特高压柔性直流输电阀区接地故障保护策略

Valve Area Grounding Fault Protection Configuration for UHV Flexible DC Transmission

特高压柔性直流换流阀的全桥子模块数目足够多时,换流阀具有阻断故障电流的能力。在保护动作以后,只通过闭锁换流阀就能隔离交流连接线区域和上、下桥臂之间区域的接地故障。换流阀隔离刀闸与直流母线之间区域和高、低压换流阀隔离刀闸之间区域的接地故障,只能采取闭锁极的方法。而换流阀与换流阀隔离刀闸之间区域的接地故障,乌东德特高压混合直流工程采用了闭锁极的处理策略,另外提出了这一区域接地故障闭锁换流阀的处理策略。然后针对这两种处理策略分别给出了测量设备和保护配置,并提出了直流谐波差动保护和桥臂电抗器谐波差动保护解决在极中性母线侧的桥臂电抗和换流阀的引线上发生接地故障时差动保护灵敏性不足的问题。

When the UHV flexible DC converter valve includes enough full-bridge sub-modules,the valve can block the fault current.After the protection action,grounding faults in the area of the AC connection line and the area between upper bridge arm and lower bridge arm can be isolated only by blocking the valve.For the grounding faults in the area between the valve isolators and DC bus as well as the area between high-voltage valve isolator and low-voltage valve isolator,only the blocking pole method can be adopted,while for the grounding faults in the area between converter valve and valve isolators,the treatment strategy of locking pole is adopted in the Wudunde UHV Hybrid DC Project.In addition,this paper puts forward the strategy of blocking converter valve to deal with the grounding fault in this area.Then,the paper gives the measuring equipment and protection configuration respectively for these two treatment strategies,and finally proposes adopting DC harmonic differential protection and bridge arm reactor harmonic differential protection to solve the problem of insufficient sensitivity of differential protection when a grounding fault occurs on the bridge arm reactance and the lead of converter valve at the side of the pole neutral bus.