中文摘要：

根据函数逼近和投影变换理论,微分函数可视为微分算子的投影与函数自身的卷积,可以建立输电线路的数字方程;然后,通过z变换,得到线路采样数字方程的解及z域内的传播函数、波阻抗。同时,利用零极点估计法,求解出传播函数和波阻抗的冲击响应。根据区外故障两侧行波满足传播关系,区内故障两侧传播关系被打破这一特征,提出了利用线路两端行波进行差动判别区内外故障的方法,并提出了保护的原理和算法。典型线路的ATP仿真验证了新方法的准确性和正确性。

英文摘要：

Based on function approximation and projection transform theorems,the differential function is approximated to convolution of the projection of differential operators and the function itself,subsequently the digital equation of transmission line is established.The z-transform is employed to obtain the solution of the sampling equation,by which the propagation function and surge impedance in z domain are obtained.The impulse response of propagation function and surge impedance are solved by the zero-pole estimation method.According to the fact that traveling waves satisfy the propagation relationship in external fault while break it in internal fault,the method for identifying external fault from internal fault by using the traveling waves at both ends of the line is proposed,and the protection principle and algorithm are also provided.The ATP simulations associated to a typical transmission system show that the algorithm is right and accurate.