Transmission And Distribution Objective Questions

[Ramya Bradbury]

Inan electrical distribution network, increasing the voltage level has a significant impact on the weight and cost of the conductor material required for the same power transmission. This can be explained by considering the relationship between voltage, current, and conductor size:

Therefore, with the increase in the voltage level of the distribution network, the weight and corresponding cost of the conductor material will be decreased and decreased, respectively, for the same voltage drop.

2. By which of the following methods string efficiency can be improved?A)Using a guard ringB)Grading the insulatorC)Any of these answersD)Using long cross armE)None of these answers3. The cause of damage to the lead sheath of a cable is

8. The loads on distributors systems are generallyA)either unbalanced or balancedB)unbalancedC)none of these answersD)balanced9. 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 asA)Faraday effectB)Skin effectC)Kelvin effectD)Ferranti effectE)Proximity effect10. Power loss due to corona is not directly proportional toA)phase-neutral voltageB)supply voltage frequencyC)all of these answersD)spacing between conductors11. A feeder, in a transmission system, feeds power to

16. In the case of transmission line conductors with the increase in atmospheric temperatureA)both the length and stress decreaseB)length decreases but stress increasesC)length increases but stress decreasesD)both the length and stress increase17. Which of the following bus-bar schemes has the lowest cost?A)Main and transfer schemeB)Ring bus-bar schemeC)Single bus-bar schemeD)Breaker and a half scheme18. Galvanised steel wire is generally used asA)structural componentsB)earth wireC)stay wireD)all of these answers19. With which of the following are step-up substations associated?

24. In the analysis of which of the following lines shunt capacitance is neglected?A)Short transmission linesB)Long transmission linesC)Medium as well as long transmission linesD)Medium transmission lines25. Transmission voltage of 11 kV is normally used for distances up toA)20-25 kmB)80-100 kmC)40-50 kmD)60-70 km26. Due to which of the following reasons aluminium is being favoured as busbar material?A)Low densityB)Low costC)None of these answersD)Ease of fabrication27. Which of the following D.C. distribution system is the simplest and lowest in first cost,?

28. Conductors for high voltage transmission lines are suspended from towers toA)reduce clearance from the groundB)reduce wind and snow loadsC)none of these answersD)take care of extension in length during summerE)increase clearance from ground29. On which of the following factors skin effect depends?A)Size of the conductorB)All of these answersC)The resistivity of the conductor materialD)Frequency of the current30. A 3-phase 4 wire system is commonly used onA)primary distributionB)secondary transmissionC)primary transmissionD)secondary distribution31. Floating neutral, in 3-phase supply, is undesirable because it causesA)low voltage across the loadB)none of these answersC)high voltage across the loadD)unequal line voltages across the load32. 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

33. For transmission of power over a distance of 200 km, the transmission voltage should beA)33 kVB)11 kVC)66 kVD)132 kV34. When a conductor carries more current on the surface as compared to the core, it is due toA)skin effectB)coronaC)permeability variationD)none of these answersE)unsymmetrical fault35. When the interconnector between two stations has a large reactanceA)the stations will fall out of step because of large angular displacement, between the stationsB)the transfer of power will take place with the least lossC)the transfer of power will take place with voltage fluctuation and noiseD)none of these answers36. The charging current in the cablesA)lags the voltage by 90B)leads the voltage by 180C)leads the voltage by 90D)lags the voltage by 18037. In medium transmission lines the shunt capacitance is taken into account in

43. Which of the following equipment, for regulating the voltage in the distribution feeder, will be most economical?A)Static condenserB)Synchronous condenserC)Tap changing transformerD)Booster transformer44. A gay wireA)protects conductors against short-circuitingB)provides emergency earth routeC)supports the poleD)provides protection against surges45. The material used for the manufacture of grounding wires isA)cast ironB)stainless steelC)galvanised steelD)aluminium46. The colour of the neutral of the three-core flexible cable isA)redB)blueC)blackD)brown47. By using bundled conductors which of the following is reduced?

