Dielectric Loss Characteristics of Copper-Contaminated Transformer Oils

The relationships between the total copper content, both in dissolved and suspended form, and the dielectric loss characteristics were examined in transformer-type oils. It was established that the dielectric losses in the oils are a function of the total copper content. However, no measurable influence of the sulfur corrosivity of the oils was detected upon the magnitude of the dielectric losses in the oils, notwithstanding that the conductive copper sulfide deposits on the paper tapes impregnated with corrosive sulfur oils resulted in the tapes having highly augmented dielectric losses. It was demonstrated that oil chemical treatment processes that are capable of reducing copper content in the oil, result in a significant improvement of the dielectric losses of the oil.