Nova metodologia baseada nos critérios de Von Mises e de fadiga para avaliação dos esforços eletromecânicos causados pela circulação de correntes de curto circuito nos enrolamentos de transformadores.

Abstract

In this work is presented a new methodology to evaluate the electromechanical efforts caused by short circuit currents on the transformers windings. The methodology is based on the use of computer simulations, the finite element method and two mechanical failure criteria: Von Mises criterion and Fatigue criterion. From the results, it was verified that the possibility of mechanical failures by fatigue, in the windings, to mechanical stresses values below the critical stress values of the windings. Additionally, it was observed that the failures by fatigue depend on the amplitude of mechanical stress and residence time, and the number of times that such stresses are applied on the windings. The use of the proposed methodology also allowed the evaluation of the failure proximity in the windings. Moreover, it was possible to correlate the withstand short circuit number, the short circuit current intensity and the windings percentage reduction of life. The use of the methodology also allows evaluating the plastic failure proximity by the use of Von Mises criterion. Thus, it is emphasized that the use of the methodology proposed in this work allows contribute to the improvement in studies related to methodologies to assess the electromechanical efforts occurring in the transformers windings. Furthermore, the methodology can be used during the stage of equipment design, with order to increase the safety margin against mechanical failures and, thus, their useful life span.