中文摘要：

负序方向元件的主要缺点是不能反应三相短路，针对这一问题提出了改进的负序方向元件。改进负序方向元件利用了微机保护的存贮记忆功能，人为控制采样数据的选取，三相对称故障时制造出负序分量，实现对三相对称故障的反应，而在不对称故障时仍正确动作。改进后负序方向元件能够反应对称及不对称故障，是一种性能完备的保护原理。同时针对故障开始付氏算法存在跨窗问题，提出在故障后半周内采用小矢量算法。理论分析和大量仿真证明了该改进负序方向元件用在特高压输电线路上的可行性和优越性。

英文摘要：

Traditional negative sequence directional relay is unable to operate during three-phase fault. An improved negative sequence directional relay was proposed in the paper. The selection of sampling data was artificially controlled by using the storage memory of microprocessor based protection, and the negative sequence components were created during three-phase symmetrical fault with above method. The improved negative sequence directional relay has a perfect protection principle and is able to response both to symmetric and asymmetric faults. According to cross window problem of Fourier algorithm,a phaselet algorithm during half-cycle after fault was also proposed in the paper. Theoretical analysis and simulation test show the feasibility and superiority of improved relay when it used in the protection of the special high-voltage transmission lines.