Transient Characteristics Analysis of Switching Overvoltage in High-Speed Railways Based on a Network-Vehicle-Ground Coupling Model

High-speed electric multiple units (EMU) utilize pantographs to draw power from a single-phase catenary system. While ensuring high-speed operation, their power systems face complex transient impact challenges. During the phase-changing transition process, transient overvoltage caused by nonlinear switching operations imposes frequent short-term impacts on primary-side equipment, degrading onboard insulation performance and propagating to low-voltage devices through rooftop high-voltage cables via coupling. Therefore, based on the electrical coupling characteristics of the “ catenary-EMU-grounding” system, it is necessary to perform full-process inversion of overvoltage transient behaviors through field-circuit equivalent simulations and systematically analyze each transient stage of the phase-changing process. This study constructs an electrical coupling model of “traction network-EMU-comprehensive grounding” according to the actual energy flow of EMU traction power supply systems. Equivalent simulations are conducted to investigate the generation mechanisms and influencing factors of switching overvoltage during phase-changing transients. Finally, simulation verification is performed using pre-operational joint commissioning test data from a railway section in eastern China, providing a systematic explanation and validation of the transient processes during high-speed EMU phase-changing operations.