- Extension with original equipment: This is the preferred solution as long as the type of GIS is still produced. After production has ceased it can be more expensive for the GIS but total project costs including civil works need to be taken into account
- Extension with new type of GIS and interfaces to the existing busbar:
In different of GIS of the same manufacturer available. Space requirements are to be considered for the interface. In general technically interfaces can be achieved but issues of differences between the GIS types need to be evaluated.
- Extension using feeder bay(s) as interface to the busbar: This way can be attractive for multi-bay extensions by providing a high flexibility in the location of the extension bays. It also overcomes interface issues between GIS of different types. This way is costly and may not be possible within all configurations.
- Replacement of complete GIS step by step or offline to a new type: Is clearly the highest capital cost option and therefore needs to be considered on a residual life basis for both the old and new equipment to assess whether this option is the most appropriate.
Photo show a extension of 230 kv GIS with new GIS.