某变电站500kV母线保护TA断线保护闭锁分析

The Analysis on 500kV Bus-differential Protection Latch of a Substation because of TA Break

某3/2主接线的500k V变电站母线保护报出5053断路器支路TA断线导致母线保护闭锁,检查发现5053断路器支路三相电流不平衡,导致其零序电流满足母线保护TA断线逻辑判据。现场主回路直阻测量发现,5053断路器支路A相主回路隔离开关接触电阻偏大,致使5053断路器支路三相主回路电阻不平衡,最终导致在3/2系统内产生零序环流。通过Simulink建模对5053断路器支路三相主回路电阻不平衡在3/2系统内产生的零序环流进行仿真验证,并提醒相关人员在检修试验时要注意对比支路三相电阻的不平衡偏差。

The bus-differential protection of a 500kV 3/2 connection substation reported 5053 circuit breaker branch TA break, check found to be due to 5053 circuit breaker branch three-phase current imbalance caused by the zero sequence current to meet the bus protection TA off Line logic criterion. The main circuit of the 5053 circuit breaker branch circuit A-phase main circuit isolation switch contact resistance is too large, resulting in 5053 circuit breaker three-phase main circuit resistance imbalance, resulting in the 3/2 system zero sequence circulation. The simulation of the zero sequence circulation generated by 3/2 system of 3-phase main circuit resistance imbalance of 5053 circuit breaker is simulated by Simulink model. It is also reminded to pay attention to the unbalance of the three-phase resistance in the maintenance test deviation.