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 Post subject: Calculations for 132kV/300 kV
PostPosted: Thu Jan 18, 2018 7:51 am 

Joined: Wed Nov 01, 2017 6:09 am
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As I understand the IEEE1584 method is only valid up to 15 kV. What is the best/easiest method for estimating safe distance and energy for an 300 kV outdoor switch gear(typical overhead lines and circuit breaker).
Any advise about witch software or standard to buy(cheaper is better since this is only one calculation).
Very thankful for any good advice


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Thu Jan 18, 2018 12:14 pm 
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You don't say where you are from but if in the United States you would be under OSHA 1910.269 regulations. In those regulations, OSHA lists the use of ArcPro for >15kV.

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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Fri Jan 19, 2018 1:03 am 

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Sorry about that. This is in Europe. As I understand just by reading in this excelent forum there are two ways to calculate arc flash in high voltage systems(typically 60, 130, 300 kV). One is to use ETAP the other is ArcPro(?).

Anyone know if this recognized in Europe?

What is the difference between this methoods?

I must say there are very much knowledge and firendly people on this forum. A place for making the world a safer place :D


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Fri Jan 19, 2018 10:04 pm 
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ETAP reverts to Lee.

There are basically 3 models out there for 115 or 300 kV: Duke Heat Flux, ArcPro, and Lee.

Lee is actually in the IEEE 1584 standard. In fact there are 3 different models in IEEE 1584-2002. One is Lee and that one doesn't have a voltage or current limit. One is the empirical formulas which is what is generally referred to as "IEEE 1584" even though it is just one of several models. The third is a set of simple equations developed by Mersen that do a really good job for low voltage current limiting fuses but they are rarely used.

Duke Heat Flux and Arcpro are proprietary computer programs. Duke Heat Flux is free and readily available although it was written to run on older Windows software so you might have to run it on a virtual machine since I'm not sure if it will even run on current Windows operating system software. Arcpro costs money but runs on curent Windows software.

In terms of the results, Lee will give wild and crazy and basically invalid and very high results. Duke Heat Flux will give a lower result and Arcpro will give something higher than Duke but definitely lower than Lee.

So I guess at this point it depends on your goal. If your goal is to provide the most popular and best result, then either purchase Arcpro or find someone that can run the calculation for you since you need a single result. If you don't mind a crazy high value and when I say this, I mean that you can live with the crazy result, Lee is priced right since the IEEE paper is free and widely available and you can practiaclly "Goggle" the equation. So I'd go ahead and suggest running the numbers through Lee and see if you feel comfortable with the result. If so even knowing it is much higher than the real result, at least you know that you have produced a "conservative" result. Finally since this in Europe another option would be Duke Heat Flux. The result will be low and seems to be questionably low but since all 3 models are equally weighted in terms of their credibility, you could just run Duke Heat flux and use the result. It will be low but anything at 115 or 300 kV is just guessing anyways. In overhead switchgear in general arc flash isn't much of a hazard anyways. Unless it is obstructed in some way, arcs will be magnetically propelled down the line away from the power source so even if an arcing fault occurred, it is most likely going to travel further down the line away from the initial fault at hundreds of feet per second.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Wed May 09, 2018 11:44 pm 

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Note that ETAP has released ArcFault module for HV Arc Flash Calculations up to 800 kV based on NESC C2
https://etap.com/product/arcfault
We are currently ETAP users and are planning to switch over to this module versus ArcPro. If you are familiar with ETAP Arc Flash, then it is a smooth transition.
;)


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Thu May 10, 2018 7:00 am 
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albedo wrote:
Note that ETAP has released ArcFault module for HV Arc Flash Calculations up to 800 kV based on NESC C2
https://etap.com/product/arcfault
We are currently ETAP users and are planning to switch over to this module versus ArcPro. If you are familiar with ETAP Arc Flash, then it is a smooth transition.
;)


Forum Notice: Generally, links to commercial sites/promotion are deleted. However, this one is an exception due to the nature of the issue and people seeking alternatives for arc flash calculations outside the scope of IEEE 1584.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Fri May 11, 2018 10:59 am 
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albedo wrote:
Note that ETAP has released ArcFault module for HV Arc Flash Calculations up to 800 kV based on NESC C2
https://etap.com/product/arcfault
We are currently ETAP users and are planning to switch over to this module versus ArcPro. If you are familiar with ETAP Arc Flash, then it is a smooth transition.
;)


The table in IEEE C2 is directly from ArcPro calculations. This would be table lookup. It is only valid for a vertical arc in open air which matches open/outdoor overhead line equipment, and specific currents. You enter the table with a specific PPE system and it provides a specific required clearing time. In reality the way ETAP works is that it would calculate voltage, current, and clearing time, and then this would result in an incident energy value. So this is basically the tail wagging the dog. I don't see how/why this would make any sense at all except that ArcPro does not provide a command line or "library" version that can be called from ETAP. It would work and probably matches the table in OSHA 1910.269 but it's opposite the direction you would want to go in. Arcpro itself will give lower values by design.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Fri May 11, 2018 4:18 pm 

