In this article, we shared the transmission and distribution objective questions and answers for electrical and electronics engineers.
Transmission and Distribution Objective Questions
The below list provides all the multiple-choice questions related to electrical transmission and distribution.
Answers are available at the bottom of the article.
1. In the context of the corona, if the conductors are polished and smooth, which of the following statement is correct?
| A) | Corona glow will not occur |
| B) | A hissing sound will be more intense |
| C) | Power loss will be least |
| D) | Corona glow will be uniform along the length of the conductor |
2. By which of the following methods string efficiency can be improved?
| A) | Using a guard ring |
| B) | Grading the insulator |
| C) | Any of these answers |
| D) | Using long cross arm |
| E) | None of these answers |
3. The cause of damage to the lead sheath of a cable is
| A) | mechanical damage |
| B) | the crystallisation of the lead through vibration |
| C) | chemical action on the lead when buried in the earth |
| D) | all of these answers |
4. In which of the following voltage regulators the effect of dead zero is found?
| A) | All of these answers |
| B) | Electromagnetic type |
| C) | Electronic type using integrated circuits |
| D) | Magnetic amplifier |
5. Which of the following can be used for bus bars?
| A) | Bars |
| B) | Tubes |
| C) | Any of these answers |
| D) | Rods |
6. Poles which carry transformers are usually
| A) | none of these answers |
| B) | H-type |
| C) | A-type |
| D) | circular |
| E) | I-type |
7. Which of the following is the demerit of a ‘constant voltage transmission system’?
| A) | Possibility of carrying increased power for a given conductor size in case of long-distance heavy power transmission |
| B) | Possibility of better protection for the line due to possible use of higher terminal reactances |
| C) | Increase of short-circuit, current of the system |
| D) | Improvement of power factor at times of moderate and heavy loads |
| E) | Availability of steady voltage at all loads at the line terminals |
8. The loads on distributors systems are generally
| A) | either unbalanced or balanced |
| B) | unbalanced |
| C) | none of these answers |
| D) | balanced |
9. When the load at the receiving end of a long transmission line is removed, the sending end voltage is less than the receiving end voltage. This effect is known as
