Análise do desempenho de transformadores frente a curtos-circuitos empregando simulações computacionais.

Abstract

This work deals with the performance evaluation of power transformers against short-circuit magnetic forces. The influence of temperature, type of connection and level of geometric detail attributed to the winding simulation were analyzed by computer simulations. Initially, with the objective of evaluating the influence of the thermal phenomena, the temperature rise of the windings during short circuit was calculated. Then, simulations of mechanical stresses considering variation of the windings initial temperature were performed. Magnetic forces and maximum stresses were calculated. Subsequently, a comparative analysis of the circuits and short-circuit stresses was carried out on a transformer and on the equivalent autotransformer. Finally, in order to analyze the computational efficiency and accuracy of different geometric winding models, 3D and 2D axisymmetric geometric representations were simulated and compared. The results of the simulations with temperature variation indicate that the maximum main stress increases with the increase in winding temperature. It has also been confirmed that mechanical short-circuit stresses are higher for an equivalent autotransformer, in this case reaching 231% with respect to the transformer. The analysis of the geometric models indicated that the use of less detailed representations underestimates the magnetic force density in the conductors and the axial forces.