Power Systems Questions and Answers

1. Which of the following has least effect on corona ?

(a) Atmospheric temperature
(b) Number of ions
(c)Site and charge per ion
(d) Mean free path


Answer: (a) Atmospheric temperature
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2. In context of corona, if the conductors are polished and smooth, which of the following statements is correct ?

(a) Hissing sound will be more intense
(b) Power loss will be least
(c) Corona glow will be uniform along the length of the conductor
(d) Corona glow will not occur.


Answer: (c) Corona glow will be uniform along the length of the conductor
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3. Power loss due to corona is not directly proportional to

(a) spacing between conductors
(b) supply voltage frequency
(c) phase to neutral voltage
(d) all of the above.


Answer: (a) spacing between conductors
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4. The effect of ice on transmission line conductors is to increase the

(a) transmission losses
(b) weight of the conductor
(c) tendency for corona
(d) resistance to flow of current


Answer: (b) weight of the conductor
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5. If the height of transmission tower is increased

(a) the line capacitance will decrease but line inductance will remain unchanged
(b) the line capacitance and inductance will not change
(c) the line capacitance will increase but line inductance will decrease
(d) the line capacitance will decrease and line inductance will increase


Answer: (a) the line capacitance will decrease but line inductance will remain unchanged
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6. If string efficiency is 100 percent it means that

(a) potential across each disc is zero
(b) potential across each disc is same
(c) one of the insulator discs is shorted
(d) none of the above.


Answer: (b) potential across each disc is same
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7. In a 70/6 A.C.S.R conductor there are

(a) 35 aluminum conductors and 3 steel conductors
(b) 70 aluminum conductors and 6 steel conductors
(c) 70 steel conductors and 6 aluminum conductors
(d) none of the above.


Answer: (b) 70 aluminum conductors and 6 steel conductors
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8. On which of the following does the size of a feeder depend ?

(a) Voltage drop
(b) Voltage
(c) Frequency
(d) Current carrying capacity


Answer: (d) Current carrying capacity
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9. Which of the following are connected by the service mains ?

(a) Transformer and earth
(b) Distributor and relay system
(c) Distributor and consumer terminals
(d) Distributor and transformer.


Answer: (c) Distributor and consumer terminals
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10. In the design of a distributor which of the following is the major consideration ?

(a) Voltage drop
(b) Current carrying capacity
(c) Frequency
(d) kVA of system


Answer: (a) Voltage drop
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11. In a distribution system major cost is that of

(a) earthing system
(b) distribution transformer
(c) conductors
(d) meters.


Answer: (b) distribution transformer
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12. A booster is connected in

(a) parallel with earth connection
(b) parallel with the feeder
(c) series with the feeder
(d) series with earth connection.


Answer: (c) series with the feeder
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13. With which of the following are step-up substations associated ?

(a) Concentrated load
(b) Consumer location
(c) Distributors
(d) Generating stations.


Answer: (d) Generating stations.
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14. Which of the following equipment should be installed by the consumers having low power factor?

(a) Synchronous condensers
(b) Capacitor bank
(c) Tap changing transformer
(d) Any of the above


Answer: (b) Capacitor bank
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15. Which of the following equipment is used to limit short-circuit current level in a substation ?

(a) Isolator
(b) Lightning switch
(c) Coupling capacitor
(d) Series reactor


Answer: (d) Series reactor
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16. Steepness of the travelling waves is altered by ……….. of line.

(a) capacitance
(b) inductance
(c) resistance
(d) all of the above


Answer: (c) resistance
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17. The limit of distance of transmission line may be increased by the use of

(a) series resistances
(b) shunt capacitors and series reactance
(c) series capacitors and shunt reactors
(d) synchronous condensers.


Answer: (c) series capacitors and shunt reactors
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18. The voltage drop, for constant voltage transmission, is compensated by installing

(a) inductors
(b) capacitors
(c) synchronous motors
(d) all of above.


Answer: (c) synchronous motors
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19. By which of the following factors is the sag of a transmission line least affected?

(a) Current through the conductor
(b) Ice deposited on the conductor
(c) Self weight of conductor
(d) Temperature of surrounding air
(e) None of the above


Answer: (a) Current through the conductor
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20. Which of the following causes transient disturbances?

(a) Faults
(b) Load variations
(c) Switching operations
(d) Any of the above


Answer: (d) Any of the above
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21. A gay wire

(a) protects conductors against short-circuiting
(b) provides emergency earth route
(c) provides protection against surges
(d) support the pole


Answer: (d) support the pole
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22. Which of the following is neglected in the analysis of short transmission lines?

(a) Series impedance
(b) Shunt admittance
(c) None of the above
(d) All of the above


Answer: (b) Shunt admittance
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23. Basically the boosters are

(a) synchronous motors
(b) capacitors
(c) inductors
(d) transformers


Answer: (d) transformers
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24. Which of the following is a static exciter ?

(a) Rectifier
(b) Rotorol
(c) Amplidyne
(d) D.C. separately excited generator


Answer: (a) Rectifier
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25. 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 linear portion of its V-I characteristics
(d) must work on nonlinear portion of its V-I characteristics.


Answer: (c) must work on linear portion of its V-I characteristics
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26. The purpose of using a booster is to

(a) increase current
(b) reduce current
(c) reduce voltage drop
(d) compensate for voltage drop


Answer: (d) compensate for voltage drop
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27. Induction regulators are used for voltage control in

(a) alternators
(b) primary distribution
(c) secondary distribution
(d) none of the above.


Answer: (b) primary distribution
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28. A synchronous condenser is generally installed at the ………..of the transmission line.

(a) receiving end
(b) sending end
(c) middle
(d) none of the above


Answer: (a) receiving end
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29. The area of cross-section of the neutral in a 3-wire D.C. system is generally ………….. the area of cross-section of main conductor

() same as
(a) one-fourth
(b) one half
(c) double


Answer: (b) one half
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30. For which of the following, the excitation control method is satisfactory?

(a) Low voltage lines
(b) High voltage lines
(c) Short lines
(d) Long lines


Answer: (c) Short lines
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Power Systems Questions and Answers

 

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