| A) | Faraday effect |
| B) | Skin effect |
| C) | Kelvin effect |
| D) | Ferranti effect |
| E) | Proximity effect |
10. Power loss due to corona is not directly proportional to
| A) | phase-neutral voltage |
| B) | supply voltage frequency |
| C) | all of these answers |
| D) | spacing between conductors |
11. A feeder, in a transmission system, feeds power to
| A) | service mains |
| B) | all of these answers |
| C) | generating stations |
| D) | distributors |
12. In transmission and distribution system the permissible voltage variation is
| A) | ± 1 percent |
| B) | ± 10 percent |
| C) | none of these answers |
| D) | ± 20 percent |
| E) | ± 30 percent |
13. Distribution lines in India generally use
| A) | none of these answers |
| B) | steel towers |
| C) | R.C.C. poles |
| D) | wooden poles |
14. Which of the following is a static exciter?
| A) | Amplidyne |
| B) | Rectifier |
| C) | Rotorol |
| D) | D.C. separately excited generator |
15. The following system is not generally used
| A) | 1-phase 4 wire |
| B) | 1-phase 3 wire |
| C) | 3-phase 4 wire |
| D) | 3-phase 3 wire |
16. In the case of transmission line conductors with the increase in atmospheric temperature
| A) | both the length and stress decrease |
| B) | length decreases but stress increases |
| C) | length increases but stress decreases |
| D) | both the length and stress increase |
17. Which of the following bus-bar schemes has the lowest cost?
| A) | Main and transfer scheme |
| B) | Ring bus-bar scheme |
| C) | Single bus-bar scheme |
| D) | Breaker and a half scheme |
18. Galvanised steel wire is generally used as
| A) | structural components |
| B) | earth wire |
| C) | stay wire |
| D) | all of these answers |
19. With which of the following are step-up substations associated?
| A) | Consumer location |
| B) | Distributors |
| C) | Concentrated load |
| D) | Generating stations |
| E) | None of these answers |
20. Transmission lines link
| A) | distribution transformer to consumer premises |
| B) | none of these answers |
| C) | receiving end station to distribution transformer |
| D) | generating station to receiving end station |
| E) | service points to consumer premises |
21. The current drawn by the line due to corona losses are
| A) | square |
| B) | non-sinusoidal |
| C) | triangular |
| D) | sinusoidal |
22. Which of the following relays is used on long transmission lines?
| A) | Impedance relay |
| B) | None of these answers |
| C) | Reactance relay |
| D) | Mho’s relay |
23. In which of the following cases shunt capacitance is negligible?
| A) | Long transmission lines |
| B) | Medium transmission lines |
| C) | Short transmission lines |
| D) | All transmission lines |
24. In the analysis of which of the following lines shunt capacitance is neglected?
| A) | Short transmission lines |
| B) | Long transmission lines |
| C) | Medium as well as long transmission lines |
| D) | Medium transmission lines |
25. Transmission voltage of 11 kV is normally used for distances up to
| A) | 20-25 km |
| B) | 80-100 km |
| C) | 40-50 km |
| D) | 60-70 km |
26. Due to which of the following reasons aluminium is being favoured as busbar material?
| A) | Low density |
| B) | Low cost |
| C) | None of these answers |
| D) | Ease of fabrication |
27. Which of the following D.C. distribution system is the simplest and lowest in first cost,?
| A) | None of these answers |
| B) | Radial system |
| C) | Ring system |
| D) | Inter-connected system |
28. Conductors for high voltage transmission lines are suspended from towers to
| A) | reduce clearance from the ground |
| B) | reduce wind and snow loads |
| C) | none of these answers |
| D) | take care of extension in length during summer |
| E) | increase clearance from ground |
29. On which of the following factors skin effect depends?
| A) | Size of the conductor |
| B) | All of these answers |
| C) | The resistivity of the conductor material |
| D) | Frequency of the current |
30. A 3-phase 4 wire system is commonly used on
| A) | primary distribution |
| B) | secondary transmission |
| C) | primary transmission |
| D) | secondary distribution |
31. Floating neutral, in 3-phase supply, is undesirable because it causes
| A) | low voltage across the load |
| B) | none of these answers |
| C) | high voltage across the load |
| D) | unequal line voltages across the load |
32. If the 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
| A) | none of these answers |
| B) | Ohm’s law |
| C) | Kelvin’s law |
| D) | Faraday’s law |
| E) | Kirchhoffs law |
33. For transmission of power over a distance of 200 km, the transmission voltage should be
| A) | 33 kV |
| B) | 11 kV |
| C) | 66 kV |
| D) | 132 kV |
34. When a conductor carries more current on the surface as compared to the core, it is due to
| A) | skin effect |
| B) | corona |
| C) | permeability variation |
| D) | none of these answers |
| E) | unsymmetrical fault |
35. When the interconnector between two stations has a large reactance
| A) | the stations will fall out of step because of large angular displacement, between the stations |
| B) | the transfer of power will take place with the least loss |
| C) | the transfer of power will take place with voltage fluctuation and noise |
| D) | none of these answers |
36. The charging current in the cables
| A) | lags the voltage by 90° |
| B) | leads the voltage by 180° |
| C) | leads the voltage by 90° |
| D) | lags the voltage by 180° |
37. In medium transmission lines the shunt capacitance is taken into account in
| A) | all of these answers |
| B) | steinmetz method |
| C) | π-method |
| D) | T-method |
38. For an overhead line, the surge impedance is taken as
| A) | 500-1000 ohms |
| B) | 100-200 ohms |
| C) | none of these answers |
| D) | 70-80 ohms |
| E) | 20-40 ohms |
39. The power transmitted will be maximum when
| A) | sending end voltage is more |
| B) | corona losses are minimum |
| C) | reactance is high |
| D) | receiving end voltage is more |
40. For transmission of power over a distance of 500 km, the transmission voltage should be in the range
| A) | 60 to 100 kV |
| B) | 150 to 220 kV |
| C) | 100 to 120 kV |
| D) | 20 to 50 kV |
41. 310 km line is considered as
| A) | any of these answers |
| B) | a medium line |
| C) | a long line |
| D) | a short line |
42. Besides a method of trial and error, which of the following methods is employed for the solution of network problems in an interconnected system?
