不对称电网单相接地故障中性点位移电压轨迹分析及应用

忽略不对称电压方向的任意性,不能准确表达配电网单相接地时中性点位移电压随过渡电阻变化的轨迹。考虑系统对地泄露电导及不对称电压方向,建立单相接地故障精确模型,准确分析出非全补偿状态下中性点位移电压随过渡电阻变化的轨迹是一段圆弧,全补偿状态下中性点位移电压随过渡电阻变化的轨迹是一条直线段。分析中性点位移电压轨迹,得到以下结论:接地后故障相电压幅值降低,欠补偿状态下接地后故障相电压超前于故障前该相电压,过补偿状态下接地后故障相电压相位滞后于故障前该相电压,全补偿状态下接地前后故障相电压相位保持不变。比较故障前后三相电压幅值与相位的相对变化关系可实现接地故障相辨识。最后,通过MATLAB/Simulink仿真验证了分析结果。

Analysis and Application of Trajectory of Neutral Point Displacement Voltage During Single-phase Grounding Fault in Asymmetrical Power Grid

If the arbitrariness of the asymmetrical voltage direction is ignored, it is impossible to accurately describe the trajectory of neutral point displacement voltage varying with the transition resistance when a single-phase grounding fault occurs in the distribution network. Considering the conductance of ground leakage and the direction of asymmetrical voltage, an accurate model of single-phase grounding fault is established. In the incomplete compensation state, the trajectory of neutral point displacement voltage varing with transition resistance is a circular arc; in the full compensation state, the trajectory of neutral point displacement voltage varied with transition resistance is a straight-line segment. According to the analysis: the amplitude of fault phase voltage decreases after grounding, the fault phase voltage after grounding is ahead of the phase voltage before fault in the under-compensated state, the fault phase voltage after grounding lags behind the phase voltage before fault in the over-compensated state, the voltage of the fault phase before and after grounding remains unchanged in the fully compensated state. By comparing the relative change of amplitude and phase of three-phase voltage before and after fault, the grounding fault phase can be identified. Finally, the analysis are verified by MATLAB/Simulink simulations.