Correntes transitórias de Inrush e forças eletromagnéticas em transformadores de potência: uma análise baseada em engenharia assistida por computador

Abstract

Quality, quantity and consistency in the supply of electricity are the main challenges for companies in the energy sector, which are being increasingly demanded by regulatory bodies. To ensure these requirements, from generation to distribution of electrical energy, the energy system needs to have equipment with a high degree of reliability and be subject to proper operation. However, during the operation of the electrical system, electrical transients may occur, where the energization current transient or inrush current stands out. This current transient occurs during the energization of electrical transformers, due to the constructive non-linearities of this equipment. The inrush currents are unbalanced and of high magnitude, consequently, they affect the integrity of the transformer, and can permanently damage and render the equipment unusable. Given this, the present work carries out the electromagnetic study of a transformer prototype, through the application of computer simulations with the Finite Element Method (FEM), using the program Ansys Electronics Desktop© . The study aims to analyze the transient energizing currents in transformers and the consequent Lorentz electromagnetic forces in the equipment windings. For this, the geometry of the transformer windings is designed with divisions, allowing the measurement of radial and axial Lorentz forces at different locations in the windings. Four cases were simulated, each case refers to a reclosing instant in the voltage wave angle. Two cases are recurrent in the bibliography, such as maximum and minimum inrush current situations. The other two cases are intermediate and proved to be relevant for understanding the operation and design of transformers.