The term “moisture” in the transformer industry is commonly used to indicate water which is absorbed in the paper or dissolved in the oil. Occasionally, the terms “water” or “water content” are used as an alternative way to describe the same substance.

Water in transformers can be found in different parts of the insulation system. It can accumulate in solid insulation, be dissolved in oil, or be found in the form of liquid water at the core or bottom of a transformer.

If it has been determined that a transformer has an excessive moisture content, either through water-in-oil analysis or dew-point analysis, the transformer should be dried out. Otherwise, the presence of moisture in the kraft paper will definitely shorten the life due to chemical decomposition through oxidation of the cellulose.

Present and future transformer ratings require high quality and high purity insulating oils at the point of use. The increasing voltage and rating of the modern transformer and electrical apparatus results in greater electrical stress in insulating material and fluids. To handle these greater stresses, oils with better dielectric qualities are required. Also lower residual water content in insulating fluids and material must be maintained. The proper treatment and upgrading of the insulating fluid will result in the improvement of the properties of the entire insulating media of power transformers. The principal functions of the insulating fluid are to serve as a dielectric material and as an effective coolant. To perform these functions, the insulating fluid must have the necessary qualities at the time of initial impregnation and filling at the factory and later maintain the same quality in the field operation. High Vacuum Process upgrades the new or used electrical insulating fluids including transformer oils, polybutenes and silicone fluids. These systems and equipment were developed as a result of 50 years of experience in vacuum treatment of electric insulating fluids.