Transmission and Distribution Mcq

21. 66 kV is suitable for transmission of power over

(a) 30 km
(b) 60 km
(c) 120 km
(d) 200 km

22. If 3 MW power is to be transmitted over a distance of 30 km, the desirable transmission voltage will be

(a) 11 kV
(b) 33 kV
(c) 66 kV
(d) 3.3 kV

23. The highest transmission voltage used in India is

(a) 400 kV
(b) 220 kV
(c) 132 kV
(d) 765 kV

24. If variable part of annual cost on account of interest and depreciation on the capital out lay 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 the most economical. This statement is known as

(a) Lenz’ s law.
(b) Faraday’s law.
(c) Kelvin’s law.
(d) Ohm’s law.

25. The supports used for transmission lines should have the characteristic(s) of

(a) high mechanical strength and longer life.
(b) good looking, light in weight and easily accessible for painting and erection of line conductors.
(c) cheap in initial as well in maintenance cost.
(d) all of the above.

27. The wooden poles well impregnated with kerosene oil or any preservative compound have life of

(a) 25 – 30 years.
(b) 20 – 25 years.
(c) 10 – 15 years.
(d) 5 – 10 years.

28. Steel poles for transmission lines need protection against

(a) borer.
(b) termites.
(c) corrosion.
(d) all of these.

29. RCC poles usually have the spans of

(a) 250 – 400 m.
(b) 80 – 150 m.
(c) 50 – 80 m.
(d) 25 – 50 m.

30. In India for distribution of electric power we usually use

(a) wooden poles.
(b) steel poles.
(c) RCC poles.
(d) both (b) and (c).

31. Conductors used in HT transmission lines are stranded because of

(a) increased tensile strength.
(b) ease in handling.
(c) cheaper in cost.
(d) reduced resistivity.

32. Consider the following materials for line conductors :

1. Hard drawn copper.
2. Cadmium copper.
3. Aluminum.
4. Galvanized steel.

The correct sequence of the descending order of their electrical conductivities is
(a) 1, 2, 4, 3
(b) 2, 1, 4, 3
(c) 2, 1, 3, 4
(d) 1, 2, 3, 4

33. Which of the following properties has got higher value for aluminum in comparison to that of copper ?

(a) Electrical resistivity.
(b) Melting point.
(c) Thermal conductivity.
(d) Specific gravity.

34. In a 7/30 ACSR conductor why is grease put between steel and aluminum conductors?

(a) To reduce corrosion by electrolytic action between zinc (galvanizing agent on steel) and aluminum.
(b) To reduce friction between the strands.
(c) To reduce leakage of current from aluminum strands to steel strands.
(d) To eliminate air pockets.

35. ACSR is used in place of copper in overhead lines because of

(a) higher current carrying capacity.
(b) being lighter in weight.
(c) economy.
(d) higher tensile strength.

36. ACSR conductors have

(a) all conductors made of aluminum.
(b) outer conductors made of aluminum.
(c) inner conductors made of aluminum.
(d) no conductors made of aluminum.

37. “Expanded ACSR” are conductors composed of

(a) larger diameter individual strands for a given cross section of the aluminum strands.
(b) larger diameter of the central steel strands for a given overall diameter of the conductor.
(c) larger diameter of the aluminum strands only for a given overall diameter of conductor.
(d) A filter between the inner steel and the outer aluminum strands to increase the overall diameter of the conductor.

38. The function of steel wire in an ACSR conductor is to

(a) compensate for skin effect.
(b) take care of surges.
(c) provide additional mechanical strength.
(d) reduce inductance.

39. The material used for the manufacture of ground wire is

(a) aluminum.
(b) galvanized steel.
(c) cast iron.
(d) stainless steel.

40. Guy wire is employed for

(a) providing protection against surges.
(b) providing emergency earth route.
(c) supporting the pole.
(d) all of the above.