基于模糊理论的小电流接地系统选线装置研制

发布时间：2018-08-25 15:03

【摘要】：电网中性点非有效接地运行方式即小电流接地系统,以其供电可靠性被广泛的应用于中压配电网中。单相接地故障在小电流接地系统故障中占了很大的比例,虽然系统发生单相接地故障后,不会马上断电,能继续运行两小时,但是如果不在允许带故障运行时间内排除故障,继续运行就会引发危害更大的事故。所以小电流接地系统单相接地故障选线问题就成了电力工作者面临的一大难题。近几十年来,有大量的电力工作者和科研人员从事这一问题的研究,但是都没能找到很好的解决方法。因此对小电流接地系统单相接地故障选线的研究是很有意义的。本文在前人的研究基础上致力于找出更有效的选线判据。首先对中性点非有效接地的几种接地方式进行了简介并在此基础上分析了发生单相接地故障时,中性点经消弧线圈系统和中性点绝缘系统的暂稳态特性,对故障特征量进行了深入的探讨,为选线理论的建立提供了理论基础。在对现有比较成熟的选线技术进行介绍和综合评价后,发现单一的选线技术对某些特定的情况有很好的选线效果,但是并不能完全适用于复杂多变的电网系统,因此得出了利用具有互补性的多判据通过信息融合得出新选线方法的结论。通过对比分析,本着极大的利用故障各信息量为原则,本文选取了稳态信号,暂态信号和注入信号三种故障信号作为选线基础,并列出基于以上三种信号比较有效的选线方法：零序电流基波群体比幅比相法,小波分析法和注入法。小电流接地系统发生单相接地故障时的故障特征信息受很多因素的影响,其中接地故障类型对其影响较大,要想准确的判断出故障线路首先得了解接地故障类型。分形理论对突变信号的奇异性有很好的辨识能力,单相接地故障发生后,系统中只会产生一个零序电压,而各线路会产生不同的零序电流,所以利用多重分形理论对系统产生的零序电压进行分析就能很好的辨别出接地故障类型。对选定的选线方法进行理论分析并在此基础上得到各选线方法的故障测度隶属度函数和权重隶属度函数。再结合多重分形理论辨别的接地故障类型,赋予不同的选线技术各自的权重,就能得到各选线技术的综合权重。为了很好的将各选线判据进行有效的信息融合,本文选取了信息融合效果好的模糊理论来实现信息融合。经过利用Matlab做大量的仿真实验,设定不同的接地故障类型和系统模型,实验的结果表明利用模糊理论进行信息融合的综合判据能很好的完成故障选线。最后,在选线判据建立的基础上进行了选线装置的软硬件设计,给出了各硬件电路连接图和软件设计的流程图,并对其进行了详细的说明。
[Abstract]:The neutral point non-effective grounding operation mode of the power network, i.e., the small current grounding system, is widely used in the medium voltage distribution network because of its power supply reliability. The single-phase grounding fault accounts for a large proportion of the low-current grounding system faults. Although the system will not be cut off immediately after the single-phase grounding fault occurs, it can continue to run for two hours, but if the fault is not eliminated within the allowable operating time with the fault, Continuing to run will lead to a more damaging accident. Therefore, the problem of single-phase grounding fault line selection in low-current grounding system has become a difficult problem for power workers. In recent decades, a large number of electric power workers and researchers engaged in the study of this problem, but failed to find a good solution. Therefore, the study of single-phase grounding fault line selection in low-current grounding system is of great significance. On the basis of previous studies, this paper tries to find more effective criteria for line selection. First of all, several kinds of grounding methods of neutral point are introduced and the transient characteristics of neutral point through arc-suppression coil system and neutral point insulation system are analyzed on the basis of this. The fault characteristic quantity is discussed in depth, which provides a theoretical basis for the establishment of line selection theory. After the introduction and comprehensive evaluation of the existing mature line selection technology, it is found that the single line selection technology has a good effect on some specific cases, but it can not be fully applied to the complex and changeable power grid system. Therefore, a conclusion is drawn that a new route selection method is obtained by information fusion using complementary multi-criteria. Based on the principle of making great use of fault information, three fault signals, steady state signal, transient signal and injection signal, are selected as the basis of line selection. The effective line selection methods based on the above three signals are listed as follows: zero sequence current fundamental wave population ratio and phase ratio method, wavelet analysis method and injection method. The fault characteristic information of single-phase earthing fault in small current grounding system is affected by many factors, among which the type of grounding fault has a great influence on it. In order to accurately judge the fault line, it is necessary to know the fault type. Fractal theory has a good ability to identify the singularity of the sudden change signal. After the single-phase grounding fault occurs, only one zero-sequence voltage will be generated in the system, and different zero-sequence currents will be generated in each circuit. Therefore, the zero sequence voltage generated by the system can be well identified by multifractal theory. Based on the theoretical analysis of the selected line selection methods, the membership function of fault measure and the weight membership function of each line selection method are obtained. Combined with the multi-fractal theory to identify the types of grounding faults, different line selection techniques are given their respective weights, and then the comprehensive weight of each line selection technology can be obtained. In order to effectively fuse the information of each criterion, this paper selects the fuzzy theory with good information fusion effect to realize the information fusion. Through a large number of simulation experiments with Matlab, different grounding fault types and system models are set up. The experimental results show that the comprehensive criterion of information fusion based on fuzzy theory can complete fault line selection well. Finally, the hardware and software design of the line selection device is carried out on the basis of the establishment of the line selection criterion, and the connection diagram of each hardware circuit and the flow chart of the software design are given, and the detailed explanation is given.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM862

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