Underground Cable MCQ

41. Loading of a cable is done to

  1. Increase its inductance
  2. Increase its leakage resistance
  3. Decrease its leakage resistance
  4. Achieve distortionless condition
  1. 1, 3 and 4
  2. 1 and 3
  3. 2 and 4 only
  4. 1 and 4 only

Answer. d

42. For LV applications (below 1 KV) ______ cables are used.

  1. Plastic
  2. Paper insulated
  3. Oil-filled
  4. Single-core

Answer. d

43. An overhead line having a surge impedance of 400 ohms is connected in series with an underground cable having a surge impedance of 100 ohms. If the surge of 50 kV travels from the line towards the cable junctions, the value of transmitted voltage wave at the junction is

  1. 30 kV
  2. 20 kV
  3. 80 kV
  4. −30 kV

Answer. b

44. The attenuation and propagation constants are applicable to

  1. Both underground cables and transmission lines
  2. Only transmission lines
  3. Only underground cables
  4. Neither transmission lines not underground cables

Answer. a

45. What is the main drawback of the underground transmission system compared to the overhead transmission system?

  1. Exposure to lightning
  2. Heavy initial cost
  3. Exposure to atmospheric hazards such as smoke, ice, wind
  4. Induction interference between power and communication circuits

Answer. b

46. Impregnated paper is used in an insulator

  1. In between the armature stamping
  2. High voltage cables
  3. Commutator
  4. H.T. line

Answer. b

47. Cables in the power transmission line are provided with inter sheaths to

  1. Minimize charging current
  2. Minimize stress
  3. Provide uniform stress distribution
  4. Minimize high voltage

Answer. c

48. The insulation resistance of a cable of length 10 km is 1Mohm. For a length of 100 km of the same cable, the insulation resistance will be

  1. 1 Mohm
  2. 10 Mohm
  3. 0.1 Mohm
  4. 0.01 Mohm

Answer. c

49. The minimum permissible size of the aluminium cable for lightning circuits is ________

  1. 1.1 sq.mm
  2. 1.5 sq.mm
  3. 2.4 sq.mm
  4. 3.6 sq.mm

Answer. b

50. The maximum value of potential gradient in a cable occurs in

  1. Conductor
  2. Insulation
  3. Outer sheath
  4. None of these

Answer. a

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