基于差流检测法的分布式直流接地巡检系统

Development of distributed DC grounding detecting system based on differential current detecting method

绝缘监察装置是变电站和发电厂用直流操作电源必备的检测装置。对传统的绝缘监测的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。介绍了以此为基础的分布式直流接地巡检系统的工作原理,该系统能准确定位绝缘电阻下降或接地分支,既可监测输出直流支路任意极性绝缘下降或接地故障,也可监测直流支路正极、负极绝缘同时下降的情况。该系统组态灵活,尤其适合监测范围大,分支回路多的直流电源系统。

Insulation monitoring device is necessary detecting device of DC operation power supply in substations and power plants. The principle of conventional insulation supervision and measurement was analyzed, and the existing problems are 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 grounding resistances to positive bus and negative bus can be detected. Based on unbalanced bridge, the polarity and the value of grounding resistances can be detected by using leak current sensors. The principle of distributed DC grounding detecting system based on differential current detecting method was introduced, the system can exactly discover DC branch that has insulation fault. It can not only detect grounding polarity of any branch, but also inspect the instance that has insulation faults both on positive output and negative output. The system has flexible configuration, which is suit to DC power supplies that have excessive output branch and large inspecting range.