【作者】 魏子镪；

【导师】 张艳霞；

【作者基本信息】 天津大学 ， 电力系统及其自动化， 2010， 硕士

【摘要】 小电流接地系统由于其供电可靠性高,在我国6-66kV配电网广泛采用。随着电网容量和输电线路长度的增加,电网对地电容电流不断增加,使得弧光接地越来越不可避免,这增加了小电流接地系统单相故障选线的难度。本文从传统电弧物理数学模型入手,建立了针对小电流接地系统的电弧仿真模型。该模型设置了电弧的稳态峰值电流和弧长两个输入参数,通过改变这两个参数可以方便地获得不同稳态电流下的不同弧长电弧。将此模型嵌入到由MATLAB/SIMULINK构建的小电流接地系统仿真模型中,即可进行单相接地的故障选线研究。本文分析了小电流接地系统弧光单相接地的故障特性,对“基于小波包重构算法的小电流单相接地故障选线原理”在弧光接地时的动作行为进行了研究。由于受到弧光接地中产生的非线性、时变性、阻尼性电弧的影响,该选线原理在相电压过零处发生弧长100cm的弧光接地故障的极端情况下会发生选线错误。对此,本文提出了改进措施:以小波包分解提取出故障电弧引起的暂态特征频段,对其重构后进行选线,仿真结果证明了其能够实现各种弧光单相接地故障的正确选线。更多还原

【Abstract】 Neutral un-effectual grounding system (NUGS) is widely used in 6-66kVdistribution networks in China because of its high reliability. With the increase of netcapacity and length of transmission lines, the grounding capacitance current becomeslarger which leads to inevitable arc’s earthing faults. As a result it raises the difficultyof line detection for single-phase-to-earth fault.After theoretical analyzing on traditional arc model which is based on physicalconcept and mathematical derivation, arc simulation model for NUGS is established.Two parameters, which are the peak value of steady state arc current and arc length,are introduced in this model. By setting these two parameters, various arcs can beeasily obtained under different steady state arc current. With the model embedded inthe NUGS simulation model, research on line detection for single-phase-to-earth faultin NUGS can be implemented.Fault features of single-phase arc’s earthing in NUGS are analyzed, and then theoperating behavior of“Principle of Fault line-detection based on wavelet packetsreconstruction algorithm in NUGS”for arc’s earthing fault is studied. As a result ofthe nonlinear, dynamic and damping behavior of arc, the above methodology fails todetect the fault line at the extreme case of arc’s earthing fault that happens near zeropoint of the phase voltage and with the arc’s length exceeding 100cm. Consideringthis extreme case, improved measure is proposed in this paper. It extracts thecharacteristic frequency bands, which compose arc transient feature, fromzero-sequence current of each line via wavelet packets decomposition algorithm. Thenreconstructed coefficients are utilized to detect the faulty line. Simulation resultsprove that it is reliable under whatever arc’s earthing fault condition.更多还原