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 Post subject: EPRI Distribution Research Arc Flash
PostPosted: Tue Mar 15, 2011 3:04 pm 

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Interesting video:
http://www.youtube.com/watch?v=fZP47mlELSc&feature=related
EPRIvideos on Feb 16, 2011


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PostPosted: Tue Mar 15, 2011 4:31 pm 

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Clothing performance

Interesting statement from the one gentleman at EPRI who said clothing doesn't perform as rated. I've heard this stated informally by arc flash experts, but it will take professionals willing to take a stand like this gentleman and say, "This clothing didn't perform as rated". Thanks for the reference to the video.


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PostPosted: Wed Mar 16, 2011 6:30 am 
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twm22 wrote:
Interesting statement from the one gentleman at EPRI who said clothing doesn't perform as rated. I've heard this stated informally by arc flash experts, but it will take professionals willing to take a stand like this gentleman and say, "This clothing didn't perform as rated". Thanks for the reference to the video.


It is a correct statement for some instances. I have been quite active in Europe working on this issue. I can not divulge any info yet due to confidentiality but it is being addressed (although slowly). The problem stems predominantly from arcs that are more of a blast out of an enclosure with significant plasma.

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PostPosted: Wed Mar 16, 2011 2:09 pm 
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Couple of observations:'
1. the clothing in the video appeared to be tightly bound across the thermal sensors. Loose fitting would probably have performed better.

2. Doesn't the ANSI test performed on the clothing stipulate that there is only a 50% probability that the interior of the garment will not exceed 1.2 cals, or that the garment will not be torn open - which ever comes first. With a 50% probability, that means half those tested will exceed the 1.2 cal limit. This is something that needs to be accounted for and I believe there are multipliers to do this. Wonder how the results would have differed if the multipliers were applied to a 80% probability.


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PostPosted: Wed Mar 16, 2011 6:33 pm 
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Need for more research

Marcia is on NFPA 70E and ASTM F18. The research EPRI is doing will make medium voltage powerline energy levels better known. The issue of clothing performance is not anything we don't know. ASTM F18 has been working on a "better" clothing test but this isn't going to be easy. The current test is mostly IR. The problem is IF you do a plasma test only, you will have to add a lot of protection. If you do an IR test only you will think you are better protected.

We have a test in ASTM right now that is almost pure plasma, ASTM F2676 for blankets. The IEC has two tests, neither are perfect. If you use the IEC 61482-1-1 test it is the same as ASTM F1959 (this was taken from the research word for word) and you have a low level of plasma until you hit about 20 cal/cm2. Greater than 20 cal/cm2 the ASTM F1959 has lots of plasma too. This is why clothing systems in IEC 61482-1-2 (Box Method) Level 2 (even though the copper calorimeters say it is 12 cal require about 25 cal in ASTM F1959 to pass). ASTM F1959 test was developed around a powerline fault like most of the EPRI testing. The IEC 61482-1-2 test uses 600V in a box. This test was built around a meterbase. This is like Marcia's PG&E testing. Neither test is bad. The standards committees, IEEE 1584 and NFPA 70E have to get to understand what the clothing tests tell them and don't tell them. Anyone who thinks you will not ever be burned in an 8 cal arc calculated by IEEE 1584 or ArcPro doesn't understand the test methods or the calculation standards.

There really are advantages of arc rated clothing.

With arc rated daily wear you basically prevent ignition of clothing. You take your risk of dying from 50% to 5%.

If you want to protect from all hazards you will need to move to 40-100 cal systems that can take plasma hits. The best items for this are unpermeable today so arc-rated rainwear, arc-rated faceshields rubber gloves etc. The reality is that arcs are very focused events. If you put a small piece of cloth over a sensor in the worst part of an arc you are really going to worry about the clothing. If you put the clothing on a mannequin and look at the whole system you will understand that with one layer you MIGHT get burned in a small area (less than 25% of the body is painful but rarely life threatening). If you want NO body burn, wear 40 cals all day long head to foot and 95% of you will never get burned. If you want to reduce fatalities and prevent most burns, do what we have been doing and find tweaks. Interesting that electrical fatalities have dropped more than 60% since 1994 when OSHA implemented the arc flash clothing standard. More than 50 fewer deaths in 2009. Could that have been because folks started moving more and more to imperfect arc-rated clothing??? I think that is part of it.

The future of standards for clothing testing is a mix test: Plasma rating and arc thermal rating. The real need is to have better hazard assessment information. That is why I support EPRI and IEEE/NFPA partnership's research. Wish I was more on the inside but they have highly intelligent folks and there is so much to do.

