A Review of Research Progress on Residual Magnetism Detection Methods for Power Transformer Cores

When the power transformer is out of operation, due to the inherent hysteresis properties of the iron core material, the residual magnetism will be appeared in the iron core and then a large inrush current may be generated, which will lead to the closing failure of the transformer. Therefore, the study of accurate residual magnetism detection methods can avoid the harm of inrush current to the power grid. This article first analyzes the formation mechanism and detection principle of residual magnetism. Then, the existing detection methods are summarized, mainly including empirical estimation method, voltage integration method, premagnetization method, and dc and ac indirect detection methods. On the basis of summarizing the advantages and disadvantages of existing methods, their accuracy, directionality, and applicability are compared and analyzed in this article. Finally, the problems and development trends of these methods are summarized and prospected. This research in this article can not only provide reference for the demagnetization of transformer cores but also provide a certain theoretical basis for solving the problem of inrush current.