As a guide the faulted segment location should ideally match with the physical location of the fault on the grid.
This How to guide relates to the use of SafeGrid Earthing Software (V5.2 is shown).
The faulted segment location is shown and can be changed in the Build Grid module.
Right-click the segment you would like to change to the faulted segment and select Set as faulted segment.
The faulted segment location will be updated as indicated by the grid preview.
The faulted segment location will affect the results. Note however for a meshed grid the effects will be minimal but for a long radial earth grid such as for a wind farm the fault location can have a big affect on the grid resistance (which is as seen from the fault location) and the soil voltage distribution.