中文摘要：

针对超高压输电线路分布电容电流对差动保护的影响，提出了一种从原理上完全不受电容电流影响的线路纵差保护新原理。该原理是选择线路两侧电流突变量的最大有效值与差动电流突变量的有效值进行比较来区分区内、外故障，无需考虑分布电容的影响因素。当空载合闸与区外故障时能够可靠闭锁差动保护，而区内故障时差动保护能够准确动作。新原理思路简明，计算快速。经大量仿真实验酗正该原理有效消除了分布电容电流对差动保护的不利影响，提高了差动保护的可靠性。

英文摘要：

Based on the study about the influence of the distributed capacitance current of UHV transmission line on differential current protection, a principle which is free from capacitance current impact is put forward in this paper. This method carries on the comparison between the maximal virtual value of current mutational volume which is chosen in the two sides of transmission line, and the virtual value of differential current mutational volume, to distinguish internal fault from external fault. Differential protection still could operate reliably regardless of the influence factor of the distributed capacitive current. When switching unloaded or a external fault occurs, the algorithm can latch up protection reliably, While a internal fault occurs, it still operate accurately. The new method needs a little calculation, a short data windows and has reliable performance, Lots of simulation results demonstrate that the algorithm can effectively eliminate the advanced influence of distributed capacitive current on the differential current protection, then it can improve the reliability of the transmission line protection, This project is supported by National Natural Science Foundation of China（No,50277012 and No.50607006）.