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 did not effectively mitigate corrosive sulfur, however, it did enhance oxidation stability.