一种基于边界特性的高压直流输电线路单端量保护方法

A single-terminal protection method for HVDC transmission line based on boundary characteristics

分析高压直流输电线路和线路边界对高频信号的衰减作用在目前高压直流线路保护方面的影响。研究边界和线路的频率特性,针对传统基于电气量导数的行波保护耐受过渡电阻能力差的问题,提出一种基于电气量二阶微分量的单端保护方法。经过二阶微分变换后放大暂态故障分量信息,并利用边界内外的二阶微分量差异进行故障判别。在所提出的直流保护方案中,仅利用单端故障暂态信息即可实现全线路保护。在PSCAD/EMTDC中进行仿真分析,结果表明,所提出的判据能够对区内外故障进行准确识别,且该方法不受线路长度和过渡电阻的影响,可以实现全线速动。

This paper analyzes the influences of the attenuation of high frequency signals by the HVDC transmission lines and line boundaries on the current HVDC transmission line protections.The frequency characteristics of boundary and line are also studied.The traditional traveling wave protection approaches based on the derivative of electrical quantity generally have poor tolerance to transition resistance.To solve this,a single-ended protection method based on the second-order micro-component of electrical quantity is proposed,where the transient fault component information after the second-order differential transformation will be amplified,and the difference of second-order differential variables inside and outside the boundary are utilized to judge the fault.In the proposed DC protection scheme,full line protections can be realized only by the single-ended fault transient information.The simulation analysis is carried out in PSCAD/EMTDC,and the results show that this criterion can accurately distinguish internal and external faults,and select fault poles,which indicates its strong ability to withstand the influence of transition resistance and long transmission lines,thus can realize full-line quick action.