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208V equipment fed from 750kva 600/208V transformer

Discussion in 'System Modeling and Calculations' started by J.T, Jan 30, 2009.

  1. J.T New Member

    I am a new member. Please let me post a question.
    IEEE 1584 states:"Equipment below 240v need not be considered unless it involves at least one 125kva or larger low impedance transformer in its IMMEDIATE supply"
    My case: 750kVA 600/208-120V 7.1% transformer supplys 208V switchboard A. Switchboard A supplys 208V panel B via cables, and panel B supplys another 208V panel C via cables. I need to do arc flash analysis for switch board A based on IEEE 1584. Do I need to do arc flash analysis for panel B and C? Or just label panel B and C according to NFPA 70 table 130.7(C)(9)(a)? I do not think the 750kva transformer is immediate supply to panel B. C. Thanks!
    J.T, Jan 30, 2009
    #1

  2. RECS New Member

    I don't think that the transformer is Panel B or C immediate power supply. I understand that the calculation is not necessary.
    RECS, Apr 20, 2009
    #2

  3. stevenal Well-Known Member

    The same standard says "The arc-flash hazard need only be considered for large 208 V systems: systems fed by transformers smaller than 125 kVA should not be a concern." No "immediate" qualifier there. Also note that NFPA avoids the "immediate" qualifier.

    Also see http://www.arcflashforum.com/showthread.php?t=324
    stevenal, Apr 21, 2009
    #3

  4. haze10 Well-Known Member

    YOU don't have to list the the HRC Task Matrix. Since it is outside the analysis,, you can just list a single HRC of 1 or 0 for all tasks.
    haze10, Apr 21, 2009
    #4

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