Study on the Influence of Parasitic Inductance of Connection Path on SPD Protection Effect for Plateau Rail Vehicles

Abstract:The power supply lines of plateau rail vehicles are vulnerable to lightning surges, and the parasitic inductance of connecting paths may raise the actual residual voltage at equipment terminals above the rated residual voltage of Surge Protective Device (SPD). To quantify the influence of such inductance on SPD protection performance, an equivalent model consisting of power supply cable, inverter input terminal, SPD and grounding path is established. With the 3 kA, 8/20 μs surge current as excitation, three simulation conditions including no SPD, ideal SPD and SPD with parasitic inductance are configured for comparative analysis. Simulation results demonstrate that SPD can effectively suppress the residual voltage at the equipment side. Nevertheless, after taking the parasitic inductance of connecting and grounding paths into consideration, the terminal residual voltage rises from approximately 37 kV under ideal SPD condition to 55 kV, and the residual voltage reduction ratio drops from 61.9% to 43.3%. This research indicates that the practical residual voltage on equipment terminals shall be taken as the core indicator for SPD protection design, and the wiring length as well as grounding impedance should be strictly controlled.