Transmission and Distribution of Electrical Energy | Set 1
1. By which of the following systems electric power may be transmitted ?
Correct : C. Both (a) and (b)
2. are the conductors, which connect the consumer’s terminals to the distribution
Correct : B. Service mains
3. The underground system cannot be operated above
Correct : D. 66 kV
4. Overhead system can be designed for operation up to
Correct : C. 66 kV
5. If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as
Correct : A. Kelvin’s law
6. The wooden poles well impregnated with creosite oil or any preservative compound have life
Correct : C. 25 to 30 years
7. Which of the following materials is not used for transmission and distribution of electrical
power ?
Correct : D. Tungsten
8. Galvanised steel wire is generally used as
Correct : D. all of the above
9. The usual spans with R.C.C. poles are
Correct : C. 80—100 meters
10. The corona is considerably affected by which of the following ?
Correct : D. All of the above
11. Which of the following are the constants of the transmission lines ?
Correct : D. All of the above
12. 310 km line is considered as
Correct : A. a long line
13. The phenomenon qf rise in voltage at the receiving end of the open-circuited or lightly loaded
line is called the
Correct : B. Ferranti effect
14. The square root of the ratio of line impedance and shunt admittance is called the
Correct : A. surge impedance of the line
15. Which of the following is the demerit of a ‘constant voltage transmission system’ ?
Correct : A. Increase of short-circuit current of the system
16. The operating voltage of high voltage cables is up to
Correct : D. llkV
17. The operating voltage of supertension cables is up to
Correct : D. 33 kV
18. The operating voltage of extra high tension cables is upto
Correct : D. 66 kV
19. Which of the following methods is used for laying of underground cables ?
Correct : D. All of the above
20. Which of the following is the source of heat generation in the cables ?
Correct : D. All of the above
21. Due to which of the following reasons the cables should not be operated too hot ?
Correct : D. All of the above
22. Which of the following D.C. distribution system is the simplest and lowest in first cost ?
Correct : A. Radial system
23. A booster is a
Correct : A. series wound generator
24. Besides a method of trial and error, which of the following methods is employed for solution of network problems in interconnected system ?
Correct : D. All of the above
25. Which of the following faults is most likely to occur in cables ?
Correct : D. All of the above
26. The cause of damage to the lead sheath of a cable is
Correct : D. all of the above
27. The voltage of the single phase supply to residential consumers is
Correct : C. 230 V
28. Most of the high voltage transmission lines in India are
Correct : B. overhead
29. The distributors for residential areas are
Correct : C. three-phase four wire
30. The conductors of the overhead lines are
Correct : B. stranded
31. High voltage transmission lines use
Correct : A. suspension insulators
32. Multicore cables generally use
Correct : D. sector-shaped conductors
33. Distribution lines in India generally use
Correct : B. R.C.C. poles
34. The material commonly used for insulation in high voltage cables is
Correct : B. paper
35. The loads on distributors systems are generally
Correct : B. unbalanced
36. The power factor of industrial loads is generally
Correct : B. lagging
37. Overhead lines generally use
Correct : C. A.C.S.R. conductors
38. In transmission lines the cross-arms are made of
Correct : D. steel
39. The material generally used for armour of high voltage cables is
Correct : B. steel
40. Transmission line insulators are made of
Correct : B. porcelain
41. The material commonly used for sheaths of underground cables is
Correct : A. lead
42. The minimum clearance between the ground and a 220 kV line is about
Correct : C. 7.0 m
43. The spacing between phase conductors of a 220 kV line is approximately equal to
Correct : C. 6 m
44. Large industrial consumers are supplied electrical energy at
Correct : C. 66 kV
45. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
Correct : D. equalize voltages on the positive and negative outers
46. In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides
Correct : D. balancer connected to heavily- loaded side runs as a motor
47. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased
100 percent, saving in copper is
Correct : B. 50 percent
48. A uniformly-loaded D.C. distributor is fed at both ends with equal voltages. As compared to a similar distributor fed at one end only, the drop at the middle point is
