I understood the need to use Iarc600 in the numerator for the calculation of IE and AFD for both the 100% arcing current and the reduced arcing current when Voc ≤ 600 V.

But this leads me to ask another question:

Why use, as in the D1 example, the currents Iarc_600/2700/14300_min in this same numerator for the calculation of IE and AFD with the reduced arcing current?

Let's take an example:

Let's use the same system as in the D2 example but with a Voc=600 V. For the reduced arcing current (28.65 kA), with the equations D101 and D104 we find (keeping T=319 ms) IE=14.34 cal/cm2 and AFB=2879 mm.

Let's repeat the same example with a Voc=601 V. The equations D53, D55, D57 of the D1 example must then be used. It is then found (keeping T=319 ms) Iarc_min=28.66 kA, IE=9.95 cal/cm2 and AFB=2290 mm.

So for a Voc variation of 1 V, IE drops 30% and AFB drops 20% which does not seem to me very consistent.

If we replace in the equations D53, D55, D57 the numerator values Iarc_600/2700/14300_min per Iarc_600/2700/14300, then we get the following results: Iarc_min=28.66 kA, IE=14.35 cal/cm2 and AFB=2880 mm, which is more consistent.

On the other hand, if we redo the D1 example by replacing the numerator value Iarc_600/2700/14300_min by Iarc_600/2700/14300 for equations D53, D55, D57 the results become IE=3.21 cal/cm2 (instead of 3.19) and AFB=1712 mm (instead of 1704). The difference is small, which is normal since the influence of the reduced arcing current decreases as the voltage increases.

It should also be noted that the Excel calculator available on the "https://ieee-dataport.org/open-access/arc-flash-ie-and-iarc-calculators" website uses the numerator value Iarc_600/2700/14300 for the equations D53, D55, D57.

Do you not think that a clarification would be useful on this problem? This may be important in Europe where 690V voltage is commonly used in industrial facilities and where the use of the numerator value Iarc_600/2700/14300_min in equations D53, D55, D57 could lead to calculated values of IE and AFB underestimated in relation to reality.

At your disposal to discuss it more precisely if necessary.

Regards

Philippe

Statistics: Posted by Ph. Aupetit — Tue Dec 01, 2020 4:09 am

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The adjustment to the specific voltage is accounted for with Iarc for 100% and Iarc_min for minimum. Where both are at the specific nominal voltage (Voc)

This is quite different than the medium voltage solution where you calculated everything at two voltages (often 2.7 and 14.3 kV) and interpolate between the two values.

Statistics: Posted by Jim Phillips (brainfiller) — Sun Nov 29, 2020 4:27 pm

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I am developing an arc flash calculator and I have the same question as Balaji:

Why in equation D101, "k3*Iarc_600" is used in place of "k3*Iarc_600_min" which is not complying with the title of Step 10 "Repeat Step 4 using the

Thanks for your answer.

Regards

Philippe Aupetit

Statistics: Posted by Ph. Aupetit — Thu Nov 26, 2020 3:34 am

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Wound rotor induction motors have an external circuit coming from the motor rotor, through slip rings, to a variable resistor bank. The slip ring enclosure and the resistor bank cabinet have an arc flash risk. Is there an established method/standard for calculating the incident energy along the motor secondary circuit? Have you ever run into the situation before?

I do not have any experience with wound rotor induction motors.

Any one cares to enlighten me? Thanks.

Statistics: Posted by RECS — Thu Aug 13, 2020 11:35 am

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Hi Jim: Does the IEEE 1584 committee have any plans for higher voltage overhead lines? Like Arc Pro?

Thanks for all you do!

There has been some discussion about extending to the 35-38 kV range for equipment but it is just an informal discussion. So nothing anytime soon. There is nothing about higher voltage overhead lines. Too much left to do at lower voltages first.

Statistics: Posted by Jim Phillips (brainfiller) — Tue Aug 11, 2020 9:26 am

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Statistics: Posted by K. Engholm — Mon Aug 10, 2020 11:18 am

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My understanding is that the first priority will probably be some DC content.

My personal desire would be acquiring data at higher fault current values, hopefully all the way to 200kA.

Both of these type of projects require testing few laboratories can provide and have significant cost associated. As Jim stated, this is expensive and funds are limited.

BUT keep your cards and letters coming to whoever you know in the IEEE working group. It is important that whatever expansion is undertaken it addresses real needs in the industry.

Yes DC is high on the list. I have been pushing DC for years and a while ago it up on the radar screen. Single phase is also on the list as mentioned. Going to 200 kA will be quite difficult due to lab constraints. We were limited this time around. As I understand, one of the labs had some damage at higher currents and throttled the upper current capabilities back. It is also expensive as we all know. Stay tuned, it all moves slow but it is moving in the right direction!

