The Nature and Practice of Gases as Electrical Insulators

The gaseous state of matter is an excellent high voltage insulator which nonetheless is subject to overstresses and electrical breakdown. The main parameters which govern insulation strength in gases are identified as gas density and time duration of applied voltage. Several gases show similar effects of density and time changes so that generalized breakdown curves are presented. Practical considerations for the design of high voltage equipment are also developed through examples of insulation performance in compressed SF6. Features emphasized include the influence of electrode surfaces, particle contamination and solid insulating supports. Significant achievements in the application of gases to high voltage equipment and expected areas for future fundamental and applied developments are discussed.