基于边界特征的高压直流输电长线路故障判别方法

A fault identification method for HVDC transmission with long line based on boundary characteristics

分析了高压直流输电长线路的高频信号衰减作用对目前基于线路边界保护原理的影响。研究了边界的频率特性以及平波电抗器对电流变化率的抑制作用,进而提出了由单端特征频率电流构造的直流线路故障判别方法。在所提出的直流保护方案中,使用特征谐波电流幅值构造启动判据,同时使用特征谐波电流变化量构造保护判据,算法简便且更加充分地利用了基于线路边界的暂态特征。在PSCAD/EMTDC中搭建了双极24脉动直流输电系统模型并进行了仿真分析。结果表明,该判据能准确地区分区内外故障并进行故障选极,受过渡电阻和长线路的影响很小,可以实现全线速动。

This paper analyzes the influence of the attenuation of long transmission line to high frequency signal on the principle of line boundary protection.Based on the study of boundary frequency characteristics and the suppression of flat wave reactor to the change rate of current,a new method of line protection is proposed,which is composed of single-ended characteristic harmonic current.In the proposed protection method,by using the amplitude of characteristic harmonic current to construct the start criterion and using the variation of characteristic harmonic current as a protection criterion,the algorithm is simple and transient characteristics of line boundary are fully used.A bipolar 24-pulsating HVDC system model is established in PSCAD/EMTDC.The simulation results show that the criterion can accurately distinguish the fault inside and outside the line and realize the fault pole selection,which is less affected by the transition resistance and long line,and can protect the whole line rapidly.