基于零序电流-电压波形相似度的小电阻接地系统高阻接地故障检测方法

肖瑞超 徐涵

摘要：由于配电馈线往往深入负荷中心，所处环境较为复杂，对于小电阻接地系统，现阶段采用的阶段式零序电流保护方案无法有效解决高阻接地故障难以检测的问题。针对此现象，通过分析高阻接地故障时故障线路与健全线路零序电流-电压之间不同的约束关系，进而提出一种基于零序电流电压波形相似度的高阻接地故障检测方法。所提方法通过对各馈线检测点零序电流与母线零序电压进行采样，并通过计算波形相似度相关系数进行故障检测，该方法可显著提高保护耐受过渡电阻的能力。最后，通过 PSCAD对典型系统的仿真测试验证了该方法的有效性。

关键词：小电阻接地系统;单相接地故障;高阻接地故障;波形相似度;PSCAD

中图分类号：TM77             文献标志码：A        文章编号：1009-9492（2021）12-0064-04

High-resistance Grounding Fault Detection in Low-resistance Grounding System Based on Similarity Difference of Zero-sequence Current-voltage Waveform

Xiao Ruichao1，Xu Han2

（1. South China University of Technology， Guangzhou 510641， China;2. Guangzhou Bureau of China Southern Grid EHV Transmission Company， Guangzhou 510670， China）

Abstract： Since the distribution feeder is often deep into the load center and the environment is more complicated， for the low-resistance grounding system， the staged zero-sequence current protection scheme adopted at this stage cannot effectively solve the problem of high-resistance grounding fault detection. In response to this phenomenon， the different constraint relationships between the zero sequence current-voltage of the faulty line and the sound line when the high resistance ground fault occurs were analyzed， and then a high resistance ground fault detection method based on the difference in the similarity of the zero sequence current and voltage waveforms was proposed. The proposed method sampled the zero-sequence current and the zero-sequence voltage of the busbar at each feeder detection point， and used the waveform similarity correlation coefficient for fault detection. The method could significantly improve the ability of the protection to withstand the transition resistance. Finally， the simulation test of PSCAD on a typical system verifies the effectiveness of the method.

Key words： low-resistance grounding system; single-phase grounding fault; high-resistance grounding fault; waveform similarity; PSCAD

0 引言

受弧光接地过电压、单相接地电流越限以及设备绝缘水平较高等因素的影响，近年来中性点经小电阻接地系统成为我国大中型城市配电网的主要发展趋势[1-2]。单相接地故障是配电系统中最常见的故障类型之一，占高压线路总故障次数的80%以上[3]，由于配电馈线往往深入负荷中心，所处环境较为复杂，容易发生高阻接地故障，目前为解决配电网高阻接地故障所采用的保护方案主要以阶段式零序电流Ⅱ段保护为主[4]，但是其按照躲开区外故障时本线路流过的最大对地对电容电流值来整定，通常耐受的过渡电阻值不超过100Ω[5-6]。高阻接地故障大约占据配电网所有故障的5%～10%，雖然高阻接地故障发生时产生的故障电流很小，但是由于其难以检测的特征会导致长期存在于配电网中，将对设备的绝缘造成巨大的威胁，从而引发更严重的故障，甚至威胁人身安全。……