Gas-insulated switchgear (GIS) can form part of a substation's switching arrangement. Its configuration depends on the equipment selected. Hitachi Energy describes its BLF/PASS as fully encapsulated switchgear for GIS substations.
What equipment can be included?
For its BLF/PASS product, Hitachi Energy lists a circuit breaker, a combined disconnector and earthing switch, and a cast-resin-insulated current transformer. Each pole has an aluminium-alloy enclosure. The manufacturer also lists an SF6-insulated voltage transformer, cable outgoing, surge arrester and fast earthing switch as available on request. These are features and options of the described product family, not a component list or layout that can be assumed for every GIS installation. Their availability does not by itself establish which options can be combined in a particular design.
The listed components serve different functions. NIMI describes a circuit breaker as a device that can open or close a circuit under normal and fault conditions. It describes current transformers supplying measuring instruments and protective relays. The actual connections and protection and control arrangements depend on the installation.
For an example of how one SF6 circuit-breaker design interrupts current, see SF6 Circuit Breaker Gas Compartments.
How does GIS relate to air-insulated equipment?
The NIMI power-distribution training text distinguishes conventional air-insulated, SF6 gas-insulated and composite substation configurations. In its classification, a composite substation combines the conventional air-insulated and SF6 gas-insulated approaches.
These categories do not by themselves establish a space comparison or identify the best choice for a particular site. Equipment selection requires consideration of the actual station design and the manufacturer's documentation.
Can the same equipment be used indoors and outdoors?
Hitachi Energy describes BLF/PASS as suitable for both indoor and outdoor applications. That statement applies to the product described in its documentation. The installation conditions and components for another GIS design must be checked against its own specifications.
Safety and scope
Substation equipment can present serious electrical hazards. Operation, inspection and maintenance require qualified personnel, approved procedures and the manufacturer's documentation. This overview does not provide switching, gas-handling, opening or repair instructions.
Sources: Hitachi Energy, BLF/PASS product description; and NIMI, Electrician (Power Distribution), 2nd Year Trade Theory, PDF pages 65–67 and 193.