| 1. | By which of the following methods string efficiency can be improved ? | |
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Using a guard ring
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Grading the insulator
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Using long cross arm
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Any of the above
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Report Question| 2. | Constant voltage transmission entails the following disadvantage ? | |
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large conductor area is required for same power transmission
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short-circuit current of the system is increased
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either of the above
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none of the above
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| 3. | If the voltage is increased x times, the size of the conductor would be ? | |
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reduced to 1/x2 times
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reduced to 1/x times
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increased x times
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increased to x2 times
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| 4. | Corona usually occurs when the electrostatic stress in air around the conductor exceeds ? | |
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6·6 kV (r.m.s. value)/cm
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11 kV (r.m.s. value)/cm
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22 kV (maximum value)/cm
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30 kV (maximum value)/cm
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| 5. | Which of the following materials is used for overhead transmission lines ? | |
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Steel cored aluminium
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Galvanised steel
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Cadmium copper
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Any of the above
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| 6. | Which of the following methods is used for laying of underground cables ? | |
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Direct laying
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Draw-in-system
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Solid system
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All of the above
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| 7. | Due to which of the following reasons the cables should not be operated too hot ? | |
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The oil may loose its viscosity and it may start drawing off from higher levels
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Expansion of the oil may cause the sheath to burst
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Unequal expansion may create voids in the insulation which will lead to ionization
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All of the above
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| 8. | Which of the following faults is most likely to occur in cables ? | |
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Cross or short-circuit fault
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Open circuit fault
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Breakdown of cable insulation
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All of the above
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| 9. | The operating voltage of supertension cables is upto ? | |
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3.3 kV
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6.6 kV
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11 kV
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33 kV
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| 10. | The usual spans with R.C.C. poles are ? | |
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40-50 metres
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60-100 metres
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80-100 metres
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300-500 metres
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