VOLTAGE IMBALANCE ITS CAUSES AND ITS EFFECTS ON POWER SYSTEM

Voltage imbalance is regarded as any differences in the three phase voltage magnitudes and/or shift in the phase separation of the phases from 120 degrees.It is normally expressed as the negative phase sequence divided by the positive phase sequence,as a percentage, measured using line to line voltages.

EFFECTS OF VOLTAGE IMBALANCE:

1. The effects of voltage unbalance are mainly associated with three phase motors. These effects are namely:
2. Increased motor losses, reduced efficiency and therefore increased running costs; 
3. Increased losses results in additional heating and loss of motor insulation life; 
4. Effective torque and speed will be reduced; 
5. Increased motor noise;

CAUSES OF VOLTAGE IMBALANCE:

1. The causes of voltage imbalance include: 
2. Large and/or unequal single phase loads; 
3. The uneven connection of single phase customers to the distribution system; 
4. The uneven connection of single phase transformers or spur lines to distribution lines; 
5. Unequal impedances of the three phase transmission and distribution lines; 
6. Blown fuses on capacitor banks.
7. Connection of Rail traction supplies.