变压器并联与串联和应涌流对差动保护影响的比较研究

Comparison of sympathetic inrush influence on differential protection between parallel and series transformers

通过分析并联和应涌流与串联和应涌流等效电路的异同,结合仿真分析和理论推导,深入比较研究了并联与串联和应涌流的产生过程及其衰减特点;从电力系统规程出发,综合考虑电流互感器饱和、电流互感器参数及运行变压器负荷等多个因素,进一步比较研究了并联和应涌流与串联和应涌流对变压器差动保护的影响。研究表明:串联和应涌流出现的时间较晚,所达到的幅值较小,衰减速度明显快于并联和应涌流;和应涌流造成电流互感器饱和时,差动保护差流的间断角会消失,但二次谐波含量仍很高;在运行变压器带负荷情况下,差动保护的制动电流较大,而和应涌流减小,差动保护不易误动。

The equivalent circuits of parallel and series sympathetic inrushes are analyzed and the generation and decay of parallel and series sympathetic inrushes are compared based on the simulative and theoretical analysis. With the consideration of current transformer saturation, current transformer parameters and operating transformer load, the influence of both parallel and series sympathetic inrushes on differential protection is analyzed according to the rules of power system. The analysis shows that, the series sympathetic inrush occurs later and decays more quickly than the parallel sympathetic inrush, and its magnitude is smaller; the current transformer saturation caused by sympathetic inrushes will lead to the disappearance of differential current dead angle with higher second harmonic component; the restraining current of differential protection is bigger than the sympathetic inrush when the operating transformer has load, hardly causing the misoperation of differential protection.