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Suppose you have a panel. The arc flash incident energy for this panel is computed based largely on the available short-circuit current (SCCA) to the panel, and the protective devices upstream of the panel. Now, if there are current-limiting fuses upstream of the panel, the incident energy should be greatly reduced in many (if not all) cases. Yet SKM Powertools does not account for this phenomenon; the current-limiting behavior of current-limiting fuses is not simulated.

Most of the documentation I'm seeing involves the use of current-limiting fuses to increase the short-circuit current rating (SCCR) of the panel. So for the purpose of computing whether equipment is rated for the SCCA, ignoring the current-limiting behavior is correct, but this has no impact on arc flash incident energy calculations.

Mersen argues that using current-limiting fuses to reduce arc flash energy is valid.

https://ep-us.mersen.com/sites/mersen_us/files/2018-11/TT-AFN2-Reducing-Arc-Energies-with-Current-Limiting-Fuses-Tech-Topic.pdf

Two IEEE papers seem to agree, though I can't access the full text: https://ieeexplore.ieee.org/document/806456 https://ieeexplore.ieee.org/document/7549099

What is standard industry practice on this subject? Do other simulators besides SKM Powertools account for current-limiting effects? Do engineers do these calculations manually, or is the current-limiting effect ignored for arc-flash purposes? If so, why?

EDIT: Easypower does support computation of arc flash incident energy using current-limiting fuses! At least, it did at the time this video was made:

https://www.easypower.com/resources/article/current-limiting-fuses-in-easypower

JRE
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Stephen Collings
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    That really depends how fast the fuses are . What is their trip curve? Is that trip curve acceptable for arc surppression? – Harper - Reinstate Monica Mar 30 '23 at 00:41
  • On further reflection, I'm presently suspecting that the reason this doesn't get discussed much is because there are so few cases where it might be helpful. Most industrial equipment in my experience ends up requiring PPE of category 0 or 1, with higher categories only required on service equipment. The size of fuses necessary to protect service equipment might make current-limiting fuses prohibitive, and there are perhaps better ways to achieve the goal of reducing the incident energy in the gear, like optical flash detection opening the upstream breaker. All speculation, of course. – Stephen Collings Mar 30 '23 at 15:25

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