Prediction of remaining life of the paper insulation by the analysis of new oil-soluble compounds in power transformers

The evaluation of the state of the paper insulation of a power transformer can be assessed by the analysis of specific degradation by-products of paper such as CO, CO₂ and furanic compounds. However it is still difficult to differentiate an incipient fault from the normal aging of an equipment. There is a need to develop more precise diagnostic tools. An experimental accelerated aging test conducted on kraft paper and oil samples at 150°C, allowed us to observe the production of new oil-soluble species. New compounds analogous to furanic derivatives were detected by high performance liquid chromatography. Specific sugars such as rhamnose and mannose were also detected by high performance ionic chromatography. The evolution of some of these species are correlated with the aging of the paper (decrease of the paper polymerization degree). Their presence in samples obtained from the field leads us to believe that selected molecules could play an important role in the prediction of remaining life of power transformers.