特高压荆门站串联变压器间单相接地故障分析

摘要

对特高压荆门站站用电两级变压器串联的接线方式下发生的小电流接地系统单相接地故障进行分析,指出故障原因是两级变压器之间连接电缆无保护,提出了通过在高压站用变l0kV出线侧加装一个电压互感器的改进措施,以开口三角接线接入变压器后备保护,避免该段电缆无绝缘监测.两级变压器串联接线方式的保护配置,不仅需要将两个变压器看成一个整体进行考虑,还要关注故障发生在设备连接部分的情况,避免保护配置不完善的情况.%Based on the analysis of the single-phase-to-ground fault in power system with ungrounded neutralbetween the two-stage series transformers in UHV JingMen substation, this paper points out that the fault isdue to non-protection for the cable between the two-stage series transformers. A solution to the problem is thata 10 kV PT with secondary windings as open-delta connection access to backup protection of the two transformers is installed at 10 kV side of high voltage transformer, which is used to avert the cable lack of isolation inspecting between the transformers. The protection set requires not only considering the two series as a unity, but also the fault condition in the connection, which is helpful to avoid the incomplete protection.