| A) | Direct application of Kirchhoff’s laws |
| B) | Circulating current method |
| C) | All of these answers |
| D) | Thevenin’s theorem |
| E) | Superposition of currents |
43. Which of the following equipment, for regulating the voltage in the distribution feeder, will be most economical?
| A) | Static condenser |
| B) | Synchronous condenser |
| C) | Tap changing transformer |
| D) | Booster transformer |
44. A gay wire
| A) | protects conductors against short-circuiting |
| B) | provides emergency earth route |
| C) | supports the pole |
| D) | provides protection against surges |
45. The material used for the manufacture of grounding wires is
| A) | cast iron |
| B) | stainless steel |
| C) | galvanised steel |
| D) | aluminium |
46. The colour of the neutral of the three-core flexible cable is
| A) | red |
| B) | blue |
| C) | black |
| D) | brown |
47. By using bundled conductors which of the following is reduced?
| A) | All of these answers |
| B) | None of these answers |
| C) | Power loss due to corona |
| D) | Capacitance of the circuit |
| E) | Inductance of the circuit |
48. If the voltage is increased x times, the size of the conductor would be
| A) | none of these answers |
| B) | increased to 1/x times |
| C) | reduced to 1/x2 times |
| D) | increased x times |
| E) | reduced to x2 times |
49. Power system stability is least affected by
| A) | input torque |
| B) | the reactance of transmission line |
| C) | reactance of generator |
| D) | losses |
50. Which of the following short-circuits is most dangerous?
| A) | Line to line and ground short-circuit |
| B) | Line to line short-circuit |
| C) | Line to ground short-circuit |
| D) | Dead short-circuit |
| E) | All of these answers |
51. By which of the following methods voltage of transmission can be regulated ?
| A) | Use of series capacitors to neutralise the effect of series reactance |
| B) | Any of these answers |
| C) | Switching in shunt capacitors at the receiving end during heavy loads |
| D) | Use of tap changing transformers |
52. In overhead transmission lines the effect of capacitance can be neglected when the length of the line is less than
| A) | 210 km |
| B) | 110 km |
| C) | 80 km |
| D) | 150 km |
53. The wooden poles well impregnated with creosote oil or any preservative compound have life
| A) | 25 to 30 years |
| B) | 60 to 70 years |
| C) | from 2 to 5 years |
| D) | 10 to 15 years |
54. The effect of ice on transmission line conductors is to increase the
| A) | resistance to the flow of current |
| B) | transmission losses |
| C) | weight of the conductor |
| D) | tendency for corona |
55. The area of cross-section of the neutral in a 3-wire D.C. system is generally ____ the area of crosssection of main conductor
