Is your organization in the scope of NESC? If so, it would be appropriate to use the tabulated IE values.

The 10 cycle limit isn't really a part of the code, just an explanation for a table entry. The EPRI study referenced is publicly available at https://www.epri.com/research/products/000000000001022218.

Looks like they needed 40kA at a half inch to get it to sustain past 9 cycles.

The maintenance contractor should have the final say regarding his own safety if more conservative.

If it was common knowledge on how little testing was done on <= 240V, more engineers would be using the NESC tables. I should have said successful testing, if you look at the IEEE testing on <= 240V, there is a common theme, a large number of the tests are incomplete due to the arc self extinguishing.

If you can find the following paper done by a senior 1584 member (in the past), "Calculating Arc Flash Energies and PPE for Systems < 250V", it is a good read. You will also see that the recommendations (.5sec clearing) line up very close to the NESC 4 cal/sqcm findings.

This continues to be a subject that requires more work. The IEEE 1584 project team has been looking more closely at this however due to NDA, I can't provide any details (yet). As pointed out in a few of the posts, there are several observations.

Duration is important (sustainability) but this isn't all. Fault current is important. A small fault current that sustains for 5 or 10 cycles is likely to be more of a "POP" A larger current that sustains for a few cycles is another matter.

I am familiar with the paper (and author) that uses 0.5 seconds. It seems reasonable but is not supported by any standard so it's use is up to someone else's decision.

As many know, the 2018 Edition of IEEE 1584 cut the 240V fault current down to 2000A at which point with the help of lots of disclaimer language, someone may choose to exclude those locations. One reason this is such a low value is legal asked: can we guarantee the arc will not sustain below _____amps?

From 2018 IEEE 1584:
Sustainable arcs are possible but less likely in three-phase systems operating at 240 V nominal or less
with an available short-circuit current less than 2000 A.

I had an inquiry from a utility around 2004-05 that had an electrical worker on the 208V secondary side of a padmounted transformer sustain a large second degree arc flash burn on their upper arm. So: Never say never!