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 Post subject: Arc Pro Multipliers
PostPosted: Fri Apr 04, 2014 4:47 am 
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Does anyone know the basis for the multipliers that Arc Pro uses for situations outside of an open air, vertical, single phase fault?

The Help menu lists the following multipliers:
1 phase in a box.....1.5x
3 phase.................1.2 to 2.2x
3 phase in a box.....3.7 to 6.5x

I have asked Kinectrics and am awaiting a response but maybe somebody has already done that.

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PostPosted: Wed Apr 16, 2014 10:47 am 
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Just an update: I have not had any response from the people at Kinectrics to my email, nothing at all. So far, I am not impressed with support.
As soon (if) I get a response, I will post it here.

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PostPosted: Thu Apr 17, 2014 7:57 am 
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For those interested, here is the response I received:
We did testing at our high current laboratory and compared the results against Arcpro when deriving the multipliers. We believe they compare pretty well to IEEE 1584 as well.

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PostPosted: Thu Apr 17, 2014 10:41 am 
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I really only have two issues with using ArcPro:
1. Whatever the algorithm is, it is not documented anywhere so no way to validate any of it.
2. The range on the multipliers is almost a factor of 2.

That being said, bbove 15 kV the choices are Lee (invalid and grossly overestimates), Duke Heat Flux (same issues as ArcPro, and produces unrealistically low values under 15 kV where it can be validated), and ArcPro. At least ArcPro seems to compare favorably with test data.


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PostPosted: Thu Apr 17, 2014 10:50 am 
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Well, I agree and that is why I am questioning some of this. The other item I have discovered with Arc Pro is the Current and Clearing times that are inputted into the program are supposed to be the arcing current and clearing time but that is not clear in the documentation. So, when one receives the fault current and clearing time from the utility's engineering group this is the bolted fault current and corresponding trip time. One must then use the formula in IEEE 1584 to calculate the arcing current and either submit that back to the utility to get corresponding trip time or have the TCC for their protective device plus any operating time of breaker and/or signal response times.

From a recent email from Arc Pro:

Yes, you will need the time-current curve of the protective device to attain the clearing time with your arcing fault current.
For Arcpro, you will input the arcing fault current and the corresponding fault clearing time.

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PostPosted: Fri Apr 18, 2014 5:06 am 
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All,
I received the following from Stephen Cress of Kinectrics. Mr. Cress joined this forum but is unable to post for awhile as a new member, so I will post what he wanted below. I hope that Mr. Cress will visit the forum periodically as his insight would be valuable.


As a co-developer of Arcpro, my apologies for the delayed response to Barry's e-mail. I would encourage anyone to ask us at Kinectrics if you have questions on Arcpro and we'll provide you with a factual answer. Call me at 416-207-6557 if you wish to discuss. Kinectrics is the Consulting Engineering and test lab where virtually all of the North American testing is done to establish ATPVs. We have conducted arc hazard assessments for some of North Americas largest utilities. We also provide Courses on the proper application of most of the arc hazard analysis techniques available.

Regarding the Factors: first please be sure you are using the latest set of factors from Disk 2 on your Arcpro CD. The factors referred to by Barry from the Help Menu have been refined to reduce the range based on comparisons with test data. When we are discussing the factors we are referring to this upgraded Table.

The basis for the factors is an engineering analysis of all published test data both from Kinectrics and IEEE and a comparison of this with Arcpro outputs. Arcpro models single arcs, either phase to phase or phase to ground, so without the factors it produces results applicable to single arc situations. Note that IEEE1584 models only 3-phase situations. Essentially the factors adjust the output of Arcpro to yield the best match to the 3-phase and in-box test data that exists. Feel free to call if you wish more detail.

On the subject of Arcpro algorithm and equations - there are 6 references in the Arcpro manual that provide the base peer reviewed engineering papers upon which the methodology is based. Unlike most of the other methods that are simple single equation curve fits to test data Arcpro is a finite element analysis iterative model of arc plasma, its conductivity and the radiation and convection from an arc. The theory and equations are readily available in these published papers. It is correct to say that the Arcpro equations are not simple - but they are available

Yes Arcpro requires the arcing current. On medium voltage systems it is reasonable to assume that this is equivalent to the bolted current. On low voltage systems the arcing current can be as low as 40% of the arcing current. A proper engineering analysis would involve putting the arc resistance in your symmetrical component model and determine the resulting arc current. Arcpro tells you what that arc resistance should be. Please beware with IEEE 1584 equations that compute arcing from bolted current. Under certain conditions the results will yield the result that arcing current is greater than bolted - clearly incorrect. A circuit analysis approach is more accurate. In our Course we show some simple engineering ways to determine arcing current.

