Test of ionization level of rubber-insulated cables

It has been found that the inception point of ionization or corona within electrical components, especially solid dielectric cables, should exceed the normal operating voltage of the component in order to eliminate deleterious physical and electrical effects associated with ionization. Most of the equipment so far developed to determine ionization point has been designed individually for specific laboratory applications and, consequently, presented certain shortcomings for general purpose and production use. Commercial equipment now has been developed to overcome such objections and has been applied successfully in laboratory and production testing. Destructive ionization occurs at voids or air spaces within the component or dielectric and since evidence necessary for a critical analysis of this action generally is destroyed through the mechanism of breakdown, the need for a method to detect voids by a nondestructive and practical means is self-evident.