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VOLTAGE IMBALANCE ITS CAUSES AND ITS EFFECTS ON POWER SYSTEM

VOLTAGE IMBALANCE:

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.

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