Furfural analysis for assessing degradation of thermally upgraded papers in transformer insulation

Furfural analysis by high performance liquid chromatography (HPLC) has gained increasing favor as a means of estimating degradation of insulating papers in power transformers. We have studied this technique in some detail as applied to thermally upgraded kraft papers. Significant differences in the results for papers of several manufacturers were found, which could influence diagnosis after extended operation. As a result, we believe that the current practice of simply identifying a transformer as manufactured with common or thermally upgraded paper will not be enough to interpret results at a later date. A detailed identification of the paper, and information on its accelerated aging behaviour should be kept on record.