串联电容补偿线路的相差保护特性研究

高压输电线路上靠近串补电容处发生故障时，由于电容的补偿作用，线路两端电流、电压的相位差可能达到180°，远远超出了传统相差保护的整定值，导致保护无法判别故障。为此，作者提出一种改进算法，对故障时的暂态电流信号进行小波变换，获取暂态相位差值作为保护动作的依据，并考虑了金属氧化物变阻器不能导通时串补电容对保护性能的影响。仿真结果表明，改进算法能快速准确地判断故障区域，弥补了传统保护的缺陷，且不受串补电容补偿度、安装地点的影响，对普通线路同样适用。

Study on Phase Comparison Protection for Series Compensated Lines

When fault of high voltage transmission line locates near the position where series compensating capacitors are installed, due to the compensation of capacitors the phase difference between the currents at both ends of the transmission line as well as that between the voltages at both ends of the transmission line may reach 180°, this value goes far beyond the setting value of traditional phase comparison protection, and it leads to that the occurred fault cannot be distinguished. For this reason, an improved algorithm is proposed in which the wavelet transform is applied to transient current signal during the faulty period, the obtained transient phase difference is taken as the foundation of the protection action, in the meantime the influence of series compensating capacitors on protection performance is taken into account while the breakover of metal oxide varistor (MOV) does not take place. Simulation results show that the improved algorithm can locate the faulty region quickly and accurately, so the defect of traditional phase comparison protection is remedied. The improved algorithm is not affected by compensation degree of series compensating capacitors and the position where the series compensating capacitors are installed, thus this improved algorithm is available for common transmission lines.