A comparative investigation of electromechanical stresses on transformers caused by inrush and short-circuit currents

Abstract

This paper presents the mechanical effect on transformers when subjected to one of the power quality indicators, i.e., the electromagnetic transients. A common reason for internal faults in transformers windings is the weak insulation. This effect can be caused and accelerated by the electromechanical efforts produced by the inrush and short-circuit currents. Even though the transformer energizing is considered a normal operation, it produces high currents and this phenomenon significantly reduces the transformer life expectancy and may even lead to its instantaneous or timing destruction. Moreover, taking into account the same magnitude of current, the inrush currents can produce greater forces than those caused by short-circuit currents. Therefore, this papers aims to present and compare the electromechanical effects produced by the inrush and short-circuit currents in the transformers windings. To conduct this research, FLUX software in its 3D version, based on the finite element method (FEM) will be used. To highlight the overall model and the software performance, a laboratory 15 kVA transformer is utilized. It has been built with concentric double-layer windings and ferromagnetic core with three columns.