Partial discharge in dielectric fluids

Summary form only given. The primary interest of this study was in the temporal and spatial development of partial discharges at voltages near their inception. Results were obtained during a short time interval after the application of a DC voltage to the test gap. Photographs showed the structure of the cavity and suggested the onset of fingerlike projections in the cavity wall. The structure of the cavity at the negative point was nonisotropic, suggesting that forces were of primary importance in driving its expansion. The fingerlike projections are consistent with instabilities, either hydrodynamic or electrostatic, in the cavity wall. The onset for partial-discharge current was found to be highly correlated with the onset of the growth of the cavity. The experimental method also provided an estimate of the total charge emitted from the electrode during the discharge. Results were obtained for both polarities in hexane and for PXE