Reviews on sulphur corrosion phenomenon of the oil–paper insulating system in mineral oil transformer

Abstract The active sulphur compounds in transformer oil would react with copper wires and produce cuprous sulphides, which then attach themselves to the surface of copper wires and insulating paper, thus reducing the electrical performance of oil–paper insulation and causing insulation failure. This article aims to make a comprehensive summary on the field of sulphur corrosion of oil–paper insulation in the mineral oil transformer, including the corrosion mechanism of sulphide on copper sheets, the deterioration mechanism of sulphide on oil–paper, the factors influencing sulphur corrosion reaction, the method of characterising the degree of sulphur corrosion, the protection technology of sulphur corrosion and the field operation measures for sulphur corrosion. Moreover, four key problems that need to be further solved were sorted out: the synergistic deterioration mechanism of sulphide and its transformation mechanism, the micro‐process and forming path of sulphur corrosion reaction, the characteristic parameters and quantitative characterisation methods of sulphur corrosion degree, and the effective protection technology of sulphide corrosion. To solve these problems, efforts will be made for deeper understanding of the sulphur corrosion phenomenon and its deterioration mechanism based on theoretical background, the assessment methods and protection technology, endeavouring to put forward solid theoretical basis and feasible technical means for preventing sulphur corrosion insulation failure.