The Lee formula - while valid for the test results it was deigned to emulate - is clearly incorrect for high voltage applications.

IEEE 1584 - while valid for relatively small arc gaps for which it was derived is clearly incorrect for large arc lengths ie certainly anything 2' or greater.

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 Post subject: Re:
PostPosted: Sun Dec 14, 2014 1:57 pm 

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[quote="wbd"]Regarding the Factors: first please be sure you are using the latest set of factors from Disk 2 on your Arcpro CD. The factors referred to by Barry from the Help Menu have been refined to reduce the range based on comparisons with test data. When we are discussing the factors we are referring to this upgraded Table.[/font][/color][/i]

Would someone please post the updated ARCPRO adjustment factors? My ARCPRO help menu lists the factors as noted within this original post. Please let this forum know what the updated factors are.


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 Post subject: Re: Arc Pro Multipliers
PostPosted: Sun Dec 14, 2014 2:11 pm 
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The updated multipliers are contained on the CD with the program but I have attached it here.


You do not have the required permissions to view the files attached to this post.

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 Post subject: Re: Arc Pro Multipliers
PostPosted: Sun Dec 14, 2014 2:27 pm 

Joined: Wed Jun 24, 2009 4:45 pm
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Thank you very much for sharing this info.


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 Post subject: Re: Arc Pro Multipliers
PostPosted: Thu Dec 03, 2015 8:52 pm 

Joined: Mon Jan 31, 2011 2:53 pm
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Hi, someone knows the cost of the arcpro software?


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 Post subject: Re: Arc Pro Multipliers
PostPosted: Fri Dec 04, 2015 4:23 am 
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Not sure what cost is now but it is around $2000. It is very specific for the type of use in that it is Open Air, SLG type faults.

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 Post subject: Re: Arc Pro Multipliers
PostPosted: Fri Dec 04, 2015 7:20 am 

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Thank you very much


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 Post subject: Re: Arc Pro Multipliers
PostPosted: Sun Dec 06, 2015 9:03 pm 
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Perhaps the ArcPro multipliers are based on R. Wilkins "Simple improved equations for arc flash hazard analysis". According to the article, the equation for an arc being focused out of an enclosure is:

Eibox = K * Earc/(A*A + D*D),

where:

Eibox - incident energy from an arc flash in a box at distance d in J/mm2
Earc - arc energy in Joules
D - distance from the arc source in mm

A and K are obtained from optimal values defined in the paper and vary for different enclosure types and system voltages. The incident energy for an arc in open air ca be calculated based on the following equation:

Eiair = Earc/(4 * pi * D*D),

As an example, the reported A and K are equal to 400 and 0.312 for low voltage switchgear. Hence, the Eibox/Eiair ratio varies between 1.1 and 3.0 for working distances between 10 and 30 inches respectively.

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 Post subject: Re: Arc Pro Multipliers
PostPosted: Wed Dec 09, 2015 8:12 am 
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arcad wrote:
Perhaps the ArcPro multipliers are based on R. Wilkins "Simple improved equations for arc flash hazard analysis".


Simply put, I doubt it. First, the multipliers in ArcPro predate Wilkins calculations. They have been around since the software was published back in the 1990's.

The vague hand waving that ArcPro documentation gives is that the multipliers are based on internal data at Kinetrics. Since they do the overwhelming vast amount of arc flash testing, you can imagine how they would collect a huge amount of very proprietary data over time. The problem though is that the owners of the data in the majority of cases would not allow it to be published, even if it was sanitized or aggregated in a way that it hides the underlying source. Even trying to liberate data is frequently time consuming.

Thus I'm sure that this data exists within Kinetrics but faced with the daunting task of publishing it, they had two choices. Either publish a value totally unattributed to anything with lots of handwaving and no attribution whatsoever (which is what they did) or don't publish anything at all and give no guidance whatsoever to the customer.

That being said, I agree that a 2:1 range on the values makes it pretty vague at best.


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