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

Answer With Explanation:
C. Both A and B

Explanation:
Transmission and distribution of electric power can be carried out by overhead as well as underground systems.

Overhead transmission lines are the bare conductors that are supported on pylons.

Transmission line poles are installed at a certain distance to hang these conductors above in the air.

Underground lines are the insulated cables that are buried under the earth. Underground vaults, cables, and trenches are installed.

Underground transmission lines are 5 to 10 times more expensive than overhead transmission lines.

Underground lines require special cruises for digging trenches.

Furthermore, vaults should be installed after every 1200 feet where lines are connected.

Low voltage distribution lines cost somewhat less but HVUG transmission lines are very expensive.

The lifespan of Underground transmission lines (UG) is half that of an overhead line (OH). Generally, UG lines last for 35 years, whereas OH lines work fine for up to 70 years.

OH conductors hang in the air at a certain distance, the required insulation is provided via air and no other insulation is required.

In the case of an underground line, the conductor should have a proper thickness of insulation to ensure a high degree of safety.

Overhead lines are exposed to thunder and natural lighting, whereas overhead lines are buried deep under the earth and there is no danger of lightning.

The frequency of outages on UG lines is half that of OH lines.

The outage frequency on UG lines is half that of OH lines, but once an outage occurs, it takes a couple of days to weeks and even months to find and repair the problem.

UG transmission lines should be used in cities and congested areas while OH lines are more practical in open areas.

Modification and up-gradation of OH lines is an easy task while replacing UG lines is a tedious task.

Underground lines are generally recommended for LV levels (usually below 66 kV) while the overhead systems can be designed for operation up to 400 kV or higher even.

Electrical Facts:

Most Asked  Transmission and Distribution Mcqs With Full Explanation and Exam notes 

1. Under overexcitation synchronous phase modifier works as

2. The neutral of the power system may be connected to earth

3. A 100 Ah capacity battery should deliver a current of 10 A for approximately _____ hrs.

4. For the 400KV line, The Spacing Between phase conductors is around 

5. Shunt capacitors in a sub-station

6. An alternator is said to be over-excited when it is operating at

7. Series capacitors are used to

8. Disadvantage of low power factor is

9. The color of neutral three core flexible cable is

10. The location of ground faults in underground cables can be found by

11. Fault location in an HV cable is done by

12. The insulation resistance of a cable of length 10 km is 1 MΩ. its resistance for 50 km length will be

13. Which of the following is not a valid advantage of bundle conductor?

14. The surge resistance of cables is

15. Skin effect is only noticeable at _______ frequencies. 

16. When transmission voltage is increased, the line losses are

17. Var compensators are used to

18. High voltage transmission lines use

19. The material used for insulators are

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

21. The surge impedance value of overhead lines is

22. Surge impedance loading of a transmission line is also known as

23. Cables used for underground services from 33 kV to 60 kV are

24. The minimum clearance distance that equipment should be kept away from 50 kV power lines is

25. The cheap and temporary system of the internal wiring is?

26. As per the Indian Electricity rule in overhead systems, the recommended span in the case of wooden poles is ______.

27. To improve power factor and feeder voltage controller, which compensation is required

28. Method of voltage control adopted for transmission lines in AC systems is

29. The skin effect in a transmission line is affected by

30. What is the result of the Skin Effect?

31. Transmission efficiency increases as

32. An isolator in Hv substation is used for

33. For a short tie line fed at both end , what is the best choice of protection?

34. For protection of transformer, restraint used to guard against

35. In overhead transmission line the effect of capacitance can be neglected when the length of the line is less than 

36. Pin insulators are used up to voltage of about 

37. Corona effect can be detected by 

39. The effect of wind pressure is more predominant on

40. Transposition of the transmission line is adopted to make ......... uniform throughout the line.

41. The Power Transmitted will be maximum when 

42. In a substation the equipment used to limit short circuit current level is

43. In order to increase the limit of the distance of transmission line

44. In series R - L - C circuit the condition for resonance is 

45. The most commonly used method for the protection of three phase feeder is

46. Power station and substations are protected against Direct  strokes lightning using

47. For differential protection of power transformer (delta-delta) the current transformers will have

48. Simultaneous tripping of the circuit breaker at both ends of transmission line is achieved by

49. Interposing current transformer is used in differential protection of a transformer to 

50. The magnitude of generator earth fault current is limited by

51. A wire pilot is Generally economical for distance up to 

52. An overhead transmission line is provided with earth wire for protection against

54. The grounding method that is employed to reduce the tower footing resistance where earth resistance is low

55. The statutory limit for voltage variation at the consumer's terminal is

56. A line from which loads are tapped off is called

57. The bulk power consumers are supplied at

58. By which of the following a bus-bar is rated?

59. Which of the following equipment will be most economical for regulating the voltage in distribution feeder ?


Transformer Most asked Mcqs With Full Explanation and Exam Notes 

1. The secondary winding of which of the following transformers is always kept closed?

2. Which type of connection is employed for current transformers for the protection of star- delta connected 3-phase transformer?

3. Star-star power transformer is protected by current transformer having

4. In the case of transformer Buchholz relay is used to protect from 

5. During short-circuit test of transformer, which winding of transformer is short-circuited

6. Natural air cooling is usually restricted for transformers up to

7. The distribution transformer is rated in

8. A core type transformer provides

9. The temperature rise of transformer is directly proportional to

10. When secondary of the transformer is short-circuited, the primary inductance

11. With the increase in load, the eddy current


More Circuit Breaker MCQS with Full Explanation


More Earthing MCQs with Full Explanation and Important Notes

1.  The neutral of the power system may be connected to the earth

2. Grounding of substation provides

3. Earthing is necessary to give protection against

4. Standard wire gauge used for earthing lead should not be thinner than

5. What should be the value of earthing resistance for large power stations?

6. The earthing wire should have

7. The size of the earth wire is determined by

8. The minimum length of pipe electrode used for earthing should not be less than

9. A ground wire is used to

10. Earth resistance in a typical domestic wiring is

11. From the point of view of safety, the resistance of the earthing electrode should be


Induction Motor Most asked MCQs with Full Explanations and Exam Notes 

1. If frequency of 3-phase supply to the stator of 3-phase induction motor is increased. What happens to synchronous speed. It
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