The methodology listed in Annex R of the latest NFPA 70E 2021 draft gave me the impression its expected for users to determine the permanently mounted discharge resistance in order to list the discharge time of the bank when disconnected from the source.

If a facility wants to generate Warning labels for capacitor banks is it safe to say most would not follow the equations in annex R?

Would one simply print on the labels the banks indicated discharge time (if its readily available that is) ?

It seems it may be unrealistic attempting to calculate the potential discharge time using the equations in Annex R since the oem mounted discharge resistor values are not readily available from what I have seen in sample equipment.

Statistics: Posted by wfg42438 — Fri Sep 04, 2020 9:12 am

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As many of you may know in the 2021 edition there will be a new informative annex R which deals with Capacitor Banks.

This annex provides equations for the estimation of the stored energy in Capacitor banks which can be used to generate labels for these pieces of equipment.

The equations seem straightforward however one thing that is puzzling is the determination of the discharge time from nameplate data.

When sampling various capacitor banks I noticed that most banks advertise a specific discharge time however typically the discharge R is not mentioned. .

For example take this sample capacitor bank :

https://www.ebay.com/itm/GE-Power-Facto ... SwJ-9exYlN

If the discharge time is not legible on the nameplate what approach can be taken to find the discharge R?

Has anyone had experience with this or see a practical approach to determining the discharge resistance?

Statistics: Posted by wfg42438 — Mon Aug 24, 2020 8:02 pm

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A couple of points:

----1---- IEEE 1584 is the "science" of arc flash... regardless what other text reference or do not reference the science has changed... once it was realized the world was round there was little point in making your sailing plans based on the presumption the world was flat just because the map you acquired last year said so!

----2---- The IEEE 15484 calculations exist to provide data used in Risk Analysis for the planning of a task. The elements of good risk analysis as defined in all relevant text sand standards state that one should use the best available information and the most timely available information... I.e. if there are two guides and one is out of date and replaced by a newer one, the case could probably be made that the newer one must be used.

It seems to me, and I am neither a lawyer, nor an expert in standards application, if one uses the older guide for risk analysis and then there is an incident, having ignored the newer guide, now available for almost two years, may be a somewhat difficult decision to defend.

Statistics: Posted by Electricidad — Mon Jul 13, 2020 8:10 am

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As other comments have mentioned, the calculations are very different and the required inputs are very different as well.

Statistics: Posted by Electricidad — Mon Jun 29, 2020 8:57 am

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Without additional guidance, good engineering practice would be to follow the current industry standards.

Statistics: Posted by JBD — Thu Jun 25, 2020 8:43 am

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Mike

Statistics: Posted by mpparent — Thu Jun 25, 2020 6:22 am

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Since IEEE 1584-2018 isn't referenced in these editions, should the earlier 2002 edition still be used in such states?

Statistics: Posted by jchristopherslice — Wed Jun 24, 2020 2:51 pm

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Ernie Bowles

Statistics: Posted by ebowles — Wed May 06, 2020 2:28 pm

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Hello Michael.....I too have developed my own spreadsheet and wish to verify my calculations. I have also signed up to use your spreadsheet via the link you provided previously. I would appreciate the opportunity to utilize the functionality of your program as you have offered.

Thank you!

Ernie Bowles

Hi Ernie,

As requested, I've granted you two months free access to the arc flash analysis web app.

Statistics: Posted by arcad — Tue May 05, 2020 7:08 am

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Thank you!

Ernie Bowles

Statistics: Posted by ebowles — Tue May 05, 2020 7:02 am

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arcad wrote:

efmsato wrote:

I am working on my own spreadsheet for the calculation of incident energy in accordance with IEEE 1584-2018.

I wonder if anyone can share numerical examples DIFFERENT from those provided by the standard in Annex D, for validation? I mean, with different types of enclosure, voltages, etc.

I wonder if anyone can share numerical examples DIFFERENT from those provided by the standard in Annex D, for validation? I mean, with different types of enclosure, voltages, etc.

Please consider signing up free for AFA arc flash analysis web app online at https://app.arcadvisor.com and running any case scenarios you need to compare against your spreadsheet calcs. Once you've signed up, feel free to contact me and I'll unlock all the app features for you and anyone interested reading this post at ArcFlash forum for a couple of months.

Dear Michael,

I appreciate your cooperation. I signed up for ArcAdvisor, I found it a great tool. I would like to do a test with medium voltage calculations. Would it be possible to have this functionality temporarily for evaluation?

Thank you!

Edson Sato

Thanks for your favorable feedback, Edson. I've granted you two months full access to the resource.

Statistics: Posted by arcad — Thu Apr 30, 2020 9:09 am

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