基于零序阻抗突变特征的谐振接地系统高阻接地故障选线方法

Fault line selection method of grounding fault with high resistance in resonant grounding system based on intensive zero-sequence impedance characteristics

针对配电网谐振接地系统高阻接地故障选线困难的问题,提出了一种利用消弧线圈并联电阻短时投入以增强线路零序阻抗特征的高阻接地故障选线方法。对发生单相接地故障时消弧线圈并联电阻投入前、后同一母线上的健全线路和故障线路的零序阻抗特征进行分析,由分析结果可知:任意健全线路在并联电阻投入前、后其零序阻抗基本保持不变,由线路自身对地电容阻抗构成;故障线路在并联电阻投入后零序阻抗减小,由所有健全线路、消弧线圈支路和并联电阻支路的并联等值阻抗构成。此外,综合考虑故障点电流的限幅要求和零序电压的启动要求分析了并联电阻的取值范围。利用消弧线圈并联电阻投入前、后线路零序阻抗的变化特征构造了故障选线判据,其能够适用于过渡电阻在3000Ω以内的高阻接地故障。利用MATLAB建模仿真,验证了所提故障选线方法的有效性。

In order to solve the difficulties of faulty line selection of grounding fault with high resistance in resonant grounding system of distribution network,it is proposed to enhance the zero-sequence impedance characteristics of the line by using the short-time switching of resistance connected in parallel with arc suppression coil.In the case of single-phase grounding fault,the zero-sequence impedance characteristics of the healthy and faulty lines on the same bus before and after switching the parallel resistance are analyzed.The analysis shows that the zero-sequence impedance of any healthy line remains unchanged before and after switching the parallel resistance,which is composed of its own capacitance impedance to ground,while the zero-sequence impedance of the faulty line decreases significantly after the parallel resistance is put into operation,which is composed of the parallel equivalent resistance of all the healthy lines,arc suppression coil branch and the parallel resistance branch.In addition,the range of parallel resistance is analyzed by considering the limiting requirements of fault current and the start-up requirements of zero-sequence voltage.Therefore,according to the change characteristics of zero-sequence impedance of the faulty line before and after switching the parallel resistance,an improved faulty line selection method is proposed,which can theoretically adapt to the grounding fault with high resistance that lower than 3000Ω.The effectiveness of the proposed method is verified by MATLAB simulation.