Performance Analysis of High-Order RC Circuit Models Applied to Insulation Broadband Impedance Reconstruction in Multi-frequency Applications

The extended Debye circuit models (EDCM) are the prevailing tool to characterize the kinetic physical behaviors and estimate the broadband impedance of insulation systems. The EDCM with 6 RC relaxation branches is commonly used to fit the broadband impedance, but its reasons and the representation of what physical mechanisms are questionable. Therefore, the EDCMs with different RC branches are reexamined to fit the frequency-domain broadband impedance of polymeric insulation systems used in multi-frequency applications. Furthermore, the performance analysis is discussed integrating the circuit topology and the underlying dynamic relaxation mechanisms, which can help us to choose an appropriate circuit model to support multi-frequency industrial applications. Results show that the fitting accuracy of broadband impedance gradually improves with the increase in the number of RC relaxation branches. From the perspective of the mathematical fitting, the EDCM with 6 relaxation branches may be a best choice for estimating the insulation broadband impedance. Notably, the EDCM following the exponential decay behavior cannot match the nonlinear kinetic relaxation mechanisms related to power-law properties. The significance of this paper is to better understand the EDCM and to develop physics-based circuit models for insulation systems used in multi-frequency applications.