Regarding OSHA - as far I saw it OSHA clearly says it is for OPEN ARC equipment only which you see in utility business however I'm looking for up to 36kV metal enclosed switchgears like from ABB, Siemens, Eaton etc whcih are used in industry or as RMU.

If you read the footnotes for the Appendix E, Table 3, you will see the Y for ArcPro in column for 3 phase in a box has the superscript 4. This refers to footnote 4 which states that OSHA will deem the results of this method reasonable when the employer adjusts them using the conversion factors for 3 phase arcs in open air or in an enclosure, as indicated in the program's instructions.

Note that this was written when the original ArcPro was in use and you hand manually do the conversion and the latest version has a drop down box where you pick the type of arc and the adjustment is done in the program.

So, if you looking for a value that you can use in your safety program and have a basis for the result, you would be in a much better legal position if something happened than if you used a method that may be harder to justify in a legal setting. Just saying.

Statistics: Posted by wbd — Tue Mar 02, 2021 6:25 am

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Marcia Eblen and I have a paper for the 2021 IEEE Electrical Safety Workshop [1] where we argue that the 1584-2018 models can be applied up to 35 kV. This is based on EPRI tests of medium-voltage equipment and the IEEE/NFPA data used to derive the IEEE 1584 models. We show that system voltage is not a key factor. The main factors for incident energy are the current, the duration, the electrode orientation, and the electrode gap. Physically, what's important is the arc voltage, not the system voltage. The arc voltage is mainly a function of arc length (with a modest multiplier based on arcing current). For the lengths of arcs you have in MV equipment, any medium-voltage source is stiff enough to supply that voltage. So, the results don't vary significantly with system voltage.

[1] Short, T and Eblen, M, "Comparison of IEEE 1584-2018 Predictions with Tests on Real-World Equipment," IEEE Electrical Safety Workshop, 2021. To be presented in a focus session on Wednesday, March 10, 2021. https://electricalsafetyworkshop.com/sc ... fe98a-d9dc

tshort - it will be great to red it once it is available. I will keep an eye on it as it is inline what I'm looking for.

Regarding OSHA - as far I saw it OSHA clearly says it is for OPEN ARC equipment only which you see in utility business however I'm looking for up to 36kV metal enclosed switchgears like from ABB, Siemens, Eaton etc whcih are used in industry or as RMU.

> Hugh I actually never had to use Arc Pro as most of my work is not utility type but it comes more often so i need to check pricing of it.

PS. I'm from Poland If I didn't present myself I'm Marcin Ruta to keep it more open (you can find me on LinkedIn).

Statistics: Posted by rutz — Tue Mar 02, 2021 3:33 am

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ArcPRO 4.0 is coming soon. Pretty major update for MV equipment.

Hugh Hoagland

ArcWear, A Kinectrics Company

hugh@arcwear.com

hugh.hoagland@kinectrics.com

Statistics: Posted by elihuiv — Mon Mar 01, 2021 8:05 am

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[1] Short, T and Eblen, M, "Comparison of IEEE 1584-2018 Predictions with Tests on Real-World Equipment," IEEE Electrical Safety Workshop, 2021. To be presented in a focus session on Wednesday, March 10, 2021. https://electricalsafetyworkshop.com/sc ... fe98a-d9dc

Statistics: Posted by tshort — Mon Mar 01, 2021 8:00 am

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20kV 8,82kA 250ms is 2,49 (IEEE1584) vs 6,66cal/cm2 (ETAP HV)

20kV 8,82kA 100ms is 0,99 (IEEE1584) vs 2,67cal/cm2 (ETAP HV)

I played with voltage in ETAP tool and it barely has influence on results (as in IEEE1584 if I take it 1 to 1 and I didn't do any errors). What seems to be a reason for results difference is probably in ETAP "reflectivity ratio" factor which was here 2,14. I used for hand calculation VCB configuration ( due to time limits I picked only one equation 14300 VCB) which gives lower results.

Will be nice to see voltage extension of IEEE1584 up to 36kV which is product range for MV switchgears. It will make life easier.

PS. I saw somewhere a paper about expanding IEEE calculations to higher level voltages (33kV or 36kV I think ) but I can't find it. Need to dig bit more.

Statistics: Posted by rutz — Mon Mar 01, 2021 2:21 am

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As you saw with the Lee Equations, since they are more heavily weighted towards voltage, the result tends to be extremely large as the voltage increases.

