A Novel Residual Magnetism Detection Method of Power Transformer Cores Based on Magnetization Time

Residual magnetism is one of the prime reasons contributing to the inrush current problem in power transformers, so effective detection of residual magnetism will help solve the inrush current problem. In this article, a residual magnetism detection method of power transformer cores based on magnetization time is proposed, and then efficient demagnetization of iron cores is realized. First, when positive and negative alternating small excitations are applied, the polarity of residual magnetism is discriminated by analyzing the positive and negative magnetization times. Second, the residual magnetism value is determined by analyzing the relations between the residual magnetism and the positive magnetization time using the finite element method, and experiments verify that the accuracy of the presented method is within 5%. Finally, based on the proposed detection method, the demagnetization excitation under known residual magnetism is determined, and the experimental results show that the demagnetization effect is better, which further proves the accuracy of the presented detection method. The research in this article will be used to test the residual magnetism of power transformers without any requirements for transformers, which has important scientific theoretical significance and engineering application value.