变压器中性点过电压分析与绝缘配合

电力系统发生不对称短路、非全相运行和雷击等故障时，变电站变压器中性点会出现较高的过电压，严重影响中性点绝缘的可靠性，因此需要对变压器中性点过电压和绝缘配合开展研究。文章在PSCAD/EMTDC中搭建110 kV输电系统仿真模型，计算分析线路发生各种故障时的中性点过电压，依据仿真所得过电压值，确定放电间隙距离以实现更加优化的绝缘配合。结果表明，线路发生单相接地故障时中性点最高过电压为117.73 kV;发生单相断线时中性点最高过电压为52 kV;发生雷击时中性点最高过电压为118 kV;采用放电间隙并联避雷器的中性点保护方式时，选取放电间隙距离为13 mm～14 mm时能达到最优的绝缘配合效果。该研究结果可以为110 kV变压器中性点的绝缘配合优化提供重要的理论和实验参考依据。

Overvoltage analysis and insulation coordination of transformer neutral point

When the 110 kV power system suffers from asymmetrical short circuit, non-full-phase operation, and lightning strikes, a large overvoltage will appear at the neutral point of the transformer in the substation and endanger the neutral point insulation. Therefore, it is necessary to study the over-voltage and insulation coordination of 110 kV transformer neutral points. This paper builds an 110 kV system simulation model in PSCAD/ EMTDC, calculates and analyzes the neutral point overvoltage when various faults occur on the line, and determines the discharge gap distance based on the obtained overvoltage value to achieve good insulation coordination. The calculation results show that the maximum overvoltage at the neutral point reaches 118 kV when a single-phase ground fault occurs on the line; the maximum overvoltage at the neutral point reaches 52 kV when a single-phase disconnection occurs; the maximum overvoltage at the neutral point reaches 118 kV when a lightning strike occurs; a better insulation coordination effect can be achieved when the discharge gap distance is 13~14 mm with the parallel arrester. The results can provide important basis for insulation coordination of 110 kV transformer neutral point.