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Thread: Underground Mine Grounding

  1. #41
    Join Date
    Oct 2015
    Location
    Vancouver BC
    Posts
    36
    Quote Originally Posted by Ingenieur View Post
    physically move the la's
    put them on the pole near the isol subs
    I did not mean run a wire from their shown location

    I don't think that would work due to the M421 Clause 4.8.2.1. The LA's need to be at the mine end of the o/h line, perhaps also at the isol sub end.

    4.8.2.1
    Where power feeders serving underground workings are connected to overhead lines longer than 90 m,
    lightning arresters or surge capacitors shall be installed at the point of connection to the underground
    feeders.

    Quote Originally Posted by Ingenieur View Post
    a seperate bed may work
    let me look at some stuff tomorrow and see what the recommended practice is
    iirc we just put them on the output of the sub cb

    if they take a hit where they are now the whole mine frame ground will be elevated

    Agreed, even if it's not against code, I still don't like it.

    Quote Originally Posted by Ingenieur View Post
    how are the isol subs bonded to the main sub?
    oh w/the phases?
    a buried copper conductor?
    what kind of swgr is at the isol subs?
    perhaps the la's can be bonded to the isol sub frames?
    - isol subs bonded to main sub via overhead shield wire
    - 15kV AIS at the main sub
    - we will have LA's at the isol sub end, and yes bonded to sub frames... but we also need LA's at the u/g mine end of the overhead line, at least such is my interpretations of M421.. I think connecting LA's at the mine end to an isolated bed is the only way to prevent GPR at that the mine, but lightning strikes on fans, etc will still cause problems underground. I will consider moving isol subs to right near the boreholes, then connecting NGRs and u/g ground conductors via insulated wire to a remote bed. Power cables going u/g would need armour, shields and ground wire isolated at the surface end.

  2. #42
    Join Date
    Feb 2018
    Location
    McConnelsville OH
    Posts
    1

    Voltage regulator grounding throug grounding resistor

    Mine has wye 7620, regulator neutral is connected to wye neutral going to 450 ohm grounding
    resistor. Tank is grounded to substation ground grid. Seems voltage is going crazy and blew
    one regulator. Is this correct?

  3. #43
    Join Date
    Jan 2016
    Location
    PA
    Posts
    5,484
    Quote Originally Posted by Joe Robb View Post
    Mine has wye 7620, regulator neutral is connected to wye neutral going to 450 ohm grounding
    resistor. Tank is grounded to substation ground grid. Seems voltage is going crazy and blew
    one regulator. Is this correct?
    just saw this
    this is how I do it
    only 3 ph loads can be comnected
    only for your consideration
    DO NOT make any changes before consulting with the mfg and an engineer

    CAUTION
    if you take one off line in the wrong sw seq you WILL fry it
    you have to also verify a neutral is available (no broken connections)
    the unit cntl pnl also will indicate it is ok
    again consult the manual and mfg

    removal steps
    switch....intial....1.....2.....3
    BP...........o........c......c.....c
    S............c........c......c.....o
    L............c........c......o.....o

    place online steps
    switch....intial....1.....2.....3
    BP...........c........c......c.....o
    S............o........c......c.....c
    L............o........o......c.....c
    Attached Images Attached Images  
    Last edited by Ingenieur; 02-23-18 at 01:36 PM.
    The difference between genius and stupidity is that genius has its limits.

  4. #44
    Join Date
    Jan 2011
    Location
    United States
    Posts
    7,291
    Just to add- before closing the bypass make sure the indicator needle on the position gauge is in neutral, the controller is showing neutral and finally hit it with something like this:


    https://www.jharlen.com/p-10759-hast...-detector.aspx


    Closing the bypass without it being in neural can make for boiling hot oil...
    I'm in over my head...

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