中文摘要：

当多端直流输电系统（MTDC）直流线路发生故障时,各换流站检测到的电气量均急剧变化,因此应保证动作的选择性。在对行波电流小波分析的基础上,提出了基于小波变换的行波电流极性比较式纵联保护原理和算法。利用行波故障电流进行极性比较,能够保证绝对的选择性,通过行波电流极性检测提高保护动作的可靠性与灵敏性,同时通过比较雷击前后电流变化量消除雷电干扰。分析和仿真表明,保护动作迅速、可靠、灵敏,且不受过渡电阻、潮流翻转、起动控制以及雷击的影响,对于多端直流输电系统的直流线路保护设计具有指导意义。

英文摘要：

Electric parameters detected by each convertor station fluctuate severely once a fauDC line of a multi-terminal HVDC transmission system and the selectivity of the relay protection should be guaranteed. The theory and algorithm of trawling wave current polarity comparison pilot protection based on wavelet analysis of traveling wave current were proposed. The protection possesses absolute selectivity via polaritycomparison of travelling wave fault current, the reliability and sensitivity are improved, and the lightning disturbance is eliminated by comparing the current before and after the lightning at the same time. The analysis and simulationindicate that tliis relay protection is fast, reliable, sensitive and is free from the influence of transitoverturn of power flow,starting control and the lightning disturbance, having a guiding significance HVDC transmission system.