Fault Current 1

[jimioy]

To get all my switchgear and transformers in compliance with NFPA 70 (NEC 110.16) as far as getting labels indicating arc flash hazards and giving appropriate PPE levels, what is the formula for calculating fault current -at the main and at subsequent sub-panels? Also, can I calculate fault current for my pad mount transformers (12470/480)? I believe the impedenace (Z%) is on the transformer label. Also, is bolted fault current the same? Thanks, Jimi

 

[RonShap]

If you are looking for compliance with the NEC, you only need a label that says "Warning: Arc Flash Hazard Present"
No calculation needed.

If you want to comply with NFPA 70E, then you need many calculations, well in excess of just the fault current.

 

[RalphChristie]

At

http://www.mikeholt.com

is some useful information

arc-flash:

http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/What-is-Arc-Flash~20040512.php

Although a lot of fault-calculations are done these days with software, this file can help you with manual calculations:

http://68.225.22.180/documents/calculations/formulas/BulletinEPR-1-contents.pdf

 

[mpparent]

You might want to get a copy of the new IEEE 1584 standard.

Mike