Electrical engineering practice MCQ : TRANSMISSION AND DISTRIBUTION

Here are some questions related to TRANSMISSION AND DISTRIBUTION, may be helpful for those who want to gain knowledge on electrical engineering or electrical system.

1. By which of the following systems electric power may be transmitted ?

(a) Overhead system

(b) Underground system

(c) Both (a) and (b)

(d) None of the above

Ans: c

2 are the conductors, which connect the consumer's terminals to the distribution

(a) Distributors

(b) Service mains

(c) Feeders

(d) None of the above

Ans: b

3. The underground system cannot be operated above

(a) 440 V (b) 11 kV

(c) 33 kV

(d) 66 kV

Ans: d

4. Overhead system can be designed for operation upto

(a) 11 kV

(b) 33 kV

(c) 66 kV

(d) 400 kV

Ans: c

5. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the

annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as (a) Kelvin's law

(b) Ohm's law

(c) Kirchhoffs law

(d) Faraday's law

(e) none of the above

Ans: a

6. The wooden poles well impregnated with creosite oil or any preservative compound have life

(a) from 2 to 5 years

(b) 10 to 15 years

(c) 25 to 30 years

(d) 60 to 70 years

Ans: c

7. Which of the following materials is not used for transmission and distribution of electrical power ?

(a) Copper

(b) Aluminium

(c) Steel

(d) Tungsten

Ans: d

8. Galvanised steel wire is generally used as

(a) stay wire

(b) earth wire

(c) structural components

(d) all of the above

Ans: d

9. The usual spans with R.C.C. poles are

(a) 40—50 metres

(b) 60—100 metres

(c) 80—100 metres

(d) 300—500 metres

Ans: c

10. The corona is considerably affected by which of the following ?

(a) Size of the conductor

(b) Shape of the conductor

(c) Surface condition of the conductor

(d) All of the aboveAns: d

11. Which of the following are the constants of the transmission lines ?

(a) Resistance

(b) Inductance

(c) Capacitance

(d) All of the above

Ans: d

12. 310 km line is considered as

(a) a long line

(b) a medium line

(c) a short line

(d) any of the aboveAns: a

13. The phenomenon qf rise in voltage at the receiving end of the open-circuited or lightly loaded line is called the

(a) Seeback effect

(b) Ferranti effect

(c) Raman effect

(d) none of the above

Ans: b

14. The square root of the ratio of line impedance and shunt admittance is called the

(a) surge impedance of the line

(b) conductance of the line

(c) regulation of the line

(d) none of the aboveAns: a

15. Which of the following is the demerit of a 'constant voltage transmission system' ?

(a) Increase of short-circuit current of the system

(b) Availability of steady voltage at all loads at the line terminals

(c) Possibility of better protection for the line due to possible use of higher terminal reactances

(d) Improvement of power factor at times of moderate and heavy loads

(e) Possibility of carrying increased power for a given conductor size in case of longdistance heavy power

transmission Ans: a

16. Low voltage cables are meant for use up to

(a) l.lkV

(b) 3.3kV

(c) 6.6kV

(d)llkV

Ans: e

17. The operating voltage of high voltage cables is upto

(a) l.lkV

(b) 3.3kV

(c) 6.6kV

(d)llkV

Ans: d

18. The operating voltage of supertension cables is upto

(a) 3.3 kV

(b) 6.6 kV

(c) 11 kV

(d) 33 kV

Ans: d

19. The operating voltage of extra high tension cables is upto

(a) 6.6 kV

(b) 11 kV

(c) 33 kV

(d) 66 kV

(e) 132 kVAns: d

20. Which of the following methods is used for laying of underground cables ?

(a) Direct laying

(b) Draw-in-system

(c) Solid system

(d) All of the aboveAns: d

21. Which of the following is the source of heat generation in the cables ?

(a) Dielectric losses in cable insulation

(b) losses in the conductor

(c) Losses in the metallic sheathings and armourings (d) All of the above Ans:

22. Due to which of the following reasons the cables should not be operated too hot ?

(a) The oil may loose its viscosity and it may start drawing off from higher levels

(b) Expansion of the oil may cause the sheath to burst



Unequal expansion may create voids in the insulation which will lead to ionization (d) The thermal instability may rise due to the rapid increase of dielectric losses with temperature (e) All of the above

