中文摘要：

在分析超高压输电线路边界频率特性的基础上，提出一种基于改进递归小波变换的超高压输电线路边界保护元件算法。采用改进递归小波变换提取故障电流信号中的暂态分量，利用小波变换后的相位信息来获取故障信号的平均频率，通过故障暂态信号的平均频率差异来识别区内外故障。改进递归小波算法采用历史数据进行计算，具有很好的实时性，提高了计算速度，能够满足电力系统超高速保护的要求。EMTDC仿真结果表明该算法不受故障类型、过渡电阻、故障位置以及故障初始角等故障条件的影响，具有可行性。

英文摘要：

On the basis of the frequency characteristics of transmission line boundary, this paper proposed a new algorithm of boundary protection unit for extra high voltage （EHV） transmission lines based on improved recursive wavelet transform （IRWT）. IRWT was used to extract the desirable frequency components of fault-induced transient current signals. According to the difference of the average frequency of the extracted signals obtained from their phase information, an internal or external fault can be distinguished. Output values of IRWT was calculated only using previous values, which reduces computational complexity, improves the real-time capability and is very desirable for ultra-high-speed protection of the EHV transmission system. The EMTDC simulation results show that the new algorithm is insensitive to fault type, fault resistance, fault location and fault initial angle, and that it is feasible.