Explanation study of frequency-domain dielectric spectroscopy for oil-paper insulation system

In order to explore the explanation of frequency-domain dielectric spectroscopy (FDS) and to improve the application to nondestructive diagnosis of insulating state for oil-paper insulation, the frequency domain dielectric response theory is studied further in this paper. Firstly, FDS measurement system for oil-paper insulation is established in the lab. Secondly, the mechanism and characteristics of conductivity loss and polarization loss are analyzed respectively. The classical loss characteristics of oil-paper insulation are outlined by a systematic analysis of the relationship between complex dielectric constant and frequency. And then a theoretical explanation for FDS is introduced based on conductivity loss and polarization loss. The test results show that at low frequencies, the characteristics of complex dielectric frequency spectra are mainly influenced by conductivity loss, which can be explained by Dyre model. At high frequencies, the characteristics are mainly influenced by polarization loss which can be explained by H-N model. In addition, the characteristics at middle frequencies are the results of conductivity and polarization loss. The reconstructed curve obtained by this method accords with the measured curve well. The presented explanation method in this paper is used to analyze and fit the complex dielectric frequency spectra of oil-paper insulation based on the test results of FDS. And the statistical function relationships either between frequency and polarization or between frequency and conductivity are obtained, which can be used to extract characteristic parameters of dielectric response. These build up the theoretical foundation for the quantitative assessment of insulating state.