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

Moisture accelerates the ageing process in the oilpaper 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 oilimpregnated pressboard samples with ageing is discussed. Further to that, change in DP value of pressboard sample with ageing is presented for different ageing periods