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

摘要

The ability to predict or confirm ferroresonance and to evaluatenits severity depends primarily on the correctness of the transformernmodel used in the computer simulation. An equivalent circuit isndeveloped here for the widely used three-phase grounded-wye tongrounded-wye five-legged wound-core distribution transformer. Recentlyndeveloped equivalent circuits are generally correct, but cannotnfaithfully reproduce all of the ferroresonant modes possible in thisntransformer. This new equivalent circuit is derived using dualityntransformations. Core saturation and losses and coil capacitances arenincluded in the model. Model parameters are obtained via measurement,nobviating the need for proprietary manufacturer design information. Thenmodel is implemented in EMTP. Simulation results are presented andncompared to measurements. A technique for predicting ferroresonance on ansystem level, based on the use of bifurcation diagrams and Poincarensections, is developed and implemented using EMTP. The model performsnquite well, even though coil capacitances are not entirely included innthe model. One of the key advancements is the development of anbifurcation simulation method to predict ferroresonant behaviors for anlarge range of capacitance values