Research on the Impact of Inrush Current of Converter Transformers on Electrical Protection Relay of Converter Transformers

When closing converter transformers without load, inrush current arise due to the invalid suppression strategies, which pose a significant threat to power system. Studying the effect of inrush currents on electrical protection relay is of great significance. To this end, this paper analyzes the characteristics of inrush current, examines its impact on the protection of converter transformers, and build simulation model with parameters of a ± 800kV converter station for analysis based on PSCAD/EMTDC. The results indicate that inrush current may cause the failure of second harmonic restraint when the residual magnetism direction is different. Moreover, the circulating current generated in the YD-connected converter transformers can trigger the converter bridge differential protection action. It is feasible to restraint the above electrical protection relay based on the variation of excitation impedance.