Simulation and Impact Analysis of Remanent Flux on Power Transformer Inrush Current

The electromagnetic characteristic of power transformer is a dynamic phenomenon. It is characterized by the changes happened in current and magnetic flux state over time. Mathematically, the dynamic process of power transformers can be described by nonlinear differential equations. The core nonlinear magnetic properties must be considered when electromagnetic equipment performance and accurate calculation of the magnetic field was analyzed. By adding Jiles-Atherton (J-A) model to realize the simulation of the transformer iron core nonlinear dynamic phenomenon, the characteristics of transformer hysteresis loop under different remanent flux conditions are simulated. In the final stage, to determine the effect of remanent flux on the inrush current, the single-phase and three-phase transformer no-load closing transient process is simulated. The inrush current is identified by the various characteristics of the fundamental factors, and the corresponding inrush current curves under different remanent fluxes are analyzed. The remanent flux is determined as the main impact factor of the inrush current through this study. By reducing the remanent flux, the performance of the transformer, and furthermore the quality of the power system can be improved. This study has practical significance to provide an adequate theoretical basis for the identification and suppression of the inrush current.