Statistics: Posted by Jim Phillips (brainfiller) — Mon Aug 10, 2020 7:55 am

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My personal desire would be acquiring data at higher fault current values, hopefully all the way to 200kA.

Both of these type of projects require testing few laboratories can provide and have significant cost associated. As Jim stated, this is expensive and funds are limited.

BUT keep your cards and letters coming to whoever you know in the IEEE working group. It is important that whatever expansion is undertaken it addresses real needs in the industry.

Statistics: Posted by Electricidad — Mon Aug 10, 2020 7:47 am

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Are there any plans for the next (3rd) edition of IEEE 1584? What would it include?

We are still catching our breath from the 2018 Edition. Many items were left out of the 2018 Edition due to budget reasons. The IEEE/NFPA Collaboration for this project had an ambitions test plan with a proposed budget of around $6.5 Million. Fundraising was cut short during the 2007-2008 economic situation so the final budget was about half of what was planned. This meant many areas were left for a future date.

IEEE has something called "dot" standards. The hope is rather than starting the whole process over again, we can address outstanding areas one at a time with it's own unique "dot" standard. We already have IEEE 1584.1 "dot-one" which I co-authored the first draft with a colleague years ago. It is undergoing revision right now.

We hope to someday add additional dot standards for areas such as single phase, DC, higher voltages and other areas although nothing has officially begun yet. The research is a continuous process and we will all keep moving the knowledge base forward.

**Usual disclaimer: Although I'm Vice Chair of IEEE 1584, this is my personal view and may or may not represent the view of IEEE or any other standards organization.

Statistics: Posted by Jim Phillips (brainfiller) — Fri Aug 07, 2020 7:39 am

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Greetings from North of the border. As your calculations are above me as an industrial electrician, just wondering about Cal/cm2 as compared to temperature in degrees F? In many cases in my sessions up here in Ontario, the tradespeople will ask as a comparison form Cal/cm2 to degrees Farenheit. Basically using simple examples such as the temperature of their BBQ, oven, etc. Considering to my knowledge there is no direct calculation from Cal/cm2 to temperature in Farenheit. I hope that this makes sense. Thank you, Len

Statistics: Posted by Leonard — Mon Jun 15, 2020 1:17 pm

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Most of the physicists we have consulted (Dr. Gordon, and Dr. Sweeting) indicate that arc in air is closer to 5000 or 10000F. But the calorie/cm2 or J/cm2 is the total heat energy but the temp of the gas ball is deceiving since up to 80% of the energy in our common arc test is infrared until it hits a surface so there is no "temperature" per se.

Stick with the IEEE numbers. ArcPro uses a physics finite elements model based on plasma density, temperature and column size, and length to predict total energy in points in the space but temperature is not a good analogy in my estimation. Comparisons to the "surface of the sun" is even less useful.

Statistics: Posted by elihuiv — Mon Jun 15, 2020 11:46 am

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This answer at least seems physically possible, thank you for the guidance. Would 77 cal/cm^2 incident energy and 35,000 degrees F be reasonable for a severe arc flash?

No.

The 35,000 number is based on the immediate localized vaporization of metals and would quickly decrease as the resulting 'plasma cloud' begins to expand.

Your 77 number is based on being at least 18" away from the point of vaporization.

You are are taking a scare tactic number and trying to use it in a rational manner.

Statistics: Posted by JBD — Fri Jun 12, 2020 6:56 am

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Suppose the gas is oxygen, and the arc flash ionized gas ball consists of 10 mol of it.

1 mole of O2 gas occupies 22.4 L at normal pressure and temperature (1 atm and 77 degrees F) (based on this: https://socratic.org/questions/56afb21b11ef6b589ee3b3bf).

10*2/22.4 = 0.89 mol.

But an arc flash is high temperature, and volume is proportional to temperature.

V1/T1 = V2/T2 = (22.4L)/(77 degrees F) =V2/(35,000 degrees F).

V2 = (35,000 degrees F)*(22.4 L)/(77 degrees F) = 10,181 L.

So, (10*2 oxygen atoms)/10,181 = 1.964E-3 mol oxygen.

1.964E-3*6.02E23 (Avogadro's #) = 1.18E21 oxygen atoms.

1.18E21*2.72E-19 J (answer from before) = 322 J.

322 J/4.184 = 77 cal.

This answer at least seems physically possible, thank you for the guidance. Would 77 cal/cm^2 incident energy and 35,000 degrees F be reasonable for a severe arc flash?

Statistics: Posted by bpjmal1 — Thu Jun 11, 2020 11:52 am

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