There is informal talk of some day (no time soon) taking IEEE 1584 to higher voltages, perhaps 35 kV. However, it is just that, informal conversation of "what if". But that is how new projects begin -as informal discussions about "what if" and "some day".

Right now there are a few other items higher up on the radar screen and nothing about higher voltages. But someday....

Statistics: Posted by Jim Phillips (brainfiller) — Sun Feb 28, 2021 3:21 pm

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Thank you for your posts.

I have the same problem with SKM/PTW software when calculating the d.c. short-circuit current supplied from a stationary lead-acid battery.

When a battery is selected from the PTW library, the user enters the following data for an example PTW project:

Battery Subview:

Rated Voltage250V

Number of Cells108

Number of Positive Plates73

Min Voltage (V/Cell)2.13

Short Circuit (ANSI) Subview:

Open-Circuit Voltage230.04V

Battery Size Type:8 Hrs Rating ( Custom, Max and One Minute also selectable )

Battery rating12A

Circuit Resistance3.000 Ohm

Circuit Inductance0.010 mH

Cell Interconnected Resistance22 Ohm

Cell interconnected inductance0.001 mH

My question for Mike is similar to Shawn’s:

How do I relate the above data to a real-life battery from Mike’s library of stationary batteries to calculate the Peak d.c. short-circuit current ?

The PTW software uses 0.5 * Peak d.c. short-circuit current and trip delay time to calculate arc flash incident energy to NFPA 70E 2021 Annex D.5.

Statistics: Posted by mnewman — Sat Feb 27, 2021 12:38 am

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I'm working on project where we have 20kV MV ring. Part of work is arc flash study. I know that IEEE1584 -2018 official equation limit is 15kV and I suppose to use NESC or EPRI or ArcPro. I have MV switchgear so arc in box VCB configuration which is not for NESC and out of range of EPRI which are available in SKM (I still need to test it in ETAP). So long story short :

- I did hand calculation for VCB Typical, short circuit of 9kA and 500ms trip time at 14.3kV I have 5.2 cal/cm2

- I played in excel and results between 15 and 20kV are slightly different 5,08 cal/cm2

- I played with SKM tool to see difference between 10 to 15kV arc for same configuration and it is 4,97 to 5,19

Of course If I use 20kV I got values like 55 cal/cm2 which comes from switching to Lee method but I don't like it. Either NESC ( OSHA table) or EPRI are not suitable but I can't verify it with ArcPro.

Question:

1. Does anyone knows any work or paper that was looking into expanding 1584 to slightly higher voltages with reasonable error ?

2. Can you verify 20kV 9kA 500ms configuration typical for 15kV in Arc Pro for results ?

Statistics: Posted by rutz — Fri Feb 26, 2021 6:48 am

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I think why some folks use 18" for the rear is because an electrician can easily remove a rear panel and measure the voltage with a hand held meter. Performing this task means the working distance is 18" (average length of a human arm when extended.)

Statistics: Posted by Robertefuhr — Mon Feb 22, 2021 12:55 pm

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There are some utility companies that still won't provide contribution for various reasons. In those cases I'll perform a sensitivity analysis (max/min), choosing values based on voltage levels from experience and taking into considering the distance from the source. Always note in the report or within the study one-line that the utility contribution is assumed or estimated in those cases.

Statistics: Posted by Bvallier1 — Mon Feb 22, 2021 8:03 am

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SKM will then be able to evaluate all the scenarios concurrently and advise which gives the worst case

I agree totally with the previous response, the infinite model frequently doesnt give the worst case IE but SKM will tell you which scenario does give worst case and what the values are. Putting realistic impedance and X/R values is crucial to getting meaningful results.

Statistics: Posted by cflatters — Mon Feb 22, 2021 6:58 am

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Use infinite bus methods to size the equipment from a short circuit current withstand perspective. Don't forget X/R ratios...

Use actual (not max) utility short circuit current availability for arc flash calculations. Infinite bus may or may not be worse case. In many cases that I've seen (from some consultants AF studies), they will use infinite bus and the AFIEs are lower than if they had used actual SCCA from the utility. Big problem...

If the utility won't give you actuals, then you're going to have to do max/min calculations to see where the worse case is and use that.

Mike

Statistics: Posted by mpparent — Fri Feb 12, 2021 8:20 am

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