Impact of moisture and ageing on the dielectric response of transformer insulation

Moisture accelerates the ageing process in the oil-paper insulation of the transformer. In order to understand an influence of moisture on the ageing process of transformer insulation, ageing experiments are carried out on oil-impregnated pressboard sample of different moisture contents, and influence of moisture and ageing on the dielectric response is studied. In this paper, variation of PDC and FDS responses of oil-impregnated pressboard samples with ageing is discussed. Further to that, change in DP value of pressboard sample with ageing is presented for different ageing periods.