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Thread: Safe de-energizing of pad mount transformer - grounds required?

  1. #1
    Join Date
    Jan 2010
    Location
    NH
    Posts
    25

    Safe de-energizing of pad mount transformer - grounds required?

    Had a situation recently where we needed a 2,000A 480V service de-energized by the PoCo so we could work on the service entrance switch gear.
    The PoCo intended on shutting off the transformer using the internal hotstick switch in the pad (not a visible opening) and calling it good. Our policy requires personnel protective grounds to be applied. Eventually, they installed the grounds, however they were not happy about it as it required pulling the load breaks, calling another truck that had a grounding elbow kit, etc.
    They also laughed at our 40-cal arc suits we used to verify the service de-energized.
    I would certainly not trust the switch. Same goes for the switch on a pole mount transformer.
    Thoughts? How do you handle this?

  2. #2
    Join Date
    Jan 2008
    Location
    NC & IN
    Posts
    3,274
    We do our thing, the poco does theirs. Some times they're real helpful, some times their not.
    I've had pretty good luck talking with poco engineers. You have to give them some days notice of what you plan or would like to do.

  3. #3
    Join Date
    Aug 2004
    Location
    Northern illinois
    Posts
    14,814
    I can see the switch on a pole mount xfmr. It is real easy to see that it is open or not.
    Bob

  4. #4
    Join Date
    Mar 2013
    Location
    Rutland, VT, USA
    Posts
    234
    If you are looking for a visible break, I would think either the riser fuse cut outs open or the primary elbows pulled and put in the parking stands would suffice. You can then check for dead on the secondary spade terminals and apply grounds.

    I can understand them laughing with your 40 cal suits as their PPE for the pad mount transformers secondary is 4 cal per the NESC.

  5. #5
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    31,289
    Quote Originally Posted by petersonra View Post
    I can see the switch on a pole mount xfmr. It is real easy to see that it is open or not.
    Exposed switch ahead of the transformer yes, internal switch with external operating lever - all you can see is which position the lever is in, can't tell if contacts are open.

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