operation of pressure relief devices, as defined in IEC 62271‐203.
1.2.17 Routine Test Pressure of Enclosures and Partitions
Relative pressure to which all enclosures and partitions are subjected after manufacturing, as defined in IEC 62271‐203.
1.2.18 Type Test Pressure of Enclosures and Partitions
Relative pressure to which all enclosures and partitions are subjected for type test, as defined in IEC 62271‐203.
1.2.19 Rated Filling Pressure pre
Insulation and/or switching pressure (in Pa), to which the assembly is filled before putting into service. It is referred to at the standard atmospheric air conditions of +20 °C and 101.3 kPa (or density) and may be expressed in relative or absolute terms, as defined in C37.122.
1.2.20 Bushing
Device that enables one or several conductors to pass through a partition, such as a wall or a tank, and insulate the conductors from it, as defined in IEC 62271‐203.
1.2.21 Main Circuit
All the conductive parts of gas‐insulated metal‐enclosed switchgear included in a circuit which is intended to transmit electrical energy, as defined in IEC 62271‐203.
1.2.22 Auxiliary Circuit
All the conductive parts of gas‐insulated metal‐enclosed switchgear included in a circuit (other than the main circuit) intended to control, measure, signal, and regulate. The auxiliary circuits of gas‐insulated metal‐enclosed switchgear include the control and auxiliary circuits of the switching devices, as defined in IEC 62271‐203.
1.2.23 Design Temperature of Enclosures
Maximum temperature that the enclosures can reach under specified maximum service conditions, as defined in IEC 62271‐203.
1.2.24 Service Period
The time until a maintenance, including opening of the gas compartments, is required, as defined in IEC 62271‐203.
1.2.25 Transport Unit
Part of gas‐insulated metal‐enclosed switchgear suitable for shipment without being dismantled, as defined in IEC 62271‐203.
1.2.26 Mixed Technologies Switchgear (MTS)
Mixed technology switchgear concerns the following combinations:
AIS in compact and/or combined design
GIS in combined design
Hybrid GIS in compact and/or combined design
As defined in CIGRE Technical Brochure of Study Committee B3 Working Group 20 from November 2008.
1.2.27 Disruptive Discharge
Phenomena associated with the failure of insulation under electric stress, in which the discharge completely bridges the insulation under test, reducing the voltage between the electrodes to zero or almost zero, as defined in IEC 62271‐203.
1.2.28 Fragmentation
Damage to enclosure due to pressure rise with projection of solid material, as defined in IEC 62271‐203.
1.2.29 Functional Unit
Part of metal‐enclosed switchgear and controlgear comprising all the components, as defined in IEC 62271‐203.
1.3 Standards and References
1.3.1 Standards
Standards are technical documents that allow the manufacturer to develop equipment to meet the majority of user applications, and users to specify equipment that meets their needs in most cases. There are always circumstances that fall outside typical cases covered by standards, but they are few. Although there are many national and regional standards, the primary standards that apply to GIS are the International Electro‐technical Commission (IEC) and the Institute of Electrical and Electronic Engineers (IEEE) standards. In recent years, great effort has been made to harmonize these standards. This effort continues, but differences between them remain. These reflect the differences in the nature of systems, applications, and practices between different parts of the world.
Gas‐insulated switchgear, components, and related equipment fall under a large number of standards. Both IEC and IEEE have standards for GIS, circuit breakers, switches, bushings, testing, instrument transformers, controls, cabinets, pressure vessels, and so on. The difference in the equipment built under the two sets of harmonized standards is small and an understanding of how the equipment is designed and tested can usually allow the user to specify equipment under either set of standards. Most manufacturers design the equipment to meet either set of standards, but often limits on testing capability or cost can leave some areas covered by one set of standards only. This requires review of the application requirements and the tested performance of the equipment to determine if it meets the requirements. There has been, and continues to be, efforts made in the standards community to harmonize the requirements between IEEE and IEC. For high‐voltage GIS, efforts on 62271‐203 (2020) and recently C37.122 (2021) have resulted in a high level of harmonization. Progress has also been made on high‐voltage circuit breaker standards, but here many differences remain. Still, by understanding the differences, a user can use either standard.
An example of differences between IEEE and IEC GIS standards is in North America, where safety requirements for maintenance personnel mandate a visible check to verify that the circuit is not energized before it can be approached for maintenance. This requires a view port or camera to verify the disconnect switch blade position. In other countries, safety requirements allow verification of the position of the disconnect switch linkage as confirmation that the switch is open, kinematic chain.
There are standards other than IEEE and IEC that cover requirements related to GIS, for example, the American Society of Mechanical Engineers (ASME), the American Society for Testing and Materials (ASTM), the European Committee for Electrotechnical Standardization (CENELEC), European Standards (EN), the National Electrical Manufacturers Association (NEMA), to name a few.
1.3.2 Current Standards Most Relevant to GIS
The following is a list of the most relevant standards that may be used for specification of a GIS. This list was developed in 2012 and revised in 2020. Historically, standards can be withdrawn or their numbering changed, but usually only every decade or so.
1.3.2.1 General
IEEE C37.122: IEEE Standard for Gas‐Insulated
