基于静态小波变换的 T 型输电线路行波测距方法

针对现有 T 型输电线路行波测距算法易受行波波速影响的不足,提出一种新的 T 型输电线路行波测距方法.采用 Clarke 变换将相电流转换为独立的模电流,对模电流进行静态小波变换(static wavelet transform,SWT)处理,实现各行波浪涌到达各母线端时刻的标定.首先利用首波头到达三端母线的3个初始时刻定义隶属度,给出利用隶属度实现故障支路判别的判据.运用已有的两端测距公式推导三端测距公式,实现 T 型线路故障点测距.研究了 T 节点附近的3种可能性故障情况,提出三次测距方法,使 T 节点附近故障测距问题得到很好的解决.与现有测距方法相比, SWT 具有时间不变性,故障点的测距过程中充分利用 T 型输电线路的三端测量数据,测距公式中不含波速,因此,所提方法具有测距可靠且精度高的特点. ATP/EMTP 仿真验证表明,所提 T 型输电线路行波测距方法简单可行,且不受过渡电阻、故障类型等因素的影响

Travelling Wave Fault Location for Three-Terminal Transmission Line Based on Static Wavelet Transform

In view of the defect in existing travelling wave fault location algorithm that this algorithm is easily affected by wave velocity,a new method for travelling wave fault location of three-terminal transmission line is proposed.Using Clarke’s transform the phase currents are turned into independent mode currents,then static wavelet transform(SWT) is applied to mode currents to determine the moments at which travelling wave surges arrive the bus terminals.Firstly the memberships are defined by three initial moments at which the first wave front arrives T-connected buses,and based on the memberships the criterion for distinguishing faulty branch is given.To implement fault location of three-terminal transmission line,based on existing fault location formula for two-terminal transmission line the fault location formula for three-terminal transmission line is derived.Three possible fault conditions near the T-connected node are researched,and a three-time fault location method is put forward to resolve the fault location for the faults occurred near the T-connected node.Comparing with existing fault location methods,due to time-invariance of SWT,making full use of the data measured at three terminals of the three-terminal transmission line and that the wave velocity does not appear in the derived fault location formula,the proposed method can provide more accurate fault location results.Results of simulation using ATP/EMTP show that the proposed fault location method for three-terminal transmission line is simple,reliable and not affected by such factors as transition resistance and fault types and so on.