Dielectric Response Model for Transformer Insulation Using Frequency Domain Spectroscopy and Vector Fitting

This paper proposes a rational approximation-based approach to find positive real parameters for the extended Debye model (EDM), aimed at condition assessment of insulation systems power transformers. The EDM can slow and fast polarization phenomenon, including relaxation mechanisms with different times within composite dielectric material. In proposed approach, complex permittivity transformer’s is approximated via functions, as given by vector fitting (VF) software tool, are identified from obtained poles/residues. To guarantee parameters, i.e., physically realizable circuit, VF internally modified calculate final residues approximation constrained linear least-squares problem without resorting further post-processing algorithms, in existing methods, hence affecting accuracy. effectiveness parametrized demonstrated two ways: (a) reconstructing frequency domain spectroscopy (FDS) curves provided measurements new oil-immersed transformers (b) comparison calculated current versus time domain. achieved accuracy most cases above 99 percent reconstructed FDS curves, while waveform reproduced good agreement.