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Thread: Grounding Power Supply Neutral at Remote end??

  1. #1
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    Grounding Power Supply Neutral at Remote end??

    Hello all! I was hoping someone could help shine some light on an issue involving substation grounding.

    I have attached a picture of the situation in question for reference... but for the most part the local site is supplying the remote site with single phase 120/240V power. Each site has their own grounding grid but are tied together by one 250MCM bare copper ground.

    I am not sure whether i need to be bonding my power supply neutral to both the local grid AND the remote grid or just the local grid. Any chance someone can help me understand what to do here and/or provide me with an NEC code that addresses this particular issue?

    Thanks in advance for your help!
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  2. #2
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    The NEC would require a 4 wire feed to the remote site, and the remote site must have a grounding electrode system. The neutral to the remote site is a current carrying conductor and if you connected to the remote grid there would be neutral current on the 250 MCM

    Assuming this is under the scope of the NEC, even it not its the best practice.
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  3. #3
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    Quote Originally Posted by tom baker View Post
    The NEC would require a 4 wire feed to the remote site, and the remote site must have a grounding electrode system. The neutral to the remote site is a current carrying conductor and if you connected to the remote grid there would be neutral current on the 250 MCM

    Assuming this is under the scope of the NEC, even it not its the best practice.
    Tom is right, you do NOT bond the neutral at 2 locations, else your EGC is a parallel neutral. It looks like your bare ground "could" serve as the EGC to remote site - note that to meet code you do need a EGC routed with your circuit conductors (not sure how this one is routed).
    "They said it couldn't be done, but the fool didn't know it..."

  4. #4
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    Quote Originally Posted by tom baker View Post
    The NEC would require a 4 wire feed to the remote site, and the remote site must have a grounding electrode system. The neutral to the remote site is a current carrying conductor and if you connected to the remote grid there would be neutral current on the 250 MCM

    Assuming this is under the scope of the NEC, even it not its the best practice.
    Thanks for the help!

    Any chance you could point me to the NEC code that specifies this?

  5. #5
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    Quote Originally Posted by patrickgro18 View Post
    Hello all! I was hoping someone could help shine some light on an issue involving substation grounding.

    I have attached a picture of the situation in question for reference... but for the most part the local site is supplying the remote site with single phase 120/240V power. Each site has their own grounding grid but are tied together by one 250MCM bare copper ground.

    I am not sure whether i need to be bonding my power supply neutral to both the local grid AND the remote grid or just the local grid. Any chance someone can help me understand what to do here and/or provide me with an NEC code that addresses this particular issue?

    Thanks in advance for your help!
    In general the previous comments would be correct but you may have other options since what you show here are transformer outside secondary conductors. See 240.21(C)(5) and 250.30(A)(1) Exception No. 2. This would allow you to omit the EGC between the 2 buildings. However, that bonding jumper you show between the 2 GES systems would have to be removed to take advantage of this design option.

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