Ageing diagnosis and life estimation of paper insulation for operating power transformer

In order to construct a model to predict the life expectancy of oil-immersed power transformer, it is needed to understand the ageing mechanism of solid insulation. As the general mechanism and changing tendency of DP, contents of CO, CO₂ and furfural during the ageing test may be obtained in the lab and combined with the statistical analysis of thousands data of DGA and furfural of operating transformer collected, some engineering conclusions had been also discovered, such as, generally, there is a rather large difference of the value of furfural content measured between the transformers operated in power plant and in substation, also between the transformers at different regions, for instance, from the Hong Kong and from the mainland of China, so some tendency in different conditions were obtained and analyzed with several statistical methods in this paper. Based on the data measured and tendency of the tested transformer, comparing with these statistical distribution curves, the synthetic analysis and diagnosis of paper insulation can be carried on. As this method of synthetic analysis is more correct comparing with the method based on using some criteria only, so it has been successfully used in utilities.