IEEE C37.20.9-2019

This standard covers the design, testing, and installation of metal-enclosed switchgear that incorporates gas (typically SF6) at higher than ambient pressure as an insulation medium for alternating-current applications rated above 1 kV to 52 kV. The contents of the switchgear may include but are not limited to circuit breakers, switches, bushings, buses, instrument transformers, cable terminations, instrumentation, metering and controls, and protective relays. In a vertical section of the switchgear, some or all of the medium-voltage compartment(s) shall be composed of a gas pressure system for the primary insulating medium. This standard covers both indoor and outdoor installations. This standard covers switchgear using sealed pressure systems or closed pressure systems. Switchgear employing controlled pressure systems is not covered by this standard. This standard also does not cover switchgear that is covered under IEEE Std C37.20.2(TM), IEEE Std C37.20.3(TM), or IEEE Std C37.74(TM)-2014 that uses individual components that are gas-insulated such as switches, circuit breakers, and other equipment, nor does it fully cover those components that are covered by their individual component standards.