Transformer Modeling. A Physically Based Three-Phase Transformer Model for the Study of Low Frequency Phenomena in Electrical Power Systems

摘要

Starting from the elementary Maxwell's equations, it is shown which assumptions and simplifications are required to arrive at what can be seen as a physically based network description of the transformer. As a result of this analysis, the link between the T-network and the Pi-network, both describing the single-phase transformer, is revealed. From a modeling point of view, the T-network results from the assumption that the total flux can be divided in main flux and leakage fluxes, while the Pi-network results from an integral flux approach. It is shown that these two approaches are mathematically related via the star-delta transformation. As a consequence, these two transformer descriptions, of which the T-network is most popular, yield the same behavior in the hypothetical case of the transformer being a linear device. It is shown that the three-phase transformer can perfectly and also more realistically be described when the integral flux approach is used.