Power System(Transmission & Distribution)-02:

25)   Which among the following properties has got a higher value for aluminium in comparison to that of copper?

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

26)   Why are galvanised steel conductors not suitable for transmitting large power over long distance?

a. Poor conductivity.
b. High resistance of steel.
c. More power loss.
d. Both (a) and (b).

27)   What is the empirical formula to calculate the number of strands?

a. 3n (n+2n) + 2
b. 3n (n+1) + 2
c. 3n (n+1) + 1
d. 3n (3+ 3n) + 1

28)   The most ideal material for the over head conductor is copper. What are the advantages of this?

a. Smaller cross sectional area.
b. Area offered by the wind loads is reduced.
c. The price of copper is less.
d. Both (a) and (b).
e. None of these

29)   Why are the conductors used for higher voltage transmission stranded?

a. Ease of handling.
b. Cheaper cost.
c. Reduced resistivity.
d. Increase in tensile strength.

30)   Which material is used for the manufacture of ground wire?

a. Aluminium
b. Galvanised steel
c. Cast iron
d. Stainless steel

31)   The following materials of line conductor are given.

i. Hard drawn copper.
ii. Cadmium copper.
iii. Aluminium.
iv. Galvanised steel.

What is the correct series in descending order of their electrical conductivities?

a. a. i, ii, iv, iii.
b. B. ii, i, iv, iii.
c. C. ii, i, iii, iv.
d. D. i, ii, iii, iv.

32)   When steel is reinforced what happens to the composite conductor?

a. 35 % more compared with equivalent weight of copper.
b. 25 % more compared with equivalent weight of copper.
c. 25 % less compared with equivalent weight of copper.
d. 35 % less compared with equivalent weight of copper.

33)   Why is A.C.S.R conductor used as the replacement or substitute for copper?

a. Higher current carrying capacity.
b. Economy.
c. Being less weight.
d. Higher tensile strength.

34)   What is the function of steel wire in A.C.S.R conductors?

a. Compensate for skin effect.
b. Takes care of surges.
c. Reduced capacitance and inductance.
d. Provide additional mechanical strength.

35)   Why is grease added between steel and aluminium conductors?

a. To reduce the corrosion by electrolytic action.
b. To reduce friction between the strand.
c. To eliminate the air gaps.
d. To reduce the leakage of current.

36)   What is the general ratio of the cross sectional area of the two metals used in the A.C.S.R conductors?

a. 1 : 8
b. 1 : 4
c. 4 : 3
d. 2 : 1

37)   Assertion (A): The maximum operating temperature of overhead line conductors made of aluminium or copper is restricted to 75 °C.
Reason (R): conductors beyond this limit may shatter the insulator.

a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true and R is not the explanation of A
c. A is true but R is false
d. A is false but R is true.

38)   For high voltage transmission lines, why are conductors suspended from towers?

a. Increase the clearance from ground.
b. Reduce clearance from ground.
c. Take care of increase in length.
d. Reduce the environmental effects.

39)   Which among these are the properties for the line supports?

a. Higher mechanical strength
b. Light in weight
c. Easy accessibility of conductors for maintenance
d. All of these

40)   To prevent rotting oil the wooden poles which oil is impregnated to it?

a. Kerosene oil
b. Mineral oil
c. Creosote oil
d. All of these

41)   Steel poles are painted so as to prevent it from ____________.

a. Corrosion
b. Borer
c. Termites
d. All of these

42)   Which among these is not a type of steel poles?

a. Rail poles
b. Tubular poles
c. Rolled steel joints
d. None of these

43)   What is the usual span of the RCC poles?

a. 250 – 400 m.
b. 80 – 150 m.
c. 50 – 105 m.
d. 10 – 75 m.

44)   What is the main purpose for guy wire?

a. Supports the pole
b. Protects against the surges
c. Provides emergency earth route
d. All of these

45)   Sag depends on which factor?

a. Span length
b. Weight of the conductors
c. Tension in the conductors
d. All of these

46)   What is the shape that is attained by the conductors if suspended from the same height?

a. Parabola
b. Catenary
c. Semi circle
d. None of these

47)   Conductor sag should be kept

a. Minimum
b. Maximum
c. Zero
d. None of these

48)   What is the minimum safety factor in respect of the conductor tension?

a. 1
b. 3
c. 2
d. 1.5

49)   A 132 kV transmission line, with the weight of conductor = 680 kg/km, length of span = 260 m, ultimate strength = 3100 kg, safety factor =2. Calculate the height above ground at which the conductor should be supported. Ground clearance required is 10 m.

a. 10.7 m
b. 13.7 m
c. 20.83 m
d. 18.75 m

50)   Sag is directly proportional to the square of span.

a. True
b. False

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