transmission and distribution Mcqs
51. A 3-phase 4 wire system is commonly used on________________?
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A. secondary distribution

B. secondary transmission

C. primary distribution

D. primary transmission

52. In transmission lines the cross-arms are made of________________?
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A. wood

B. copper

C. R.C.C.

D. steel
53. Constant voltage transmission entails the following disadvantage?
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A. large conductor area is required for same power transmission

B. none of the above

C. short-circuit current of the system is increased

D. either of the above

54. The presence of ozone due to corona is harmful because it________________?
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A. none of the above

B. transfer energy to the ground

C. gives odour

D. corrodes the material

E. reduces power factor

55. In a tap changing transformer, the tappings are provided on__________?
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A. primary winding

B. any of the above

C. secondary winding

D. high voltage winding
56. When an alternator connected to the bus-bar is shut down the bus-bar voltage will___________?
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A. none of the above

B. rise

C. fall

D. remain unchanged
57. The wooden poles well impregnated with creosite oil or any preservative compound have life_____________?
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A. from 2 to 5 years

B. 60 to 70 years

C. 25 to 30 years

D. 10 to 15 years

58. jCorona usually occurs when the electrostatic stress in air around the conductor exceeds?
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A. 22 kV (maximum value)/cm

B. 6.6 kV (r.m.s. value)/cm

C. 30 kV (maximum value)/cm

D. 11 kV (r.m.s. value)/cm

59. A booster is a_________________?
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A. series wound generator

B. shunt wound generator

C. synchronous generator

D. none of the above

60. The square root of the ratio of line impedance and shunt admittance is called the___________?
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A. regulation of the line

B. none of the above

C. conductance of the line

D. surge impedance of the line
61. There is a greater possibility of occurence of corona during______________?
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A. summer heat

B. none of the above

C. winter

D. dry weather

E. humid weather
62. The power transmitted will be maximum when____________?
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A. receiving end voltage is more

B. reactance is high

C. corona losses are minimum

D. sending end voltage is more

63. 310 km line is considered as_______________?
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A. a medium line

B. a short line

C. any of the above

D. a long line
64. A feeder, in a transmission system, feeds power to________________?
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A. all of the above

B. distributors

C. service mains

D. generating stations

65. Electro-mechanical voltage regulators are generally used in___________?
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A. all of the above

B. generators

C. reactors

D. transformers

66. Which of the following are the constants of the transmission lines ?
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A. All of the above

B. Capacitance

C. Inductance

D. Resistance

67. The voltage regulation in magnetic amplifier type voltage regulator is effected by__________?
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A. varying the reactance

B. electromagnetic induction

C. variable transformer

D. varying the resistance

68. The usual spans with R.C.C. poles are_______________?
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A. 4050 meters

B. 60100 meters

C. 300500 meters

D. 80100 meters
69. The operating voltage of supertension cables is up to_________________?
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A. 3.3 kV

B. 6.6 kV

C. 11 kV

D. 33 kV
70. By which of the following a bus-bar is rated?
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A. Current, voltage, frequency and short time current

B. Current, voltage and frequency

C. Current and voltage

D. Current only

71. In aluminium conductors, steel core is provided to____________?
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A. compensate for skin effect

B. increase the tensile strength

C. neutralise proximity effect

D. reduce line inductance

72. Large industrial consumers are supplied electrical energy at__________________?
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A. 400 V

B. 400 kV

C. 11 kV

D. 66 kV

73. By which of the following systems electric power may be transmitted ?
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A. Overhead system

B. Underground system

C. Both A. and (b)

D. None of the above

74. Series capacitors on transmission lines are of little use when the load VAR requirement is___________?
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A. fluctuating

B. small

C. large

D. any of the above

75. Which of the following relays is used on long transmission lines?
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A. Impedance relay

B. Mhos relay

C. None of the above

D. Reactance relay

76. Transmission voltage of 11 kV is normally used for distances up to_____km?
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A. 80100 km

B. 4050 km

C. 6070 km

D. 2025 km
77. Overhead system can be designed for operation up to____________?
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A. 400 kV

B. 33 kV

C. 11 kV

D. 66 kV

78. The effect of corona can be detected by___________?
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A. all of the above

B. faint luminous glow of bluish colour

C. presence of ozone detected by odour

D. hissing sound

79. Owing to skin effect:
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A. none of the above

B. portion of the conductor near the surface carries more current and core of the conductor carries less current

C. current flows through the half cross-section of the conductor

D. any of the above

E. portion of the conductor near the surface carries less current and core of the conductor carries more current

80. Aluminium has a specific gravity of___________?
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A. 7.8

B. 1.5

C. 4.2

D. 2.7
81. The following system is not generally used?
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A. 3-phase 4 wire

B. 1-phase 3 wire

C. 3-phase 3 wire

D. 1-phase 4 wire

82. In a substation the following equipment is not installed?
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A. shunt reactors

B. exciters

C. series capacitors

D. voltatre transformers

83. Most of the high transmission lines in Pakistan are_______________?
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A. none of the above

B. underground

C. overhead

D. either of the above

84. Which of the following materials is not used for transmission and distribution of electrical power________________?
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A. Steel

B. Aluminium

C. Tungsten

D. Copper

85. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is____________________?
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A. 50 percent

B. 100 percent

C. 75 percent

D. 25 percent

86. For transmission of power over a distance of 500 km, the transmission voltage should be in the range?
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A. 100 to 120 kV

B. 60 to 100 kV

C. 20 to 50 kV

D. 150 to 220 kV
87. The power factor of industrial loads is generally______________?
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A. leading

B. zero

C. lagging

D. unity

88. The underground system cannot be operated above_________________?
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A. 66 kV

B. 440 V

C. 33 kV

D. 11 kV

89. The voltage of the single phase supply to residential consumers is_____________?
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A. 230 V

B. 110 V

C. 400 V

D. 210 V

90. The corona is considerably affected by which of the following _______________?
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A. Shape of the conductor

B. Surface condition of the conductor

C. All of the above

D. Size of the conductor