Relay protection strategy for loop closing distribution network with phase shifting transformer

To address the challenges of protection device misoperation, maloperation, and low sensitivity caused by long term loop closing operation of thyristor controlled phase shifting transformers (TCPST) in distribution networks, an enhanced relay protection strategy for TCPST equipped distribution networks under long term loop closing conditions is developed. First, mathematical models of the TCPST and loop closing network are established. Then, the impact mechanism of TCPST integration on conventional protection systems is systematically analyzed. An improved adaptive current protection method is formulated through establishment of fault composite sequence networks, enabling dynamic adjustment of protection device settings after loop closing based on pre loop closing operational states. Finally, a 10kV distribution loop closing network model is implemented in PSCAD. The effectiveness of the proposed strategy is verified through comprehensive simulation studies, with results demonstrating enhanced protection sensitivity and operational reliability.