贯通线全电缆线路中性点接地方式的选择

Choice of Neutral Point Earthing Mode of 10 kV All-cable Power Transmission Line for High-speed Railway

研究目的:长期以来我国普速铁路10kV贯通线采用架空方式为主、电缆线路为辅,10kV贯通线中性点采用不接地系统。高速铁路10kV贯通线大量使用电缆线路,长距离电缆线路的对地电容电流远大于架空线路,且10kV贯通线电缆线路与通信信号电缆长距离接近平行敷设,应对系统中性点接地方式进行综合研究,提出适合我国高速铁路10kV贯通线全电缆线路特点的中性点接地方式,以指导工程设计。研究结论:经调压器供电的10kV贯通线全电缆线路中性点宜采用低电阻接地,当调压器容量为250kVA及以下时,中性点可采用直接接地;低电阻接地的电阻值宜按单相接地电流小于400A、接地故障瞬时跳闸方式选择;变配电所接地网电阻值宜按R≤1Ω设计。

Research purposes： For the 10 kV power transmission line for the ordinary railway in China, the mode of overhead line as main line with cable as auxiliary line has been adopted for a long time without neutral point earthing. For the high -speed railway, the 10 kV power transmission line is mainly cable line. Considering the capacitive current of long distance cable line is much greater than the overhead line, and the 10 kV cable line is laid together with communication and signaling cables for long distance, thus it is necessary to do the comprehensive study on the earthing mode of neutral point in order to present a proper earthing mode of neutral point of the 10 kV all - cable power transmission line for high -speed railway for providing the reference to the similar works.Research conclusions： Under condition that the voltage of 10kV all -cable power transmission line is regulated by voltage regulator, it is appropriate to use the low - resistance earthing mode whereas the capacity of voltage regulator is lower than 250 kVA, the neutral point can be grounded directly. The value of low resistance should be determined by the earthing fault instantaneous tripping mode when single phase earthing current is less than 400 A. The value of the earthing grid of substation and power distribution substation should be no more than 1 Ω.