| A) | one-fourth |
| B) | same as |
| C) | double |
| D) | one half |
56. The operating voltage of high voltage cable’s is up to
| A) | 11 kV |
| B) | 3.3 kV |
| C) | 6.6 kV |
| D) | 1.1 kV |
57. Skin effect is proportional to
| A) | (conductor diameter)3 |
| B) | (conductor diameter)2 |
| C) | (conductor diameter)1/2 |
| D) | (conductor diameter)4 |
58. Which of the following are connected by the service mains?
| A) | Distributor and transformer |
| B) | Transformer and earth |
| C) | Distributor and relay system |
| D) | Distributor and consumer terminals |
59. The material commonly used for insulation in high voltage cables is
| A) | rubber |
| B) | lead |
| C) | none of these answers |
| D) | paper |
60. The material commonly used for sheaths of underground cables is
| A) | lead |
| B) | copper |
| C) | iron |
| D) | rubber |
61. Basically the boosters are
| A) | inductors |
| B) | capacitors |
| C) | transformers |
| D) | synchronous motors |
62. A lightning arrester is usually located nearer to
| A) | transformer |
| B) | busbar |
| C) | none of these answers |
| D) | circuit breaker |
| E) | isolator |
63. Which of the following equipment is used to limit short-circuit current level in a substation?
| A) | Lightning switch |
| B) | Series reactor |
| C) | Coupling capacitor |
| D) | Isolator |
64. The topmost conductor in a high transmission line is
| A) | earth conductor |
| B) | B-phase conductor |
| C) | R-phase conductor |
| D) | Y-phase conductor |
65. A booster is connected in
| A) | parallel with the feeder |
| B) | series with earth connection |
| C) | parallel with earth connection |
| D) | series with the feeder |
66. Aluminium has a specific gravity of
| A) | 4.2 |
| B) | 7.8 |
| C) | 1.5 |
| D) | 2.7 |
67. Which of the following distribution systems is the most economical?
| A) | A.C. 3-phase 4 wire system |
| B) | A.C. 3-phase 3 wire system |
| C) | A.C. 1-phase system |
| D) | Direct current system |
68. Which of the following are the constants of the transmission lines?
| A) | Resistance |
| B) | Inductance |
| C) | Capacitance |
| D) | All of these answers |
69. The operating voltage of super tension cables is up to
| A) | 33 kV |
| B) | 6.6 kV |
| C) | 3.3 kV |
| D) | 11 kV |
70. Surge absorbers protect against ____ oscillations
| A) | high voltage low frequency |
| B) | high voltage high frequency |
| C) | low voltage low frequency |
| D) | low voltage high frequency |
71. In a distribution system major cost is that of
| A) | meters |
| B) | earthing system |
| C) | distribution transformer |
| D) | conductors |
72. Which of the following bar schemes is the most expensive?
| A) | Double bus-bar double breaker |
| B) | Single bus-bar scheme |
| C) | Main and transfer scheme |
| D) | Ring bus-bar scheme |
73. Ground wire is used to
| A) | avoid overloading |
| B) | give the support to the tower |
| C) | give good regulation |
| D) | connect, a circuit conductor or other device to an earth-plate |
74. The underground system cannot be operated above
| A) | 440 V |
| B) | 11 kV |
| C) | 33 kV |
| D) | 66 kV |
75. Which of the following methods is used for laying underground cables?
| A) | Solid system |
| B) | All of these answers |
| C) | Draw-in-system |
| D) | Direct laying |
76. By which of the following methods the protection against direct lightning strokes and high voltage sweep waves is provided?
| A) | Earthing of neutral |
| B) | Ground wire |
| C) | None of these answers |
| D) | Lightening arresters |
| E) | Lightening arresters and ground wires |
77. Which of the following regulations is considered best?
| A) | 0.02 |
| B) | 0.5 |
| C) | 0.1 |
| D) | 0.2 |
78. Induction regulators are used for voltage control in
| A) | secondary distribution |
| B) | alternators |
| C) | none of these answers |
| D) | primary distribution |
79. As compared to cables, the disadvantage of transmission lines is
| A) | exposure to lightning |
| B) | all of these answers |
| C) | exposure to atmospheric hazards like smoke, ice, etc. |
| D) | inductive interference between power and communication circuits |
80. Electro-mechanical voltage regulators are generally used in
| A) | all of these answers |
| B) | reactors |
| C) | generators |
| D) | transformers |
81. As compared to a 2-wire D.C. distributor, a 3-wire distributor with the same maximum voltage to earth uses only
| A) | 125 percent of copper |
| B) | 66.7 percent of copper |
| C) | 31.25 percent of copper |
| D) | 33.3 percent of copper |
82. Out of the following which type of poles are bulky?
| A) | Transmission towers |
| B) | Tubular steel poles |
| C) | Concrete poles |
| D) | Wooden poles |
83. If the height of the transmission tower is increased, which of the following; parameters is likely to change?
| A) | None of these answers |
| B) | Resistance |
| C) | All of these answers |
| D) | Capacitance |
| E) | Inductance |
84. Which of the following characteristics should the line supports for transmission lines possess?
| A) | Low cost |
| B) | Longer life |
| C) | High mechanical strength |
| D) | All of these answers |
85. For which of the following, the excitation control method is satisfactory?
| A) | High voltage lines |
| B) | Short lines |
| C) | Low voltage lines |
| D) | Long lines |
86. Which of the following has least effect on corona?
| A) | Size and charge per ion |
| B) | Mean free path |
| C) | Atmospheric temperature |
| D) | Number of ions |
87. Pin type insulators are generally not used for voltages beyond
| A) | 1 kV |
| B) | 11 kV |
| C) | 22 kV |
| D) | 33 kV |
88. Earthing is necessary to give protection against
| A) | danger of electric shock |
| B) | high temperature of the conductors |
| C) | voltage fluctuation |
| D) | overloading |
89. The operating voltage of extra high tension cables is up to
| A) | 33 kV |
| B) | 132 kV |
| C) | 66 kV |
| D) | 11 kV |
| E) | 66 kV |
90. Transmission line insulators are made of
| A) | P.V.C. |
| B) | iron |
| C) | porcelain |
| D) | glass |
91. System grounding is done so that
| A) | inductive interference between power and communication circuits can be controlled |
| B) | all of these answers |
| C) | the floating potential on the lower voltage winding for a transformer is brought down to an insignificant value |
| D) | the arcing faults to earth would not set up dangerously high voltage on healthy phases |
