Analysis of Sympathetic Inrush Phenomena in Transformers Using Coupled Field-Circuit Approach

Sympathetic inrush current phenomenon occurs when a transformer is switched on in a power system network containing other transformers which are already energized. In this paper, the phenomenon of sympathetic inrush current is investigated using nonlinear-transient field-circuit coupled finite element formulation. The cases of the transformers connected in parallel and in series have been considered. The results obtained for a 31.5 MVA, three-phase transformer are presented and discussed in detail. This work also includes the investigation of parameters affecting the magnitude and duration of sympathetic inrush phenomenon, such as series resistance, switching-on angle, residual flux density and load conditions. These analyses provide a sound theoretical basis for a thorough understanding of the phenomenon.