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Thread: Questions on MV transformer clearances and egress requirements.

  1. #1
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    Questions on MV transformer clearances and egress requirements.

    Hello everyone,

    I have 15KV primary - 480Y/277V secondary transformer and then I have a fence around it. I only have 22-3/4" of space on each side of the transformer and 3'-0" on the back and 7' on the front. the fence only has one door in front of the transformer.

    Q1: where in the NEC are the requirements for space clearances on the sides and back of a medium voltage transformer? i have heard it is 2 feet on the sides and on the back but haven't been able to find this in the NEC.

    Q2: Are the clearances above ok for egress? (NFPA 101) i have heard this is 36" but haven't been able to find this either.

    Thanks.
    F413

  2. #2
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    Heck if I know Bump
    Electricity is Color Blind
    Leave the shirt pocket rules in your pocket.

  3. #3
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    Are there any exposed parts on the back of the equipment?
    Does any routine maintance need to be done on the rear of the transfromer while it is energized?
    Is the primary under the control of a utility?
    Just because you can, doesn't mean you should.

  4. #4
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    It would help more to know who owns the transformer. Where is the point of delivery?

  5. #5
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    Patrox... A large HPI company I worked for required:
    a) An 8-foot high fence.
    b) 48-inch minimum distance between the fence and HV terminal side.
    c) 36-inch minimum distance between the fence and the other 3 sides; and
    d) At least two access gates on opposite sides of the fence!

    Regards, Phil

  6. #6
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    I guess it depends on the type of design. I have a dry type 500kVA 480V-4.16kV transformer in a SWGR room next to everything leaving the required working distance per Chapter 1 in the NEC.
    Ron

  7. #7
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    Quote Originally Posted by jim dungar View Post
    Are there any exposed parts on the back of the equipment?
    Does any routine maintance need to be done on the rear of the transfromer while it is energized?
    Is the primary under the control of a utility?
    Jim, the responses to your questions are 1) no, 2)no, 3) this is for a university campus, so it will be a campus feeder connecting to the transformer primary.

    i was just wondering where in the NEC the clearance requirements for an oil filled transformer were and if there were any NFPA requirements for egress from an electrical equipment courtyards. if anyone knows the answers please reply.

    thanks.
    F413

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