58. Which of the following are connected by the service mains?A)Distributor and transformerB)Transformer and earthC)Distributor and relay systemD)Distributor and consumer terminals59. The material commonly used for insulation in high voltage cables isA)rubberB)leadC)none of these answersD)paper60. The material commonly used for sheaths of underground cables isA)leadB)copperC)ironD)rubber61. Basically the boosters areA)inductorsB)capacitorsC)transformersD)synchronous motors62. A lightning arrester is usually located nearer to

63. Which of the following equipment is used to limit short-circuit current level in a substation?A)Lightning switchB)Series reactorC)Coupling capacitorD)Isolator64. The topmost conductor in a high transmission line isA)earth conductorB)B-phase conductorC)R-phase conductorD)Y-phase conductor65. A booster is connected inA)parallel with the feederB)series with earth connectionC)parallel with earth connectionD)series with the feeder66. Aluminium has a specific gravity ofA)4.2B)7.8C)1.5D)2.767. Which of the following distribution systems is the most economical?

68. Which of the following are the constants of the transmission lines?A)ResistanceB)InductanceC)CapacitanceD)All of these answers69. The operating voltage of super tension cables is up toA)33 kVB)6.6 kVC)3.3 kVD)11 kV70. Surge absorbers protect against ____ oscillationsA)high voltage low frequencyB)high voltage high frequencyC)low voltage low frequencyD)low voltage high frequency71. In a distribution system major cost is that ofA)metersB)earthing systemC)distribution transformerD)conductors72. Which of the following bar schemes is the most expensive?

73. Ground wire is used toA)avoid overloadingB)give the support to the towerC)give good regulationD)connect, a circuit conductor or other device to an earth-plate74. The underground system cannot be operated aboveA)440 VB)11 kVC)33 kVD)66 kV75. Which of the following methods is used for laying underground cables?A)Solid systemB)All of these answersC)Draw-in-systemD)Direct laying76. By which of the following methods the protection against direct lightning strokes and high voltage sweep waves is provided?A)Earthing of neutralB)Ground wireC)None of these answersD)Lightening arrestersE)Lightening arresters and ground wires77. Which of the following regulations is considered best?

78. Induction regulators are used for voltage control inA)secondary distributionB)alternatorsC)none of these answersD)primary distribution79. As compared to cables, the disadvantage of transmission lines isA)exposure to lightningB)all of these answersC)exposure to atmospheric hazards like smoke, ice, etc.D)inductive interference between power and communication circuits80. Electro-mechanical voltage regulators are generally used inA)all of these answersB)reactorsC)generatorsD)transformers81. As compared to a 2-wire D.C. distributor, a 3-wire distributor with the same maximum voltage to earth uses onlyA)125 percent of copperB)66.7 percent of copperC)31.25 percent of copperD)33.3 percent of copper82. Out of the following which type of poles are bulky?A)Transmission towersB)Tubular steel polesC)Concrete polesD)Wooden poles83. If the height of the transmission tower is increased, which of the following; parameters is likely to change?

84. Which of the following characteristics should the line supports for transmission lines possess?A)Low costB)Longer lifeC)High mechanical strengthD)All of these answers85. For which of the following, the excitation control method is satisfactory?A)High voltage linesB)Short linesC)Low voltage linesD)Long lines86. Which of the following has least effect on corona?A)Size and charge per ionB)Mean free pathC)Atmospheric temperatureD)Number of ions87. Pin type insulators are generally not used for voltages beyond

88. Earthing is necessary to give protection againstA)danger of electric shockB)high temperature of the conductorsC)voltage fluctuationD)overloading89. The operating voltage of extra high tension cables is up toA)33 kVB)132 kVC)66 kVD)11 kVE)66 kV90. Transmission line insulators are made ofA)P.V.C.B)ironC)porcelainD)glass91. System grounding is done so thatA)inductive interference between power and communication circuits can be controlledB)all of these answersC)the floating potential on the lower voltage winding for a transformer is brought down to an insignificant valueD)the arcing faults to earth would not set up dangerously high voltage on healthy phases92. In the design of a distributor which of the following is the major consideration?

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