高速铁路馈线电缆雷电过电压及防护措施

Lightning Overvoltage and Protection Measures of High-speed Railway Feeder Cable

高速铁路中雷电流是造成电缆绝缘破坏的一个重要因素,当输电线路遭受雷击时,雷电流将通过线路与电力电缆的连接点侵入电缆,并造成电缆主绝缘和护层绝缘的破坏。因此利用PSCAD/EMTDC软件建立单芯电缆的暂态分析模型,仿真分析了雷击点位置、避雷器、电缆护层保护器、电缆并联根数的影响。分析结果表明:雷电流幅值越大,离雷击点距离越近,雷电过电压越大;当雷击点与电缆接头处的距离小于100 m时,会在电缆线芯与护层上产生数十万V的电压,足以破坏电缆绝缘。此时需要加装避雷器与电缆护层保护器将电缆线芯和电缆护层的雷电过电压限制在其残压内,同时可以增加电缆并联根数来降低线芯电流与护层电压,以提高电缆的绝缘水平和供电可靠性。

In high-speed railway, lightning current is an important factor causing the damage of cable insulation. When transmission line is struck by lightning, lightning current will invade to cable by the junction of cable and transmission line, and it may damage the main insulation and sheath insulation. By using the PSCAD/EMTDC simulation software, we set up a transient state analysis model of single core cable. Through the simulation model, we analyzed the influences of lightning strike location, lightning arrester, cable sheath protector, and number of parallel cable. The analysis results show that, the greater the amplitude of the lightning current is, and the closer the lightning point is, the higher the lightning overvoltage will be. When the distance between the strike point and cable joint is less than 100 m, hundreds of thousands of volts voltage will produce on cable core and sheath, which is enough to damage the cable insulation. Therefore, it is necessary to install a lightning arrester and cable sheath protector to limit the lightning overvoltage between the cable core and sheath to the residual voltage. Meanwhile, increasing the number of parallel cable can reduce the lightning overvoltage between the cable core and sheath. The above measures can be used to improve the insulation level and power supply reliability of the cable.