Short Circuit Impedance Analysis for Cross-Coupling AT Power Traction Network Under Over-zone Feeding Operation Condition

The cross-coupling AT (Autotransformer) power supply mode is applied to high-speed railways in China. When the power failure of traction substation is caused by the incoming power supply or equipment failure, the traction network needs to adopt the over-zone feeding operation condition to ensure the continuous power supply. It is necessary to analyze the short circuit impedance of traction network under over-zone feeding operation condition. It provides a useful reference for the analysis of relay protection and power supply capacity of the traction network. In this paper, the equivalent circuit method is used to build the circuit model of cross-coupling AT power traction network under over-zone feeding operation condition, and the relationship between short circuit impedance and distance is deduced. The relation characteristics of short circuit impedance and distance is explained. The improvement of distance protection setting under the existing over-zone feeding operation condition. is proposed. The simulation result based on Matlab/Simulink shows that the application of equivalent circuits and the derivation of short circuit impedance formula are verified.