半波长输电线路短路故障后的故障方向特性

Study of Fault Direction Characteristic of Half-Wave-Length AC Transmission Lines

半波长交流输电作为超远距离输电技术受到广泛关注。半波长交流输电线路的故障特征与传统输电线路不同,原有的方向元件应用到半波长交流输电线路时需要重新研究。通过理论推导和仿真分析,研究了半波长线路发生故障后,稳态工频量、故障突变量和故障行波量表征的故障方向特性。与常规输电线路相比,半波长线路反向故障时,稳态工频量(零序量)和故障突变量的电压电流相位差不再位于(45°,90°)之间。此外,用故障行波量表征半波长线路故障后的故障方向时,不能像常规输电线路一样采用几十上百kHz的频带,而应该用相对较低的频带。研究结果表明稳态工频量、故障突变量和故障行波量基本上仍可以表示半波长线路故障后的故障方向,不过在具体的故障方向特性上不同于常规输电线路,为方向元件应用于半波长输电线路奠定基础。

As a very long-distance transmission technology,half-wave-length AC transmission（HWACT） attracts extensive attention.Fault characteristics of HWACT lines are different from those of conventional transmission lines.Therefore,conventional directional elements need to be further studied when applying to HWACT lines.This paper studied fault directionality represented with steady fundamental quantities,superimposed fundamental quantities and fault traveling waves when a fault occurs on HWACT lines by means of theoretical derivation and simulation analysis.Compared with conventional transmission lines,when a reverse faults happen on a HWACT line,phase difference between voltage and current of steady fundamental quantities（zero sequence quantity） and superimposed fundamental quantities will not fall in range of 45°~90°.Besides,when fault traveling waves are applied to characterize fault direction of HWACT lines,appropriate frequency band should be smaller than the common used value（several tens of kilohertz or a few hundred kilohertz） for conventional transmission lines.Study in this paper demonstrates feasibility of steady fundamental quantities,fault superimposed fundamental quantities and fault traveling waves in identifying fault direction,but detailed fault direction characteristics of HWACT lines are different from those of conventional transmission lines.The results can lay a foundation for directional elements applying to HWACT lines.