基于两点乘积算法的变压器励磁涌流识别新方法

New Algorithm to Identify Inrush Current Based on Two Points Product Method

为解决变压器差动保护由于励磁涌流而经常误动的问题,从变压器磁特性出发,针对励磁涌流波形畸变严重且会出现尖顶波,而故障电流基本保持基频正弦波特征的特点,提出用两点乘积算法来识别变压器励磁涌流。该方法利用三角函数定理,通过差分滤波得到差动电流,求得多组相邻2电流的平方和,然后比较相邻2组平方和的比值来判断励磁涌流,通过对动模试验数据的分析计算验证本方法的有效性。

A new algorithm based on two points product method is presented in the paper to address the mal-operation in the transformer differential protection due to magnetizing inrush current. This method is based on the principle that the waveform of the inrush is distorted seriously, while the fault current keeps nearly sinusoid. By the trigonometric function algorithm, the method samples currents with the differential filter continuously, and obtains square sums of two neighboring PI/2 currents for many groups, and then distinguishes the inrush current by the ratios of square sums of neighboring groups. Theoretical analysis and dynamic simulation results demonstrate the effectiveness, reliability, and user-friendliness of the method under various fault conditions.