Effects of Irgamet 30 as additive in transformer oil

This study was designed to examine the impact of a recently identified undeclared additive Irgamet^® 30 in transformer oils. Therefore, several laboratory studies were performed. First, the stability of Irgamet^® 39, a well-known metal passivator was tested. It was clear that Irgamet^® 39 protected copper from corrosive sulfur compounds such as dibenzyl-disulfide (DBDS). As the structure of Irgamet^® 30 is comparable to the one of Irgamet^® 39, the stability/degradability, impact on oxidation stability of the oil and corrosive sulfur compounds were tested on lab-scale. The stability was determined by performing a heating test based on IEC61125C. Irgamet^® 30 decreased to undetectable within 24h. The presence of a Cu coil could accelerate this decrease. The impact on the oxidation stability was tested by subjecting the oils to the IEC61125C oxidation stability test, once without any pretreatment, secondly after IX-resin treatment (recommended by IEC60296 Ed.4) and finally after IX-resin treatment and readdition of the initial Irgamet 30 concentration. It could be concluded that the IX-resin treatment removed the triazole-like oxidation inhibitors present in the oil, such as Irgamet^® 30 and some other (natural) inhibitors. As the oxidation stability was not fully recovered after readdition of the initial Irgamet^® 30 content this could mean that not only Irgamet^® 30 was removed during IX-resin treatment but also that some other (natural) inhibitors were present. In a final laboratory study the impact of Irgamet^® 30 on corrosive sulfur was examined. The oils were subjected to the IEC62535 before and after IX-resin treatment. It seemed that Irgamet^® 30 did not protect the oil from DBDS. Therefore, the results of this study indicated that Irgamet^® 30 di- not effectively mitigate corrosive sulfur, however, it did enhance oxidation stability.