Transformer high frequency modelling based on lumped parameter model by consideration of corelosses

Having a model accurately describing the real transformer high frequency characteristics is necessary in online examination of the physical structure of a transformer for mechanical faults detection. Comparison between simulation results and experimental data should be used in model accuracy examination. In this paper high frequency characteristic of a power transformer is modeled using lumped parameter model. Because the insulation resistances are dependent on frequency, the way in which they will be entered in the model is effective in determining the resonance amplitudes. An approximation method is used to consider the frequency dependence characteristic of the resistances. A comparison shows that the experimental data and simulation results are in a relatively good agreement except in first resonance amplitudes. This lack of coincidence is due to core losses. These losses are calculated using analytical equations, and are added to the lumped parameter model as a resistance in parallel with the high voltage winding. By comparing the simulation data and experimental results, it can be seen that there is no considerable difference in first resonance amplitudes, and both diagrams are in a relatively high coincidence.