雷击特高压直流线路行波保护误动分析与优化策略

Maloperation Analysis and Optimizing Strategy of Travelling Wave Protection for UHVDC Transmission Lines Under Lightning Strike

特高压直流工程在实际运行中存在雷电流绕击直流线路一极,非雷击线路行波保护发生误动的风险,并因此导致直流系统双极闭锁事故的发生.文中基于实际运行中某特高压直流工程的EMTDC仿真模型,建立了正确的雷击模型,并对雷击情况下行波保护特征量电压变化率d U/dt、电压变化量ΔU、电流变化量ΔI的动态响应特性以及特征量在时序上的逻辑配合情况进行研究.分析表明,线路一极遭受雷击后,非雷击极在受扰恢复过程中,两极线路间电磁耦合作用致使非雷击线路电气量剧烈波动,引起保护特征量的响应恰好满足其既定的延时逻辑关系是非雷击线路行波保护误动的重要原因.据此,提出了在原有行波保护电压判据的基础上增加一个辅助延时闭锁逻辑的行波保护的优化策略,以实现在不牺牲保护灵敏性和速动性的基础上提高选择性的目的,经过仿真验证了所提策略的有效性.

In the practical running of UHVDC,if a lightning current attacks one polar of a transmission line,the maloperation of the non-lightning traveling wave protection may occur,which is likely to result in a bipolar locking in the DC system. In this paper,based on a practical UHVDC model in EMTDC,a correct lightning strike model is constructed,and the dynamic response of the three protection criteria( namely,d U/dt,ΔU,ΔI) under lightning strikes is investigated. Moreover,the logical coordination of the three criteria is also discussed. The analysis shows that an important reason for the traveling wave maloperation of non-lightning lines is that,when one polar of a line is hit by the lightning strike,the electromagnetic coupling between circuits leads to a drastic fluctuation in the electrical quantities of the non-lightning lines,and this fluctuation will cause the response of the protection criteria in the recovery from distraction to satisfy a set time series exactly. Therefore,an optimizing strategy of adding a subsidiary locking logic on the basis of the original voltage criterion of the traveling wave protection is proposed,so as to improve the selectivity without sacrificing the sensitivity. Simulation results show that the proposed strategy is effective.