Quiznetik

Switch Gear and Protection | Set 2

1. Oil switches are employed for

Correct : C. high voltages and large currents circuits

2. A switchgear is device used for

Correct : D. switching, controlling and protecting the electrical circuit and equipment

3. The fuse wire, in D.C. circuits, is inserted in

Correct : C. both (a) and (b)

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

Correct : C. Conduction

5. A short-circuit is identified by

Correct : B. heavy current flow

6. The information to the circuit breaker under fault conditions is provided by

Correct : A. relay

7. To limit short-circuit current in a power system are used.

Correct : D. reactors

8. A balanced 3-phase system consists of

Correct : B. positive sequence currents only

9. In a single bus-bar system there will be complete shut down when

Correct : A. fault occurs on the bus itself

10. Which device is used for protection of equipment from from damage caused by overload or short circuit?

Correct : B. Circuit Breaker

11. Isolator in substation is open under ------------- condition?

Correct : A. No load

12. Earthling switch is used for

Correct : D. all of the above

13. If the time of operating of a relay for unity TMS is 10secs., the time of operation for 0.5 TMS will be

Correct : B. 5 secs.

14. A fault is more severe from the view point of RRRV if is a

Correct : A. Short line fault.

15. A reactance relay is

Correct : B. Directional restrained over-current relay.

16. For measuring positive, negative and zero sequence voltages in a system, the reference is taken as

Correct : D. None of the above.

17. Positive, negative and zero sequence impedances of a solidly grounded system under steady state condition always follow the relations

Correct : C. Z0>Z4>Z2

18. Phase comparators in case of static relays and electro-mechanical relays normally are

Correct : B. Cosine and sine comparators respectively.

19. For reducing tower footing resistance it is better to use

Correct : C. Ground rod and counterpoise only.

20. Rate of rise of restriking voltage depends

Correct : D. Inductance and capacitance of the system

21. What is the purpose of back up protection?

Correct : D. To guard against failure of primary

22. What is the actuating quantity for the relays?

Correct : D. All of these

23. Protective relays can be designed to respond to

Correct : D. All of these

24. On what factor does the operating speed of the relay depend upon?

Correct : D. All of these

25. What does the third part consist of?

Correct : C. Tripping circuit.

26. Which component ensures the safety of the line from damage?

Correct : A. Relay

27. The tripping circuit is_

Correct : C. either AC or DC

28. Plug setting of a electromagnetic relay can be altered by varying

Correct : A. Number of ampere turns

29. the most efficient torque producing actuating structure for the induction type relays is

Correct : C. Induction cup structure

30. If the power factor is zero, the active recovery voltage will be

Correct : D. Maximum.

31. Which of the following is not a part of the circuit breaker?

Correct : C. Conservator

32. Which of the following circuit breaker will produce the least arc energy?

Correct : B. Air blast circuit breaker

33. For a circuit breaker 'break time' is

Correct : C. Opening time + arc duration + resistor current duration.

34. The breaking capacity of a circuit breaker in MVA (3 phase) is given by

Correct : D. (3)1/2x rated service voltage x rated symmetrical current.

35. Which relay is used for feeders?

Correct : B. Translay relay

36. Which of the following relays is used on transformers?

Correct : A. Buchholz relay

37. MHO relay is used for

Correct : C. Transmission lines

38. Merz-price protection is used on

Correct : D. Generators.

39. The values of fault current depend on

Correct : C. Both (A) and (B) above

40. The advantage of neutral earthling is

Correct : D. all of the above.

41. The over-voltage surges in power systems may be caused by

Correct : D. Any of the above.

42. The protection against over-voltage due to lightening is provided by

Correct : D. Any of the above.

43. Which of the following is a conducting medium for electric current ?

Correct : D. Plasma.

44. In circuit-breakers the contact space is ionized by

Correct : D. Any of the above.

45. Which of the following are air-break switching devices ?

Correct : D. All of the above.

46. Which of the following statement about SF6 gas is incorrect?

Correct : D. It has dark yellow color.

47. SF6 gas is transported in

Correct : B. Liquid form in cylinders

48. duringarc extinction SF6 gas

Correct : B. Decomposes into SF4and SF2

49. Dielectric strength of SF6 is

Correct : B. less than that of oil used in OCB

50. Which of the following is the demerit of SF6 circuit breakers?

Correct : D. All of the above.