中文摘要：

采用Y，d接线的变压器三角形侧绕组中的环流难以测量，因此变压器差动保护存在相位补偿的问题，使差流不能很好地反映本相励磁电流的特征，也限制了基于等效瞬时电感变化的励磁涌流判据的应用范围，成为影响变压器保护性能提高的一个难题。在变压器回路方程的基础上，推导出了等效瞬时绕组电阻和漏电感的计算公式，提出了一种适用于Y，d接线的三相一体式变压器三角形侧绕组环流的计算方法。最后通过MATLAB仿真验证了该方法的准确性，有利于等效瞬时电感的计算及相关励磁涌流判据的实施，为变压器保护中差动电流的准确计算提供了一种新思路。

英文摘要：

The circulating currents in delta side of wye-delta connected three-phase power transformer can not be easily measured. So the current phase compensation method has to be considered for differential protection. However, the differential currents cannot really and truly reflect the exciting currents of transformer no matter what kind of current phase compensation methods is used. It also limits the application of a novel algorithm based on the equivalent instantaneous inductance to identify the inrush. How to obtain the circulating currents in delta side has become a difficult problem in transformer protection. Based on the voltage loop equations of transformer, a formula for calculating the equivalent instantaneous resistance and leakage inductance of winding is deduced. And then, a novel algorithm for calculating the circulating currents in delta side of wye-delta connected three-phase power transformer is proposed. Finally, simulation results with MATLAB verify the accuracy of this algorithm.