配合FTU的小电流系统单相接地故障定位方法

Method of single phase grounding fault locating for FTU in networks with ungrounded neutral

为解决小电流接地系统发生单相接地故障后,故障特性不明显因而故障定位困难的问题,分析了当前在小电流接地系统发生单相接地故障时故障定位常用的方法及现存的缺陷;对小电流接地系统发生单相接地故障后系统中不平衡电流分布情况作了深入的研究,并且考虑到中性点的不同接地方式以及过渡电阻、电流互感器(TA)不平衡电流、馈线终端单元FTU(FeederTerminalUnit)实际工作要求等诸多影响,提出了一种配合FTU工作有效的故障定位方法———零序电流增量法。介绍了零序电流增量法的基本原理以及如何配合FTU实际工作;说明了该方法的特点及适用范围,并用Matlab软件对其进行了仿真。

The fault characteristic of single-phase grounding is not obvious in the networks with ungrounded neutral and the fault locating becomes difficult.The commonly used fault locating me-thods in such conditions and their shortcomings are analyzed.The distribution of lopsided current in networks with ungrounded neutral is studied for single phase-to-earth fault.Various influencing factors are considered:neutral grounding mode,transient resistance,CT's lopsided current and FTU(Feeder Terminal Unit)'s requirements.Zero-sequence-current increment law,an effective fault locating method for FTU,is proposed.Its basic principle and its coordination with FTU are explained.The features and application range of the zero-sequence-current increment law are presented and the simulation of the zero-sequence-current increment law with Matlab is carried out .