Ans: e

23. Which of the following D.C. distribution system is the simplest and lowest in first cost ?

(a) Radial system

(b) Ring system

(c) Inter-connected system

(d) None of the aboveAns: a

24. A booster is a

(a) series wound generator

(b) shunt wound generator

(c) synchronous generator

(d) none of the above

Ans: a

25. Besides a method of trial and error, which of the following methods is employed for solution of network problems

in interconnected system ? (a) Circulating current method

(b) Thevenin's theorem

(c) Superposition of currents

(d) Direct application of Kirehhoffs laws

(e) All of the above Ans: e

26. Which of the following faults is most likely to occur in cables ?

(a) Cross or short-circuit fault

(b) Open circuit fault

(c) Breakdown of cable insulation

(d) All of the above

Ans: d

27. The cause of damage to the lead sheath of a cable is

(a) crystallisation of the lead through vibration

(b) chemical action on the lead when buried in the earth

(c) mechanical damage

all of the above

Ans: d

28. The voltage of the single phase supply to residential consumers is

(a) 110 V

(b) 210 V

(c) 230 V

(d) 400 V

Ans: c

29. Most of the high voltage transmission lines in India are

(a) underground

(b) overhead

(c) either of the above

(d) none of the above

Ans: b

30. The distributors for residential areas are

(a) single phase

(b) three-phase three wire

(c) three-phase four wire

(d) none of the above

Ans: c

31. The conductors of the overhead lines are

(a) solid

(b) stranded

(c) both solid and stranded

(d) none of the above

Ans: b

32. High voltage transmission lines use

(a) suspension insulators

(b) pin insulators

(c) both (a) and (b)

(d) none of the above

Ans: a

33. Multicore cables generally use

(a) square conductors

(b) circular conductors

(c) rectangular conductors

(d) sector-shaped conductors

none of the above

Ans: d

34. Distribution lines in India generally use

(a) wooden poles

(b) R.C.C. poles

(c) steel towers

(d) none of the above

Ans: b

35. The material commonly used for insulation in high voltage cables is

(a) lead

(b) paper

(c) rubber

(d) none of the above

Ans: b

36. The loads on distributors systems are generally

(a) balanced

(b) unbalanced

(c) either of the above

(d) none of the above

Ans: b

37. The power factor of industrial loads is generally

(a) unity

(b) lagging

(c) leading

(d) zero

Ans: b

38. Overhead lines generally use

(a) copper conductors

(b) all aluminium conductors

(c) A.C.S.R. conductors

(d) none of these

Ans: c

39. In transmission lines the cross-arms are made of

(a) copper

(b) wood

(c) R.C.C.

(d) steel


Ans: d

40. The material generally used for armour of high voltage cables is

(a) aluminium

(b) steel

(c) brass

(d) copper

Ans: b

41. Transmission line insulators are made of

(a) glass

(b) porcelain(c) iron

(d) P.V.C.

Ans: b

42. The material commonly used for sheaths of underground cables is

(a) lead

(b) rubber

(c) copper

(d) iron

Ans: a

43. The minimum clearance between the ground and a 220 kV line is about

(a) 4.3 m

(b) 5.5 m

(c) 7.0 m

(d) 10.5 m

Ans: c

44. The spacing between phase conductors of a 220 kV line is approximately equal to

(a) 2 m

(b) 3.5 m

(c) 6 m

(d) 8.5 m

Ans: c

45. Large industrial consumers are supplied electrical energy at

(a) 400 V (b) 11 kV

(c) 66 kV

(d) 400 kV

Ans: c

46. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to

(a) boost the generated voltage

(b) balance loads on both sides of the neutral

(c) make both machine^ run as unloaded motors

(d) equalize voltages on the positive and negative outers Ans: d

47. In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides

(a) both balancers run as generators

(b) both balancers run as motors

(c) balancer connected to lightly- loaded side runs as a motor

(d) balancer connected to heavily- loaded side runs as a motor Ans: c

48. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is

(a) 25 percent

(b) 50 percent

(c) 75 percent

(d) 100 percent

Ans: b

49. A uniformly-loaded D.C. distributor is fed at both ends with equal voltages. As compared to a similar distributor fed at one end only, the drop at the middle point is (a) one-fourth

(b) one-third

(c) one-half

(d) twice

(e) none of the above

Ans: a

50. As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to earth uses only (a) 31.25 percent of copper

(b)  33.3 percent of copper

(c)   66.7 percent of copper

(d)  125 percent of copper

Ans: a

(d) 125 percent of copperAns: a