The implication that the clothing doesn't perform to the rating is a little concerning to me since it might make folks think they should stop wearing it. Don't EVEN think that. It isn't perfect but is WAY better than playing games with heavy cotton etc. We are moving the right way. Love to see EPRI and IEEE/NFPA combine forces. I can say all of us on ASTM support it. We have shared our 15 years of data with both groups for free. It is true that the clothing doesn't perform in plasma as you might expect from arc ratings but the copper calorimeter isn't a good way to measure plasma effects outside the clothing. IEEE, NFPA and EPRI haven't focused on the sensor as much as they probably should. The IEEE/NFPA partnership folks to spend money on developing ceramic or other sensor technologies for incident energy in plasma arcs. They did improve the copper calorimeter to our knowledge but I haven't seen anyone working on a non-conductive ceramic except DuPont for the US military. Copper works fine UNDER the clothing but isn't the best thing for plasma. It is interesting that EPRI and IEEE/NFPA have now both made statements criticizing the ASTM or IEC test methods but they have spent millions on their research and we have spent thousands. We wouldn't have ANY arc rated clothing today without ASTM arc tests and they are the best thing we have today. Let's make it better but don't let the best become the enemy of the really, really good!


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PostPosted: Tue Mar 22, 2011 8:38 am 
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I was hesitant in my first post to open up a big can of worms until more is resolved but here is more of the story. I am a member of the IEC 61482-1-2 (box test) committee that was referenced. I have been spending a lot of time in Europe working with this committee as well as various other groups (6 trips last year - about 5 weeks total).

The test method of the IEC 61482-1-2 Standard uses a different approach. Instead of an open arc, a small plaster box is used that focuses the arc towards the fabric. The focused arc is rich in plasma. The box is made of plaster to minimize outside electromagnetic influences of a metallic enclosure and makes the test more repeatable. The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode.

We have been working on a revised version of this standard and it is almost completed. The test parameters use a lower voltage 400V and currents of either 4 kA or 7 kA which seem low…. Until you see the result. It produces a significant amount of plasma right at the garment.

The ASTM method in the U.S. is still a great method and the people that have invested their time and expertise in it should be commended. However like anything else, the more we learn, the more we realize things need to continue to evolve and the plasma issue is one that is taking us all in new directions.

I agree with the previous comments, it is better to use what we have now which is quite good and not wait for something better to come along.

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PostPosted: Tue Mar 22, 2011 10:11 am 
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Eli, that was a very informative post regarding the ASTM testing. I hope you come back with more details like that. Can you even elaborate on the 50% probability of greater than 1.2cals and why that value was chosen and not something higher. Also, why rate at the 1.2 cal versus the blow open point, and not two seperate tests. Which one is being hit first in the field.

With regard to the reduction in fatalites, I am positive that arc flash clothing was a substantial contributor, but statistics in small number sets just don't work. So there could have been many other factors that reduced the number of deaths.

In the electric world I live in Arc Flash has not penetrated the small industrial market as much as it should. Many companies are either ignorant, or resistant to implementing an arc flash program. Probably because of the cost.


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PostPosted: Tue Mar 22, 2011 11:19 am 
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IEC 61482-1-1 vs. IEC 61482-1-2

I addressed the issue of 50% probabality of second degree burn in my newsletter today (unrelated). Some in the EU have been stirring up negative statements about the IEC 61482-1-1 and ASTM F1959 standard. I believe these are unwarranted.

Just to set a few things straight. I have been on both committees (box and arc rating) for about 10 years. I also travel to the EU several times each year to attend committee meetings for TC 78 and ISSA in Germany. I might have missed the last one but this method is not new. It was designed about the same time as the ASTM method but the EU has tried to use the arc test believing that those two parameters are the worst case scenario. The box test was designed originally for German utilities who were having arc flashes from home service meters. They built a box. The ASTM test was designed by US electric utilities who were having clothing ignitions on line workers so they built a line. What we did first in the US and took years to do on the box test was, we added calorimeters and did a statistical test so we weren't slave to set up. If we measure the energy around the arc at a panel, mannequin etc, we don't have to have a perfect set up. We know what the energy is and we can raise and lower it until we find the Stoll curve cross over. Until just a few years ago the EN/IEC Box test didn't have any calorimeters. They just looked at the fabric and a t-shirt underneath and passed or failed things. This method is why the EU still has a faceshield standard that says, "you don't have to measure anything. Just make the faceshield polycarbonate this thick and it is OK". Not the exact words but this is still in the EU standard and had no calorimetry under the shield to see that the face was burned. Now they know and are working on a new standard but the statement is still there.

I have been on an ISSA committee on this issue for about 10 years. The politics are complicated but the standards are pretty clear. At 4 kA you don't get much plasma. You do get a more focused arc. At 7kA, they are getting closer to the arc current front but I seriously doubt they even get "plasma" there with the low voltage arc. It is very tough to get plasma to eject 30cm at that voltage from a 300mm arc at 600V. On this method being more repeatable, I haven't seen a study yet that it is close to the ASTM method in repeatablity. One lab has it down and they are very repeatable. I have received fabrics many times which passed one lab in the box test, failed another lab and they just decided to send to us to get something with a precision statement.

How you build the box and everything makes so much difference on the box test. I like the idea but repeatability is something that all those labs have struggled with. Dr. Schau has the best handle on repeating at his lab but this method is not statistical in testing. It has NO measurements of energy when the fabric is is place so you have to TRUST that it is getting the same energy as its calibration shot. It is a great test IF you know what energy it is putting out. I got the calorimters added by pressure since it was something they hadn't worked with. Dr. Tom Neal and others have tried to use a box on a similar test and see interesting results.

