The Application of a New Nontracking Butyl to High-Voltage Instrument Transformers [includes discussion]

A new nontracking butyl insulation which will not carbonize even under severe surface contamination has been applied to 15,000-volt outdoor instrument current transformers, and makes practical still higher voltage outdoor butyl designs. The discovery of a novel principle 1 to overcome the susceptibility of organic materials to carbonization and tracking and the application of this principle to butyl rubber have enabled this major advance to be made.