不同电压等级同塔四回输电线路零序电流补偿系数整定研究

不同电压等级同塔四回输电线路发生接地短路时,由于零序互感对接地距离保护的影响,测量阻抗产生的偏差可能导致保护误动或者拒动。为此在现有整定方法的基础上,同时计及零序互感和零序电容电流的影响,分析了不同电压等级同塔四回输电线路在不同运行方式下的零序电流的方向,对零序电流补偿系数的计算方法进行了改进,给出了同塔四回线路在各种运行方式下的零序电流补偿系数,提出了利用微机保护的定值切换来提高接地距离保护的动作性能的措施。最后利用PSCAD对不同电压等级的500 kV/220 kV同塔四回输电线路进行了仿真,仿真结果验证了所提方法的正确性和有效性。

Setting of Zero Sequence Current Compensation Coefficient for Four-Circuit Transmission Lines in Different Voltage Classes on Same Tower

Due to the influence of zero-sequence mutual inductance among transmission lines on ground distance protection relay,when grounding fault occurred in four-circuit transmission lines in different voltage classes on the same tower the deviation measured impedance could lead to malfunction or misoperation of the relay.Based on existing setting approaches of zero-sequence mutual inductance,considering influences of both zero-sequence mutual inductance and zero-sequence capacitive current simultaneously the directions of zero-sequence current in four-circuit transmission lines in different voltage classes on the same tower under different operating modes were analyzed and the computation of zero sequence current compensation coefficient was improved and zero sequence current compensation coefficient of four-circuit transmission lines in different voltage classes on the same tower under different operating modes were given and on this basis the measures to improve operation performance of ground distance protection relay by changing-over the setting of microprocessor-based protection were proposed.Finally,the PSCAD-based simulation of four-circuit 500 kV and 220 kV transmission lines on the same tower was performed,and the correctness and effectiveness of the improved computation of zero sequence current compensation coefficient were verified by simulation results.