In addition to ‘Arc Flash Boundary’ and ‘Incident Energy at Working Distance’ SKM PTW32 Ver 9003 calculates additional arc flash boundaries at user defined incident energies. The PTW attribute is AF_FB@IE.

In the attached file, the AF_FB@IE values at 11) to 14) appear incorrect.
SKM insists the AF_FB@IE values at 11) to 14) are correct.

My manual calculations for items 1) to 10) and 15) to 18) agree with PTW.
Given that the 'Arc Flash Boundary' is 2524mm, therefore the Incident Energy at 2514mm is 1.2 Cal/cm2. The distance from the arc for 1.2 Cal/cm2 is 2524mm not 609.61mm as shown in 11).

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I would suggest you send your results directly to Johnny Ma: johnny.ma@skm.com

Maybe I am misinterpreting the data but if you re-frame what AF_FB@IE means the data makes sense. Line 4) States the IE at 610mm is 11.61 and the flash boundary is 2524mm. My interpretation is that line 12) is simply restating this information, at 11.62 Cal/cm^2 the flash boundary is calculated as 2513.99. line 11) can be read as IF the IE were instead 1.2 cals at a working distance of 610, the flash boundary by definition is then 610. Looking at the data this way it makes sense that 11) -14) that the distance measurement increases as the IE value increases. I do not think that lines 11-14 are looking at the calculated arc flash values from 1-10 but instead provide a "what-if" set of values for other possible IE's. With this interpretation, the data may not be useful but it makes sense.

By this same interpretation the lower lines 15) -18) are stating that with the IE calculated by 4) IF your working distance were changed to be 2524mm, 610mm, 4076mm or 5470mm the IE would be shown as calculated.

In short, I feel AF_XX@YY is stating that IF YY were to be true, XX would be the result.

Thank you cfanks for your concise logical reply.

I run your case scenario using ARCAD's web app and the results are in agreement with your findings. Namely, 1.2 cal/cm2 @ 2524 mm distance and 11.7 cal/cm2 @610 mm distance:

SKM data is wrong in this case. I found a similar result when testing the "AFB @ IE" data blocks. I would avoid using these values from SKM I think they are mixing methods from 2002 and 2018. As you say the results do not make sense. I can confirm with my independent spreadsheet that your results for AFB (1.2cal) = 2524mm and AFB (11.62cal) = 610mm are correct.

The values that you are calculating are correct and are already included in lines 15) to 18). AF_IE@WD is the data block for that exact function. AF_FB@IE is a different data block with a different function. If the data for AF_FB@IE is incorrect as specified, then AF_FB@IE and AF_IE@WD would be exactly the same. If you instead look at AF_FB@IE to mean "Arc Flash Flash Boundary IF the Incident energy is __" 11) -14) is correct and different than AF_IE@WD. As I stated above I do not think that this datablock provides useful information, but I do not think it is wrong in this sense, the values calculated by multiple people in this thread is simply AF_IE@WD.

Here is to hoping they bring back this function so you can determine the WD at a specified incident energy as most sites require their personnel to wear Cat 2 clothing.

Back in IEEE 1584 year 2002 guide for arc flash calculations, it was really easy to analytically express distance at the specified incident energy from IEEE 1584-2002 Equation 6. New IEEE 1584-2018 incident energy calculations are way more complicated to the point you can't really analytically express distance as a function of incident energy. I believe this is the reason why SKM dropped the function. I'm sure fellow engineers can do it by means iteration with the help of brute computer power