Research on Diagnosis of Damp State of Smart Transformer Dry Type Bushing (iSPEC2021)

The bushing is one of the important components of the smart transformer. The main insulation of dry-type bushing capacitor core is epoxy resin impregnated paper made of crepe paper poured by epoxy resin. The molecular chains of epoxy resin and crepe paper easily absorb water due to the presence of hydrophilic groups. In order to clarify the moisture diffusion characteristics in the two materials and its influence on the dielectric properties, this paper prepared epoxy resin impregnated paper insulation samples, carried out moisture diffusion experiments and dielectric properties test experiments under different moisture contents. The results show that the diffusion characteristics of moisture in epoxy resin impregnated paper can be explained by the Langumir model; the decrease of moisture content causes the loss peak of the dielectric spectrum curve of epoxy resin impregnated paper to shift to the low frequency direction. Furthermore, this paper extracts the characteristic parameters of its dielectric spectrum curve, and proposes a new method for evaluating the damp condition of dry-type bushing insulation.