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Hazard Risk Category Help

Discussion in 'IEEE 1584 - IEEE Guide for Performing Arc-Flash Ha' started by Yuna, Nov 11, 2009.

  1. Yuna New Member

    Currently, i do the arc flash calculation based on calculation method in IEEE1584-2004. However, the calculated incident energy is too high beyond 40cal/cm2. How can i define the PPE for that device?NFPA 70E table only proposed less than 40cal/cm2. Please throw me a light.

    Thank you.:confused:
    Yuna, Nov 11, 2009
    #1

  2. jghrist Well-Known Member

    You could label the PPE by specifying the calculated IE, which would require clothing with a rating in excess of the IE. A more common approach would be to label the equipment "Dangerous! Do not operate energized" or something to that effect.

    It is possible to get PPE rated higher than 40 cal/cm², but with this high an IE, the blast hazard is probably high and high IE PPE won't be protect against the blast.
    jghrist, Nov 11, 2009
    #2

  3. WDeanN Well-Known Member

    You specify adequate for the energy calculated.

    But, as jghrist suggested, the industry consensus is that over 40 cal/cm2, the blast hazard is sufficient to significantly injure the person, regardless of the flash hazard PPE worn, most will label the equipment as Dangerous, and require that the equipment be deenergized before any work is performed.
    WDeanN, Nov 12, 2009
    #3

  4. THE CABLE GUY Well-Known Member

    The guy would need to know how to verify de-enerigized. I would recommend a non-contact voltage detector on a pole maybe according to the situation.
    THE CABLE GUY, Nov 12, 2009
    #4

  5. brainfiller Administrator

    How long is the clearing time? Often incident energy becomes quite large because of a low fault current causing the upstream protective device to take a long time to trip. The result is low current X long clearing time = high incident energy which may not be explosive.

    What I am still holding out for is a cut off of energy per time. That would help define how explosive an event is. In your case did you try cutting the time of at 2 seconds per IEEE 1584? Did you try to see what happens if you lower the protective device setting? (assuming it is adjustable).

    Just a few ideas and thoughts for you.
    brainfiller, Nov 12, 2009
    #5

  6. THE CABLE GUY Well-Known Member

    I do believe, that is a good catch.
    THE CABLE GUY, Nov 12, 2009
    #6

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