基于改进小波包熵的SSSC串补线路故障位置识别

摘要

静态同步串联补偿器(SSSC)的应用会对距离保护的测量阻抗产生影响,使得距离保护发生拒动或超越.文中采用改进小波包熵分析了SSSC串补线路保护安装处的暂态故障电流特征,结果表明:故障点在SSSC之前和之后时串补线路的小波包熵值明显不同,故障点在SSSC之前的小波包熵值远大于故障点在SSSC之后时的小波包熵值.根据该特征提出了SSSC串补线路的故障位置识别判据,并在此基础上提出了距离保护测量阻抗调整方案.当保护安装处的小波包熵小于小波包熵整定值时,故障点在SSSC之后,需要在原测量阻抗的基础上减去附加阻抗,再与定值进行比较;相反,则实际测量阻抗就是测量阻抗.仿真结果验证了该方案的正确性和可行性.%Application of static synchronous series compensator (SSSC) results in impacts on the measured impedance of distance protection, which will cause under-reaching or over-reaching of the distance protection. The improved wavelet packet entropy is used to analyze the transient fault current in the protection location of the series compensated transmission line with SSSC. The results show that the values of wavelet packet entropy are obviously different between fault points located before SSSC and behind SSSC. The value of wavelet packet entropy with fault point before SSSC is much larger than that with fault point behind SSSC. According to abovementioned characteristic, the identifying criterion of fault position for series compensated lines with SSSC is put forward, and based on the criterion an adjusted scheme for measured impedance of distance protection is proposed. When the value of wavelet packet entropy at the protection location is smaller than the setting value of wavelet packet entropy, and the fault point is behind SSSC, the actual fault impedance should be the original measured impedance minus additional impedance. On the contrary, the actual impedance is just the same as measured impedance. Simulation results verify the correctness and feasibility of the method proposed.