Enhanced Transformer Model for Low- and Mid-Frequency Transients—Part I: Model Development

Based on an enhanced topological representation of the transformer core, flux air paths, and tank, a duality-based transformer model is proposed for low and mid-frequency transients analysis. In the developed transformer model, the core and tank iron are represented based on a frequency-dependent hysteresis model. The winding capacitances and the frequency dependency of the winding resistance are also incorporated in the developed model. Furthermore, a detailed model is developed for the air gap and tank, and the corresponding average equivalent is presented which is more appropriate for extracting the parameters from the measurement. In addition, the nonuniform air gap and the fringing flux effects are taken into account, and an approach is presented to obtain the corresponding parameters. The developed models also include the equivalents of the tank magnetic shield and the structural parts. Part II of this paper provides validations and further simulation results.