Power System MCQ With Answers PDF

21. The fault(s) which are likely to occur in cables is/are

(a) breakdown of cable insulation.
(b) cross- or short-circuit fault.
(c) open-circuit fault.
(d) all of the above.

22. The lead sheath of the cable may get damaged due to

(a) mechanical injury.
(b) crystallization of lead through vibrations.
(c) chemical action with impurities present in the soil when buried in earth.
(d) any of the above.

23. The cables should not be operated too hot otherwise

(a) expansion of oil may cause sheath to burst.
(b) the oil may lose its viscosity and it may start drawing off from higher levels.
(c) unequal expansion may create voids in the insulation leading to ionization.
(d) rapid increase in dielectric losses with temperature may cause thermal instability.
(e) all of the above.

24. The breakdown voltage of a cable depends upon

(a) presence of moisture.
(b) operating temperature.
(c) time of application of the voltage.
(d) all of the above.

25. Breakdown of cable insulation may occur due to

(a) thermal instability.
(b) puncture.
(c) tracking.
(d) any of the above.

26. Fiber-optic cables are used in power system applications mainly for

(a) SCADA.
(b) communication between power station and substation.
(c) communication between power station and load control center.
(c) all of the above.

27. The main criterion for selection of the size of a distributor for a radial distribution system is

(a) voltage drop.
(b) corona loss.
(c) temperature rise.
(d) capital cost.

28. The distribution systems in India are mostly

(a) radial.
(b) parallel.
(c) network.
(d) either (b) or (c).

29. Why is a ring main distribution system preferred to a radial system?

1. Voltage drop in the feeder is less.
2. Power factor is higher.
3. Supply is more reliable.

Select the correct answer using the code given below:
(a) 1 and 2 only.
(b) 2 and 3 only.
(c) 1 and 3 only.
(d) 1, 2 and 3.

30. As per electricity regulations in India the maximum permissible voltage change at consumer premises should be

(a) ±5% of declared voltage.
(b) ±6% of declared voltage.
(c) ±10% of declared voltage.
(d) ±12% of declared voltage.

31. The cost of material used in a distribution circuit per kVA of distributed power varies as

(a) square of linear dimensions of supply area.
(b) directly according to (supply area)².
(c) cube of linear dimensions of supply area.
(d) none of the above.

32. An approximate formula for loss factor in a distribution system is

(a) Loss factor = 0.3 x load factor + 0.7 (load factor)² .
(b) Loss factor = 0.5 (load factor).
(c) Loss factor = load factor.
(d) Loss factor = 0.7 x load factor + 0.3 (load factor)².

33 In a distribution system, which of the following items shares the major cost?

(a) Conductors.
(b) Earthing system.
(c) Distribution transformer.
(d) Insulators.

34. The distributors in residential areas are

(a) single phase, two-wire.
(b) three phase, three-wire.
(c) three phase, four-wire.
(d) two phase, four-wire.

35. The loads on 3-phase, 4-wire distributors are usually

(a) balanced.
(b) unbalanced.
(c) either of above.
(d) none of above.

36. A uniformly loaded DC distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, the maximum voltage drop will be

(a) one-fourth.
(b) one-half.
(c) one-third.
(d) one-sixth.

37. The null point of a uniformly loaded distributor fed at equal voltage at both ends lies at

(a) midpoint.
(b) either end.
(c) two-third distance from one end.
(d) one-fourth distance from one end.

38. A uniformly loaded dc distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, the drop at the mid-point will be

(a) one-fourth.
(b) one-half.
(c) one-third.
(d) one-sixth.

39. In a dc 3-wire distributor using balancers and having unequal loads on the two sides

(a) both balancers operate as generators.
(b) both balancers operate as motors.
(c) balancer connected to lightly loaded side operates as a generator.
(d) balancer connected to heavily loaded side operates as a generator.

40. In a dc 3-wire distribution system, balancer fields are cross-connected in order to

(a) equalize voltages on +ve and -ve outers.
(b) boost the generated voltage.
(c) make both machines operated as unloaded motors.
(d) all of the above.