Evaluation of Aging for Thermally Upgraded Paper in Mineral Oil

Abstract

– The life of a transformer is limited by the degradation of its solid insulation. Winding conductors and other solid insulation materials in oil-immersed transformers have been insulated using cellulose products. For many years, manufacturers have met the needs of special applications by designing transformers using thermally upgraded materials to achieve lighter weight, higher power density and increased life. Recently, the effects of thermally upgraded insulation on diagnostic techniques such as gas-in-oil analysis, and indicators of their insulation degradation, have been reviewed. This paper describes evaluations of amine-impregnated thermally upgraded paper insulation's thermal degradation characteristics and decomposition reactions in mineral transformer oil. The thermal resistance of the thermally upgraded paper is evaluated by comparison with Kraft paper insulation. Further, aging degradation mechanisms of decompositional degradation of the thermally upgraded paper due to aging in mineral transformer oil are proposed.