Effect of electric field at 150 °C on the formation of corrosive sulfur in mineral transformer oil

The effect of the application of 12 kV at 150 °C on the formation of corrosive mineral copper sulfide in mineral transformer oil was investigated. It is considered that the presence of sulfur corrosion causes failures in operating windings transformers above 35 kV. Research trials on mineral transformer oils were performed at 150 °C without an electric field, and also at 150 °C in electric field based on the norms for the detection of corrosive sulfur established by ASTM D-1275 and IEC 62535. The effect of the applied electric field on the process of corrosive sulfur formation was determined. Varying amounts of copper sulfide were found, both on bare Cu electrodes and Cu electrodes covered with Kraft paper, pure Cu formation was also found in the oil. Copper sulfide was quantified using the X-ray dispersion technique with a scanning electron microscope, with EDX.SEM E., and chemical methods are used to determine the quantity of Cu in the oil after the test.