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Friday, 11 November 2016

Switchgear - Multiple Choice Questions

Switchgear - Multiple Choice Questions Points : switchgear blanks, switchgear multiple choice questions and answers, electrical objective type question answers, mcqs 1. A circuit breaker performs the function of
(i) detection only
(ii) circuit interruption only
(iii) both detection and circuit interruption
(iv) none of above

2. An arc is produced when the switch of a high-voltage and large-current circuit is
(i) opened
(ii) closed
(iii) opened or closed
(iv) none of above

3. A fuse performs
(i) detection function only
(ii) circuit interruption function only
(iii) both detection and interruption functions
(iv) none of above

4. A circuit breaker is a
(i) current controlling device
(ii) circuit interrupting device
(iii) current limiting device
(iv) none of above

5. When the circuit breaker operates under fault conditions, the greatest noise is produced in
(i) oil circuit breaker
(ii) air-blast circuit breaker
(iii) vacuum circuit breaker
(iv) SF6 circuit breaker

6. Under normal operating conditions, the contacts of the circuit breaker remain
(i) closed
(ii) open
(iii) semi-closed
(iv) none of above

7. The device that detects the fault in a power system is
(i) circuit breaker
(ii) isolator
(iii) relay
(iv) none of above

8. Current chopping mainly occurs in
(i) air-blast circuit breaker
(ii) oil circuit breaker
(iii) SF6 circuit breaker
(iv) vacuum circuit breaker

9. In a bulk oil circuit breaker, the oil actually used for arc extinction is about
(i) 60% of total
(ii) 40% of total
(iii) 90% of total
(iv) 10% of total

10. When a fault occurs in a power system, the circuit breaker
(i) opens automatically
(ii) is opened manually
(iii) is opened by remote control
(iv) none of above

11. If the length of the arc in a circuit breaker increases, its resistance.
(i) decreases
(ii) increases
(iii) remains same
(iv) none of above

12. In low oil circuit breaker, the oil performs the function of
(i) insulation only
(ii) arc extinction only
(iii) both insulation and are extinction
(iv) none of above

13. A fuse is a
(i) protective device
(ii) current limiting device
(iii) current controlling device
(iv) none of above

14. A circuit breaker must perform the duty of
(i) opening the faulty circuit and breaking the fault current
(ii) being closed on to a fault
(iii) carrying fault current for a short time
(iv) all above

15. The normal practice to specify the making current of a circuit breaker is in terms of
(i) peak value
(ii) r.m.s. value
(iii) average value
(iv) none of above

16. A circuit breaker is able to open under
(i) no load conditions
(ii) load conditions
(iii) fault conditions
(iv) all of above

17. An isolator is designed to open a circuit under
(i) full load
(ii) normal conditions
(iii) no load
(iv) none of above

18. A 1 VA or a 2 VA relay is more sensitive.
(i) 1 VA relay
(ii) 2 VA relay
(iii) both equally sensitive
(iv) none of above

19. For the same power, the least size is of
(i) oil circuit breaker
(ii) air-blast circuit breaker
(iii) vacuum circuit breaker
(iv) SF6 circuit breaker

20. Most of the relays on service on electric power system are
(i) electronic relays
(ii) thermal relays
(iii) electro-mechanical relays
(iv) none of above

21. As compared to a circuit breaker, the breaking capacity of a fuse is
(i) less
(ii) more
(iii) about the same
(iv) none of above

22. The speed of circuit interruption in forced blast circuit breaker is
(i) slow
(ii) medium
(iii) fast
(iv) none of above

23. The normal current in a power line is 100 A. Suddenly, the line current becomes 150 A. One can expect
(i) open-circuit fault
(ii) short-circuit fault
(iii) overloaded condition
(iv) none of above

24. The operating time of a circuit breaker is
(i) 0.002 sec.
(ii) 0.05 sec.
(iii) 0.2 sec.
(iv) 0.001 sec.

25. Fuses are used in circuits where
(i) frequent operations are not expected
(ii) frequent operations are expected
(iii) both (i) and (ii)
(iv) none of above

25. A low oil circuit breaker has the advantage over bulk oil circuit breaker in that it
(i) requires less quantity of oil
(ii) requires less space
(iii) reduces risk of fire
(iv) all above

27. Capacitive current breaking results in
(i) short circuit
(ii) open circuit
(iii) voltage surges
(iv) none of above

28. The relay operating coil is supplied through
(i) fuse
(ii) current transformer
(iii) power transformer
(iv) none of above

29. A fuse element is generally made of
(i) steel
(ii) silver
(iii) brass
(iv) iron

30. The time-current graph of a fuse
(i) has linear characteristic
(ii) is a circle
(iii) has inverse characteristic
(iv) none of above

31. The rated secondary current of current transformer for relays is generally
(i) 10A
(ii) 5 k
(iii) 20 A
(iv) 30 A

32. Induction relays are used for
(i) a.c. quantities
(ii) d.c. quantities
(iii) both a.c. and d.c. quantities
(iv) none of above

33. Back-up protection is generally used for protection against
(i) open-circuit faults only
(ii) short-circuit faults only
(iii) both open and short-circuit faults
(iv) none of above

34. The current rating of a fuse is 5A. The fusing current will be
(i) 5A
(ii) 2.SA
(iii) 1 A
(iv) more than 5A

35. The operating time of a fuse is about
(i) 0.002 sec
(ii) 1 sec.
(iii) 0.8 sec.
(iv) 1.5 sec.

36. The advantage of high-rupturing capacity (H.R.C.) cartridge fuse is that it
(i) does not deteriorate with age
(ii) has high speed of operation
(iii) is quite cheap
(iv) all above

37. A fuse should have
(i) low melting point
(ii) high conductivity
(iii) low cost
(iv) all above

38. The present trend is to use silver for fuse element because it
(i) is free from oxidation
(ii) does not deteriorate when used in dry air
(iii) has high conductivity
(iv) all above

39. For a semi-enclosed fuse employing copper as the fuse element, the fusing factor ,
(i) 0.5
(ii) about 2
(iii) 5
(iv) 10

40. As compared to a circuit breaker, a fuse
(i) is cheaper
(ii) is costlier
(iii) has about the same cost
(iv) none of above

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