Factors Affecting Stability of Electrical Insulating Oils

Attempts to understand the mechanism of dielectric loss, based on laboratory testing of petroleum-derived transformer and cable oils, have led to several important conclusions. First, soluble copper at the parts per billion level has a large adverse effect on oil stability. Second, certain compound types tend to solubilize copper and thus lead to rapid oil degradation. Third, aromatic hydrocarbons tend to preserve oil stability. Laboratory comparisons of petroleum-derived cable oils with synthetic fluids have led to the conclusion that the petroleum oils are less reactive than the synthetic fluids. New, improved petroleum oils have been developed based on the above findings, and are briefly discussed.