【作者】 杜延辉；

【导师】 张勤；

【作者基本信息】 西南交通大学 ， 电力系统及其自动化， 2008， 硕士

【摘要】 小电流接地系统单相接地选线是电力系统中没有彻底解决的问题。利用稳态信号的方法由于稳态接地电流微弱,电弧不稳定等原因误选率很高,近年来的研究热点主要集中在利用暂态信号来构造选线算法。利用能够对突变的、微弱的非平稳的故障信号进行处理的多重分形谱分析,可以很好的分析小电流接地系统单相接地故障暂态过程并提取故障特征,所以本文利用多重分形与小波变换相结合进行故障选线的研究,更好地解决了小电流接地系统单相接地故障的选线问题。本文首先对国内外小电流系统单相接地故障选线原理和方法进行了归纳、概述和分析;然后详细的介绍了小波理论和分形理论以及它们之间的关系,为多重分形与小波变换相结合处理小电流接地单相接地故障选线提供了理论依据;并对多重分形进行了较为全面的分析,通过对小波极大模值及其在此基础上改进的基于小波系数矩的多重分形谱算法在多重分形谱中的应用,使得多重分形谱继承了小波变换的优点,对于信号的奇异性有着敏感的反映;接着从稳态和暂态两方面分析了小电流接地系统单相接地故障。分析表明,单相接地故障后各线路会产生明显的暂态零序电流,并且呈现故障线路与健全线路零序暂态电流流向相反、故障线路零序电流幅值最大的特点;最后,采用PSCAD/EMTDC4.02仿真软件,建立一35kV配电线路仿真模型,通过对小电流接地系统单相接地故障后一个周波内整体零序电流信号的多重分形谱进行对比分析,得出了一个基于多重分形谱的小电流接地系统单相接地故障选线新判据。为了综合测试该判据的可行性,充分考虑接地方式、故障接地电阻、故障点位置和故障合闸角的影响,采用大量典型算例对判据进行了验证。验证结果表明,这种基于多重分形谱的选线方法不受接地方式、过渡电阻、合闸角的影响,可靠性高,抗干扰能力强,能够准确的选出故障线路。更多还原

【Abstract】 The single phase fault line selection of neutral un-direct grounding system is still a problem in Power System now. The way used of steady signals is often unreliable because of faint permanent grounding current and unstable arc. Recently algorithm of utilizing the transient signal construct criterion becomes the researching focus. The multi-fractal spectrum which is used to deal with the discontinuous, weak and non-stationary fault signals can well analysis the process about the neutral un-direct grounding system in single phase fault transient and extract fault features. So multi-fractal combined with wavelet is used to research selecting fault line in the paper. This combination can better solve the problem of the fault line selection of neutral un-direct grounding system in single phase fault.Firstly, home principles and methods as well as abroad ones on the fault line selection of neutral un-direct grounding system in single phase fault are summed up, overview and analysis in this paper. Secondly, wavelet theory, fractal theory and the relationship between them are described in detail to provide the theoretical basis for the combination of multi-fractal and wavelet, which deal with the fault line selection of neutral un-direct grounding system in single phase fault. And then comprehensive analysis of the multi-fractal is made. The application about wavelet transform modulus maxima and the improved wavelet coefficient moment algorithm, which is on this basis, in the multi-fractal spectrum makes multi-fractal spectrum inherit the merits of wavelet transform and react sensitively to the singularity of the signal. Then fault about single phase grounding is analyzed from two sides of steady fault and transient fault. The analysis shows that after grounding fault there is zero transient sequence current in the line, and the current direction of fault line is opposite to the sound line, and the zero transient current of fault line is greater than any other sound line. Finally, a 35kV distribution lines simulation model is established by PSCAD/EMTDC4.02 simulation software, through the comparison about multi-fractal spectrum of the overall zero sequence current, the paper obtains a new line selection criterion of neutral un-direct grounding system in single phase fault criteria based on multi-fractal spectrum. In order to comprehensive test the feasibility of the criterion and fully consider the impact of earth mode, path resistance and inception angles, a large number of typical examples are used to authenticate the criterion. The results shows that the line selection method based on multi-fractal spectrum is not effected by the grounding method, transition resistance and initial current angle, and have high reliability and strong anti-interference ability, can accurately select the fault line.更多还原