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240V, 3-Wire to a Dist Panel, Need Neutral

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    240V, 3-Wire to a Dist Panel, Need Neutral

    We have a 240 VAC, three-wire plus ground service feeding a three-phase distribution system. The service is about 500 feet away from the facility it feeds. The distribution system is within the facility. The distribution system feeds a lighting panel at 240/120 VAC. There are two phase conductors and the ground conductor, which makes up the 120 and 240 feeds (the ground conductor is connected to a ground rod at the service and also routes to the neutral bus at the service transformer. The ground wire clearly has current moving through it. We discovered this current flow and the wiring and lack of a true neutral during inspection. We recorded power at the lighting panel when running modest 120 V loads. We found the potential from one phase to ground to decrease (appears as voltage drop) while the potential from the other phase to ground swelled (appears as voltage increase). I believe the voltage on the ground wire is causing this.

    So, we want to correct this issue by getting a neutral. The service is too far to run a neutral conductor. We would like to put in an isolation transformer at the lighting panel. Primary at 240 V, secondary at 240 V with a center tap. Then we would use the center tap as the neutral. I believe this would take care of giving us our 120/240 lighting panel circuits and get rid of the current on the ground.

    The questions are 1-does this all make since (in general) and 2-should there be any connection between our new neutral conductor coming off the transformer and the existing ground?

    You said that you have a 240 volt, 3 wire plus ground service. Is this service ungrounded?


    All responses based on the 2017 NEC unless otherwise noted


      what is the wiring method from the distribution panel to the panel in question ? (metallic conduit, non metallic, aerial ??)
      At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.