| The ability to accurately compute voltage transients within transformer windings is of interest to researchers and transformer designers. Attempts have been made to compute these transients using a variety of digital models. Lumped parameter based digital models, even with many shortcomings, have been used extensively. For example, coarse models lack the detail to appropriately reflect the actual electromagnetic properties of the transformer, and detailed models are often too large to be computationally efficient.; The methodology proposed here is to start with the turn to turn model of the transformer which is the most detail possible. The necessary modeling components include an air or iron core inductance model, a series and shunt capacitance model, a linear loss model, and connections.; This turn to turn model is then converted into an nodal admittance equivalent using Dommel's transformation. Before the transient calculation is made, the detailed model is further reduced using methods developed by Gutierrez. This requires a slightly more complex history term calculation. This solution is extended to include the loss model, external lumped parameter networks, switches, and nonlinear zinc oxide arresters.; Two alternative methods for obtaining frequency domain solutions are presented. The first is a method of admittance equivalents. The second is a an eigenvalue approach. Either method may be used for the computation of impedance and amplification factors vs. frequency and location of terminal resonant frequencies.; Four cases studies are used as examples to illustrate the effectiveness of these methods. These examples include a variety winding structures and the inclusion of linear and nonlinear external elements. |
