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| Arc Flash Results https://brainfiller.com/arcflashforum/viewtopic.php?f=4&t=6009 |
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| Author: | jsoar [ Mon Mar 10, 2025 7:23 am ] | |||
| Post subject: | Arc Flash Results | |||
Hello, I am working on this Arc Flash study for a company that wants the Incident energy levels below 4 cal. I can figure out why these ones are so high. I checked to make sure my data was correct. I'm not sure what to do now.
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| Author: | bbaumer [ Mon Mar 10, 2025 7:56 am ] |
| Post subject: | Re: Arc Flash Results |
What is your arcing fault current vs your breaker trip curve? Those are some fairly long feeders. I suspect the fault current is "low" and arcing fault current in the short time region of the breaker curve, not the instantaneous region. If so, that would increase breaker clearing time and therefore incident energy. |
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| Author: | bbaumer [ Mon Mar 10, 2025 8:00 am ] |
| Post subject: | Re: Arc Flash Results |
Also, is that EasyPower? Should your most downstream feeders be 3-1/C, not 1-1/C? Not an EasyPower user so not sure. Attachment: conductors.jpg [ 314.45 KiB | Viewed 109384 times ] |
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| Author: | jsoar [ Mon Mar 10, 2025 10:46 am ] | ||
| Post subject: | Re: Arc Flash Results | ||
Hey, I posted the Arc Fault from the bus. And yes this is easypower. Do i have the conductors wrong? 3-1/C instead of 1-1/C?
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| Author: | bbaumer [ Mon Mar 10, 2025 11:11 am ] |
| Post subject: | Re: Arc Flash Results |
Looks at your trip times. It is timing out per the 2 second rule. Those breakers with the higher incident energy aren't even tripping. That is why the IE is higher. I've never used EasyPower but if I modeled this in SKM and it was 3 phase and I was using individual conductors (not a multiconductor cable, like a tray cable) then yes, I would have 3-1/C cables (A, B and C) or 4-1/C cables ( A, B, C, N). Not sure how it even calculates with only 1/C if EasyPower is the same. EDIT: Also, I'm not sure what breaker is the protection, the upstream XT4N (for line side of main of the downstream panel) or the main breaker A2A in each panel. Depends on how you set up your study. If the XT4N is protection, some of those have adjustable instantaneous. If it is the A2A main breaker, they are fixed. If you run line side of main and your XT4N is adjustable, you might be able to set it to MIN and get a much lower IE. If you want to set up a TEAMS meeting and share your screen I can try to help you if you like, although I don't know much about EasyPower. |
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| Author: | bbaumer [ Mon Mar 10, 2025 11:28 am ] |
| Post subject: | Re: Arc Flash Results |
I looked at the curves with the XT4-N set to MIN. It looks like your energy is based on the A2A breaker tripping. At 1900 amps you are in the tolerance band of the breaker and it doesn't trip until well past 2 seconds. That is why you are timing out. You could re-run your study to look at both the line and load side of the main and use the line side with the upstream XT4-N breaker tripping in the instantaneous region. That will get your energy down, I think, on the one that is 1900A arcing current set to MIN. The ones that are only 1200A, neither breaker trips quickly and you still have your "high" incident energy. Attachment: ABB CB.jpg [ 351.61 KiB | Viewed 109376 times ] |
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| Author: | bbaumer [ Mon Mar 10, 2025 11:37 am ] |
| Post subject: | Re: Arc Flash Results |
Attachment: ABB CB min.jpg [ 440.58 KiB | Viewed 109376 times ] |
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| Author: | jsoar [ Mon Mar 10, 2025 11:49 am ] |
| Post subject: | Re: Arc Flash Results |
Thank you. I am not available for teams meeting today. Do you still use the 2 second rule if the panel is 208V? Lower Voltages: For voltages lower than 208V, some engineers use a shorter tripping time, such as 0.5 seconds, as the arc flash hazard is generally considered lower. I found this on google. |
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| Author: | bbaumer [ Mon Mar 10, 2025 12:01 pm ] |
| Post subject: | Re: Arc Flash Results |
I do use the 2 second rule on 208V. I'm not aware of the 0.5 second practice. I just may be ignorant though. That's not unusual, lol. IEEE does say there is a low risk for bolted fault currents under 2000A but your bolted fault currents are higher than 2000A. |
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| Author: | JBD [ Thu Mar 13, 2025 9:23 am ] |
| Post subject: | Re: Arc Flash Results |
jsoar wrote: I found this on google. I have not found AI to be very good at technical/engineering topics. I prefer dedicated forums like this one. You might also try eng-tips, forums.mikeholt, or ones sponsored by software vendors. |
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| Author: | NeDCE [ Fri Mar 28, 2025 3:45 pm ] |
| Post subject: | Re: Arc Flash Results |
bbaumer wrote: Also, is that EasyPower? Should your most downstream feeders be 3-1/C, not 1-1/C? Not an EasyPower user so not sure. Attachment: conductors.jpg @bbaumer and also @jsoar: in EasyPower, "3-1/C" means three parallel conductors per phase in a single conductor cable configuration. So the first digit is how many (parallel) line conductors per phase, and the "X/C" is how many conductors in a cable configuration. So if I had a conductor run "1-3/C", that would be something in a 3-conductor cable assembly, such SO cable or something run in cable tray. A 3-phase circuit run showing "1-1/C" would be a standard 3-phase, one conductor-per-phase circuit. (note that neutral and ground are a separate tab and aren't addressed in that nomenclature) |
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| Author: | bbaumer [ Sat Mar 29, 2025 2:04 am ] |
| Post subject: | Re: Arc Flash Results |
Makes sense. Thanks! |
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