Identification of unbalanced loads in electric power systems

Voltage unbalance is one of the main problems in electric distribution systems. The standards limit the level of voltage unbalance in a specific point without considering the agent of the network that produces it. Nevertheless, the identification of the responsible for system unbalance may be very important, for example, to establish the most suitable procedure to mitigate it. To do that, a new index, denominated unbalance current ratio, is proposed in this paper. It is based on decomposing the actual current at the input of the load in three components: the first one is that required by an unbalanced linear load, the second one is that required by a non-linear load, and the third corresponds to a balanced linear load. All of them compose the total current at the input of the analyzed load. The new index can be calculated only from the measurement of the current at the input of the load and the voltage at the point of common connection. Several simulation systems have been considered to check the index behavior, and an experimental platform has been designed to verify its validity in unbalanced non-sinusoidal systems. Copyright (c) 2013 John Wiley & Sons, Ltd.