Method of voltage control adopted for transmission lines in AC systems is

A. Excitation control

B. Synchronous condenser

C. Booster transformers

D. Auto-transformer tap changing


Answer: B. Synchronous condenser


Explanation:



The power transfer capability of EHV transmission lines can be increased by maintaining the loaded voltage within specified limits.

The following methods are used for maintaining the voltage within limits:

Shunt capacitor bank

Shunt reactors

Synchronous condensers

Static VAR compensators at heavy loads

Series compensation

 

A synchronous condenser is not a static compensation. A synchronous condenser is a synchronous motor running at no load and taking leading current.

A synchronous condenser is an overexcited synchronous motor, which draws leading currents from the system and hence compensates for lagging vars. It is used as a reactive power compensator in some systems for power factor correction purposes.


Important Point:

Whenever an inductive load is connected to the transmission line, power factor lags because of lagging load current. To compensate this, a shunt capacitor is connected which draws current leading the source voltage. The power factor can be improved.

Series capacitors are used to compensate for the inductance of the transmission line. They will increase the transmission capacity and the stability of the line. These are also used to share the load between parallel lines.

Series reactors are used as current limiting reactors to increase the impedance of a system. They are also used to limit the starting currents of synchronous electric motors and to compensate reactive power in order to improve the transmission capacity of power lines.

A shunt reactor is an absorber of reactive power, thus increasing the energy efficiency of the system.


More MCQS With Fully Explained 

1. Under over excitation synchronous phase modifier works as

2. The neutral of the power system may be connected to earth

3. The time to open the circuit breaker contact is called as

4. A 100 Ah capacity battery should deliver a current of 10 A for approximately _____ hrs.

5. For 400KV line, The Spacing Between phase conductor is around 

6. Shunt capacitors in a sub-station

7. An alternator is said to be over excited when it is operating at

8. In case of transformer Buchholz relay is used to protect from 

9. Series capacitors are used to

10. Disadvantage of low power factor is

11. The colour of neutral three core flexible cable is

12. The location of ground faults in underground cables can be found by

13. Fault location in an HV cable is done by

14. The insulation resistance of a cable of length 10 km is 1 MΩ. its resistance for 50 km length will be

15. Which of the following is not a valid advantage of bundle conductor?

16. Star-star power transformer is protected by current transformer having

17. The surge resistance of cables is

18. Skin effect is only noticeable at _______ frequencies. 

19. When transmission voltage is increased, the line losses are

20. Var compensators are used to

21. High voltage transmission lines use

22. The material used for insulators are

23. Which device is used for protection of equipment from from damage caused by overload or short circuit?   

24. Isolator in sub station is open under ------------- condition?

25. The surge impedance value of overhead lines is





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