交直流交叉跨越碰线故障分析及处理策略

Touching Fault Analysis and Clearing Action Strategy for AC/DC Crossed Transmission Lines

电网交直流系统混联运行中交流/直流线路交叉跨越现象较为常见,较容易出现交直流线路碰线故障。文中从目前国家电网和南方电网直流输电工程针对交直流碰线故障的两种不同处理方法出发,分析其中隐藏的问题。故障无法切除的情况下南网工程采用的闭锁策略出现闭锁后直流过电压;国网工程采用的闭锁再启动逻辑策略实际上不起作用。在分析交直流碰线故障特征的基础上,提出交直流碰线故障由交流线路保护系统切除故障、直流输电控制保护系统报警的处理策略建议。问题分析及所建议处理策略均采用EMTDC仿真予以佐证,还仿真了不同闭锁策略和多线路同时碰线的情形。

AC transmission lines often cross DC transmission lines in the AC/DC hybrid power system, which will easily cause a touching fault between the AC transmission line and the DC transmission line. In regard to two different clearing actions for AC/DC transmission lines touching fault used in HVDC transmission projects of State Grid Corporation of China （SGCC） and China Southern Grid （CSG）, this paper analyzes the hidden problems of two different clearing actions. Under a forever touching fault, a DC overvohage appears after blocking the converter by using clearing actions of the CSG project. The initial restart logic is in fact disabled by using the clearing actions in SGCC projects. According to the analysis of the characteristics of AC/DC transmission lines touching fault, this paper proposes a suggestion on the clearing action： AC protections trip and isolate the fault while DC protections only set an alarm for a touching fault. The EMTDC simulation experiments show that it is a proper clearing action suggestion. Simulation experiments using differential blocking methods or setting multi-line touching fault are also included.