Impact and countermeasure of three-phase unbalanced operation for low voltage distribution systems

Most of Chinese low-voltage distribution systems use three-phase four-wire Y/Yno(Y/Y) connection mode.The transformer unbalanced operation state is often caused by single-phase loads.The three-phase voltage imbalance and its impact to power quality are analyzed in this paper.Distribution transformer losses and line losses caused by the imbalance are investigated in detail.Some managing and technical countermeasures for the imbalance are also proposed.