| A comprehensive, three phase transfer model for the calculation of electromagnetic transients is presented. The model consists of a set of state equations solved with the trapezoidal rule of integration in order to obtain an equivalent Norton circuit at the transformer terminals. Thus the transformer model can be easily interfaced with an electromagnetic transients program. Its main features are: (a) The basic elements for the winding model are the turns. Very efficient methods for computing turn-to-turn leakage inductances and turn capacitances are presented. (b) The comprehensive model includes the losses due to eddy currents in the windings. Various equivalent circuits have been fitted to represent in the time domain the damping produced by eddy currents in the windings. (c) Saturation and the damping produced by eddy currents in the iron core (laminations) are represented. Optimal discretization of the laminations was used to derive the frequency dependent and nonlinear transient model. (d) The solution of the state equations is obtained in decoupled iterations for the windings, iron core, and resistive voltage drop in the windings. (e) Voltages and currents at any points in the windings can be displayed. A fitting technique for the approximation of smooth transfer function matrices has also been developed. Its applicability goes beyond the field of transformer modeling.;For validation, the frequency response of the model is compared with rests on a real transformer. Applications to the calculation of transients are given for illustration and further validation. |
