Modelling of voltage unbalance in large real medium voltage distribution networks

Abstract

Voltage unbalance is one of the power quality (PQ) parameters defined in European standard EN 50160. Major challenge in modelling unbalance in large real medium voltage (MV) distribution networks is that current unbalance factors for many different customer categories must be used, but there are no results in the published literature on current unbalance factors for majority of customer categories. In this paper, current unbalance factors for different customer categories in low voltage networks were generated from the model. Voltage unbalance is modelled for an example of a large real MV distribution network in Austria. Voltage unbalance propagation in the analysed network is calculated using unbalance transfer factors, obtained from short-circuit calculations, and general summation law from the standard IEC 61000-3-13. Conclusion of this work is that the voltage unbalance can be modelled, even in large real MV networks, if enough current unbalance factor information of customers and PQ measurements are obtained. The results of this paper will be used for PQ monitor placement algorithm.