500 kV自耦变压器中性点经小电抗接地的过电压与绝缘配合分析

为研究500 kV自耦变压器中性点由直接接地改成经小电抗接地后其各种过电压水平变化情况,笔者利用ATP-EMTP电磁暂态程序对主变中性点和端部过电压进行详细计算,对变压器中性点接小电抗后的各种过电压水平进行了分析并确定其过电压的保护方式、绝缘配合,得出安徽省500 kV肥西变主变中性点经5Ω电抗器接地后,加上氧化锌避雷器保护,可维持原绝缘水平不变的结论,对解决肥西变500 kV电网中单相接地短路电流超过开关额定遮断电流的问题具有重要意义。

Overvoltage and Insulation Coordination of 500 kV Autotransformer Neutral Grounding through Small Reactance

To understand overvoltage change at a 500 kV autotransformer neutral when the neutral is grounded from directly to through a small reactance,the overvoltage at autotransformer’s neutral and entrance is calculated respectively by ATP-EMTP,and the overvoltage for adopting small reactance grounding is analyzed to determine overvoltage protection and insulation coordination.It is concluded that the insulation level of the autotransformer in 500 kV Feixi substation can keep stable after its neutral is grounded through a 5 Ω reactance under protection of MOA.This conclusion will contribute to the solution to the problem that single phase short-circuit current exceeds the switch rate breaking current in the Feixi 500 kV grid.