Extraction method for frequency domain characteristic parameters of oil impregnated insulation paper

Frequency domain dielectric spectroscopy (FDS) based on dielectric response has been widely used for assessment the state of oil-paper insulation in transformers. However, domestic and foreign researches are mostly focused on qualitative analyzing the changing behavior of frequency domain spectrum curve for different insulation conditions, such as different temperature, moisture and aging status. It is difficult to find a method to extract the frequency-domain characteristic parameters that can be effectively quantified the state of oil-paper insulation. Thus no quantify analyzing the frequency-domain spectrum curve has been made at present. In this paper, firstly, the basic theory of dielectric polarization and a new Cole-Cole model with four polarization processes were introduced. Secondly, FDS measurements on oil impregnated insulation paper at different temperatures were made. Finally, new frequency-domain characteristic parameters for FDS curves were extracted using the new Cole-Cole model. In this way, the physical polarization process could be also clearly understood.