Transmission power transformer assessment using furan measurement with the aid of thermal model

As a potential insulation condition assessment technique for the field transformer, the correlation of the furan, or more specifically 2-furfural (2-FAL) measurement in oil and the insulating paper´s degree of polymerization (DP) has been studied intensively in the laboratory by the means of accelerated ageing experiments. However due to the complicated operating conditions and design characteristics the field transformers are subjected to, it is not sensible to directly apply the correlation of 2FAL and DP derived based on laboratory works. In this paper, the field 2-FAL measurements have been analyzed on 49 UK National Grid (NG) field transmission power transformers. The insulating paper´s DP of these transformers are estimated with the aid of the transformer thermal model, which was developed based on the thermal model in IEC transformer loading guide. As a result, a practical correlation has been established between the field 2-FAL measurement and insulating paper´s DP estimates. The fitted model indicates that there is a possibility of developing a practical furan-DP relationship as a reliable insulation condition assessment technique for the field transformer.