Copper dissolution and deposition tendency of insulating mineral oils related to dielectric properties of liquid and solid insulation

Mineral oils may react with the copper conductors in oil impregnated transformers, leading both to the formation of dissolved and suspended copper in the oil and to the deposition of copper onto the paper surface of the solid insulation. Available standard methods for copper detection in mineral oil may not be fully effective in assessing the total copper content. Dissolved and suspended copper species in the oil are shown to affect oil's losses to a different extent.