Understanding moisture diffusion process in oil-impregnated pressboard insulation of transformer

Moisture is one of the most influencing parameters, which accelerates solid insulation degradation and ageing process in transformers. Correct estimation of the moisture within solid insulation of transformer is still a challenge due to temperature driven complex moisture dynamics between oil and paper insulation. This paper investigates moisture diffusion process in oil-impregnated pressboard samples at different temperatures to understand the moisture diffusion process of transformers. Mathematical model for moisture diffusion is developed and numerical calculations are carried out using finite volume method. In experimental method, moisture diffusion process in oil-impregnated pressboard sample is investigated by continuous measurement of dissipation factor (Tan δ) at different temperatures. Finally, simulation results obtained from the moisture model are verified with the experimental method.