Extendibility
The design should allow for future extendibility. Adding bays of switchgear to a substation is normally possible and care must be taken to minimize the outages and outage durations for construction and commissioning. Where future extension is likely to involve major changes (such as from a single to double busbar arrangement) then it is best to install the final arrangement at the outset because of the disruption involved.
When minor changes such as the addition of overhead line or cable feeder bays are required then busbar disconnect switches may be installed at the outset thereby minimizing outage disruption.