Large-scale survey of furanic compounds in operating transformers and implications for estimating service life

The concentration of furanic compounds in the dielectric fluid of a transformer is a good indicator of the condition of the cellulosic materials such as paper, pressboard, and cotton materials used both as electrical insulation and as mechanical support. The condition of the cellulosic materials is vital, because those materials are the limiting factor on the life of a transformer. Over the last three years, the lab at S.D. Myers has conducted a massive survey of the concentration of furanic compounds in the dielectric fluid of operating transformers. The Myers data base now contains more than 15,000 test results on dielectric fluids, including mineral oil; silicone, PCB-askarel, high fire-point oil, and perchloroethylene. The furan test is especially valuable for the PCB-askarel units, because the dissolved combustible gas test is not very useful for such units. The furanic compounds were measured with a high performance liquid chromatograph (HPLC) per ASTM Method D 5837. Due to the massive furan survey data available, it is now possible to interpret furan test results actuarially. This approach works best for the mineral oil transformers with more than 12,000 furan test results as of January 1, 1998.