Insulating paper ageing and furfural formation

Transformer condition monitoring is carried out regularly to establish state of the health of transformer. Based on results corrective actions are taken to preserve and prolong the lifetime of the unit. All insulation materials used in construction of transformer are, made from organic compounds and therefore, decomposes and deteriorates at high temperature. Insulating oil in service will oxidise and eventually reach to a step, which is not fit for the purpose. In such case maintenance guide recommend to change the oil. Insulating paper in service is similarly subjected to beat and also damaged by the oil oxidation products. The same maintenance regime is not applicable to the paper and reaction of paper degradation is not reversible, therefore life of transformer is life of the paper. In practice, it is impossible to have an accurate condition assessment without opening the transformer and have paper sample. In the other hand this is impossible practice and condition of the paper is assessed indirectly. It is established earlier that furfurals are by-products of paper ageing and can be used as indication of paper ageing. However, to relate furfuraldehyde, also named furfural (2FAL), content of a unit to age and extend of paper deterioration more research and laboratory studies are required. This paper describes laboratory studies of paper ageing and relating by-product of paper ageing to state of the insulating paper. Oil and paper are aged at different temperature, 2FAL, gases and moisture of aged samples are measured. A model for paper ageing is established.