直流系统接地故障综合检测方法

为解决直流系统接地故障检测的难题，提出综合运用漏电流法和波形分析法实现接地故障选线.漏电流法通过检测对地直流不平衡电流检测单极接地故障.波形分析法通过分析向直流系统注入的方波信号基波及三次谐波之间的相位及幅值关系，计算接地支路电阻来检测两极同时接地故障，并且在选出接地支路后，提供注入信号，供基于此原理的便携式检测仪寻找具体接地点.两种检测方法的结合可以很好地解决直流接地故障检测的难题.介绍了利用LonWorks现场总线构成分布式直流电源绝缘监测系统的实施方案.阐述了传感器的选择、方波信号频率及幅值的确定、减小注入信号对直流系统的影响以及故障点的准确定位等关键技术问题的解决.实验表明文中提出的方法实用有效.

Integrated methods to detect earth fault in DC systems

To solve the difficult problem of fault detection in DC systems,a new method combining leakage current and waveform analysis methods is proposed to identify the branch with earth fault.The leakage current method is used to find fault in single wire.It detects imbalance DC current between positive and negative wires.The waveform analysis method is used to detect fault with insulation reduction in both wires.It injects a low frequency square wave signal to DC system.The insulation reduction of branch is detected by analyzing the relationships of phase and amplitude between fundamental and third harmonic components.The waveform analysis method can also be used in portable fault location instruments. These two methods were integrated to detect the fault perfectly.A distributed insulation monitoring system for substation DC source using LonWorks Fieldbus technology is introduced.Some key techniques,such as selection of the sensor,frequency and amplitude of square signal,reducing injected signal's influence to DC systems and locating fault point exactly are discussed.Experimental tests verify the correctness and feasibility of the proposed method.