摘要我国配电网普遍采用中性点不直接接地方式。一旦发生单相接地故障，这种系统的短路电流一般较小，因而系统仍能够继续运行1~2小时。但随着馈线的增多，容量的增大，将导致电流逐步增大，容易引发两项短路，也易诱发间歇电弧过电压，破坏系统正常运行，所以正确的故障选线很重要。然而由于故障状况较为复杂、故障电流很小、附加电流干扰等因素，使得故障选线问题难以解决。19016
本文介绍了国内外现有的选线方法，分析了中性点不接地和中性点经消弧线圈接地系统发生单相接地故障时零序电流的稳态与暂态特征。然后介绍了小波包理论、信号奇异性以及模极大值的原理，提出了利用小波包分析进行故障选线及定位方法。最后利用MATLAB软件建立模型，并设置多个实验来仿真验证，证明了可以利用小波包对单相接地故障进行故障选线。
关键词 中性点不直接接地 小波包 故障选线 MATLAB
毕业设计说明书（毕业论文）外文摘要
Title Research on Fault Feeder Selection Method in Small-current Grounding System
Abstract
The non-effectively grounding method is widely used in the distribution network in China. When single-phase fault occurs in the non-effectively grounding system, the fault current is small and the system is allowed to maintain run 1~2 hours. However, the increasing feeders and capacity make the current bigger than before, which is easy to cause two-phase shortcut and intermittent arc overvoltage complex，so it is important to select the fault feeder accurately. But because of the complex fault condition, the small fault current, additional current interference etc., it is difficult to select the fault feeder.
This paper introduces domestic and foreign methods of fault feeder selection, analyses the steady-state and transient characteristics of zero sequence current in ungrounded system and arc suppression coil grounding system when the single-phase fault occurs. Then the paper introduces the principle of wavelet packet theory, signal singularity and modulus maxima, and proposes the fault feeder selection and positioning method, using wavelet packet analysis. At last, model is set by the MATLAB software, and a number of experiments are set up, which proves that wavelet packet can be utilized to select fault feeder when single-phase fault occurs.
Keywords the non-effectively grounding wavelet packet
fault feeder selection MATLAB
目 录
1 绪论 1
1.1 引言 1
1.2 研究现状 1
1.3 本文主要工作 1
2 小电流接地系统故障时刻的特征分析 3
2.1 中性点不接地系统单相接地故障电流稳态特征 3
2.2 中性点经消弧线圈接地系统单相故障电流稳态特征 4
2.3 接地故障暂态分析 5
2.4 本章小结 6
3 小波包分解原理 7
3.1 小波包分解介绍 7
3.2 信号的奇异性与小波变换系数模极大值 8
3.3 选线原理和流程图 8
3.4 本章小结 9
4 基于MATLAB故障选线仿真 10
4.1 中性点不接地系统故障运行 11
4.2 中性点经消弧线圈接地系统故障运行 22
4.3 中性点不接地系统小波分析 34 MATLAB小电流接地系统故障选线方法研究:http://www.751com.cn/zidonghua/lunwen_40178.html