Anyone know the specs on the size of a electrical room loop ground? I cant seem to find the size of bus required. There's around 4000A fault current at 12.47kV. Im thinking its around 50 or 75mm by maybe 5mm copper bus.
The copper.org bus table is for continuous current, not fault current. There are equations for fault current capacity of conductors in IEEE Std 2000, IEEE Guide for Safety in AC Substation Grounding and in IEEE Std 605, IEEE Guide for Design of Substation Rigid-Bus Structures.