New Compact White-Box Transformer Model for the Calculation of Electromagnetic Transients

In a recent work, a successful power transformer white-box model for the calculation of electromagnetic transients has been presented. Although this model gives very satisfactory results, when applied to large transformers it requires a large number of auxiliary loops to model the damping. This can be problematic as it not only requires more computational effort, but the size of the input data may even preclude its use with ATP-EMTP and perhaps with other EMTP-based software that have limitations in this regard. In this work a new reduced model which enables its use with ATP-EMTP is presented. This model requires a much smaller number of circuit components than the original model, which allows the data size and simulation time to be substantially reduced without practically affecting the calculation results. This has been achieved through the reduction of the rank of the sub-matrices that characterize the inductive coupling between the main winding sections and the auxiliary loops used to model the damping. The new model has been validated by making comparisons of the frequency responses calculated using the new compact model with the ones calculated with the original model developed for the case study used by the CIGRE JWG A2/C4.52 to test the accuracy of various types of transformer models.