Experimentally validated reversible single-phase multiwinding transformer model for the accurate calculation of low-frequency transients

In this paper, a previously published model for the representation of the leakage inductance of multiwinding transformers is enhanced to support accurate calculations of low-frequency transients, including inrush currents, series ferroresonance, and geomagnetic-induced currents. The new circuit is obtained from the principle of duality and, therefore, is physically consistent. The unique characteristic of the improved model is that the very deep saturation behavior of the iron core is properly represented for each winding simultaneously (reversible model) without changing parameters. The hysteresis cycle and iron-core losses are also included. In addition to its reversible terminal behavior coupled with physical consistency, the proposed model can be built with circuit elements available in Electromagnetic Transients Program-type programs, and all of the parameters can be computed from terminal tests. The model is validated by comparing computer simulations versus laboratory measurements for three- and four-winding transformers.