Permissible operating temperatures of impregnated paper insulation in which the dielectric stress is low

PRESENT day practise in the operation of low-tension cables (7500 volts or less) is mainly based upon the temperature limitations generally specified by cable manufacturers and others, who from extensive experiments and research have determined the temperature at which the physical structure of impregnated paper as used for cable insulation, suffers marked deterioration in both its mechanical and electrical properties.