A Reversible Three-Phase Transformer Model for Energization Transients Based on Topological Remnant Flux Calculation

As a component in power systems, the power transformer plays an important role. Hence, precise modeling can provide useful information about transformer behavior in steady-state and transient conditions. Due to some limitations of available transformer modeling methods, especially in transients, a reversible three-phase transformer model is presented in this paper based on topological remnant flux calculation. In this model, the equivalent magnetic circuit is based on the duality principle. This concept facilitates the connection of an equivalent magnetic circuit to the leakage inductances. The two important factors for transformer energization modeling are air-core inductance and remnant fluxes in different core parts. The calculation of air-core inductance is explained in the paper comprehensively. The simulation results of the proposed topological model for a real 96 MVA, 410/6.8 kV power transformer with a shell-type core in EMTP software shows a nice match between simulated inrush currents with considering remnant flux and the measured ones.