Effects of triazole additives in transformer oils

摘要

Recently an undeclared triazole additive, TAA was detected in some commercially available transformer oils. Several laboratory studies such as stability/degradability, impact on oxidation stability and corrosive sulfur were performed. The stability of the compound was determined by performing a heating test based on IEC61125C. After 24h, TAA could not longer be detected. In the presence of a Cu coil, this decrease was accelerated. The IEC61125C oxidation stability test was performed to verify the impact of this additive on oxidation stability, once without any pretreatment, secondly after IX-resin treatment and finally after IX-resin treatment and readdition of the compound. It was clear that the resin treatment removed this additive from the oil but also some other (natural) inhibitors. Readdition did not fully recover the oxidation stability of the oil. This could indicate that not only the triazole compound was removed from the oil by the IX-resin treatment but also that some other (natural) inhibitors were present in the oil. The impact on corrosive sulfur was examined by applying the IEC62535 before and after IX-resin treatment but it seemed that the oil was not protected against DBDS. From these laboratory studies it seems that only the oxidation stability of the oil was improved.