Correct : A. one-fourth
49. As compared to a 2-wire D.C. distributor, a 3-wire distributor with same maximum voltage to
earth uses only
Correct : A. 31.25 percent of copper
50. Which of the following is usually not the generating voltage ?
Correct : B. 8.8 kV
51. For an overhead line, the surge impedance is taken as
Correct : C. 100—200 ohms
52. The presence of ozone due to corona is harmful because it
Correct : D. tr
53. A feeder, in a transmission system, feeds power to
Correct : A. distributors
54. The power transmitted will be maximum when
Correct : C. sending end voltage is more
55. A 3-phase 4 wire system is commonly used on
Correct : D. secondary distribution
56. Which of the following materials is used for overhead transmission lines ?
Correct : D. Any of the above
57. Which of the following is not a constituent for making porcelain insulators?
Correct : D. Silica
58. There is a greater possibility of occurence of corona during
Correct : D. humid weather
59. Which of the following relays is used on long transmission lines ?
Correct : B. Mho’s relay
60. The steel used in steel cored conductors is usually
Correct : C. mild steel
61. Which of the following distribution systems is more reliable ?
Correct : C. Ring main system
62. Which of the following characteristics should the line supports for transmission lines possess ?
Correct : D. All of the above
63. Transmission voltage of ll kV is normally used for distances upto
Correct : A. 20—25 km
64. Which of the following regulations is considered best?
Correct : D. 2%
65. Skin effect is proportional to
Correct : C. (conductor diameter)
66. A conductor, due to sag between two supports, takes the form of
Correct : D. catenary
67. In AC.S.R. conductors, the insulation between aluminium and steel conductors is
Correct : D. no insulation is required
68. Which of the following bus-bar schemes has the lowest cost ?
Correct : C. Breaker and a half scheme
69. Owing to skin effect
Correct : B. portion of the conductor near the surface carries more current and core of the conductor carries less current
70. By which of the following methods string efficiency can be improved ?
Correct : D. Any of the above
71. In aluminium conductors, steel core is provided to
Correct : D. increase the tensile strength
72. By which of the following a bus-bar is rated ?
Correct : D. Current, voltage, frequency and short time current
73. A circuit is disconnected by isolators when
Correct : B. there is no current in the line
74. For which of the following equipment current rating is not necessary ?
Correct : B. Isolators
75. In a substation the following equipment is not installed
Correct : A. exciters
76. jCorona usually occurs when the electrostatic stress in air around the conductor exceeds
Correct : D. 30 kV (maximum value)/cm
77. The voltage drop, for constant voltage transmission is compensated by installing
Correct : C. synchronous motors
78. The use of strain type insulators is made where the conductors are
Correct : C. any of the above
79. The current drawn by the line due to corona losses is
Correct : A. non-sinusoidal
80. Pin type insulators are generally not used for voltages beyond
Correct : D. 33 kV
81. Aluminium has a specific gravity of
Correct : B. 2.7
82. For transmission of power over a distance of 200 km, the transmission voltage should be
Correct : A. 132 kV
83. For aluminium, as compared to copper, all the following factors have higher values except
Correct : B. electrical conductivity
84. Which of the following equipment, for regulating the voltage in distribution feeder, will be
most economical ?
Correct : A. Static condenser
85. In a tap changing transformer, the tappings are provided on
Correct : C. high voltage winding
86. Constant voltage transmission entails the following disadvantage
Correct : B. short-circuit current of the system is increased
87. On which of the following factors skin effect depends ?
Correct : D. All of the above
88. The effect of corona can be detected by
Correct : D. all of the above
89. For transmission of power over a distance of 500 km, the transmission voltage should be in
the range
Correct : A. 150 to 220 kV
90. In the analysis of which of the following lines shunt capacitance is neglected ?
Correct : A. Short transmission lines
91. When the interconnector between two stations has large reactance
Correct : C. the stations will fall out of step be¬cause of large angular displacement between the stations
92. The frequency of voltage generated, in case of generators, can be increased by
Correct : C. adjusting the governor
93. When an alternator connected to the bus-bar is shut down the bus-bar voltage will
Correct : C. remain unchanged
94. The angular displacement between two interconnected stations is mainly due to
Correct : A. armature reactance of both alternators
95. Electro-mechanical voltage regulators are generally used in
Correct : B. generators
96. Series capacitors on transmission lines are of little use when the load VAR requirement is
Correct : B. small
97. The voltage regulation in magnetic amplifier type voltage regulator is effected by
Correct : A. electromagnetic induction
98. When a conductor carries more current on the surface as compared to core, it is due to
Correct : C. skin effect
99. The following system is not generally used
Correct : A. 1-phase 3 wire
100. The skin effect of a conductor will reduce as the
Correct : A. resistivity of conductor material increases