基于暂态电流极性的小电流接地系统故障选线装置

根据均匀传输线路的频率特性,对于空载线路,当频率小于fm时,线路输入阻抗呈容性,线路可用一集中电容等效.小电流接地系统发生单相接地故障时,对零序分量来讲,非故障线路相当于空载.根据这一特点,对小电流接地系统中线路的零序参数相频特性进行研究,得出系统发生单相接地故障时不同频带上暂态零序电流特性.在选定频带(Selected Frequency Band,SFB)内,非故障线路零序电流极性和故障线路相反.应用小波包对各线路的暂态零序电流进行分解,小波包系数的符号代表了相应频带零序电流的极性,通过比较SFB内小波包系数的符号,便可找出故障线路.RTDS(Real Time Digital Simulator)试验结果表明此方法可以准确地实现单相故障选线.

Study on an equipment to select faulty line in a non-solid earthed network based on polarity of transient current

According to the frequency characteristic of an even transmission line,when the frequency is lower than f_m,the input impedance of an unloaded even transmission line is capacitive,and the line maybe modeled as a capacitor.The healthy line is unloaded for the zero sequence component when single phase fault occurs in a non-solid earthed network.According to the characteristic,the zero sequence angle-frequency characteristic of the lines is studied;and the characteristic of transient zero sequence current in different frequency band is obtained when single phase fault occurs in a non-solid earthed network.In SFB(selected frequency band),the polarity of transient zero sequence current in faulty line is opposite to that in the healthy ones.Using wavelet packet to decompose transient zero sequence current and the coefficients represent the polarity of the current.Comparing the sign of the coefficients may find out the faulty line.The RTDS(real time digital simulator) simulations indicate that the method can find out the faulty line correctly.