关键词: 雷电流, 接触网支柱, 分散接地, 浪涌保护器（SPD）, 信号分支电缆

Abstract: After lightning strikes the overhead contact line or the support frame of the overhead contact line, signal devices installed nearby and signal cables laid may be damaged or broken down. In order to study the fault causes of signal devices caused by lightning overvoltage and power frequency overvoltage, the potential rise generated by lightning current and power frequency current at the entry point is calculated. It is found that when the amplitude of lightning current connected to the scattered grounded OCS pole exceeds 10 kA, the ground potential rise generated at the entry point is much larger than the impulse withstand voltage of signal cable, and can also be transmitted to the rail surface through the rail to the ground leakage impedance, resulting in the failure of the signal devices connected to the rail. Optimization measures are proposed for the signal equipment and signal cable near the OCS pole in scattered grounding mode, including outer armored grounding, enhanced insulation laying, SPD setting optimization, insulation resistance testing and other aspects, and suggestions are provided for lightning damage analysis and fault handling in similar scenarios.

Key words: lightning current, overhead contact system(OCS) pole, scattered grounding, Surge Protective Device(SPD), signal branch cable