517.13(B) says the grounding conductor shall be installed in metal raceways or metal clad cables with the branch circuit conductors. This would imply only back to the panelboard. However,517.13(A) requires a ground path for fault current by a metal raceway system of cable armor assembly.
A ground path for fault current must be continuous to the source of it's supply which in most cases is a transformer and would include the panel feeder.
