Assessment of insulation in aged power transformers by interfacial polarization spectrum and its correlation with chemical properties

The ageing process of the paper can be monitored by measuring several properties such as tensile strength, electrical properties, degree of polymerisation (DP), furan content in the oil, return voltage measurement in the dielectric, etc. The DP technique has been widely studied by Shroff and Stannett. The cellulose fibres in paper degrade to produce a range of furans, some of which dissolve in the mineral oil. The correlation between the concentration of furans in the oil and the mechanical and dielectric properties of the paper has been studied. In the interfacing of the paper and oil in the transformer, interfacial polarization may occur, resulting an increase in the loss tangent and dielectric losses. A DC method was developed for measuring the interfacial polarization spectrum