92. In the design of a distributor which of the following is the major consideration?
| A) | None of these answers |
| B) | Current carrying capacity |
| C) | Frequency |
| D) | Voltage drop |
| E) | kVA of system |
93. When a live conductor of public electric supply breaks down and touches the earth which of the following will happen?
| A) | None of these answers |
| B) | No current will flow in the conductor |
| C) | Current will flow to earth |
| D) | Supply voltage will increase |
| E) | Supply voltage will drop |
94. For exact compensation of voltage drop in the feeder the booster
| A) | must be earthed |
| B) | must work on line voltage |
| C) | must work on non-linear portion of its V-I characteristics |
| D) | must work on linear portion of its V-I characteristics |
95. High voltages for transmitting power is economically available from
| A) | carrier currents |
| B) | none of these answers |
| C) | d.c. currents |
| D) | a.c. currents |
96. Which of the following is usually not the generating voltage?
| A) | 8.8 kV |
| B) | 11 kV |
| C) | 6.6 kV |
| D) | 13.2 kV |
97. By which of the following is a bus-bar is rated?
| A) | Current, voltage and frequency |
| B) | Current, voltage, frequency and short time current |
| C) | Current only |
| D) | Current and voltage |
98. The use of strain type insulators is made where the conductors are
| A) | dead ended |
| B) | any of these answers |
| C) | none of these answers |
| D) | at intermediate anchor towers |
99. The distributors for residential areas are
| A) | none of these answers |
| B) | three-phase four wire |
| C) | single phase |
| D) | three-phase three wire |
100. Which of the following cause transient disturbances ?
| A) | Load variations |
| B) | Switching operations |
| C) | Faults |
| D) | Any of these answers |
101. The usual spans with R.C.C. poles are
| A) | 40-50 metres |
| B) | 80-100 metres |
| C) | 300-500 metres |
| D) | 60-100 metres |
102. Series capacitors on transmission lines are of little use when the load VAR requirement is
| A) | small |
| B) | large |
| C) | fluctuating |
| D) | any of these answers |
103. For aluminium, as compared to copper, all the following factors have higher values except
| A) | electrical conductivity |
| B) | specific volume |
| C) | resistance per unit length for same cross-section |
| D) | co-efficient of linear expansion |
104. For which of the following equipment current rating is not necessary ?
| A) | Load break switch |
| B) | Isolators |
| C) | Circuit breakers and load break switches |
| D) | Circuit breakers |
105. A synchronous condenser is generally installed at the of the ____ transmission line
| A) | none of these answers |
| B) | receiving end |
| C) | middle |
| D) | sending end |
106. To increase the capacity of a transmission line for transmitting power which of the following must be decreased ?
| A) | All of these answers |
| B) | Voltage |
| C) | Capacitance |
| D) | Line inductance |
107. Constant voltage transmission entails the following disadvantage
| A) | short-circuit current of the system is increased |
| B) | none of these answers |
| C) | either short-circuit current of the system is increased or large conductor area is required for same power transmission |
| D) | large conductor area is required for same power transmission |
108. When an alternator connected to the bus-bar is shut, down the bus-bar voltage will
| A) | none of these answers |
| B) | remain unchanged |
| C) | rise |
| D) | fall |
109. If string efficiency is 100 percent it means that
| A) | potential across each disc is same |
| B) | potential across each disc is zero |
| C) | one of the insulator discs is shorted |
| D) | none of these answers |
110. Transmitted power remaining the same, if supply voltage of a D.C. 2-wire feeder is increased 100 percent, saving in copper is
