Transmission and Distribution Mcq

41. The sag of a transmission line is least affected owing to

(a) weight of the conductor.
(b) current through the conductor.
(c) atmospheric temperature.
(d) ice deposition on the conductor.

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42. Effect of temperature rise in overhead lines is to

(a) increase the sag and decrease the tension.
(b) decrease the sag and increase the tension.
(c) increase both.
(d) decrease both.

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43. The sag of a transmission line conductor in summer is

(a) less than that in winter.
(b) more than that in winter.
(c) same as in winter.

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44. In a transmission line, sag depends upon

(a) span length.
(b) tension in conductors.
(c) weight of the conductor per unit length.
(d) all of the above.

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45. Which of the following statements is correct?

(a) Ice on conductors increases skin effect.
(b) Wind pressure reduces corona effect.
(c) Wind pressure is taken to act at perpendicular to that for ice.
(d) Ice on conductors reduces sag.

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46. Wind loading in coastal regions is in the range of

(a) 40 – 50 kg/m2
(b) 150 kg/m2
(c) 96 kg/m2

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47. The maximum tension in a section of overhead line conductor between two supports of unequal height occurs at

(a) the higher support.
(b) the lower point.
(c) the midpoint of the conductor.
(d) None of the above.

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48. Stringing chart is useful

(a) for finding the sag in the conductor.
(b) in the design of tower.
(c) in the design of insulator string.
(d) finding the distance between towers.

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49. Hot template curves are plots of

(a) temperature and humidity.
(b) conductor sag and span lengths.
(c) conductor weight and sag.
(d) none of the above.

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50. The effect of wind pressure is more predominant on

(a) insulators.
(b) transmission lines.
(c) supporting towers.
(d) none of the above.

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51. Galloping in transmission line conductors arises due to

(a) asymmetrical layers of ice formation.
(b) vortex phenomenon in light winds.
(c) heavy weight of the line conductors.
(d) adoption of horizontal conductor configuration.

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52. Which one of the following is reduced by using stock bridge dampers on power overhead transmission lines?

(a) Sag.
(b) Conductor vibration.
(c) Line losses.
(d) Mechanical tension.

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53. The sag of the conductors of a transmission line is 2.5 m when the span is 250 m. Now if the height of supporting tower is increased by 25%, the sag will

(a) reduce by 25%
(b) increase by 25%
(c) reduce by 12.5%
(d) remain unchanged.

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54. For a 400 kV line, the spacing between phase conductors is around

(a) 8 m.
(b) 11 m.
(c) 14 m.
(d) 17 m.

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55. Stranded conductors usually have a central wire around which there are successive layers of 6,12,18,24 wires. For n-layers, the total number of individual wires is

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

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56. The diameter of each strand is d then the diameter of n-layer stranded conductor will be

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

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57. Strain type insulators are used

(a) at dead ends.
(b) at intermediate anchor towers.
(c) on straight runs.
(d) any of (a) or (b).

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58. Wavy structure of pin insulator increases its

(a) mechanical strength.
(b) puncture strength.
(c) flash-over voltage.
(d) thermal strength.

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59. The voltage rating of a multiple shell (petticoat or rainshed) pin type insulator unit cannot be increased beyond a limiting value by increasing the number of shells, because

(a) the internal voltage distribution between shells becomes unequal.
(b) the leakage path resistance starts diminishing.
(c) the disruptive critical voltage for the material of the insulator is reached.
(d) the puncture voltage of the material of the insulator is reached.

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60. Which type of insulators are used on 132 kV transmission lines ?

(a) Pin type.
(b) Disc type.
(c) Shackle type.
(d) Pin and Shackle type.

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