Good point you raise there mxslick
In New Zealand we have exactly the same happening all over the place, wheater it is industrial or domestic.
Capacity from supply tranformers is upgraded e.g. 100 kVA to 200 kVA, existing cables very often left in place or new circuits added to TF.
If there are HRC fuses in place I can't see too much of a concern. These usually clear faults up to 80 or 120 kA level.
With MCB's it's different. The main MCB in an industrial switchboard may be able to cope with a higher fault level, the circuit MCB's may not, they are usually rated around 6 kA for clearing a fault and could fail or simply blow up when a fault occurs very nearby the main switchboard, say in the first 2 or 3 meters of the outgoing circuit.
In domestic streets for example, lots of houses on overhead supply still have rewirable fuses at point of entry and on the switchboards, With a higher fault level there could be problems although with OH supplies the cable length will reduce the available faultlevel somewhat.
A 5000 Amps faultlevel is generally quoted for domestic switchboard with a 16 mm² mains.
See what other comments we get on this interesting topic...
Cheers Raymond
