主变高压侧避雷器缺陷分析不足造成的主变三侧跳闸

Three-side Trip of Main Transformer Caused by Insufficient Analysis of Arrester of Main Transformer High-voltage Arrester

某220 kV变电站某台主变差动保护动作,主变三侧开关跳闸,35 kV低压侧自投正确动作,未损失实际负荷。现场检查发现,主变设备区220 kV相出口避雷器底部有灼伤痕迹,避雷器上、下节泄压通道处瓷套表面有灼伤痕迹。运维单位随即对该台主变进行诊断性试验,检验结果数据合格。后对220 kV出口避雷器进行高压试验发现,BC相试验合格,A相对地绝缘为零。查阅历年带电测试的试验数据发现,设备投运后某年该避雷器测试数据的阻性电流数值较BC两相存在明显偏大现象,随后对该起事故的动作原因进行了深入分析。

In a 220kV substation,a main transformer differential protection action was taken. The three-side switch of the main transformer was tripped,and the 35kV low-voltage side was self-propelled and did not lose actual load. The on-site inspection found that there were burn marks on the bottom of the 220kV A-phase outlet surge arrester in the main transformer equipment area,and there were burn marks on the surface of the porcelain sleeve at the pressure relief passages of the arrester upper and lower sections. The O&M unit immediately conducted a diagnostic test of the main transformer and the data was satisfactory. After the 220kV outlet arrester was subjected to a high voltage test,the BC phase test was found to be satisfactory,and the relative insulation of A was zero. After consulting the test data of the energized test over the years,it was found that the resistance current value of the arrester test data was significantly larger than that of the BC two phases after the equipment was put into operation,and then the cause of the accident was analyzed in depth.