The Role of Corrosive Sulfur in Transformers and Transformer Oil

Corrosive sulfur and the effect that it has in transformer systems can be significant. The extent of the corrosion damage caused by sulfur, if left unchecked, can be so severe as to cause failure of the apparatus. The problems with corrosive sulfur have been recognized for quite some time. As early as 1948, F.M. Clark and E.L. Raab [1] issued a report on the subject for method development within what is known now as ASTM Committee D 27 and eventually became ASTM Method D 1275. Sulfur is found in many materials of transformer construction including the copper, paper insulation, gaskets and oil. Not all sulfur is considered corrosive but the tendency to operate transformers at substantially higher temperatures can aggravate an already present corrosive sulfur condition or convert stable compounds into reactive ones that will cause damage.