二次交流回路异常对线路保护的影响及优化措施

Impact of secondary AC circuit anomaly on line protection and optimum measures

总结目前常规采样线路保护识别二次交流回路异常的难点,主要包括负荷很小时的CT断线、电流相序错误、IN断线、UN多点接地、IN多点接地、保护启动后发生PT断线及线路单相接地故障时非故障相出现尖波电流等,结合现场实际故障分析对保护的不利影响。在不能及时判别出二次交流回路异常的情况下,需要通过优化保护逻辑等措施,降低异常发生的概率及对保护的影响。其中,对于非故障相出现的尖波电流可能导致分相电流差动保护误动的情况,提出分相电流差动保护经两侧故障电流闭锁的优化措施,该措施已在现场应用,取得了良好的效果。

The difficulties in identifying secondary AC circuit anomalies with conventional sampling line protection are summarized,including CT break with very low load,phase sequence error of current,IN break,UN multi-point grounding,IN multi-point grounding,PT break after protection start-up and spike current in non-fault phase when line single-phase grounding fault occurs,etc.The adverse effects on protection are analyzed in combination with actual faults.In case the anomaly of secondary AC circuit can not be identified in time,measures such as optimizing protection logic are needed to reduce the probability of abnormal occurrence and its impact on protection.In the case that spike current in non-fault phase may lead to incorrect operation of phase-split current differential protection,an optimum measure for phase-split current differential protection locked by fault current on both sides is put forward,which has been applied in the field and achieved good results.