How Improve Voltage Regulation in Power System

Voltage Regulation Improve in Transmission Lines

If we consider how the high voltage in the transmission lines should regulate, then the answer is with a transformer.


But if we consider how the voltage is increased in an already operating transmission line this can be done by couplers in the transformer in- or decreasing the number of turns in the transformer, hereby raising or lowering the voltage.

Under heavy load condtions, more current drawn from your TL and this increases the voltage drop V=IZ and to increase the voltage at the sending end there is some methods can be used:

Method-1 changes Z, where method-2 changes current I. And these is what voltage drop depend on Vdrop=IZ. Decreasing voltage drop means raising voltage at receiving end. 


  1. You can add series capacitors to your TL with each phases at some distances of your line. The capacitive reactance Xc will remove part of the inductive reactance Xl and hence the total impedance Z will decrease. And when Z decrease that means your voltage will rise because voltage drop now is small.
  2. Using shunt capacitors, using shunt capacitors at receiving end or at selected points accross your TL will compensate part of the inductive reactance, and hence will decrease the current that flow in the TL and this will decrease the voltage drop and hence increases the voltage. This shunt capacitors in fact acts like power factor correctors, they increase pf and then decrease the current: I=P3√∗V∗pf as you see when pf increases the current will decrease from this equation.


In most cases the shunt capacitors are used at the receiving end of the TL in the substations.


How Improve Voltage Regulation in Power Distribution Line

Mainly controlling the voltage level in distribution system voltage regulation is improve. The possible way to improve voltage regulation in electrical power distribution system network is as below:


1. Use of generator voltage regulators;

2. Application of voltage-regulating equipment in the distribution substations;

3. Application of capacitors in the distribution substation;

4. Balancing of the loads on the primary feeders;

5. Increasing of feeder conductor size;

6. Changing of feeder sections from single-phase to multiphase;

7. Transferring of loads to new feeders;

8. Installing of new substations and primary feeders;

9. Increase of primary voltage level;

10. Application of voltage regulators on the primary feeders;

11. Application of shunt capacitors on the primary feeders;

12. Application of series capacitors on the primary feeders;

How is voltage regulation calculated?

Voltage Regulation for 11KV, 22KV, 33KV Overhead Line
  • % Voltage Regulation = (1.06 x P x L x PF) / (LDF x RC x DF)
  • RC = (KV x KV x 10) / ( RCosΦ + XSinΦ)
  • Required size of Capacitor (Kvar) = KVA1 (Sin ø1 – [Cos ø1 / Cos ø2] x Sin ø2)
  • L = [1 – (KVARC / 2 KVARL) x (2n – 1)]
  • % Voltage Rise = (KVAR(Cap) x Lx X) / 10 x Vx2

Nominal Valu of Voltage Regulation:

  • Above 33kV (-) 12.5% to (+) 10%.
  • Up to 33kV (-) 9.0% to (+) 6.0%.
  • Low voltage (-) 6.0% to (+) 6.0%

What is Voltage Regulation in Power System

By deffination voltage regulation is “the ratio of voltage drop from no load to the full load to the no load voltage”.

There are two ways to express the voltage regulation:

One is voltage regulation up and another is voltage regulation down.

Consider general formula for voltage regulation up as

Voltage Regulation Formula-1


Here Vnl is the no load voltage and Vfl is the full load voltage.

The voltage regulation up is normally used in case of transformers.

Consider general formula for voltage regulation down as

Voltage Regulation Formula-2

The voltage regulation is normally used in case of alternators and power system calculations and its efficiency scalling.