| A) | 100 percent |
| B) | 50 percent |
| C) | 25 percent |
| D) | 75 percent |
111. A.C.S.R. conductor having 7 steel stands surrounded by 25 aluminium conductors will be specified as
| A) | 7/25 |
| B) | 50/15 |
| C) | 25/7 |
| D) | 7/25 |
112. The string efficiency of an insulator can be increased by
| A) | increasing the number of strings in the insulator |
| B) | none of these answers |
| C) | reducing the number of strings |
| D) | correct grading of insulators of various capacitances |
113. The limit of distance of transmission line may be increased by the use of
| A) | shunt capacitors and series reactors |
| B) | series capacitors and shunt reactors |
| C) | none of these answers |
| D) | synchronous condensers |
| E) | series resistances |
114. The effect of wind pressure is more predominant on
| A) | neutral wires |
| B) | supporting towers |
| C) | transmission lines |
| D) | insulators |
115. The conductors are bundled primarily to
| A) | none of these answers |
| B) | reduce reactance |
| C) | increase reactance |
| D) | reduce radio interference |
116. The minimum clearance between the ground and a 220 kV line is about
| A) | 5.5 m |
| B) | 10.5 m |
| C) | 4.3 m |
| D) | 7.0 m |
117. Which of the following is not a constituent for making porcelain insulators ?
| A) | Quartz |
| B) | Kaolin |
| C) | Felspar |
| D) | Silica |
118. Which of the following distribution systems is more reliable ?
| A) | Tree system |
| B) | All are equally reliable |
| C) | Ring main system |
| D) | Radial system |
119. By which of the following factors is the sag of a transmission line least affected ?
| A) | Ice deposited on the conductor |
| B) | Temperature of surrounding air |
| C) | None of these answers |
| D) | Current through the conductor |
| E) | Self weight of conductor |
120. Impedance relay is used on ____ transmission lines
| A) | short |
| B) | all |
| C) | medium |
| D) | long |
121. Multicore cables generally use
| A) | rectangular conductors |
| B) | sector-shaped conductors |
| C) | none of these answers |
| D) | square conductors |
| E) | circular conductors |
122. The voltage drop, for constant voltage transmission is compensated by installing
| A) | synchronous motors |
| B) | all of these answers |
| C) | capacitors |
| D) | inductors |
| E) | none of these answers |
123. Resistance grounding is used for voltage between
| A) | 11 kV to 33 kV |
| B) | 33 kV to 11 k V |
| C) | 33 kV to 66 kV |
| D) | none of these answers |
124. Most of the high voltage transmission lines in India are
| A) | none of these answers |
| B) | overhead |
| C) | either overhead or undergound |
| D) | undergound |
125. ___ are the conductors, which connect the consumer’s terminals to the distribution
| A) | None of these answers |
| B) | Service mains |
| C) | Feeders |
| D) | Distributors |
126. The surge resistance of cables is
| A) | 300 ohms |
| B) | 200 ohms |
| C) | 50 ohms |
| D) | 20 ohms |
127. Which of the following materials is not used for transmission and distribution of electrical power?
| A) | Tungsten |
| B) | Steel |
| C) | Aluminium |
| D) | Copper |
128. The frequency of voltage generated, in case of generators, can be increased by
| A) | none of these answers |
| B) | increasing the load |
| C) | using reactors |
| D) | reducing the terminal voltage |
| E) | adjusting the governor |
129. In a 70/6 A.C.S.R. conductor there are
| A) | 70 aluminium conductors and 6 steel conductors |
| B) | 35 aluminium conductors and 3 steel conductors |
| C) | 70 steel conductors and 6 aluminium conductors |
| D) | none of these answers |
130. The steel used in steel cored conductors is usually
| A) | mild steel |
| B) | high speed steel |
| C) | stainless steel |
| D) | alloy steel |
| E) | all of these answers |
131. A tap changing transformer is used to
| A) | supply low voltage current for instruments |
| B) | step up the voltage |
| C) | step down the voltage |
| D) | none of these answers |
| E) | step up as well as step down the voltage |
132. If the height of transmission tower is increased
| A) | the line capacitance and inductance will not change |
| B) | the line capacitance will increase but line inductance will decrease |
| C) | the line capacitance will decrease and line inductance will increase |
| D) | the line capacitance will decrease but line inductance will remain unchanged |
