In the paper "Impact of Available Fault Current Variation on Arc-Flash Calculations" presented in the PCIC the authors discussed the maximum incident energy (IE) may not occur at the calculated arcing current or at 85% of the arcing current. Instead the maximum IE occurs some place where the 2 second rule and overcurrent protection curve meet or somewhere else (see fig 5 of the paper).

It seems to me the maximum IE may be determined without going through an arc flash/short circuit study. This can be calculated by determining the worst case IE for a protective device. This is especially true when utility data is unknown or estimated.

What is needed is the Time-current curve, system voltage, bus gap, the enclosure type, and grounding. From this the worst-case IE can be determined.

Thoughts?

Paper can be found here ~

http://www.eatoncorp.com.au/ecm/idcplg% ... PCT_372889