Electromagnetic and thermal behavior of a single-phase transformer during Ferroresonance considering hysteresis model of core

Abstract

Ferroresonance leads to a high saturation of the transformer core. This causes severe rise of the amplitude of current and voltage of the transformer and leads to current and voltage non-sinusoidal waveforms. Therefore, the increase of the transformer losses and its temperature rises during Ferroresonance can overstress the transformer insulation system and elevate the chance of the transformer failure. In this paper electromagnetic and thermal behaviors of the transformer during Ferroresonance are investigated using a three dimensional finite element model. The modeling of the core is the most important challenge in the solution of the transformer electromagnetic equations during Ferroresonance. Thus, the Jiles-Atherton (JA) model is employed to model the core hysteresis loop. Based on the proposed approach, the behavior of a single-phase transformer under fundamental and sub-harmonic Ferroresonance modes are simulated and the results are compared with the experimental results. Furthermore, a thermal equivalent circuit is developed, based on the simulated transformer losses and thereby, the transformer temperature rises are estimated during Ferroresonance.