On the Consistency of Tap-Changing Transformer Models in Power System Studies

The tap-changing transformer models used in steady-state power system studies have been recognized as somehow controversial for a long period. Indeed, discrepant versions arise depending on slightly different underlying assumptions. As a consequence, two alternative models are traditionally implemented in power system simulation software packages. A new model, recently proposed by the authors, has reconciled those versions, leading the way in removing the ensuing ambiguity. In this work, several case studies are introduced in order to highlight the important inconsistencies which can be drawn from the use of the traditional versions. Furthermore, this contribution presents a framework for the correct configuration of the new model in the usual scenario of imperfect information on transformer construction data. This work demonstrates that the adoption of the new model solves the aforementioned ambiguity, thus being a valuable tool to provide consistent results in power system studies on grids with embedded tap-changing transformers.