Thermal stability test methods to establish dielectric loss limits in EHV bushings and current transformers

The existence of dielectric heating in any kind of solid insulation has been known for many years, and the dangers of destructive temperatures have long been recognized. Designers have been careful to avoid destructive dielectric heating in their bushings or current transformers. As voltages have increased the problem has become more difficult, and more formal and elaborate methods have been devised to make certain of the adequacy of the insulation. It is one purpose of this paper to describe how this has been done.