Life Assessment of Electric Arc Furnace Transformers

Electric arc furnace transformers are very important in the steel production industry. Currently, it is very common for companies to buy used transformers considering the huge investment that represents the acquisition of a new transformer and also the delay in the purchase transaction. Before accepting a commercial agreement and putting the transformer into operation, it is necessary to evaluate the level of wear out due to the electrical and magnetic stresses to which the transformer is subjected. Electrical, mechanical, and insulation tests, that follow procedures stipulated in guides and standards, are performed on used transformers during the purchase process in order to identify incipient faults and to determine their general condition. A methodology is proposed to carry out these tests. In addition, a new model based on fuzzy logic is implemented to assess the level of wear of the transformer, its remaining life, and its feasibility of reuse. The fuzzy input variables of this new model are the results of the tests performed on each element of the transformer.