Five-legged wound-core transformer model: derivation, parameters, implementation and evaluation

The ability to predict or confirm ferroresonance and to evaluate its severity depcnds primarily on the correctness of the transformer model used in the computer simulation, An equivalent circuit is developed here for the widely used thrce-phase groundcdwyc to grounded-wye five-leggcd wound-core distribution Ininsformcr. Rcccntly devclopcd equivalent circuits arc generally correct, but cannot faithfully rcproduce all of the ferroresonant modes possible in this transformer. This new cquivalcnt circuit is derived using duality transformations. Core saturation and losscs and coil capacitances are included in the model. Model parameters are obtained via measurement, obviating the nccd for proprietary manufacturer design information. The modcl is implcmcntcd in EMTP. Simulation results are presented and compared to measuremcnts. A technique for predicting ferrorcsonance on a system level, based on the use of bifurcation diagrams and PoincarB scctions, is dcvclopcd and iinplcmcntcd using EMTP. The model performs quite well, even though coil capacitanccs arc nut entirely included in the model. One of thc kcy advancements is the development of a bifurcalion simulation method to predict fessoresonant behaviors for a large range of capacitance valucs.