Evaluation of the thermal stability of electrical insulating paper

Cellulose in the form of paper and pressboard has been used as electrical insulation in transformers for many years. Its low cost ready availability, good electrical properties when immersed in oil´ ease of storage and installation, and general reliability have made it virtually a universal choice. It is, however, generally recognized by the electrical industry as the most significant limiting factor in the operating temperature and thermal life of transformers furthermore m a sealed system such as a transformer, the accumulated thermal degradation products of cellulose accelerate cellulose deterioration, and in addition, significantly affect the life of other components.