特高压同塔双回线路零序电流补偿系数整定对接地距离保护的影响研究

Influence of Zero-Sequence Current Compensation Coefficient Setting on Earth-Fault Distance Protection for Double Circuit UHVAC Transmission Lines on the Same Tower

为提高特高压同塔双回线路接地距离保护的动作性能,分析了特高压同塔双回线路在不同运行方式下,零序互感对接地距离保护零序电流补偿系数K和测量阻抗的影响,讨论了使用双K值及单K值整定方法的接地距离保护的有效保护范围。分析发现,由于特高压同塔双回线路的互感系数较大,采用上述2种整定方法,大大减小了双回线正常运行方式下接地距离I段的动作范围,同时也给接地距离II(III)段的整定配合带来困难。为此提出了通过切换定值区的方式进行接地距离保护零序电流补偿系数整定的建议。建立了基于1 000 kV特高压同塔双回交流输电工程实际参数的动态模拟系统,对不同运行方式下接地距离保护的有效保护范围进行了试验验证,试验结果与理论分析一致。

To improve the performance of earth-fault distance protection for double circuit UHVAC transmission lines on the same tower, the influences of zero-sequence mutual inductance on zero-sequence current compensation coefficients and corresponding measured impedances of earth-fault distance protection under different operating modes of double circuit UHVAC transmission lines on the same tower are analyzed, and the effective protection zones by earth-fault distance protection under the setting with single or dual values of zero-sequence current compensation coefficient respectively are discussed. Analysis results show that due to the higher coefficient of mutual inductance of double circuit UHVAC transmission lines on the same tower, under above-mentioned two setting methods the protective scope of the first zone of earth-fault distance protection is obviously shortened during normal operation of two transmission lines on the same tower, meanwhile it also bring troubles in the setting and coordination of the second and the third zones of earth-fault distance protection. For this reason, a suggestion that the zero-sequence current compensation coefficient of earth-fault distance protection is to be set by changing-over the setting value ranges is proposed. A dynamic simulation system based on actual parameters of the project of double circuit 1 000 kV UHVAC transmission lines on the same tower is built, and the experimental verification on effective protective range of earth-fault distance protection under different operating modes are performed, and obtained results of experimental verification conform to those from theoretical analysis.