不平衡零序电流对纵联零序保护的影响分析及其对策

Analysis of Influence of Unbalanced Zero-sequence Current on Pilot Zero-sequence Protection and Its Countermeasures

线路参数不对称及电流互感器的传变特性等会造成保护装置采样出现不平衡零序电流。当电网发生两相故障或三相故障时,不平衡零序电流增大,将影响纵联零序保护的正确动作。结合两次电网事例,分析了保护装置不正确动作的原因,并对纵联零序保护各类改进措施进行了讨论,最后针对相间和三相故障的情况分别提出对策,数模试验验证了措施的有效性。

When two-phase fault or three-phase fault occurs, owing to line asymmetry parameters and current transformer transfer characteristics, unbalanced zero-sequence current occur in protective equipment samples which will affect the correct operation of the pilot zero-sequence protection. By referring to two incidents of the power grid, an analysis is made of the causes of the protection equipment incorrect action, and the feasibility of various improvements of pilot zero-sequence protection is studied. Finally, countermeasures for two-phase fault and three-phase fault are proposed. And the effectiveness of the measures is verified by dynamic simulation test.