Dielectric strength of impregnated pressboard

THE IMPULSE dielectric strength of pressboard impregnated with insulating liquids is of interest where such insulation has to withstand high transient impulse voltages. A comparison of the impulse dielectric strength of dry pressboard impregnated with a variety of insulating liquids of differing chemical structure has indicated that, in pressboard, chlorinated compounds of the Askarel type show appreciably lower impulse strength than mineral oil, perfluorinated compounds, or a variety of other liquid compounds. Impulse tests were conducted using the standard 1½ × 40-microsecond wave shape.