Electrical Breakdown at Solid-Liquid Interfaces

Observations of the electrohydrodynamic (EHD) motion of insulating oils in a static electric field, between plane parallel electrodes separated by an insulating support, are reported. A transition from laminar to turbulent flow in the bridged gap is observed near breakdown voltages. Velocity measurements support the observations of the onset of turbulent flow prior to flashoever while photographic observations show the breakdown to be away from the solid. Flashover measurements with increasing pressure indicate that the breakdown at the interface between solid and liquid is a liquid controlled phenomenon. The results are consistent with a liqûid breakdown model dependent upon the formation of a gas bubble of critical size by a gaseous cavitation mechanism in the turbulent flow.