A. Oil

B. SF6

C. Air

D. Water

25. Ionization in circuit breaker is facilitated by___________?
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A. increase of mean free path

B. all of the above

C. increasing field strength

D. high temperature

26. The power loss is an important factor for the design of_______________?
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A. motor

B. generator

C. transmission line

D. feeder

27. The ground wire should not be smaller than No _________ copper
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A. 6

B. 2

C. 4

D. 10
28. If the fault occurs near the impedance relay, the VII ratio will be____________?
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A. higher than that of if fault occurs away from the relay

B. constant for all distances

C. none of the above

D. lower than that of if fault occurs away from the relay
29. A transmission line is protected by_____________?
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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

30. Arc in a circuit breaker is interrupted at___________?
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A. zero current

B. minimum voltage

C. maximum voltage

D. maximum current

31. The under voltage relay can be used for______________?
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A. motors

B. transformers

C. busbars

D. all of the above

E. generators

32. For which of the following protection from negative sequence currents is provided ?
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A. Transmission line

B. Transformers

C. Generators

D. Motors

33. To limit short-circuit current in a power system are used______________?
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A. earth wires

B. reactors

C. isolators

D. H.R.C. fuses

34. The current zero interruption, in oil and air blast circuit breakers, is achieved by____________?
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A. lengthening of the gap

B. cooling and blast effect

C. both (A) and (B)

D. deionizing the oil with forced air

E. none of the above

35. To protect most of the electrical equipment handling low power, the types of relays used are______________?
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A. thermocouple

B. electronic and bimetallic

C. both (A) and (B)

D. none of the above

36. Resistance grounding is used for voltage between_________________?
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A. 33kVto66kV

B. 3.3kVandllkV

C. HkVto33kV

D. none of the above

37. A thermal protection switch can protect against_____________?
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A. temperature

B. overload

C. short-circuit

D. over voltage

38. By which of the following methods major portion of the heat generated in a H.R.C. fuse is dissipated ?
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A. Radiation

B. All of the above

C. Conduction

D. Convection

39. Burden of a protective relay is the power______________?
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A. none of the above

B. required to operate the circuit breaker

C. absorbed by the circuit of relay

D. developed by the relay circuit

40. Circuit breakers are essentially______________?
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A. any of the above

B. transformers to isolate the two systems

C. arc extinguishers

D. circuits to break the system

E. current carrying contacts called electrodes
41. Fault diverters are basically____________?
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A. circuit breakers

B. fuses

C. relays

D. fast switches
42. When a wave propagates on a transmission line, it suffers reflection several times at_____________?
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A. tapping

B. sending end

C. load end

D. sending and other end

E. all of the above

43. Overload relays are of_______________type
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A. electromagnetic

B. all above

C. solid state

D. induction

E. thermal

44. The current zero interruption, in oil and air blast circuit breakers, is achieved by_______________?
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A. lengthening of the gap

B. cooling and blast effect

C. both A. and B

D. deionizing the oil with forced air

E. none of the above

45. SF6 gas______________?
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A. none of the above

B. is lighter than air

C. is yellow in colour

D. is nontoxic

E. has pungent small

46. H.R.C. fuse, as compared to a rewirable fuse, has_________________?
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A. high speed of operation

B. all of the above

C. no ageing effect

D. high rupturing capacity

47. Directional relays are based on flow of____________?
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A. voltage wave

B. all of the above

C. current

D. power
48. A switchgear is device used for_____________?
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A. switching an electrical circuit 111.

B. interrupting an electrical circuit

C. switching and controlling an electrical circuit

D. switching, controlling and protecting the electrical circuit and equipment
49. The relay operating speed depends upon_________________?
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A. all of the above

B. armature core air gap

C. the spring tension

D. the rate of flux built up

50. Protective relays are devices that detect abnormal conditions in electrical circuits by measuring_____________?
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A. none of the above

B. voltage during abnormal condition

C. constantly the electrical quantities which differ during normal and abnormal conditions

D. current during abnormal condition