switchgear and protection MCQs – Page 2

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

switchgear and protection Mcqs

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

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