Calculation of Moisture Content Of Oil-Immersed Paperboard Based on 10−4 Hz Relative Permittivity

Ageing and moisture affect the dielectric response of the oil-paper insulation of the transformer, such as frequency domain spectroscopy, it is difficult to distinguish these two factors. However, the effect of ageing and moisture on the relative permittivity at 10
^-4
Hz is different. In this paper, the frequency domain spectroscopy of oil-immersed paperboards with different degree of polymerization and different moisture content were measured. The experiments in this paper show that the relative permittivity at 10
^-4
Hz is much more affected by moisture than by ageing. Based on this characteristic, a method for calculating the moisture content is proposed. Experimental results show that this method can effectively calculate the moisture content of oil-immersed paperboards.