适用于半波长输电线路的快速方向纵联保护方法

Fast Directional Pilot Protection Method for Half-wavelength Transmission Lines

基于工频故障分量和序分量的功率方向元件利用背侧阻抗特征可以准确识别线路正、反向故障,但由于半波长输电线路波过程的折反射时间很长,因此常规方向元件在保护启动后无法快速、准确判别反向故障。为此,提出了一种适用于半波长输电线路的新型故障分量方向保护方法。该方法利用半波长输电线路反向故障初期电压相间差故障分量和电流相间差故障分量的幅值相位关系,在线路两端分别计算反向识别系数;通过反向识别系数的大小来实现反向故障的识别。同时,采用工频故障分量方向元件和负序方向元件作为判定正向故障的辅助判据,与新方法一起构成了半波长输电线路快速方向纵联保护方案。该方案采用基于反向识别系数的快速动作逻辑,利用保护对反向故障的快速识别实现区内故障的快速动作。PSCAD/EMTDC仿真表明,所提方法可以准确识别线路正向故障和反向故障,实现半波长输电线路全线速动。

Directional power components based on fundamental frequency components and sequence components can identify the positive-direction faults and anti-faults of traditional transmission lines by taking advantages of line backside impedance.However,due to the long refraction and reflection time of wave processes in half-wavelength lines,the directional components cannot determine quickly and accurately the anti-faults after protection startup.Thus,a new fault-component based directional protection method for half-wavelength lines is proposed.In this method,the special amplitude phase relationship of phase-tophase deviation between super-imposed fundamental frequency components of voltage and current is utilized at the initial stage of the anti-fault,and then the waveform identification coefficient at each end of lines is calculated respectively.At the same time,the super-imposed fundamental frequency components and negative-sequence components are used as the auxiliary criterion to judge the positive-direction faults,which constitute the fast directional protection scheme of the semi-wavelength transmission lines together with the proposed new method.In this scheme,the fast action logic based on the waveform identification coefficient and the fast recognition of the anti-fault is adopted to realize the fast action of the zone faults.Finally,the simulation results by PSCAD/EMTDC show that the method can accurately identify the positive-direction faults and antifaults to achieve the fast tripping of half-wavelength lines.