133. High voltage is primarily used, for long distance power transmission, to
| A) | none of these answers |
| B) | reduce the time of transmission |
| C) | make the system reliable |
| D) | reduce the transmission losses |
134. The presence of ozone due to corona is harmful because it
| A) | transfer energy to the ground |
| B) | reduces power factor |
| C) | corrodes the material |
| D) | gives odour |
| E) | none of these answers |
135. In transmission lines, the cross-arms are made of
| A) | wood |
| B) | copper |
| C) | steel |
| D) | R.C.C. |
136. Which of the following is the main advantage of A.C. transmission system over D.C. transmission system ?
| A) | Less insulation problems |
| B) | Easy transformation |
| C) | Less instability problem |
| D) | Less losses in transmission over long distances |
137. Steepness of the travelling waves is alternated by ____ of the line
| A) | inductance |
| B) | all of these answers |
| C) | capacitance |
| D) | resistance |
138. Skin effect exists only in
| A) | low voltage d.c. overhead transmission |
| B) | cables carrying d.c. current |
| C) | a.c. transmission |
| D) | high voltage d.c. overhead transmission |
139. The skin effect of a conductor will reduce as the
| A) | frequency increases |
| B) | diameter increases |
| C) | permeability of conductor material increases |
| D) | resistivity of conductor material increases |
140. The material generally used for the armour of high voltage cables is
| A) | brass |
| B) | copper |
| C) | steel |
| D) | aluminium |
141. A conductor due to sag between two supports takes the form of
| A) | triangle |
| B) | ellipse |
| C) | catenary |
| D) | semi-circle |
142. Which of the following is the source of heat generation in the cables?
| A) | Dielectric losses in cable insulation |
| B) | Losses in the metallic sheathings and armourings |
| C) | All of these answers |
| D) | IR losses in the conductor |
143. Solid grounding is adopted for voltages below
| A) | 660 V |
| B) | 200 V |
| C) | 400 V |
| D) | 100 V |
144. The square root of the ratio of line impedance and shunt admittance is called the
| A) | none of these answers |
| B) | regulation of the line |
| C) | surge impedance of the line |
| D) | conductance of the line |
145. The electrostatic stress in underground cables is
| A) | maximum at the conductor and minimum at the sheath |
| B) | same at the conductor and sheath |
| C) | zero at the conductor as well as on the sheath |
| D) | minimum at the conductor and minimum at the sheath |
146. On which of the following does the size of a feeder depend?
| A) | Frequency |
| B) | Voltage |
| C) | Current carrying capacity |
| D) | Voltage drop |
147. 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
| A) | one-fourth |
| B) | one-half |
| C) | none of these answers |
| D) | twice |
| E) | one-third |
148. In aluminium conductors, a steel core is provided to
| A) | compensate for skin effect |
| B) | reduce line inductance |
| C) | increase the tensile strength |
| D) | neutralise proximity effect |
149. Which of the following materials is used for overhead transmission lines?
| A) | Any of these answers |
| B) | Cadmium copper |
| C) | Galvanised steel |
| D) | Steel cored aluminium |
150. The spacing between phase conductors of a 220 kV line is approximately equal to
| A) | 2 m |
| B) | 3.5 m |
| C) | 6 m |
| D) | 8.5 m |
151. The effective resistance of a conductor will be the same as ‘ohmic resistance’ when
| A) | voltage is low |
| B) | current is uniformly distributed in the conductor cross-section |
| C) | current is in true sine waveform |
| D) | power factor is unity |
152. The conductors of the overhead lines are
| A) | both solid and stranded |
| B) | solid |
| C) | none of these answers |
| D) | stranded |
153. In a D.C. 3-wire distribution system, balancer fields are cross-connected in order to
| A) | make both machines run as unloaded motors |
| B) | equalize voltages on the positive and negative outers |
| C) | boost the generated voltage |
| D) | balance loads on both sides of the neutral |
154. Due to which of the following reasons the cables should not be operated too hot?
| A) | All of these answers |
| B) | Unequal expansion may create voids in the insulation which will lead to ionization |
| C) | The oil may loose its viscosity and it may start drawing off from higher levels |
| D) | Expansion of the oil may cause the sheath to burst |
| E) | The thermal instability may rise due to the rapid increase of dielectric losses with temperature |
155. A circuit is disconnected by isolators when
| A) | there is no current in the line |
| B) | line is energized |
