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Thread: Protective grounding size

  1. #1
    Join Date
    Sep 2003
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    15

    Protective grounding size

    Does anyone know of a specific reference for minimum size protective grounding jumpers to be installed on de-energized overhead lines, for use in employee protection.

    thanks

  2. #2
    Join Date
    Feb 2003
    Location
    Indianapolis
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    6,102

    Re: Protective grounding size

    When we use a "set of grounds", they are generally 4/0 Cu. but to answer your question, I don't know. I would think the minimum would be at least as large as the phase wires that you are grounding out. Maybe someone else can answer your question if they are not utility owned conductors.
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  3. #3
    Join Date
    Aug 2004
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    11,554

    Re: Protective grounding size

    I have seen people use big chains. in one case they wrapped them around the three bus bars.

    I also saw once what looked like some kind of homemade rig that was pretty nifty looking. It used some serious copper bars.
    Bob

  4. #4
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    Feb 2003
    Location
    Massachusetts
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    Re: Protective grounding size

    Originally posted by petersonra:
    I have seen people use big chains. in one case they wrapped them around the three bus bars.


    That sounds like an extraordinarily BAD idea!

    Someone turns the power on, sparks and molten metal fly from every link.

    I know this was not your idea.

  5. #5
    Join Date
    May 2004
    Location
    MA
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    1,472

    Re: Protective grounding size

    try this site
    http://www.whsalisbury.com/configurator/index.php
    the task you are suggesting is addressed in NFPA70E 250.3 with references to the following publications.

    NFPA70B, NFPA70 (of course) , NETA Maintenance Testing Spec International Electrical testing assoc.

    The Salisbury Company is very help full for PPE and Equipment.
    edited for the URL sorry!!

    Charlie

    [ February 14, 2005, 06:42 PM: Message edited by: cpal ]
    Charlie

  6. #6
    Join Date
    Feb 2003
    Location
    Indianapolis
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    Re: Protective grounding size

    Thanks Charlie, that's what our guys use.
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  7. #7
    Join Date
    Aug 2004
    Posts
    11,554

    Re: Protective grounding size

    I never really thought much about it, but the chain thing is not the ideal solution.

    I always though the bus bar thing someone came up with was much better.

    It may have been that at the time there was not a commercial product available so they used what they had at the time.
    Bob

  8. #8
    Join Date
    Feb 2005
    Location
    Charlotte, NC
    Posts
    6,368

    Re: Protective grounding size

    Ground used for personel protection must be tested and rated for the available fault current in the system for at least 15 cycles in order to ensure the protective device will deenergize the circuit. They should be connected in a manner so that an equipotential zone is created in the work area. Refer to the NFPA 70E or OSHA 1910.269 for additional information.

    Using logging chains is about as safe as checking a circuit denergized with your bare fingers.

  9. #9
    Join Date
    Sep 2004
    Location
    Norfolk, VA
    Posts
    166

    Re: Protective grounding size

    I also recommend Salisbury. Their website has an online gounding set builder. I put one together using 4/0 CU that has the insulation marked "for grounding" or something like that. I have eight clamps - 4 flat jaw (standard bus bars) and four ball stud. The ball stud clamps are for some large soft start cabinets we have where the vertical bussing is too close together to fit a flat jaw clamp. The ball studs themselves are retrofitted to the bussing so they that are ready to accept the grounding clamp whenever the need arises. The stuff's not cheap, but my life isn't either!

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