配电网经消弧接地系统不对称度对高阻接地故障选线影响研究

Influence of Asymmetric Degree of Anti-Arc Ground System on Fault Line Selection of High Resistance Ground in Distribution Network

针对中性点经消弧线圈接地方式的不对称配电网发生高阻接地故障时选线难的问题,首先建立了经消弧线圈系统发生高阻接地的电路模型,对不同不对称度下不同阻值接地故障的故障线路与非故障线路的零序电流及零序电流5次谐波进行定量分析,随之提出一种阻性电流增量的方法,即在中性点加入阻性电流,该阻性电流通过大地流入到故障点使故障线路零序电流增大,最后通过MATLAB/SIMULINK软件仿真验证该方法的正确性。通过仿真及定量分析表明:配电网经消弧线圈接地方式发生高阻接地故障时,零序电流5次谐波随着不对称度的增大,故障线路与非故障线路的零序电流5次谐波幅值差值会越来越小,甚至出现非故障线路的零序电流5次谐波幅值比故障线路的还要大,保护易误动;阻性电流增量法可以有效增加故障线路的零序电流,可以利用零序电流正确选线,而零序电流5次谐波失真。

In order to solve the problem of high resistance grounding failure in asymmetric distribution network with neutral point through arc suppression coil grounding,the circuit model of high resistance grounding in the arc suppression coil system is first established. A quantitative analysis of the five harmonics of zero-sequence current and zero-sequence current of fault lines and non-fault lines with different resistance grounding faults at different degrees of asymmetry is carried out. Then a method of resistive current increment is proposed,that is,adding resistive current at neutral points. The resistive current flows through the earth to the fault point to increase the zero-sequence current of the fault line.Finally,the correctness of the method is verified by MATLAB/SIMULINK software simulation. Through simulation and quantitative analysis,it is shown that when the distribution network has a high resistance grounding failure through the arc cancellation coil grounding mode,the five harmonics of the zero-sequence current increase with the degree of asymmetry,and the difference between the zero-sequence current of the fault line and the non-fault line will be smaller and smaller. Even if there is a zero-sequence current of the non-fault line,the five-harmonic amplitude is larger than that of the fault line,and the protection is easy to move by mistake. The resistive current increment method can effectively increase the zero-sequence current of the fault line,and can use the zero-sequence current to correctly select the line,while the zero-sequence current is five harmonic distortions.