A New Identification Method for Transformer Inrush Current Based on Fast S- transform and Information Entropy

To settle the problem that identifying inrush current and fault current of large transformer is difficult, a new identification method which is a combination of fast S transform and information entropy theory is come up with. Firstly, the inrush current signals of transformer and fault current signals of different fault types are subjected by fast S transform, extracting the feature information after fast S transform. Secondly, the information entropy of the feature information is calculated. The information entropy of fault current, which is larger than that of inrush current, is a protection criterion for distinguishing inrush current and fault current. Through the simulating tests of transformer with different capacity, the results show that this method can be a reliable method to identify transformer inrush current and fault current. Fast S transform, comparing with traditional S transform, reduces computational complexity greatly, and founds the foundation for the application of the engineering application.