A Sequence Impedance Matrix Approach to Current Unbalance Detection for Grid Code Fulfillment

Abstract

This work presents a novel method to identify the source of current unbalance during the interaction between industrial consumers and the utility. Since such unbalance yields detrimental effects over the network operation and efficiency; it must be mitigated to avoid their propagation towards the whole grid. To prevent this situation, regulations about the maximum permissible limits of unbalance are recently incorporated in grid codes. Unfortunately, in the absence of an accurate method to identify the agent inducing the unbalance; the problem, responsibility, as well as the solution, is vulnerable to misinterpretation. This situation is quite relevant, for both the consumer and the utility since imputations are subject to penalties. Prompted by this issue, we devised a method based on the computation of sequence impedance matrices. Then the underlying elements of the sequence impedance matrix will expose the occurrence of an unbalance as well as its source, which leads to a theoretically derived metric. This method is tested using real measurements of actual industrial loads connected to different voltage levels (i.e. 230 kV, 161 kV and 115 kV). The results demonstrate accuracy in the detection and identification of the cause of unbalance, considering a wide range of power consumption.