Avaliação dos estresses mecânicos nos enrolamentos de transformadores.

Abstract

There is a lack of robust methodologies and tools to evaluate the effects of electromechanical efforts caused by high transient currents on transformers. Thus, this work aims to study electromechanical efforts caused by short-circuit currents through transformer windings, as well as to analyze the windings failure proximity by comparing two mechanical failure criteria: the maximum tension criterion and the Von Mises criterion. Mechanical efforts were studied for two cases, a single-phase 75 MVA transformer and a three-phase 180 MVA transformer. It was found that modeling based on the Finite Element Method, compared to analytical formulation, is the mors appropriate for determining electromagnetic forces in transformer. Furthermore, it was found that a 3D graphic representation of the transformer windings is necessary for a correct determination of electromechanical efforts, since the geometry directly influences the effort configuration. Finally, it was found that the Von Mises criterion is more appropriate to evaluate the windings failure proximity, since this criterion use more parameters for decision-making, which make it more accurate. It is concluded that the comparisons and verifications obtained in this work can be generalized to other transformers. Enabling a more appropriate analysis of electromechanical efforts that occur in large power transformers.