Arc Flash Forum
https://brainfiller.com/arcflashforum/

Unreasonable current during study
https://brainfiller.com/arcflashforum/viewtopic.php?f=15&t=6465		 Page 1 of 1
Author:  Jake Kingsbury [ Fri Jun 26, 2026 11:26 am ]
Post subject:  Unreasonable current during study
I'm running an arc flash study on some medium voltage gear--and from the utility company I have their available short circuit from the utility side (~5.5kA). Yet when i run an arc flash study I'm getting 3phase fault currents Upwards of 10 million amps (I've tried to attatch a screenshot of my schematic below for reference). Now oddly enough when i run a short circuit study im getting much more reasonable numbers of fault current, ~5.3kA. Any idea why there might be such a discrepancy and what is causing it?

Thanks

Attachments:
SKM high current question.png
SKM high current question.png [ 385.05 KiB | Viewed 28905 times ]
Author:  bbaumer [ Sat Jun 27, 2026 8:22 am ]
Post subject:  Re: Unreasonable current during study
Couple of questions:


Are you using the same Data Block to display the results of the short circuit study results and the AF study results?

Can you post a screen shot of your "reasonable" short circuit study results for comparison to the "unreasonable" results?

Are you using the same short circuit calculation method for both the short circuit study and the AF study?

What attribute in the Data Block is Isc 3P? Isc 3P is not an SKM default/base attribute name so whatever attribute it is has been renamed to Isc 3P. It is possible something has been edited incorrectly in the attribute in addition to the renaming.
Author:  Win Engineer [ Fri Jul 10, 2026 9:11 am ]
Post subject:  Re: Unreasonable current during study
Use the Branch fault Current data block and see what fault current you have flowing through the system. I had a model years ago that was yielding some ridiculous fault currents on a 208V system and discovered that a bunch of 10HP motors had been entered at 10,000HP. You can imagine at 208V the fault contribution from the motors! That data block showed me the fault current coming back into the bus was really high and pointed me straight to the issue.
Page 1 of 1 All times are UTC - 7 hours
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
http://www.phpbb.com/