An Accurate Hysteresis Model for Ferroresonance Analysis of a Transformer

This paper introduces an accurate transformer core model, using the Preisach theory, to represent the core magnetization characteristic. This modeling approach provides the required precision to match major and minor hysteresis loops of the model with those of the actual transformer core material. Using the proposed model, the ferroresonance phenomenon of a voltage transformer (VT) is simulated and compared to the corresponding experimental results. In addition, the simulated ferroresonance behavior of the VT based on: (1) the Electromagnetic Transients Program (EMTP)-RV hysteric reactor model, (2) the EMTP reactor type-96 model, and (3) a single-valued polynomial as magnetization characteristic, is also deduced and compared with the proposed model and the experimental results. The investigations conclude that the proposed model provides the most accurate results in terms of the VT core losses and the VT voltage waveforms and their peak values during (1) normal operating conditions, (2) ferroresonance transients and jumping from normal to ferroresonance operating conditions, and (3) ferroresonance steady-state conditions. Furthermore, higher accuracy of the proposed model in representing the hysteresis loop provides the highest and the most accurate bifurcation point and the transient loss when compared with other models. This paper also concludes that major and minor hysteresis loops must be represented in the core model to accurately simulate ferroresonance phenomenon of the VT.