Relay Protection Configuration for the Thyristor Controlled Phase Shifting Transformer

Based on the topology and equivalent circuit of thyristor controlled phase shifting transformer (TCPST), the current amplitude equal characteristic of TCPST is deduced in this paper. The differential protection criterion of series transformer and excitation transformer is proposed based on the flux balance principle. The differential protection criterion of TCPST winding is proposed based on Kirchhoff's current law. The main relay protection strategy of TCPST is constructed. Furthermore, the transient characteristics of bypass switch stealing and thyristor control circuit fault under abnormal conditions are analyzed, and the protection strategy for abnormal conditions and the backup protection scheme of winding overvoltage and overcurrent are formulated. Finally, the fault at different locations is simulated to verify the completeness and effectiveness of the protection strategy.