DIELECTRIC MATERIALS IONIZATION STUDY
GENERAL ELECTRIC CO SCHENECTADY N Y
Pagination or Media Count:
Voltage breakdown of 100-mil Teflon occurred between 50 and 100 vmil on over-voltage aging. Surface voids on Teflon caused a smaller time lag to breakdown than volume voids. This was presumed to be caused by field concentration in the region in which the void passes under the electrode edge. The first failures of polyethylene with 25-mil-diam voids centered in the dielectric on over-voltage aging occurred at the end of the void between the electrodes. The corona starting voltage of a 25-mil diam virgin void in polyethylene may be as high as 12 kv 120 vmil, but after corona occurs the corona starting voltage in this void may drop to 6 kv. The corona within a void in polyethylene decreases with time, at any voltage, as the voltage is being raised, and increases with time as the voltage is decreased.