This standard establishes ratings and requirements for planning, design, testing, installation, and operation of gasinsulated substations (GIS) for alternating-current applications for voltages from 72.5 to 800 kV. Typical installations are assemblies of specialized devices such as circuit breakers, switches, bushings, buses, instrumentation, and the gasinsulating system. It does not include certain items that may be directly connected to gas-insulated substations, such as power transformers and protective relaying.