基于小波分析的配电网电弧接地故障选线方法

Research on Arc Grounding Fault Selection Method of Distribution Network Based on Wavelet Analysis

鉴于城市中低压配电网电容电流急剧上升,单相接地故障电弧难以自熄,易产生电弧接地过电压及扩大事故,探究谐振接地系统(NES)电弧接地故障的可靠选线方法是保障配网稳定安全运行的基础。首先,建立NES发生电弧接地故障的等值电路,分析故障、健全线路之间零序电流存在的差异。其次,通过引入动态弧长参数改进Schwarz电弧模型,并采用MATLAB/Simulink搭建改进Schwarz电弧仿真模型,在此基础上搭建某城市中压配电网电容电流超标场景下的纯电缆线路系统电弧接地故障模型。再次,设置典型故障条件模拟任意线路的电弧接地故障,提取各线路零序电流进行coif小波分解,提出当出线发生电弧接地故障时,故障线路与健全线路非工频零序电流模极大值的极性相反;当母线发生电弧接地故障时,提出所有出线非工频零序电流模极大值的极性相同的电弧接地故障选线判据。最后,设置典型的故障条件验证了该方法对NES电弧接地故障选线的有效性。结果表明:在不同的过渡电阻、故障点距离、故障时刻相位角等典型故障工况下,所提方法均能正确选择出电弧接地故障线路。

Chinese urban low-voltage distribution network capacitance current rose sharply,single-phase ground fault arc was difficult to self-extinguish and easy to produce arc light ground overvoltage and expansion lead to accidents.explore t The resonant grounding system(NES)arc ground fault reliable line selection method to ensure the stable and safe operation of the distribution network basis was explored.The equivalent circuit of arc ground fault in NES was first established,and the difference between the zero-sequence current between the fault and the sound line was analyzed.Secondly,the Schwarz arc model was improved by introducing dynamic arc length parameters,and the Schwarz arc simulation model was improved by using MATLAB/Simulink,and on this basis,the arc-optic grounding fault model of the pure cable line system under in the scenario of exceeding the capacitance current of a medium-voltage distribution network in a city was constructed.Then,the typical fault conditions were set to simulate the arc grounding fault of any line,and the zero sequence current of each line was extracted for coif wavelet decomposition,and it was proposed that when the arc grounding fault occurred in the outlet line,the polarity of the fault line and the non-power frequency zero sequence current mode maximum of the sound line was opposite.When the arc ground fault occurred on the busbar,the polarity of the non-power frequency zero sequence current mode maximum of all out lines was the same as the arc ground fault selection criterion.Finally,the typical fault conditions were set to verify the effectiveness of the method for selecting wires for NES arc ground faults.The results showed that under in different typical fault conditions such as transition resistance,fault point distance,and phase angle at fault time,this method could correctly select the arc light ground fault line.