Abstract :
A topology-based and duality-derived three-phase,
three-winding, core-type transformer model is presented. The
model treats the leakage inductances and the coupling effects of
the core in a straightforward and integrated way. The longestablished
positive- and zero-sequence star equivalent circuits
of a three-phase three-winding transformer are derived from
the original equivalent magnetic circuit of the transformer by
applying duality. Formulations for determining the values of
the leakage inductances and the core loss resistances from
transformer open- and short-circuit test data are presented. A
supporting routine is written to generate the Li curves for each
segment of the core and the other input data for EMTP. Since
the duality-derived model consists of only RLC elements, no
device-specific code to EMTP time-siep code is needed. Winding
capacitances are lumped to the terminals. The model is suitable
for simulation of power system low-frequency transients such as
inrush currents and ferroresonance, short circuits, and
abnormalities including transformer winding faults.
