To keep required dryness/improve dryness of the transformer insulation, internal part of transformer. When transformer operates, due to pressure head between top and bottom small quantity of oil flows through filters (absorbent material activated alumina grade g-80 removes the moisture from oil). Absorbent material remove slag, acids, peroxides, ionic impurities from oil, which otherwise accelerate against of oil. Absorbent unit is reactivated at regular intervals.