基于无功电流的中性点不接地系统小电流接地选线方案

A Novel Fault Line Selection Scheme for Isolated Neutral System When Single － phase Short Circuit Faults Occur Based on Ｒeactive Current

摘要:

针对中性点不接地系统发生单相故障后难以准确选取故障回线的问题，提出一种基于无功电流的选线方案。 单相短路故障发生后的，故障相各回馈线的电流变化主要来自线路分布电容电流变化，此电流为无功电流。其中故 障回线无功电流为非故障回线与故障回线无功电流变化量之和，非故障回线无功电流变化量为该回线无功电流变化 量。在此基础上提出基于无功电流变化量的中性点不接地系统小电流接地选线方案。单相短路故障发生后，比较故 障相各回馈线无功电流变化量，变化量最大的馈线为故障馈线。利用 PSCAD 电磁暂态仿真软件搭建中性点不接地系 统，对配电网中的架空线路和电缆线路单相短路故障进行了仿真研究，结果表明所提方法可靠性高，有较强带过渡电 阻能力，且不受线路架设方式影响。

Abstract:

Fault line selection is difficult in isolated neutral system． A novel fault line selection scheme based on reactive current is proposed． After single － phase short circuit faults occur，the current change of fault phase in each line is mainly composed of capacitive current，and the current is reactive current． For fault phase，the reactive current change of fault line is larger than that of normal line． On this basis，the novel fault line selection scheme is proposed． A isolated neutral system model is built in PSCAD to research the reliability of the proposed scheme． The type of transmission line and grounding resistance are considered in simulation． Simulation results show that the proposed scheme can select the fault line with a high reliability．