High Altitude Flashover and Corona Correction on Small Ceramic Bushings

A marked improvement in corona starting voltage and flashover voltage for small ceramic bushings has been obtained by the use of semiconducting coatings. This is of special importance for air-borne radio and radar equipment. The results cover both a-c and d-c behavior for several sizes of solder-seal bushings. A sensitive oscilloscopic method detects disturbances at voltage gradients where the ionization-by-collision process begins. These gradients, far below the visual corona points, are calculated from graphical maps of the dielectric fields associated with the bushings.