1. If the supply frequency of a transmission line increases, the skin effect
(a) is increases
(b) is decreases
(c) remain same
(d) become very low
Answer: (a) is increases
Explanation:
Skin effect increases with the increase in the conductor diameter (size), increase in the frequency and increase in the permeability and skin effect decrease with the increase in the resistivity of the material.
2. If the length of a transmission line increases, its capacitive reactance
(a) decreases
(b) increases
(c) remain same
(d) becomes very high
Answer: (a) decreases
3. If the spacing between the conductors of overhead transmission line increases, its inductance is
(a) decreases
(b) increases
(c) remain same
(d) none of above
Answer: (b) increases
4. The potential across the various discs of suspension string is different due to
(a) self capacitance
(b) shunt capacitance
(c) skin effect
(d) corona losses
Answer: (b) shunt capacitance
5. If shunt capacitance of a string of suspension insulators is increases, then its string efficiency is
(a) decreases
(b) increases
(c) remain same
(d) none of the above
Answer: (a) decreases
6. When the string efficiency is increased, then the voltage across the discs nearest to the conductor
(a) increases
(b) decreases
(c) remain the same
(d) none of above
Answer: (b) decreases
7. If the spacing between conductor is increased, the inductance of transmission line
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Answer: (a) increases
8. If the spacing between conductors is increased, the capacitance of transmission line
(a) increases
(b) decreases
(c) remains same
(d) none of the above
Answer: (a) increases
9. In overhead lines, if the string efficiency is maximum which means
(a) self capacitance is zero.
(b) shunt capacitance is maximum.
(c) shunt capacitance is zero.
(d) self capacitance is maximum.
Answer: (c) shunt capacitance is zero.
10. In order to improve power factor of a distribution system, the synchronous capacitors are installed at the
(a) receiving end
(b) sending end
(c) intermediate point
(d) substation
Answer:(a) receiving end
11. Static capacitors used in transmission line are rated in terms of
(a) kW
(b) kWh
(c) kVAR
(d) farad
Answer: (c) kVAR
12. Transposition of transmission line is done to
(a) decrease skin effect.
(b) decrease I2R losses.
(c) balance line voltage drop.
(d) decrease corona.
Answer: (c) balance line voltage drop.
13. The constants of the transmission lines are
(a) resistance
(b) inductance
(c) capacitance
(d) all of the above
Answer: (d) all of the above
14. Feeder are designed mainly from the point of view of
(a) voltage drop in it.
(b) its current carrying capacity.
(c) operating frequency.
(d) operating voltage.
Answer: (b) its current carrying capacity.
15. For 66 kV lines the number of insulator discs used are
(a) 2
(b) 5
(c) 8
(d) 10
Answer: (b) 5
16. While analysing a short transmission line, we can neglect the
(a) skin effect.
(b) line losses.
(c) shunt admittance.
(d) series impedance.
Answer: (c) shunt admittance.
17. The string efficiency of a high voltage line is around
(a) 20.
(b) 40.
(c) 80.
(d) 100.
Answer: (c) 80.
18. If the transmission voltage is increased, the percentage resistance drop will
(a) increases.
(b) decreases.
(c) remain same.
(d) none of the above.
Answer: (b) decreases.
19. Material generally used for bus bar is
(a) copper
(b) aluminium
(c) steel
(d) tungsten.
Answer: (b) aluminium
20. The effect due to which a conductor carries more current on the surface as compared to core is
(a) proximity effect.
(b) corona effect.
(c) skin effect.
(d) Kelvin effect.
Answer: (c) skin effect.
21. Power transmission capacity of a transmission line can increase by decreasing
(a) transmission voltage.
(b) capacitance.
(c) line inductance.
(d) all of the above.
Answer: (c) line inductance.
22. In a transmission line booster transformer must be located at
(a) receiving end.
(b) sending end.
(c) intermediate point.
(d) any where in the line.
Answer: (c) intermediate point.
23. A booster is a
(a) series wound generator.
(b) shunt wound generator.
(c) synchronous generator.
(d) none of the above.
Answer: (a) series wound generator.
24. Pin type insulators are generally not used for voltages beyond
(a) 66 kV.
(b) 11 kV.
(c) 22 kV.
(d) 33 kV.
Answer: (d) 33 kV.
25. A 3-phase 4 wire system is commonly used on
(a) primary transmission.
(b) secondary transmission.
(c) primary distribution.
(d) secondary distribution.
Answer: (d) secondary distribution.
26. Boosters are basically
(a) inductors.
(b) capacitors.
(c) transformers.
(d) synchronous motors.
Answer: (c) transformers.
27. The skin effect of a conductor will reduce as the
(a) diameter increases.
(b) frequency increases.
(c) permeability of conductor material increases.
(d) the resistivity of conductor material increases.
Answer: (d) the resistivity of conductor material increases.
28. If the frequency of a transmission system is increases, the string efficiency will
(a) increase.
(b) decrease.
(c) remain same.
(d) none of the above.
Answer: (c) remain same.
29. The equipment used to limit short circuit current in power system is
(a) series reactor.
(b) relay.
(c) lightening switch.
(d) capacitor.
Answer: (a) series reactor.
30. If the lagging power factor of the load decreases, the line losses will
(a) decrease.
(b) increases.
(c) remains same.
(d) none of the above.
Answer: (b) increases.