Water saturation limit of transformer oils

The stable functioning of power transformers is closely related to the state of their insulation systems [1]. Most power transformers at present employ paper/oil insulation [2]. This type of insulation has many advantages, but deteriorates under the combined influence of a number of interrelated factors. The insulation properties of the paper/oil system depend strongly on the degree of aging, moisture accumulation in the oil and the paper, and the migration of moisture between them.