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ETAP has two methods. Both are fully tested and derived based on physical equations derived from ANSI/EPRI/IEEE (United States) and European recognized organizations and publications. The comment on IEEE C2 lookup table is incorrect. ETAP ArcFault was designed to help comply with the requirements on utilities as described in NESC C2 example tables and IT DOES NOT UTILIZE a lookup table approach. ETAP ArcFault analyses the equations derived by EPRI (US) and Terzija and Konglin (Germany Europe) and applies them to a full-networks solution which integrates the actual arc current and the response of both phase and ground protective devices. The methods are fully tested and the resources are available for public domain review. ETAP determines the heat-flux at a unit distance for Line-to-ground faults. To summarize, ETAP ArcFault is not tail wagging anything. It calculates the actual arc current, arc voltage, arc voltage gradients, arc resistance, arc power, arc energy, energy flux, incident energy and all the physical values required for this analysis. It is a full LG arc fault simulator with proprietary methods to also extend to other less likely types of arc faults (such as LL, LLL). In other words, it is a game changer on the arena of Arc-Flash (Arc Fault) analysis outside the range of IEEE 1584 because it has a fully-iterative method with a full-network solution which includes the effect of transmission and distribution system protective devices.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Fri May 11, 2018 6:33 pm 
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Raghu wrote:
ETAP has two methods. Both are fully tested and derived based on physical equations derived from ANSI/EPRI/IEEE (United States) and European recognized organizations and publications. The comment on IEEE C2 lookup table is incorrect. ETAP ArcFault was designed to help comply with the requirements on utilities as described in NESC C2 example tables and IT DOES NOT UTILIZE a lookup table approach. ETAP ArcFault analyses the equations derived by EPRI (US) and Terzija and Konglin (Germany Europe) and applies them to a full-networks solution which integrates the actual arc current and the response of both phase and ground protective devices. The methods are fully tested and the resources are available for public domain review. ETAP determines the heat-flux at a unit distance for Line-to-ground faults. To summarize, ETAP ArcFault is not tail wagging anything. It calculates the actual arc current, arc voltage, arc voltage gradients, arc resistance, arc power, arc energy, energy flux, incident energy and all the physical values required for this analysis. It is a full LG arc fault simulator with proprietary methods to also extend to other less likely types of arc faults (such as LL, LLL). In other words, it is a game changer on the arena of Arc-Flash (Arc Fault) analysis outside the range of IEEE 1584 because it has a fully-iterative method with a full-network solution which includes the effect of transmission and distribution system protective devices.


I'm confused. IEEE C2 is table based. Values below 1000 V are based on laboratory tests. Values at 1000 V or higher are a table which is created using ArcPro. So how can one not do table look up and yet provide values as per IEEE C2 without using ArcPro?


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Sat May 12, 2018 4:13 am 
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[Raghu]
Quote:
It is a full LG arc fault simulator with proprietary methods


This line bothers me as what are these methods? Are they based on actual testing? Are they from a peer reviewed document? What happens in a liability case in a courtroom when you can't defend proprietary methods as ETAP will not provide them or there basis? I don't know about anyone else but a statement like that tends to raise a red flag for me.

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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Sat May 12, 2018 8:26 am 
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Raghu wrote:
ETAP has two methods. Both are fully tested and derived based on physical equations derived from ANSI/EPRI/IEEE (United States) and European recognized organizations and publications. The comment on IEEE C2 lookup table is incorrect. ETAP ArcFault was designed to help comply with the requirements on utilities as described in NESC C2 example tables and IT DOES NOT UTILIZE a lookup table approach. ETAP ArcFault analyses the equations derived by EPRI (US) and Terzija and Konglin (Germany Europe) and applies them to a full-networks solution which integrates the actual arc current and the response of both phase and ground protective devices. The methods are fully tested and the resources are available for public domain review. ETAP determines the heat-flux at a unit distance for Line-to-ground faults. To summarize, ETAP ArcFault is not tail wagging anything. It calculates the actual arc current, arc voltage, arc voltage gradients, arc resistance, arc power, arc energy, energy flux, incident energy and all the physical values required for this analysis. It is a full LG arc fault simulator with proprietary methods to also extend to other less likely types of arc faults (such as LL, LLL). In other words, it is a game changer on the arena of Arc-Flash (Arc Fault) analysis outside the range of IEEE 1584 because it has a fully-iterative method with a full-network solution which includes the effect of transmission and distribution system protective devices.


