Optical studies of electrokinetic processes in dielectric fluids

The behavior of transformer oil and other fluids used for the cooling and insulation of power system equipment is significantly influenced by enforced motion. Spatially resolved optical emission which illustrates the changes brought about by increased velocity in a stressed oil duct is presented. Schlieren records taken under the same circumstances permit the examination of concomitant hydraulic instabilities and their dependence on electric field through EHD vorticity generation. Optical data to show the influence of dielectric interfaces in the stressed gap and the impact of upstream charge injection on prebreakdown light emission are also presented. The results indicate that the modification of flow patterns and formation of a stagnant area are important aspects in determining the events leading to liquid breakdown, and have indicated the importance of oil motion per se in electrokinetic effects in liquid-cooled power system equipment.