| C) | line is on full load |
| D) | circuit breaker is not open |
156. The phenomenon of rise in voltage at the receiving end of the open-circuited or lightly loaded line is called the
| A) | none of these answers |
| B) | Seeback effect |
| C) | Ferranti effect |
| D) | Raman effect |
157. The power factor of industrial loads is generally
| A) | unity |
| B) | zero |
| C) | leading |
| D) | lagging |
158. By using bundle conductors, the critical voltage for the formation of corona will
| A) | decrease |
| B) | not occur |
| C) | remain same |
| D) | increase |
159. By which of the following systems electric power may be transmitted?
| A) | None of these answers |
| B) | Both Overhead system and Underground system |
| C) | Overhead system |
| D) | Underground system |
160. Skin effect is noticeable only at ____ frequencies
| A) | all |
| B) | audio |
| C) | low |
| D) | high |
161. The purpose of using a booster is to
| A) | increase current |
| B) | none of these answers |
| C) | compensate for voltage drop |
| D) | reduce current |
| E) | reduce voltage drop |
162. Which of the following equipment should be installed by the consumers having low power factor?
| A) | Capacitor bank |
| B) | Tap changing transformer |
| C) | Any of these answers |
| D) | None of these answers |
| E) | Synchronous condensers |
163. The voltage regulation in magnetic amplifier type voltage regulator is effected by
| A) | variable transformer |
| B) | varying the resistance |
| C) | electromagnetic induction |
| D) | varying the reactance |
164. Overhead lines generally use
| A) | all aluminium conductors |
| B) | A.C.S.R. conductors |
| C) | copper conductors |
| D) | none of these answers |
165. Corona results in
| A) | none of these answers |
| B) | radio interference |
| C) | better regulation |
| D) | power factor improvement |
166. Corona is likely to occur maximum in
| A) | all of these answers |
| B) | distribution lines |
| C) | domestic wiring |
| D) | transmission lines |
167. Which of the following faults is most likely to occur in cables?
| A) | Cross or short-circuit fault |
| B) | Open circuit fault |
| C) | All of these answers |
| D) | Breakdown of cable insulation |
168. High voltage transmission lines use
| A) | suspension insulators |
| B) | pin insulators |
| C) | both suspension insulators and pin insulators |
| D) | none of these answers |
169. The voltage of the single-phase supply to residential consumers is
| A) | 210 V |
| B) | 230 V |
| C) | 400 V |
| D) | 110 V |
170. Which of the following is neglected in the analysis of short transmission lines?
| A) | Series impedance |
| B) | All of these answers |
| C) | None of these answers |
| D) | I2R loss |
| E) | Shunt admittance |
171. The size of the earth wire is determined by
| A) | the atmospheric conditions |
| B) | the voltage of the service wires |
| C) | none of these answers |
| D) | the ampere capacity of the service wires |
172. The ground ring transmission lines are used to
| A) | reduce the transmission losses |
| B) | reduce the earth capacitance of the lowest unit |
| C) | increase the earth capacitance of the lowest unit |
| D) | none of these answers |
173. In the cables sheaths are used to
| A) | prevent the moisture from entering the cable |
| B) | provide strength to the cable |
| C) | provide proper insulation |
| D) | none of these answers |
174. Low voltage cables are meant for use up to
| A) | 3.3 kV |
| B) | 6.6 kV |
| C) | 1.1 kV |
| D) | 11 kV |
175. Owing to skin effect
| A) | portion of the conductor near the surface carries less current and core of the conductor carries more current |
| B) | any of these answers |
| C) | none of these answers |
| D) | portion of the conductor near the surface carries more current and core of the conductor carries less current |
| E) | current flows through the half cross-section of the conductor |
176. In a D.C. 3-wire distributor using balancers and having unequal loads on the two sides
| A) | both balancers run as generators |
| B) | both balancers run as motors |
| C) | balancer connected to heavily- loaded side runs as a motor |
| D) | balancer connected to lightly- loaded side runs as a motor |
177. The corona is considerably affected by which of the following?
| A) | All of these answers |
| B) | Size of the conductor |
| C) | Shape of the conductor |
| D) | Surface condition of the conductor |
178. In A.C.S.R. conductor the function of steel is to
| A) | take care of surges |
| B) | provide additional mechanical strength |
| C) | prevent corona |
| D) | reduce inductance and subsequently improve power factor |
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