Influence of Field Nonuniformity on the Breakdown Characteristics of Suliur Hexafluoride

A methodical variation of the radius of curvature of the electrode reveals interesting electrical breakdown properties of the sulfur hexafluoride (SF6) which may be useful to the designer of high-voltage apparatus. The pressure range under consideration was 1-5 kg/Cm2 absolute. The tests were performed under 60-Hz voltages. For a given electrode configuration and a specified operation voltage, there exists a region for the value of the radius of curvature within which flashover occurs. At high pressures this region may be restricted to a narrow zone of low values of the radius of curvature. Very sharp electrodes usually lie outside of this region. The field in the hemispherically capped rod-plane is analyzed by the finite-element method for values of d/r between 0.8-40. The critical field was found, at high pressures, to tend towards a constant value, which is that prevailing under uniform-field conditions irrespective of radius of curvature.