Prebreakdown studies using sphere-hemisphere electrode system

Abstract

Measurements have been made of corona-threshold and breakdown voltages in dry air in nonuniform fields for a sphere-hemisphere electrode configuration. For a particular size of outer hemisphere, the electrostatic field was changed from quasiuniform to nonuniform either by using various sizes of inner spheres for concentric arrangements, or, for eccentric arrangements, by varying the eccentricity of the inner sphere. Two outer hemispheres of radius 7.25 cm and 3.81 cm, respectively, were used in the present investigation. For direct voltage, with concentric arrangements, the present results are in general agreement with those previously obtained by Hermstein, and photographic evidence is given of the transition from streamer to glow. Measurements have been extended to eccentric gaps and power-frequency voltages. Finally, some power-frequency-breakdown results are given for concentric conditions, for pressures up to 8atm. The significance of these new results is discussed.