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Home / Technical Articles / Main components of a Gas Insulated Substation (GIS) you should know about

GIS components

Gas-insulated substations (GIS) use circuit breakers, disconnect switches, and grounding switches, and have various means of indicating their position, either opened or closed, so the same as in air-insulated substation (AIS).

Main components of a Gas Insulated Substation (GIS) you should know about
Main components of a Gas Insulated Substation (GIS) you should know about

Operation of a GIS uses most of the same principles as operating an air insulated substation (AIS) although the various active components are physically configured differently. The first obvious difference is that the blades of the disconnect switches and the grounding switches used in a GIS are surrounded by grounded metallic enclosures.

This enclosure prevents the blades from being readily and easily visible to determine their fully opened or fully closed position. The second obvious difference relates to the bus conductors being located inside grounded metallic enclosures.

These enclosures prevent the bus from being grounded with portable personnel grounds except at very discrete locations, such as air-to-gas bushing terminations at transmission lines and transformer banks.

Generally a GIS requires more extensive electrical interlocking between the circuit breakers, disconnect switches (isolators), and grounding switches. The specific detailed method of operating and interlocking is generally specified by the ultimate user of the GIS.


  1. Circuit Breaker
  2. Disconnect Switches
  3. Nonfault-Initiating Grounding Switches
  4. High Speed (Fault-Initiating) Grounding Switches
  5. Three-Position Disconnect/Grounding Switches
    1. Voltage Transformers (VTs)
    2. Current Transformers (CTs)
  6. Switch Viewports
  7. Gas Compartments and Zones
  8. Interlocking
  9. Local Control Cabinets (LCCs)

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Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.

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