I think there is a lot of learn from plasma rich arcs but switching to the EU method is not the answer. FAR more research has gone into IEEE 1584 and ASTM test methods than anywhere else. I see consultants getting $$$ to challenge our tests but they never participate in our committees. Wonder why that would be. "People get the standards they deserve" a good friend in AU said to me recently. I think he is right. If anyone is interested in this subject, join ASTM and IEEE 1584. Donate money and let's make those great.

Those who do calculations have the ASTM method with a long history and many fabrics. The plasma rich point hasn't been looked at hard enough yet. Are copper calorimeters going to measure plasma energy accurately or wash out (I believe we have the answer to that).

Our IEEE 1584 numbers are based on the copper calorimeter and our ASTM testing uses the copper calorimeter to measure the actual arc flash. The fact that the clothing in real life accidents back checking to IEEE 1584 is working means what we are doing is good. I wouldn't be worried in the least. Is there more to learn? Absolutely. I haven't seen any changes in the box method that would make me think it will be better than the ASTM method. It has more plasma in the 7 kA than we do up to about 20 cal/cm2 but at that point the two have strong plasma current fronts (probably not plasma) which make them start eating fabric. I have supported research to state that the box test 7kA is more like 25 cal/cm2 ASTM arc (even though their sensors measured closer to 12 -18 cal. This was in a draft of the standard but was left out of the published version for political reasons). The 4kA arc looks more focused than ours but the fabric results are about 4-8 cal as the original data the IEC box test labs produced. Much work is being done on both methods but neither is perfect. No "can of worms" but when you really study both methods and sit on both committees you will see both offer much. Sorry to respond but "everyone sounds right until someone comes forward and questions him". Sounded like brainfiller was stating the IEC Box Method might be "better" because it had more plasma. I'd challenge "better" and say "different at certain levels". If you want plasma, we can give you plasma!

I still say we could see a more plasma rich test method in the future but at 20-100 cal you get a lot more plasma in the ASTM test than at 8 cal. Most single layer fabrics pass box test Level 1 (4kA) and multilayer fabrics are usually needed to pass Level 2 (7kA) in the box test. But what if you have more than 7kA? Or what if you need more than 12-25 cal/cm2? Some work has been done to see how far the box test can be extrapolated but it has limits unless you move the samples closer. That hasn't been done to date. I'm fine with using box testing IF that gets done but I haven't seen much to date. It is popular in the EU because it can be done at more labs but the cost is the same as the ASTM test, it hasn't been as repeatable intra lab and it has a real upper limit well below the 40 cal/cm2 commonly used in industry.
Because the ASTM F1959/IEC 61482-1-1 tests use calorimeters in every shot to measure the incident energy we can measure energy at every level. I'm all for the box test. But ONLY if those proposing it address its limitations rather than just "singing its praises". It does make cool videos though.


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PostPosted: Tue Mar 22, 2011 11:32 am 
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haze on Number sets

You are so right. The other problem is we don't have ANY OSHA numbers on arc flash deaths. The only numbers are from EDF in France and they haven't done numbers AFTER they added arc rated clothing. But they did use the numbers to justify moving to arc rated clothing.

I can say anecdotally I used to get lots of bad burns in law suits but now we see many more folks saved from any burns.

The IEEE ESW paper by Dan Doan, Tom Neal and I tabulated this clearly. Folks wearing 70E or IEEE 1584 matched clothing walked away with little or no burns. Those who didn't died or were very badly burned.

I think Jim has it right above. Don't wait for something better. Do the right thing with what you have today.

I know we could be losing manufacturing jobs but we aren't losing electrical linemen or electricians last time I looked. Shovelers are going but mechanizers, repair persons and power lines are on the rise. If things weren't getting safer in the electrical world we wouldn't be seeing the fatalities down by more than 60%.


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PostPosted: Tue Mar 22, 2011 2:11 pm 
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elihuiv wrote:
Sounded like brainfiller was stating the IEC Box Method might be "better" because it had more plasma. I'd challenge "better" and say "different at certain levels".


Where did I say better? The only use of better was in my last sentence which was agreeing with your last sentence.

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PostPosted: Tue Mar 22, 2011 2:17 pm 
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elihuiv wrote:
I'm all for the box test. But ONLY if those proposing it address its limitations rather than just "singing its praises".


The limitations of the box test, specifically with regard to the measurement end, is why I have been working with several of the committee members for many years and was ultimately asked to be on the committee. Most of the people that are on the box test committee would probably agree, I have been quite vocal about the box test short comings both in the meetings and at my trips to the various labs.

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PostPosted: Wed Mar 23, 2011 1:26 pm 

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Can you clarify "The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode."? Are these the arcing electrodes? Is the current passing through a copper electrode in series with an aluminum electrode? Copper and aluminum have different characteristics. