Dielectric frequency response of mineral oil impregnated pressboard

The degradation processes of pressboard, paper or oil used in transformer are influenced by many factors. One of them is the moisture which is usually inhomogeneous distributed in oil-paper insulation, especially for power transformer. The dielectric properties of mineral oil impregnated pressboard with various moisture concentrations were measured. These measurements were made at different temperatures. The measured dielectric parameters were modeled by Debye model. Two different instruments: IDAX and LCR Meter with various frequency ranges for the measurements were used.