中文摘要：

提出一种基于幅值特征的变压器差动保护原理，利用经验模态分解（empiricalmodedecomposition，EMD）奇异点检测算法准确定位故障时刻，然后利用两点乘积算法计算出对应基波幅值。结果表明，由于非饱和阶段的存在，励磁涌流的基波幅值很小，而由于故障支路的影响，故障电流的基波用幅值远大于阈值，因此可以用幅值相对门槛值的大小来反映是否发生了内部故障。动模实验验证了此算法易于实现，计算量小，动作可靠、迅速。

英文摘要：

An amplitude characteristic based principle for transformer differential protection is proposed. The proposed principle uses empirical mode decomposition （EMD） and singular point detection algorithm to accurately fault moment, and then corresponding amplitude of fundamental current is calculated by two-instantaneous-value-product algorithm. Calculation results show that due to the existence of non-saturation stage, the fundamental amplitude of inrush current is small, however because of the influence of faulty branch the fimdamental amplitude of fault current is far larger than the threshold, therefore whether internal fault of power transformer occurs or not can be reflected by the fundamental amplitude relative to the threshold. Dynamic simulation results show that the proposed algorithm is convenient to implement and possesses following advantages： light calculation burden and reliable and rapid action.