Degradation of oil-paper systems due to the electrical field enhanced absorption of water

Oil-impregnated paper used as an insulating medium in oil-filled transformers degrades over a period of time. The degradation and resulting depolymerisation of the paper is caused by the absorption of water. The present investigation was undertaken with a view to quantifying the damage done to the paper by the water. For this purpose the tensile strength as well as the electrical strength of paper was measured as a function of the water content of the paper. The experiments consisted of a number of simple tests. Controlled amounts of de-ionised and ionised water were injected into the oil. The oil impregnated paper assembly was placed in the oil/water mixture for a fixed time and measurements of tensile and electrical strength were subsequently made