Aging performance of Natural Ester Impregnated Nomex Paper Insulation

In the power transformer, the oil-impregnated paper is used for providing insulation between live conducting parts, which comprises of transformer oil and insulating paper (either Kraft paper/Pressboard). These insulating papers are made up of cellulose fibers and it gets easily degraded at higher hot-spot temperature with increase in aging periods. So this affects the lifetime of solid insulation and further transformer life. In this research work, the latest advanced solid insulation named “Nomex paper” made up of aramid polymers is considered as a solid insulating paper material for analyzing the aging behavior. Furthermore, the electrical properties such as breakdown voltage of both oil and paper, flash point and fire point, viscosity have been measured to study the change in characteristics during aging. Also, the level of degradation of solid insulation has been identified by measuring Breakdown voltage of paper under all aging times. On looking standard IEEE C57.91, all these samples were analyzed at the maximum hot-spot temperature of about $130^{\mathbf {\circ }}$C. The results clearly show that the solid insulation gets affected due to deterioration and decomposition.