Correlation between Aging Status and Space Charge Behaviors in Samples Consisting of Oil Immersed Paper and Oil

摘要

Electrical and mechanical degradation of oil immersed paper insulation during long-term operation has always been a critical issue for the assessment of the reliability of oil immersed transformers. As to the converter transformers, the electric field modification in multi-layer insulation system caused by space charges accumulation is a substantial threat to the maintenance of insulations. It is generally believed that the degree of polymerization (DP) of cellulose paper is a reliable characteristic parameter to determine aging status of insulations. Therefore, it is expected to study the interface charge behaviors in aged samples under different aging status. In this paper, we investigated the relationship between degree of polymerization of paper and space charges behaviors in samples consisting of two layers of paper and oil. Accelerated thermal and electrical aging experiments of oil immersed paper insulation in laboratory were conducted. The pulsed electro-acoustic (PEA) method is applied to obtain space charge in samples consisting of an oil immersed paper layer and an oil layer. The correlation between interface charges behavior and DP value of paper is analyzed. It is indicated that the interface charge could act as an alternatively valuable index to evaluate the aging status of insulations.