High-Voltage Impregnated Paper Cables

A limit of carrying capacity was reached in high voltage cables due to high dielectric losses, and in order to overcome this limitation, science had to be called upon to introduce measurements and tests to control this quality. The exact experience gained in the development of these tests by scientific men working in cooperation with the men of practical experience enabled the cable industry to attack the next limitation that confronted it, namely, dielectric strength. The industry has already made considerable progress, and the present problem is the complete elimination of occluded air and vapor from the insulation. Air films have been regarded as causes of low dielectric strength, due to ionization of the air and consequent formation of hot spots. It is advanced, herein, that a more useful conception of the danger of air films, is that they promote internal surface leakage. It has also been generally believed that air films can be detected by the slope of the voltage power-factor characteristic. It is contended herein that such is not the case. It is pointed out that the foundation for future developments has been laid by the equipment and organization of American cable manufacturing plants for accurate quality control by continual testing of raw and process materials.