数字式接地距离保护零序电流补偿的研究

Study of Residual Compensation for Earth-fault Digital Distance Protection

本文在分析了接地距离保护中常规零序电流补偿方法——实因子补偿法的线路阻抗测量误差的基础上,提出了一种新的适用于数字式距离保护的零序电流精确补偿法,即改进的零序电流补偿法。研究结果表明,该方法能显著地提高阻抗测量精度且可加速测量值的收敛。

This paper discusses the erros caused by using traditional residual compensation factor, i.e.real factor, in digital distance protection and the presents a new modified residual compensation method which can be simply implementted in a digital distance relay.The paper begins with the frequency response of comlex residual compensation factor. It can be seen from the frequency response that only one absolute value of complex factor under power frequency is taken the compedance measurement is introduced due to this simplification.From the analysis of error, it can be seen that the error in impedance measurement is quite considerable and much affectted by variaty of operation conditions of power system due to using the real factor. It is also shown that overreach and underreach under double phase to ground fault condition are introduced due to using the real compensation factor as well.A modified residual compensation current is derived in frequency domain by using z transform technique. From the results of computer simulation, it can be concluded that the new modified method is superior to pervious one in several aspects such as unhan-cement of accuracy of measurement, elimilation of overreach and underreach ender double phase to ground fault and improvement of convergence of impedance measurement.