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Thread: Transformer secondary ground conductor

  1. #1
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    Transformer secondary ground conductor

    I have 225kVA 480/277V to 208/120V transformer with phase conductor of 2 sets of 350kcmil. The transformer is grounded. As I understand it the ground conductor would be sized based on Table 250.102(C)(1) since these are transformer secondary conductors. Would the size of the ground be sized based on each conduit #350kcmil which equals to #2 ground for each conduit or sized based on 2x350 = 700kcmil which equals 2/0AWG for entire system?

  2. #2
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    You need to clarify what you mean by "ground conductor" In general a transformer will involve a GEC (grounding electrode conductor), a SSBJ (supply side bonding jumper), an EGC (equipment grounding conductor) and a SBJ (system bonding jumper). It sounds like you're referring to the SSBJ(s) run with the secondary conductors?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Transformer secondary ground conductor I mean supply side bonding jumper.

  4. #4
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    Quote Originally Posted by hhsting View Post
    Transformer secondary ground conductor I mean supply side bonding jumper.
    That's what I thought but didn't want to guess.

    As you stated in the OP you would size each SSBJ in the parallel raceways based on the size of the conductors within each raceway using T250.102(C). So for 350 kcmil you would need a #2 SSBJ in each raceway. For the SBJ you would use the total of the secondary conductor size (2*350=700 kcmil) and the same table.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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