变压器空投导致相邻元件差动保护误动分析及防范措施

现场发生多起变压器空投导致相邻正常运行的发电机、变压器以及线路差动保护误动的事故,严重影响电网的安全稳定运行。结合现场录波数据与数字仿真,考虑励磁涌流、和应涌流以及互感器饱和等影响因素,文中对差动保护误动的原因展开研究,指出励磁涌流导致的互感器饱和是差动保护误动的主要原因。在此基础上提出了投入谐波闭锁判据、改进比率制动特性等防范措施。现场录波数据和仿真试验结果验证了所研究结论的正确性及应对措施的有效性。

Analysis on Mal-operation for Current Differential Protection Due to Adjacent Transformer Switching-on and Its Countermeasures

Cases of unusual mal-operation of differential protection for transformer, generator and transmission line in operation due to adjacent transformer switching-on have seriously threatened the safe and stable operation of the power grid. An investigation is made on the causes of mal-operation by analyzing the main factors, such as magnetizing inrush, sympathetic inrush, and current transformer saturation, including field recorded fault data and simulation results. It is pointed out that the current transformer transient or current transformer local transient saturation induced by the long-lasting aperiodic component from the magnetizing inrush current is the major cause of mal-operation. To solve this problem, the harmonic restraining criterion and the improved ratio restrained characteristic of current differential protection are proposed to avoid this sort of mal-operation. The research results are verified by field recorded fault data and simulation results. This work is supported by National Natural Science Foundation of China(No. 51277084, No. 51177058)and China Southern Power Grid Company Limited(No. K-GD2012-324).