Coupled numerical modelling of power loss generation in busbar system of low-voltage switchgear

Abstract

This paper presents a coupled mathematical model of the heat transfer processes in an electric switchgear. The considered problem required the computation of the detailed distribution of the power losses and all the heat transfer modes (radiation, convection, and conduction) within a unit. In this complex thermal analysis, different definitions of electric busbar heating were considered and compared. The most advanced model, which couples the thermal and electromagnetic fields in two ways, was also compared with the simplified approaches. First, the direct current loading of the busbar, which neglected the alternating current effects, was considered. Second, models that included only one method of coupling were calculated for different assumed average busbar temperatures. Finally, the model with the two-way coupling, which took the eddy currents and proximity effects into account, was simulated using an iteration loop between the electromagnetic and fluid flow solvers. This study employed a geometrical model of industrial low-voltage switchgear. The presented mathematical model was also validated against temperature measurements carried out by a certified laboratory. The obtained results show that a fully coupled model produces very satisfactory agreement between computed and experimental data.