变电站直流接地巡检的选线校核机制研究

变电站直流接地巡检装置选线时,会受巡检装置互感器零漂、互感器剩磁、互感器稳定性等因素影响而发生误选或漏选,影响故障排查。在推导平衡电桥法和不平衡电桥法计算接地电阻的基础上,分析接地故障误选、漏选的原因及两种电桥法的局限性。根据故障前后电流电压的状态量、接地电阻的计算量及三者的电气联系进行故障特征辨识,提出基于逻辑事件驱动的自动巡检模式来辨识零漂支路和接地支路,并采用归谬法对接地电阻计算过程进行校核。该巡检模式及校核方法经现场实际数据验证正确、实用,不仅能提高直流查找效率,还为直流系统的状态检修提供了有效信息。

Research on line selection checking mechanism of substation DC ground fault patrol

When the grounding inspection device of substation DC system selects fault branch, the existences of zero point drift, transformer remanence, and transformer stability may impact the efficiency of grounding troubleshooting, which will lead to wrong selection or missed selection. The calculation of grounding resistance based on balanced bridge and unbalanced bridge method is derived, and the reasons of wrong selection or missed selection are analyzed. According to the logical relationship between state variables such as voltage, current and calculated value such as grounding resistance before and after the fault, the characteristics of the faults are identified based on circuit schematic. Automatic inspection mode based on logic event driven is proposed to identify branch with zero drift and grounding branch, and the calculation process of grounding resistance is checked based on absurdum. The real data validate this inspection mode and check method, which can not only improve the accuracy of DC lookup, but also provide useful information for status maintenance.