基于EMD分解的变压器励磁涌流鉴别

One New Scheme to Discriminate Inrush Current from Internal Fault of Power Transformer Based on EMD Decomposition

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,提出了一种利用HHT(Hilbert-Huang Transform)的EMD(Empirical Mode Decomposition)分解来识别变压器励磁涌流的新方法。该方法利用EMD将数据分解成有限个IMF(Intrinsic Mode Function),定义并计算各个IMF在X轴上的投影面积、Simf的比重系数及其最大值Kmax。在比较励磁涌流和故障电流Kmax不同特点的基础上,提出了一种变压器保护新方案。理论分析及动模实验结果表明,该方法能够正确区分励磁涌流及故障电流,其判断时间约20ms;方法实现方便,不受非周期分量等影响。

One new algorithm based on EMD was presented for fast discrimination between inrush current and fault current of power transnformers. The method was based on that the waveform of the inrush distorts seriously, while the fault current nearly keeps sinusoid. The complicated signal can be decomposed into a finite intrinsic mode functions （IMF） by the EMD, then defined and computed the projection area on X-axis of each IMF, the specific gravity of SIMF-KCi, and the maximum of KCi-Kmax. We can get a new scheme of transformer-protection based on comparing the difference between inrush and fault current. Theoretical analysis and dynamic simulation results showed that the method can precisely distinguish inrush and fault current, fault clearance time is about 20ms. Moreover, it is convenient to achieve and hardly to be affect by aperiodic component.