Impact of Benzotriazole on the Degradation Performance of Ester Fluid

Ester fluids are now being widely considered as an alternative insulating liquid for application to transformers. One of the major reasons for internal flashover and fire hazards occurring in power transformers is due to static electrification. It is well known that benzotriazole (BTA) is used to suppress the charging tendency of insulating fluids at the pressboard interfaces. This paper addresses this issue and reports the results of an experimental investigation on the thermal degradation of ester fluid with and without the effect of BTA. The results show that addition of BTA to ester fluid upon degradation reduces the surface potential of pressboard material and dielectric dissipation factor (DDF) of fluid. The study also indicates a reduction in the flow current with degraded ester fluid containing BTA due to its neutralization of positive ions at the pressboard/fluid interface but the reduction in corona inception voltage (CIV) is inferred because of increased charge carrier formation.