利用暂态信息的小电流接地故障选线方法研究

发布时间：2018-11-19 10:57

【摘要】：非有效接地电网允许系统带单相接地故障继续运行1-2小时,对供电可靠性的提高十分有利,因此我国及很多国家的中压配电网广泛采用非有效接地运行方式。当配电网发生单相接地故障时,故障馈线的电流突变量很微弱,对于电容电流较大的电网又需要利用消弧线圈补偿接地电容电流,多种因素严重影响小电流接地故障选线保护的选择性和灵敏性。经过多年努力,国内外专家在小电流接地故障选线技术方面取得了一定的成绩。按照利用信号的不同,小电流接地选线保护可分为主动式选线保护和被动式选线保护。主动式选线保护需要增加额外的设备,经济性差。被动式选线保护分为利用故障稳态信息保护和利用故障暂态信息保护两类。对于谐振接地系统,稳态量保护并不适用。由于故障瞬间暂态故障分量远大于稳态故障分量,受谐振接地运行方式的影响小,因此利用故障暂态信息保护的灵敏度较高。本文对故障后的暂态信息加以利用而提出两种新的选线方法。针对小电流接地故障选线理论分析的缺失,本文基于相模变换理论,透过故障的表面现象看本质,建立了用于分析故障暂态分量特征的简化模型,列出高阶电路动态方程,分析了故障电流的暂态成分,详细研究了非有效接地电网发生单相接地故障时的电流振荡机理。最终,通过对故障暂态信号特征的分析,从本质上揭示了非有效接地电网发生单相接地故障的暂态特征规律。本文介绍了小波变换的基本原理,具有良好时频分析特性的小波变换是处理暂态非平稳信号的理想数学工具。通过对信号作小波变换的方法来获取暂态分量,本文基于零模电流和零模电压的小波变换模极大值,定义了暂态幅值和暂态极性故障测度。提出了两种新的小电流接地故障选线方法：基于小波变换的暂态幅值和暂态极性故障测度法。幅值法利用故障馈线零模电流小波变换模极大值的幅值远远大于非故障馈线进行选线;极性法利用故障馈线与非故障馈线零模电流小波变换模极大值的极性相反进行选线。最后,本文建立了非有效接地电网的ATP仿真模型。针对中性点不接地电网和谐振接地电网,改变故障点位置、过渡电阻和故障初相角三种主要影响因素,模拟了单相接地故障,计算出各馈线的暂态幅值和暂态极性故障测度,通过比较其大小来确定故障馈线,从而验证选线方法的正确性。
[Abstract]:The non-effective grounding network allows the system to continue to run for 1-2 hours with single-phase grounding fault, which is very beneficial to the improvement of power supply reliability. Therefore, the non-effective grounding operation mode is widely used in the medium-voltage distribution network of our country and many countries. When the single-phase grounding fault occurs in the distribution network, the sudden change of the fault feeder current is very weak, and the arc-suppression coil is needed to compensate the grounding capacitance current for the power network with large capacitance current. Many factors seriously affect the selectivity and sensitivity of low current grounding fault line selection protection. After years of efforts, domestic and foreign experts in small current grounding fault line selection technology has made certain achievements. According to the difference of using signal, the low current grounding line selection protection can be divided into active line selection protection and passive line selection protection. Active line selection protection requires additional equipment and low economy. Passive line selection protection can be divided into two categories: using fault steady-state information protection and using fault transient information protection. For resonant grounding system, steady-state protection is not applicable. Because the transient fault component is much larger than the steady-state fault component and is less affected by the resonant grounding operation mode, the fault transient information protection is highly sensitive. In this paper, two new methods of line selection are proposed by using transient information after fault. In this paper, based on the theory of phase mode transformation, a simplified model is established to analyze the characteristics of fault transient components, and the dynamic equations of high-order circuits are listed, which is based on the theory of phase mode transformation and the essence of the surface phenomenon of the fault, aiming at the lack of theoretical analysis of the fault line selection for small current grounding faults. The transient components of fault current are analyzed, and the mechanism of current oscillation is studied in detail. Finally, by analyzing the characteristics of fault transient signals, the law of transient characteristics of single-phase grounding faults in non-effective grounding power network is revealed in essence. The basic principle of wavelet transform is introduced in this paper. Wavelet transform with good time-frequency analysis is an ideal mathematical tool for processing transient non-stationary signals. The transient components are obtained by wavelet transform. Based on the wavelet transform modulus maximum of zero-mode current and zero-mode voltage, the transient amplitude and the measure of transient polarity fault are defined in this paper. In this paper, two new methods of fault line selection for small current grounding are proposed: transient amplitude based on wavelet transform and fault measurement method of transient polarity. The amplitude method makes use of the amplitude of zero mode current wavelet transform modulus maximum of fault feeder line to select line, and polarity method uses the polarity of fault feeder line and non-fault feed line zero mode current wavelet transform modulus maximum to select line. Finally, the ATP simulation model of non-effective grounding power network is established in this paper. For neutral ungrounded power network and resonant grounding power network, three main influencing factors such as changing fault point position, transition resistance and fault initial phase angle, the single-phase grounding fault is simulated, and the transient amplitude and transient polarity fault measure of each feeder are calculated. The fault feeder is determined by comparing its size to verify the correctness of the line selection method.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM862

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