Research On Oil-paper Insulation Based On Dielectric Spectroscopy

Oil-immersed transformer has played a significant role in the deliver ofelectricity. It’s critical to estimate the transformer oil-paper insulationsystem.The moisture content of the transformer pressboard has no good way ofnon-destructive testing. The frequency domain spectroscopy(FDS)method whichis fast and effective is described in this paper.The dielectric response theory is introduced and the relationship betweencharacteristic parameters and insulation material is analyzed. Three commonmethods of dielectric response measurement are summarized(recovery voltagemeasurement, polarization and depolarization current and FDS).Then design and build the transformer insulating oil test system platform.Oil-paper insulation system is tested by thermal aging experiment, frequencyresponse analyzer IDAX300is used to the dielectric spectroscopy of differentaging time samples and use Debye relaxation theory to analyze the experimentdata. Use MODS software to analyze the dielectric spectroscopy to caculate themoisture content of pressboard. Oommen water balance curve is used to contrastthe numerical data consistent with theoretical data, it is demonstrated that usingdielectric spectroscopy to measure moisture content is feasible.Finally，it can be found from the dielectric spectroscopy that the FDS curvemoves to high frequency region with the test temperature increase. Thedissipation loss factor is bigger with the aging time increase, the moisture contenthas the same feature. It is because the dissipation loss factor increases with therelaxation loss increase. So the FDS measurement method can be used todiagnose the aging condition of transformer oil.