Q-hour meter performance under unbalanced voltage supply

This article investigates the error associated with reactive power and power factor when calculated from a set of watt-hour and Q-hour meters in a circuit where an unbalanced sinusoidal supply feeds a linear balanced load. An analytical expression of the error is derived in terms of the level of voltage unbalance. It is found that this method under-estimates reactive power thus leading to higher power factor at all times but the error is well within meter tolerance for typical levels of unbalance.