Besides normal ageing, insulation in power transformers operating in electrical systems is also subject to deterioration for different reasons. Some of the most destructive regimes are electrical faults and overheating. Oil paper insulation is achemically complex system and the ageing process is manifested by changes in the chemical structure of the oil and reduction in dielectric strength of solid insulation. These changes seriously affect normal operation of the transformer and can result inexpensive damage.The basic requirement is that insulating materials must be chemically and thermally stable. During transformer manufacture the insulation must be adequately dried. This task is not so simple since oil and cellulose have different absorptioncharacteristics. Cellulose is known to be hydrophilic, and oil is hydrophobic. Total dehydration of cellulose would cause loss of its mechanical properties.The stabilization of insulating oil has not been solved in a satisfactory manner. This problem with insulating oil is the result of a complex oxidation process in the oil during regular transformer operation. The oxidation mechanism further helps theformation of lower carbonyls, carboxyls, water and gases in oil. These materials are actually by-products of the ageing of the oil.Combining the ageing mechanisms in cellulose and oil, results in very complex mechanisms, which accelerate degradation of the oil-cellulose insulation many times.At the present, looking for the solution to this problem, corrective action can take two directions:1. Slowing the degradation process by adding inhibitors.2. Removing by-products of oil and cellulose degradation using an adsorption method to restore initial quality.We utilize newly developed adsorbents and specially formulated materials to regenerate oil directly in the transformer tank.
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