12470 -7200 system grounded, Switchgear belongs to the owner,out of switch gear 3 - 12470 circuits. thur a duct bank and manhole system. when system was installed over 30yrs ago they ran 12470 circuits in the conduits,with no grounds, BUT they ran two 500 mcm insulated (600 volts) in the concrete of each ductbank from manhole to manhole and tied these to a ground bar and ground rod in each manhole.Shields are then tied to theses gr bars where cable t:s off to a bldg. Ciruits are fused at 400 amps each.(CODE QUESTION)By reading the 2002 NEC and the 2002 ieee The grounds in the concrete
are adquate equipment grounds , If under 600 volts grounds in most cases would be required in each PVC conduit.If the conduits were Metal the Ground wires would be required to be in each conduit.Don;t tell me an eng, shold answer this as I have talked to Several Electrical eng,s and they all agree its not spelled out clearly in the nec or ieee.