Transmission and Distribution MCQ PDF

81. Multi-core cables generally use

(a) oval shaped conductors.
(b) sector shaped conductors.
(c) square conductors.
(d) either (a) or (b).

82. In a 3-phase, 4-wire cable, the x-sectional area of neutral conductor is

(a) half of the area of phase conductor.
(b) equal to the area of phase conductor.
(c) double the area of phase conductor.
(d) 1.5 times the area of phase conductor.

83. The belted type construction is not suitable for cables used for voltages exceeding 22 kV because of

(a) development of both radial and tangential stresses.
(b) formation of vacuous spaces and voids on loading and unloading owing to non-homogenity of dielectric in belted construction.
(c) local heating caused by power loss at the centre filling owing to leakage current produced by tangential stresses along the impregnated paper insulation resulting in breakdown at any time.
(d) all of the above.

84. SL type cables, over H-type cables, have the advantage(s) of

(a) possibility of bending of cables owing to no overall lead sheath.
(b) less tendency for oil drainage on hilly routes owing to elimination of filler spaces containing compound.
(c) easy manufacturing.
(d) both (a) and (b).

85. Screened type cables, over belted cables, have the advantage(s) of

(a) reduced possibility of core to core faults.
(b) uniform radial electric stresses in all sections of the dielectric.
(c) no possibility of formation of voids within the dielectric.
(d) increased current carrying capacity.
(e) all of the above.

85. Solid type cables are not considered suitable for operating voltages exceeding 66 kV because

(a) skin effect dominates on the conductor.
(b) there is a danger of breakdown of insulation because of formation of voids in the layers of dielectric.
(c) there is a corona loss between conductor and sheath material.
(d) insulation may melt due to heating.

86. In a 3-core extra high voltage cable, a metallic screen around each core insulation is provided to

(a) facilitate heat dissipation.
(b) give mechanical strength.
(c) obtain radial electric stress.
(d) obtain longitudinal electric stress.

87. As the operating voltage and consequently the electric stress on the dielectric of solid type cable is increased from 4 low value, the dielectric power factor cos φ remains almost unchanged up to a certain value of the stress beyond which cos φ increases very rapidly. This is due to increase in

(a) resistivity of dielectric material.
(b) ionization in the voids present in the dielectric.
(c) core-to-core capacitance of the cable.
(d) core-to-earth capacitance of the cable.

88. Oil-filled cables have the advantage(s) of

(a) no ionization, oxidation and formation of voids.
(b) possibility of increased temperature range in service.
(c) more maximum permissible stresses .
(d) all of the above.

89. Oil-filled cables have the advantage(s) of

(a) smaller overall size.
(b) most perfect impregnation.
(c) easy detection of fault.
(d) all of the above.

90. Oil-filled cables have the drawback(s) of

(a) no possibility of impregnation after sheathing.
(b) greater cost and complicated laying of cables and maintenance.
(c) high thermal resistance.
(d) all of the above.

91. Cables used for 220 kV lines are invariably

(a) compressed oil or compressed gas insulated.
(b) paper insulated.
(c) mica insulated.
(d) none of the above.

92. The insulation used in a cable designed for use on 1,000 kV is usually

(a) impregnated paper.
(b) compressed SF₆ gas.
(c) PVC.
(d) any of the above.

93. Sulphur hexafluoride cable is insulated by

(a) impregnated paper.
(b) polyvinyl chloride.
(c) high pressure oil.
(d) compressed gas.

94. In compressed gas insulated cable SF₆ has the gas pressure in the range of

(a) 10 – 20 mm Hg
(b) 80 – 100 mm Hg
(c) 3 – 5 kg/cm²
(d) 40 – 50 kg/cm₂

95. At bridge crossings and near the railway track ternary lead cables are used because they

(a) are of high tensile strength.
(b) are of low coefficient of thermal expansion.
(c) are of low specific gravity.
(d) can withstand shocks and vibrations.

96. Internal pressure cables have the advantage(s) of

(a) elimination of external accessories.
(b) suitability for vertical run without any fear of drainage with suitable designs.
(c) marked improvement in the pf of the cable dielectric with the increased pressure.
(d) all of the above.

97. With the rise in temperature, the insulation resistivity

(a) remains unchanged.
(b) decreases linearly.
(c) increases linearly.
(d) reduces exponentially.

98. The insulation resistance of a single-core cable is 200 MΩ/km. The insulation resistance for 5 km length is

(a) 40 MΩ
(b) 1000 MΩ
(c) 200 MΩ
(d) 8 MΩ

99. The power factor of an open-ended cable can be improved by

(a) increasing the capacitance.
(b) decreasing the capacitance.
(c) increasing the conductor resistance.
(d) increasing the insulation resistance.

100. The capacitance of a cable increases

(a) linearly with the increase in cable length.
(b) linearly with the decrease in cable length.
(c) exponentially with the increase in cable length.
(d) none of the above.

 

• Power System MCQ Part – 1
• Power System MCQ Part – 2
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• Transmission and Distribution MCQ PDF

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