Contribuição da corrente de inrush para a fadiga mecânica dos enrolamentos de transformadores de potência.

Abstract

This work presents a study regarding the contribution of inrush current to the occurrence of mechanical fatigue in windings of a power transformer and, consequently, the impact of that phenomenon on the equipment’s lifetime. In order to perform the study, it was used electromagnetic transient simulations to determine the inrush current in a three-phase transformer model. Then, simulations, based on the Finite Element Method, were performed to determine the electromechanical stresses in the equipment windings, under the effect of the inrush current. Next, the methods of Critical Plans and Palmgren-Miner were applied to perform the fatigue study. From the simulations results, it was possible to determine the impact of inrush current on the integrity of the windings of a transformer, as well as, to estimate the lifetime reduction of the equipment due to inrush occurrence. It was also possible to determine the number of inrushes needed to estimate the total lifetime reduction of the equipment due to the mechanical fatigue. The results can also be used in transformers design stage, with the purpose of assisting the evaluation of mechanical withstand of an equipment, which can minimize the possibility of failure and increase its lifetime.