In most GIS there are two grounding grids:
- The station grounding grid, which is similar to a typical AIS installation.
- The GIS grounding mesh, which is a narrowly spaced grounding grid embedded into the concrete slab in which the GIS is installed.
GIS grounding and bonding typical rule:
- All grounding conductors should be as short as possible.
- The grounding mesh and interconnections should be capable of carrying the system’s fault currents.
- All exposed grounding conductors should be protected against mechanical damage.
- Proper grounding and bonding techniques, such as multiple conductors or voltage limiters, are required at all discontinuities within the GIS.
- Ensure all metallic building components, GIS support structures, and GIS maintenance platforms are properly grounded.
- Reinforcement steel in the building floor should be connected to the GIS grounding mesh to further equalize ground potentials.
- All secondary cables should be shielded with both ends of each cable shield grounded to mitigate possible electromagnetic interference.
In pic show a connecting of the insulation between the metal enclosure of a GIS and the metal part of the cable by means of nonlinear resistors.