Influence of transformer oil acidity on insulating paper degradation

The transformer oil on Hydro-Québec's grid is a major investment. Therefore, it is essential to preserve the oil's quality thus the value of the asset is maintained and, more important, a high level of reliability on the equipment is ensured. In order to preserve this non-renewable resource, Hydro-Québec decided in the 1990's to reclaim the oil of its power transformers. The quality of the oil has an impact on its own properties (dielectric, physico-chemical), and eventually on the solid insulation and its degradation rate. In order to optimize the reclamation activities and establish criteria to initiate the reclaiming operation, this manuscript presents the preliminary results on the influence of the initial oil acidity on the paper degradation rate. The results show that the degradation rates for Kraft paper and thermally upgraded paper at 110°C increase when using oil with a relative low acidity. Moreover, the degradation rate of the thermally upgraded paper seems to be relatively more affected by oil acidity than for Kraft paper.