I've done some further digging here. Back before IEEE 1584-2002 came out Terzija and Konglin published a series of papers on the subject of arc resistance modelling for long free air arcs. Here is one of those papers but there are several others, almost all identical in content, and I'm not even sure how they managed to publish so many since they are almost word-for-word identical among them:
https://ieeexplore.ieee.org/document/1308321/

This is a step. It allows us to calculate the power consumed in a long arc since we have the relationships between voltage and current across the arc (current-dependent resistance). I would go so far as to say that this makes it very easy to estimate arcing current in the context of a utility system. BUT we're still missing the big piece here. Do we simply then take the arc energy calculated with this new formula and apply the area-of-a-sphere model to derive incident energy? Not all the arc power goes into incident energy. Some goes into heating air components, sound, melting components, etc. So we're still a long ways from a complete arc flash model here.

On ETAP's web site other than an advertising brochure that even claims to do arc-in-a-box modelling from 15 to 35 kV, there is basically nothing there indicating what the basis for the model is. EPRI has done some testing and modelling for longer arcs up to I think 12" but again not for voltages above 15 kV. I suppose in the end that there is little difference between the "black box" model provided in the Duke Heat Flux model, the ArcPro model, or the ETAP ArcFault model except that it is known that the Duke model gives consistently lower values than ArcPro and that OSHA 1910.269 specifically mentions and condones ArcPro (and condemns Heat Flux) but that's it for what I see as far as I can find...no "open source" medium voltage arc flash model.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Thu Feb 07, 2019 10:38 am 

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We analyzed and compared the results for both the overhead 115kV transmission line systems as well as 34.5 kV switchgear --- compared varying short circuit current values, voltage magnitudes, conductor gap, 1LG vs 3LG, Fault Clearing times, etc. In this analysis, we would say that that Terzija, EPRI, and Arc Pro had very reasonable results across the board. There were certainly some differences, but it was consistent. Overall, we think that anyone method would provide a reasonable HV Incident energy calculation.

One thing that distinguishes the ETAP ArcFault module is that we can use it for either a single bus or multi-bus system. For example, we were able to simulate faults on various segments of a HV Transmission line to get the worst-case incident energy for the entire line in one shot in a nicely formatted report. Furthermore, the HV ArcFault module is embedded in the native ETAP modeling environment. It was easy to perform HV Arc Flash Analysis for both HV, MV, and LV power system all in one model.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Sun Feb 17, 2019 11:14 am 
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Raghu wrote:
We analyzed and compared the results for both the overhead 115kV transmission line systems as well as 34.5 kV switchgear --- compared varying short circuit current values, voltage magnitudes, conductor gap, 1LG vs 3LG, Fault Clearing times, etc. In this analysis, we would say that that Terzija, EPRI, and Arc Pro had very reasonable results across the board. There were certainly some differences, but it was consistent. Overall, we think that anyone method would provide a reasonable HV Incident energy calculation.

One thing that distinguishes the ETAP ArcFault module is that we can use it for either a single bus or multi-bus system. For example, we were able to simulate faults on various segments of a HV Transmission line to get the worst-case incident energy for the entire line in one shot in a nicely formatted report. Furthermore, the HV ArcFault module is embedded in the native ETAP modeling environment. It was easy to perform HV Arc Flash Analysis for both HV, MV, and LV power system all in one model.


OK so let's say I'm in the U.S. (which is where my customer base is). OSHA recommends ArcPro on what I call the Goldilocks method. OSHA "tested" the Lee model, the Duke Heat Flux Model, and the ArcPro model. On that basis they determines that Lee is "too hot", Duke is "too cold", and ArcPro is "just right". Not that they were comparing it to actual known lab data, just that they were picking the middle value. In a similar direction, you've thrown several more theoretical models out there and also included ETAP's own proprietary modelling. So I'm sure if we compared these all, we'd find that we get more examples of "too hot" or "too cold" but what is "just right" without actual lab test data to compare it to? This isn't a matter of convenience or how pretty the formatting is. It's a matter of what would be considered an acceptable result, one that would stand up to a legal challenge in court if someone was severely injured. OSHA has all but endorsed ArcPro. I don't care how good or easy or nicely formatted or how well ETAP compares to ArcPro, as of right now unless I can show comparison to actual test results, ArcPro is the only model with any kind of endorsement. I find it troubling and I agree that it's not the best software for modern use but it will stand up in court if I point to OSHA's regulation supporting that decision. With ETAP I have to prove the validity of it's modelling compared to ArcPro. I can't do that. ETAP doesn't publish their model (and neither does ArcPro). Without published test data at 115 kV I can't compare either model to actual results. So that means ArcPro is the only viable option at this time from a legal challenge point of view.


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 Post subject: Re: Calculations for 132kV/300 kV
PostPosted: Tue Mar 05, 2019 9:35 am 

Joined: Mon Dec 03, 2018 11:09 am
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EPRI has tested longer arcs and came up with formulas that predicted incident energies better than ARCPRO. See the following:

https://www.epri.com/#/pages/product/000000000001022632/?lang=en-US
https://www.epri.com/#/pages/product/000000000001022633/?lang=en-US

(I wasn't involved in this testing.)


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