Voltage Control


The control of transmission voltage through adjustments in generator reactive output and transformer taps, and by switching capacitors and inductors on the transmission and distribution systems.

Importance of voltage control

In case of lighting load, the lamp characteristics are very sensitive to changes of voltage. For instance, if the supply voltage to an incandescent lamp decreases by 6% of rated value, then illuminating power may decrease by 20%. On the other hand, if the supply voltage is 6% above the rated value, the life of the lamp may be reduced by 50% due to rapid deterioration of the filament.

In case of power load consisting of induction motors, the voltage variations may cause erratic operation. If the supply voltage is above the normal, the motor may operate with a saturated magnetic circuit, with consequent large magnetising current, heating and low power factor. On the other hand, if the voltage is too low, it will reduce the starting torque of the motor considerably.

Too wide variations of voltage cause excessive heating of distribution transformers. This may reduce their ratings to a considerable extent.

Location of voltage control equipment

The voltage control equipment is used at more than one point in the system for two reasons.

  • Firstly, the power network is very extensive and there is a considerable voltage drop in transmission and distribution systems.
  • Secondly, the various circuits of the power system have dissimilar load characteristics.

voltage control equipment is used at :

  1. generating stations
  2. transformer stations
  3. the feeders if the drop exceeds the permissible limits

Methods of voltage control

  1. By excitation control
  2. By using tap changing transformers
  3. Auto-transformer tap changing
  4. Booster transformers
  5. Induction regulators
  6. By synchronous condenser

Method (i) is used at the generating station only whereas methods (ii) to (v) can be used for transmission as well as primary distribution systems. However, methods (vi) is reserved for the voltage control of a transmission line.

4 thoughts on “Voltage Control

  1. Just desire to say your article is as amazing. The clarity to your put up is just excellent and i could think you’re a professional in this subject. Well with your permission allow me to grab your RSS feed to keep updated with drawing close post. Thanks a million and please keep up the enjoyable work.

  2. Thanks for the nice post! It was really helpful. I think you have directly copied it from a book called Principles of Power System by V.K Mehta. Though it was really good of you that you atleast posted. Thumbs up!

    • Ya most of the posts in the Power Electronics category has been taken from V.K Mehta those that are not from V.K Mehta are either from S.S Rao or from everyone’s favorite Wikipedia or combo of both.
      Thanks for the thumbs up.

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