【摘要】：電網中性點非有效接地運行方式即小電流接地系統,以其供電可靠性被廣泛的應用于中壓配電網中。單相接地故障在小電流接地系統故障中占了很大的比例,雖然系統發(fā)生單相接地故障后,不會馬上斷電,能繼續(xù)運行兩小時,但是如果不在允許帶故障運行時間內排除故障,繼續(xù)運行就會引發(fā)危害更大的事故。所以小電流接地系統單相接地故障選線問題就成了電力工作者面臨的一大難題。近幾十年來,有大量的電力工作者和科研人員從事這一問題的研究,但是都沒能找到很好的解決方法。因此對小電流接地系統單相接地故障選線的研究是很有意義的。 本文在前人的研究基礎上致力于找出更有效的選線判據。首先對中性點非有效接地的幾種接地方式進行了簡介并在此基礎上分析了發(fā)生單相接地故障時,中性點經消弧線圈系統和中性點絕緣系統的暫穩(wěn)態(tài)特性,對故障特征量進行了深入的探討,為選線理論的建立提供了理論基礎。在對現有比較成熟的選線技術進行介紹和綜合評價后,發(fā)現單一的選線技術對某些特定的情況有很好的選線效果,但是并不能完全適用于復雜多變的電網系統,因此得出了利用具有互補性的多判據通過信息融合得出新選線方法的結論。通過對比分析,本著極大的利用故障各信息量為原則,本文選取了穩(wěn)態(tài)信號,暫態(tài)信號和注入信號三種故障信號作為選線基礎,并列出基于以上三種信號比較有效的選線方法：零序電流基波群體比幅比相法,小波分析法和注入法。小電流接地系統發(fā)生單相接地故障時的故障特征信息受很多因素的影響,其中接地故障類型對其影響較大,要想準確的判斷出故障線路首先得了解接地故障類型。分形理論對突變信號的奇異性有很好的辨識能力,單相接地故障發(fā)生后,系統中只會產生一個零序電壓,而各線路會產生不同的零序電流,所以利用多重分形理論對系統產生的零序電壓進行分析就能很好的辨別出接地故障類型。對選定的選線方法進行理論分析并在此基礎上得到各選線方法的故障測度隸屬度函數和權重隸屬度函數。再結合多重分形理論辨別的接地故障類型,賦予不同的選線技術各自的權重,就能得到各選線技術的綜合權重。為了很好的將各選線判據進行有效的信息融合,本文選取了信息融合效果好的模糊理論來實現信息融合。經過利用Matlab做大量的仿真實驗,設定不同的接地故障類型和系統模型,實驗的結果表明利用模糊理論進行信息融合的綜合判據能很好的完成故障選線。 最后,在選線判據建立的基礎上進行了選線裝置的軟硬件設計,給出了各硬件電路連接圖和軟件設計的流程圖,并對其進行了詳細的說明。
[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.
【學位授予單位】：廣西大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM862

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