Corona rings are used on very high voltage power transmission insulators and switchgear, and on scientific research apparatus that generates high voltages.
In either case, the generator, traction motors and interconnecting apparatus are considered to be the power transmission system and not part of the prime mover.
Although relatively low in conductivity, surfaces can be made suitable for electroplating, low-frequency shielding, or for creating large conductive geometries for high voltage apparatuses.
