逆变型分布式电源接入对接地距离保护的影响与对策

Influence of Inverter-interfaced Distributed Generation Integration on Grounding Distance Protection and its Strategies

针对IIDG接入系统的110 kV联络线金属性单相接地故障,分析了线路两侧正序电压极化接地距离保护的动作性能,指出存在由故障位置和IIDG容量决定的保护失效功率边界,若负荷无功高于此边界,IIDG侧接地距离保护在正向区内故障时拒动、在正向区外故障时误动,电网侧接地距离保护在反向区外故障时误动。提出两种应对策略,对策一将IIDG接入的110 kV变压器中性点直接接地,此时正序电压极化原理仍适用于IIDG接入系统;对策二采用零序无流判据和相电压极化距离元件构成接地距离保护方案,该保护判断不受IIDG接入的影响且无死区问题。

Aiming at the metallic single-phase grounding fault in 110 kV tie line in IIDG access system,the paper analyzes the action performance of positive sequence voltage polarization grounding distance protection on both sides of the line.It is pointed out that there is a protection failure power boundary determined by the fault location and IIDG capacity.If the load reactive power is higher than this boundary,the IIDG side grounding distance protection refuses to act when faults occur in the forward zone and causes the protection malfunction when faults occur outside the forward zone,and the grid-side grounding distance protection malfunction occurs when faults occur outside the reverse zone.Therefore,two strategies are proposed.The first strategy is to ground the neutral point of 110 kV transformer connected by the IIDG directly,while the principle of positive sequence voltage polarization is still applicable to the IIDG access system.The second strategy is to form a grounding distance protection scheme using zero sequence no current criterion and phase voltage polarization distance element,which is not affected by the IIDG access and has no dead zone problem.Simulation is conducted using PSCAD/EMTDC.