Future requirements for switchgear insulation

Over the years there has been a continual increase in the rating requirements for metal-clad switchgear. Both the continuous ratings and the interrupting values have been pushed upwards in order to keep pace with the growing needs of industrial and utility electric power systems. Each rating increase has generally led to the need for better insulation for one or more of the following reasons: higher voltage, increased operating temperature, greater short-circuit forces, improved reliability, and increased operator safety.