Analysis on Transformer Protection Maloperation Caused by Single-Phase Tripping of Wind Farm Transmission Lines

This paper introduces a case of transformer voltage and overcurrent composite protection maloperation caused by single-phase tripping of a wind farm transmission line. Firstly, the case is briefly introduced as a background. Then, the system operating mechanism and the electrical characteristics after single phase-tripping of the wind farm transmission line are analyzed. Subsequently, the reason for protection maloperation is revealed combined with the principle of transformer voltage and overcurrent composite protection. Finally, improvement measures to avoid protection maloperation are proposed. The research results show that the single-phase tripping of the wind farm transmission line will generate high negative voltage and overcurrent, leading to maloperation of the transformer's voltage and overcurrent composite protection. The time delay of the transformer's voltage and overcurrent composite protection should be greater than the single-phase tripping operation time to avoid protection maloperation.