Q9Power Quality and FACTS
Question
2 marks
Q.9. Define the term voltage imbalance. [2]
Answer
Voltage imbalance (or unbalance) is a condition in a three-phase system in which the RMS magnitudes of the phase voltages or the phase angles between them are not equal.
It is quantified either by the NEMA definition (maximum deviation from average voltage divided by average voltage, expressed as percentage) or by the symmetrical-component method (ratio of negative-sequence to positive-sequence voltage). It is caused by unbalanced single-phase loads, untransposed lines, or blown fuses on capacitor banks, and can cause overheating of induction motors.