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Thread: 4160 Delta Secondary Grounded or Ungrounded

  1. #21
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    Quote Originally Posted by don_resqcapt19 View Post
    I think the grounding electrode system and GECs are required. The only real difference between the rules for a grounded and ungrounded transformer is that the ungrounded one does not have a system bonding jumper.
    Where would the requirement for a GEC be in the NEC for an ungrounded Delta and where would you connect it?
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  2. #22
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    Quote Originally Posted by infinity View Post
    Where would the requirement for a GEC be in the NEC for an ungrounded Delta and where would you connect it?
    Metal parts likely to become energized, I imagine. As mentioned, the case of the step up transformer would be connected to the primary EGC, while the case of the step down transformer would be bonded to the GEC of the resulting separately derived system. If the run is connecting two buildings, IMHO there is no requirement to bond the two GESs together. If in the same building there must be a wire bond between all ground electrodes, probably in the form of an EGC connecting the two ends, even though there is no grounded conductor.

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    Quote Originally Posted by infinity View Post
    Where would the requirement for a GEC be in the NEC for an ungrounded Delta and where would you connect it?
    IT is analogous to a detached structure under current code with separate N-G. The GEC lands on the ground bar, but doesnt hit a conductor of the system. See 250.30(B)
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Sounds like a waste of time. There are 8-500 kcmil EGC's run to the primary and since the secondary is #2 a #8 GEC landed with those 8-500's would be a joke.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by infinity View Post
    Where would the requirement for a GEC be in the NEC for an ungrounded Delta and where would you connect it?
    250.30(B)
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

  6. #26
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    i would be more concerned with your primaries. what are you doing with the neutral? i need to refresh my memory but systems with wye primaries can have some serious issues.

    http://apps.geindustrial.com/publibrary/checkout/GET-3388B?TNR=White%20Papers|GET-3388B|


    are you really wiring them wye-delta?

    or are you just saying wye because you have 120/208? but actually wiring it delta
    Last edited by Wire-Smith; 07-10-18 at 06:27 PM.

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    Quote Originally Posted by infinity View Post
    Where would the requirement for a GEC be in the NEC for an ungrounded Delta and where would you connect it?
    we investigated a fatal involving ungroundd delta
    common in some mining
    bonding of all frames was not in place
    a phase faulted to one piece of equipment
    a different phase faulted to a different piece of equip in close proximity to the first
    the victim came in contact with both while moving thru the tightly packed equip room

  8. #28
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    Quote Originally Posted by Wire-Smith View Post
    i would be more concerned with your primaries. what are you doing with the neutral? i need to refresh my memory but systems with wye primaries can have some serious issues.

    http://apps.geindustrial.com/publibrary/checkout/GET-3388B?TNR=White%20Papers|GET-3388B|


    are you really wiring them wye-delta?

    or are you just saying wye because you have 120/208? but actually wiring it delta
    If i may nit pick a bit....Im not exactly sure what you mean by "wiring it delta". Obviously, generally the winding configuration is fixed and not changeable. Even if it was, changing from wye to delta or vice versa would change the voltage change ratio. I suspect you mean "delta" in the "jargon" sense of three phase conductors with no neutral. A wye delta transformer would be fed with three phases and no neutral. The point on the primary would float. Bad things can happen if the primary neutral is landed or the wye point bonded. Wye wye transformers have some potential issues, as the paper notes.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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    Quote Originally Posted by electrofelon View Post
    If i may nit pick a bit....Im not exactly sure what you mean by "wiring it delta". Obviously, generally the winding configuration is fixed and not changeable. Even if it was, changing from wye to delta or vice versa would change the voltage change ratio. I suspect you mean "delta" in the "jargon" sense of three phase conductors with no neutral. A wye delta transformer would be fed with three phases and no neutral. The point on the primary would float. Bad things can happen if the primary neutral is landed or the wye point bonded. Wye wye transformers have some potential issues, as the paper notes.
    you've never seen a three phase transformer that you can configure the primary anyway you want? i know there not as common as they used to be.

    and either way i'm still asking him whether it truly is a wye-delta transformer or if he is just calling it that because he is using 120/208 system.

    i believe a floating wye primary can come with many problems as well, i need to refresh my memory though.


    http://forums.mikeholt.com/showthread.php?t=53682


    https://www.eng-tips.com/viewthread.cfm?qid=374777
    Last edited by Wire-Smith; 07-11-18 at 01:42 PM.

  10. #30
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    maybe it's not as big a deal as i think since he might be using 3p breakers on primary feeder, what i have heard about using wye primary on is MV distribution that typically use fuses.

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