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Thread: Underground Mine Grounding

  1. #11
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    Quote Originally Posted by ActionDave View Post
    You'd be surprised what you can get away with electrically though. Rubber cords are the rule not the exception and they are strung out everywhere.
    If you are referring to DLO cable, yeah but the stuff is wicked tough. Double insulated.

    http://www.southwire.com/ProductCata...rodcatsheet429
    "Electricity is really just organized lightning." George Carlin


    Derek

  2. #12
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    Mines do not fall under the purview of the NEC so what do they fall under?

    90.2(B) Not Covered. This Code does not cover the following:
    (1) Installations in ships, watercraft other than floating build-
    ings, railway rolling stock, aircraft, or automotive vehicles
    other than mobile homes and recreational vehicles
    Informational Note: Although the scope of this Code in-
    dicates that the Code does not cover installations in ships,
    portions of this Code are incorporated by reference into
    Title 46, Code of Federal Regulations, Parts 110–113.
    (2) Installations underground in mines and self-propelled
    mobile surface mining machinery and its attendant
    electrical trailing cable
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  3. #13
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    Quote Originally Posted by infinity View Post
    Mines do not fall under the purview of the NEC so what do they fall under?
    MSHA and 1968 NEC in PA. That is all I know. Iggy told me.
    "Electricity is really just organized lightning." George Carlin


    Derek

  4. #14
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    Bump.
    "Electricity is really just organized lightning." George Carlin


    Derek

  5. #15
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    a basic mining power system
    substation w/station ground grid (la's and surface equip frames are ties to this)
    a ngr on the secondary mine power feed
    the ngr low side is tied to a seperated and isolated ground bed (safety or neutral bed)
    this is used for the mine grounding system
    all xfmrs in the mine are ngr and tied to this
    do not combine mine and surface power, each have their own xfmr

    this is basically the law for underground coal mines
    many deep non coal mines do the same
    in Canada I believe it is similar
    Last edited by Ingenieur; 01-20-18 at 04:26 PM.
    The difference between genius and stupidity is that genius has its limits.

  6. #16
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    Quote Originally Posted by Ingenieur View Post
    a basic mining power system
    substation w/station ground grid (la's and surface equip frames are ties to this)
    a ngr on the secondary mine power feed
    the ngr low side is tied to a seperated and isolated ground bed (safety or neutral bed)
    this is used for the mine grounding system
    all xfmrs in the mine are ngr and tied to this
    do not combine mine and surface power, each have their own xfmr

    this is basically the law for underground coal mines
    many deep non coal mines do the same
    in Canada I believe it is similar
    Hmm, I’m basically doing that except for the LA’s and some surface infrastructure right at the shaft. there’s an overhead line going between the station sub and where the feeders to U/G go... where can I ground the LA’s and surface infrastructure? Is the isolated bed supposed to have nothing but the NGR tied to it?

  7. #17
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    Quote Originally Posted by Bigjabe View Post
    Hmm, I’m basically doing that except for the LA’s and some surface infrastructure right at the shaft. there’s an overhead line going between the station sub and where the feeders to U/G go... where can I ground the LA’s and surface infrastructure? Is the isolated bed supposed to have nothing but the NGR tied to it?
    only ug equip on the isolated bed
    everything else (la's, equip frames, etc) on the station bed
    some run a shield wire on the pole top tied to station and bond surface stuff to it
    we typically do not use la's at the mine mouth since everything is insulated (inc the gnd)

    what are you mining?
    any ignition hazard?
    you do not want a strike carried into the mine or raising the frame potential of ug equipmemt
    or worse a substation primary ground fault to raise the mine equip frame potential
    The difference between genius and stupidity is that genius has its limits.

  8. #18
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    ‘Bout time you showed up Iggy!

    I yell, I bump, I hint in other threads.......
    "Electricity is really just organized lightning." George Carlin


    Derek

  9. #19
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    Quote Originally Posted by jumper View Post
    ‘Bout time you showed up Iggy!

    I yell, I bump, I hint in other threads.......
    lol
    I saw it and posted around 4 pm est
    The difference between genius and stupidity is that genius has its limits.

  10. #20
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    Quote Originally Posted by ActionDave View Post
    You'd be surprised what you can get away with electrically though. Rubber cords are the rule not the exception and they are strung out everywhere.
    every ckt has 3 levels of gf protection
    is on a ngr system
    redundant series sc protection
    all egc's are monitored, if >3 Ohm trip the ckt
    all cb's have uv coils
    all plugs are interlocked, pull it a bit and a pilot ckt drops uv, can't open under load
    cables are double insulated with bare grounds, more likely to gf if pinched
    most equip has powered reel to play out/take up the cable to keep it out of the way
    and only certified electricians can work on any of it

    shocks are rare
    90% are lock out / tag out violation
    Last edited by Ingenieur; 01-20-18 at 09:59 PM.
    The difference between genius and stupidity is that genius has its limits.

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