Parameters Identification of the Electrical Debye Model for Power Transformers Multilayer Insulation Systems

This paper proposes an approach to parameterize the extended Debye model (EDM) employing rational approximation of dielectric frequency response (DFR) curves via the vector fitting (VF) technique. The rational approximation, expressed as a set of partial fractions with corresponding poles and residues, provides straightforwardly the EDM RC parameters. In the proposed approach, the VF algorithm is internally modified to compute the residues as a constrained linear least-squares problem to guarantee positive RC elements, i.e., a physically realizable circuit, unlike existing methods that use post-processing algorithms.Validation of the proposed technique is performed by reconstructing the DFR curves of new transformers and by the comparison of calculated polarization current from DFR versus real-time domain measurements.