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ekstra   ara
 Post subject: 208V equipment fed from 750kva 600/208V transformer
PostPosted: Fri Jan 30, 2009 10:42 am 

Joined: Fri Jan 30, 2009 10:04 am
Posts: 10
Location: Toronto
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!


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PostPosted: Mon Apr 20, 2009 8:37 pm 
Sparks Level

Joined: Sat Apr 04, 2009 9:50 pm
Posts: 104
Location: San Antonio, TX
I don't think that the transformer is Panel B or C immediate power supply. I understand that the calculation is not necessary.


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PostPosted: Tue Apr 21, 2009 1:13 pm 
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Joined: Tue Jan 13, 2009 5:00 pm
Posts: 532
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 [url="http://www.arcflashforum.com/showthread.php?t=324"]http://www.arcflashforum.com/showthread.php?t=324[/url]


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PostPosted: Tue Apr 21, 2009 4:30 pm 
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Joined: Thu Jan 10, 2008 8:49 pm
Posts: 498
Location: New England
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.


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