Necessary and sufficient conditions for load balance in three-phase power systems

The symmetrical components have been traditionally used in analyzing unbalance in polyphase systems. These analyses are normally exact when the voltage source is balanced. In this paper, a simple and easy to measure index which is independent of the source voltage balance condition is proposed. We show that the proposed index possesses two major features: (i) it is an exact measurement of apparent power increase due to load unbalance, and (ii) it is applicable to all possible metering configuration including asymmetrical ones. Implicit in our development, the right definitions of apparent power for every metering service are given