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I found this last night and I am a bit confused. This picture is from down inside a 6'X 8' manhole. The three feeders you see are 12.47KV and they have an equipment grounding conductor pulled with each run as one would expect to see. One the other hand the single conductors that run with this duct bank are a bit of a mystery. They run all the way back to the 12KV substation and terminate on the equipment grounding bus. I haven't been in the MV Switches on the other end but I can assume they terminate in the same manor there. What would be the purpose of running these extra grounding conductors in a medium voltage duct bank? I have run and seen run a bare copper conductor in the encasement of similar duct banks but again I am at a lose to the theory behind it. Any one have any insight?

PS: The conductors were not continuous in this man hole. They were just coiled up on the floor. But that is a subject for another thread.

- Nick