基于时域的交直流混联系统抗过渡电阻的单相接地距离保护研究

Research on Anti-transition Resistance Single-phase Ground Distance Protection of AC-DC Hybrid Power System Based on Time-domain

交直流混联系统中由于直流接入所带来频率偏移的问题,会导致交流输电线路工频量距离保护存在不稳定动作的风险。本文提出基于时域的交直流混联系统抗过渡电阻距离保护方案。首先对时域距离保护在交直流混联系统中的适应性进行深入分析,利用时域全量进行距离保护计算,从原理上弥补了工频量距离保护在交直流混联系统中不稳定动作的问题。然后讨论了接地故障过渡电阻大小对故障电流的影响,对时域方程添加过渡电阻待识别量,有较好的抗过渡电阻能力。仿真结果表明,基于时域的抗过渡电阻距离保护能有效地解决交直流混联系统保护动作不稳定的情况,且有效避免了距离保护Ⅰ段发生经过渡电阻单相接地时保护动作不稳定的问题。

The frequency offset caused by DC access to an AC/DC hybrid power system leads to the risk of unstable action of distance protection for AC transmission line based on power-frequency components.To solve this problem,an anti-transition resistance distance protection scheme for the AC/DC hybrid power system is proposed based on time domain.First,the adaptability of time-domain distance protection for the AC/DC hybrid power system is analyzed in depth,and the whole amount of time domain is used to calculate the distance protection,thus solving the unstable action of distance protection for the AC/DC hybrid power system based on power-frequency components in principle.Then,Considering the influences of transition resistance on the fault current,the amount of transition resistance to be recognized is added to the time domain equation,which has better capability of anti-transition resistance.Simulation results show that the anti-transition resistance distance protection based on time domain can effectively mitigate the instability in the AC/DC hybrid power system,and effectively avoid the problem of unstable distance protection under singlephase ground fault with transition resistance in SectionⅠ.