多直流支路接地检测方法的研究

Study of detecting method for several branchs grounding

绝缘监察装置是变电站和发电厂用直流操作电源系统必备的检测装置。本文对传统的绝缘监测方法的原理进行了分析,并指出其存在的问题。在此基础上,对差流检测法的基本原理进行分析,其采用对正负母线绝缘检测电阻的定时切换,形成不平衡桥,可检测出正负母线对地绝缘电阻;与直流漏电传感器相结合,可实现直流馈出支路绝缘故障的极性和阻值检测。本文详细推导了不引入不平衡桥与引入平衡桥相结合的方法,可有效解决目前基于不平衡桥的差流检测法难以正确测量多支路正负同时接地故障的问题,并通过实验证明其可行性。

Insulation monitoring device is necessary detecting device of DC operation power supply system in sub-stations and power plants.The principle of conventional insulation supervision and measurement was analyzed,and the existing problems were discussed.Based on these analyses,the principle of differential current method was analyzed.The unbalanced bridge is formed by switching insulation detecting resistances to positive bus and negative bus,so the ground-ing resistances to positive bus and negative bus can be detected.Based on unbalanced bridge,the polarity and value of grounding resistances can be detected by using leak current sensors.The troublesome problem of DC grounding detecting system based on differential current detecting method is that the grounding resistances can not detected accurately when several output branchs break down with positive and negative grounding samely.To resolve this problem,unbalanced bridge is adopted comprehensively in this paper,which effectiveness is verified by experiment.