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Thread: Testing for absence of voltage on MCHL cable

  1. #1
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    Testing for absence of voltage on MCHL cable

    We are getting ready to start a demolition project in a mine, that we have to demo out cables with voltages ranging from 4160 to 120V. The drawings are sketchy to non-existent. Is there a tool that we can run over the MCHL cables that could tell us if the cable is de-energized and safe to cut. There is no drawings that show what cables are in what trays and this will just be weeks and weeks of tracing cables out. Does anyone have any ideas for tools or procedures we can use prior to cutting into the trays and cables to verify a safe working condition. Thanks

  2. #2
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    Hmmm... something I would stake my LIFE on? No.

    There are these for MV cables, which will only be useful if NONE of the cables are energized:
    http://www.davis.com/Product/HD_Elec...UaAqLXEALw_wcB
    But they can't be used for anything under 2400V L-G and if there is a bundle of cables, it will not tell you WHICH one has a field around it. If it were me, I would ONLY start at one end and remove it, then use voltage meters to find the other end and remove it, then take out the KNOWN cable in verifiable chunks, even if it boils down to line of sight, no matter how long it took.
    __________________________________________________ ____________________________
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  3. #3
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    Quote Originally Posted by Pete27696 View Post
    We are getting ready to start a demolition project in a mine, that we have to demo out cables with voltages ranging from 4160 to 120V. The drawings are sketchy to non-existent. Is there a tool that we can run over the MCHL cables that could tell us if the cable is de-energized and safe to cut. There is no drawings that show what cables are in what trays and this will just be weeks and weeks of tracing cables out. Does anyone have any ideas for tools or procedures we can use prior to cutting into the trays and cables to verify a safe working condition. Thanks
    Standard procedure for MV cables is to spike them remotely.

    http://www.mitchellinstrument.com/hy...awg-cable.html

    Mark

  4. #4
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    Quote Originally Posted by Jraef View Post
    Hmmm... something I would stake my LIFE on? No.

    start at one end and remove it, then use voltage meters to find the other end and remove it, then take out the KNOWN cable in verifiable chunks, even if it boils down to line of sight, no matter how long it took.
    start at one end, hand over hand remove the wire from the cable tray before you cut out that section and proceed, hand over hand until you reach the other end.
    or shut down and lock out all supply and whack away.
    jerryalan

  5. #5
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    Quote Originally Posted by Pete27696 View Post
    We are getting ready to start a demolition project in a mine, that we have to demo out cables with voltages ranging from 4160 to 120V. The drawings are sketchy to non-existent. Is there a tool that we can run over the MCHL cables that could tell us if the cable is de-energized and safe to cut. There is no drawings that show what cables are in what trays and this will just be weeks and weeks of tracing cables out. Does anyone have any ideas for tools or procedures we can use prior to cutting into the trays and cables to verify a safe working condition. Thanks
    Nope, and if there was a tool that did that, who says you don't cut a de energized motor feeder cable that becomes energized later on after the starter engages.

  6. #6
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    Quote Originally Posted by AKElectrician View Post
    Nope, and if there was a tool that did that, who says you don't cut a de energized motor feeder cable that becomes energized later on after the starter engages.
    If you've spiked the cable properly with an appropriate ground then the OCPD opens.

    Mark

  7. #7
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    Quote Originally Posted by busman View Post
    If you've spiked the cable properly with an appropriate ground then the OCPD opens.

    Mark
    The OP was looking for short cuts, and MCHL would need stripped to properly access the wires to put a "spike". Why would they do more if they are looking for short cuts?

  8. #8
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    Quote Originally Posted by Pete27696 View Post
    We are getting ready to start a demolition project in a mine, that we have to demo out cables with voltages ranging from 4160 to 120V. The drawings are sketchy to non-existent. Is there a tool that we can run over the MCHL cables that could tell us if the cable is de-energized and safe to cut. There is no drawings that show what cables are in what trays and this will just be weeks and weeks of tracing cables out. Does anyone have any ideas for tools or procedures we can use prior to cutting into the trays and cables to verify a safe working condition. Thanks
    Personally, I would not want to be taking any shortcuts. It is too easy to fool one's self into believing one can't be hurt because of one's genius at finding some way to move things along faster.

    Even if there were perfect drawings how would that change anything? Do it right and go home safe.
    Bob

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