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| incident energy calc https://brainfiller.com/arcflashforum/viewtopic.php?f=4&t=6467 |
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| Author: | arcflashprimero [ Thu Jul 30, 2026 4:32 am ] | ||||
| Post subject: | incident energy calc | ||||
how is it that at 1000 INST the level is 1, but if INST is 1200 it jumps to level 3? worst case arcing fault is 4005A so I assume anything under this and it trips instaneously. no other sources or motor loads in the circuit
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| Author: | mparenteau [ Thu Jul 30, 2026 5:21 am ] |
| Post subject: | Re: incident energy calc |
Take a look at your arcing fault numbers... Mike |
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| Author: | Jim Phillips (brainfiller) [ Thu Jul 30, 2026 8:06 am ] |
| Post subject: | Re: incident energy calc |
Protective device clearing time defines the arc duration. Elaborating on what mparenteau stated, the device clearing time is a function of the arcing fault current and devices time current curve. The clearing time has the largest effect on the incident energy. i.e. clearing time doubles = incident energy doubles. Also, IEEE 1584 has an arcing current variation factor so if the arcing current is slightly to the right of the instantaneous, the adjustment could push it just to the left resulting in a longer duration. |
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| Author: | arcflashprimero [ Thu Jul 30, 2026 12:15 pm ] |
| Post subject: | Re: incident energy calc |
mparenteau wrote: Take a look at your arcing fault numbers... Mike I did look at the arcing fault, both values are to the right of the INST settings. So I was thinking it should trip, but as Jim mentioned below it may be due to the tolerance used not only in the equations, but in the breaker characteristics as well. This one in particular shows =-20% |
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| Author: | arcflashprimero [ Thu Jul 30, 2026 12:25 pm ] | ||
| Post subject: | Re: incident energy calc | ||
Jim Phillips (brainfiller) wrote: Protective device clearing time defines the arc duration. Elaborating on what mparenteau stated, the device clearing time is a function of the arcing fault current and devices time current curve. The clearing time has the largest effect on the incident energy. i.e. clearing time doubles = incident energy doubles. Also, IEEE 1584 has an arcing current variation factor so if the arcing current is slightly to the right of the instantaneous, the adjustment could push it just to the left resulting in a longer duration. Is there a way to determine what SKM is using for the arcing current? Because I still don't see why its not tripping even at 1200A INST
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