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Have you seen reports/labels with an incident energy greater than 200 cal/cm2?
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 Post subject: Incident Energy Greater than 200 cal/cm2
PostPosted: Sun Nov 07, 2021 6:01 pm 
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Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1628
Location: Scottsdale, Arizona
Extremely large incident energy values are almost always due to a long arc duration/protective device clearing time. The 2 second cut off can help reduce the values but it can still be well above 100 cal/cm2. Now and then I still run into a label that is very extreme. This week’s question is simple:

Have you seen reports/labels with an incident energy greater than 200 cal/cm2?
Yes
No


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 Post subject: Re: Incident Energy Greater than 200 cal/cm2
PostPosted: Mon Nov 08, 2021 9:46 am 
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Joined: Tue Oct 26, 2010 5:00 pm
Posts: 200
Location: Maple Valley, WA.
Sometimes this is a result of a location that does not meet the IEEE 1584 parameters. For example, if the voltage is above 15 kV, the enclosure is too large or small then this does not meet the IEEE 1584 parameters. At these locations, many of the software programs will revert to using the Lee Equations. The Lee Equations typically will produce extremely conservative high energy and arc flash boundary values.

Above 15 kV, different methods should be used to estimate the arc flash energy and boundaries.

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Robert Fuhr, P.E.; P.Eng.
PowerStudies


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 Post subject: Re: Incident Energy Greater than 200 cal/cm2
PostPosted: Mon Nov 08, 2021 3:55 pm 

Joined: Fri Sep 24, 2021 7:17 am
Posts: 2
I sure did. I have a picture of label that is showing 104311.9 cal/cm^2, analysis date 12/2017.......40kA of available fault current, 480VAC system....arc flash boundary was listed at 3366'-8"

Clearly they weren't modeling correctly. I wonder if they ever thought about the degree of precision. I'm guessing they never looked at it. The printed the label and slapped it on.


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 Post subject: Re: Incident Energy Greater than 200 cal/cm2
PostPosted: Tue Nov 09, 2021 12:09 pm 

Joined: Mon Mar 09, 2020 9:27 am
Posts: 18
I see them semi regularly at the line side of the main breaker, directly off the utility transformer. I believe its because the utility fuse is not modeled.


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