The life of impregnated paper

IT IS generally agreed that the most important factor limiting the life of the so-called solid type of impregnated paper insulated cable is internal ionization in voids or gas pockets. The much higher stresses in oil filled cables and their exceptional performance in service are commonly attributed to the absence of gaseous ionization. These facts have served to draw increased attention to the question of the type of oil to be used in such cables. The oils for solid cables have been selected from the standpoint of their susceptibility to the formation and ultimate action of internal ionization. With ionization absent, as in the oil filled cable, the question then becomes one of the inherent dielectric and insulating properties of the oil.