一种基于差动电流波形特征的励磁涌流识别新方法

分析变压器励磁涌流和内部故障电流的波形特征,提出励磁涌流识别的新方法。内部故障电流的全波傅氏计算结果与半波傅氏计算结果接近,而励磁涌流的全波傅氏计算结果与半波傅氏计算结果差别较大。根据差动电流的全波傅氏算法计算结果以及全波傅氏算法计算结果与半波傅氏算法计算结果的差值,求取半个工频周期内该差值的积分与全波傅氏算法计算结果的积分的比值。若比值大于整定值判为励磁涌流,否则判为内部故障电流。理论分析和动模试验结果表明,该方法能够快速区分励磁涌流和内部故障电流,同时可以分相制动,提高了差动保护的可靠性和安全性。

Magnetizing inrush identification based on differential current characteristics

The waveform characteristics of transformer magnetizing inrush and internal fault current are analyzed and a method to identify magnetizing inrush is presented.The internal fault current calculated by full-wave Fourier algorithm is close to that by half-wave Fourier algorithm.Contrastively,the magnetizing inrush calculated by full-wave Fourier algorithm is quite different to that by half-wave Fourier algorithm.Calculate the differential currents by both full-wave and half-wave Fourier algorithms and their difference,then calculate the ratio of the integral of the differential currents calculated by full-wave Fourier algorithm for half power frequency period and that of the differences.The differential current is taken as the magnetizing inrush if the ratio is greater than a setting value,otherwise as the internal fault current.The theoretic analysis and the dynamic emulational test results indicate that,it can distinguish the magnetizing inrush from internal fault current rapidly and can be applied to each phase separately,improving the reliability and security of differential protections.