Unique antioxidant and sulfur corrosion retardant properties of transformer oil blended with turmerone extract

One of the most detrimental effects associated with transformer insulating materials (paper and oil) and copper windings is the corrosive action of certain sulfur components found in transformer oil. Consequently, transformer oil is typically blended with both antioxidant and anti-corrosive agents in an attempt to prolong ageing effects and hinder copper sulfide deposition respectively. This study focusses on the effect antioxidants have on corrosive sulfur deposition on copper metal surfaces. To this end transformer oil was blended with a natural extract from turmeric powder and tested for its ability to act as an antioxidant and to retard copper sulfide deposition. The efficacy of this blended oil was compared with that of oil blended with either of two commonly used antioxidants, namely, 2,6-di-tert-butyl- 4-methylphenol or 2,6-di-tert-butylphenol. Tests for corrosive sulfur showed that for the turmerone oil blend there was a substantial delay in the onset of copper sulfide deposition on the surface of copper metal. Open circuit potential studies showed that the turmerone fraction that was blended into the transformer oil was adsorbed onto the copper surface. This unique property was not observed for the other two antioxidants in this study and can account for the retardation of copper sulfide deposition. In addition, the turmerone-virgin oil blend did not alter the thermal stability of the Kraft insulation paper in direct contact with the oil. The performance of the turmerone oil blend as a dual antioxidant and retardant of copper sulfide deposition renders it eminently suitable for extending the lifetime of insulation in fluid-filled transformers.