Dissolved Gas Analysis for the evaluation of the corrosive sulphur activity in oil insulated power transformers

This work will present a study of Dissolved Gas Analysis findings in mineral insulating oil samples with corrosive or suspicious corrosive action according to the test ASTM D1275B. The tests samples were taken from oil insulating power transformers operating in Greece. The gases that are indicative and common in almost all samples were mainly saturated hydrocarbons (methane, ethane, propane) and in many cases investigated the hydrogen. Particularly interesting and important, are the finding of increased concentrations of these gases in tens or thousands ppm,v (μl/lt) during operational time, indicating the evolution of corrosion. From the results it can be concluded that this method can be an additional diagnostic "tool" for confirmation and monitoring of the evolution of the phenomenon, especially when control is systematic and starts before transformers´ operation under voltage and load, especially due to the fact that the required equipment is a typical one in chemical laboratories.