Evaluation Method for Moisture Content of Oil-Immersed Bushing Based on Davidson-Cole Model

The oil paper insulating bushing is the core components which power transformer connects the external equipment. There is a risk of external moisture entering during operation. An increase in moisture content will significantly reduce the oil paper insulation characteristics. To achieve a non-destructive testing method for moisture content in oil-paper insulation bushing, the paper analyzes the complex frequency domain dielectric spectroscopy of oil-paper insulation bushing based on the double relaxation Davidson-Cole model, and proposes a method for extracting moisture characteristic parameters and evaluating moisture degree. Firstly, the double relaxation Davidson Cole model was used to analyze the model parameters of the frequency domain dielectric parameters of oil-immersed bushings with different moisture content. Secondly, the variation pattern of parameters in the double relaxation Davidson-Cole model was analyzed, and the DC conductivity $\sigma$ and polarization intensity $\triangle \varepsilon 1$ were determined as a characteristic parameter to characterize the moisture content in oil-immersed bushings, and the two have an exponential relationship with moisture content. Finally, the fitting formula with moisture content and the characteristic parameter (DC conductivity $\sigma$ and polarization intensity $\triangle \varepsilon 1$) were proposed, and a moisture evaluation method for oil-paper insulating bushing based on frequency domain dielectric spectroscopy and double relaxation Davidson-Cole model was proposed. Related research can provide a basis for evaluating the degree of moisture content of oil-immersed bushings.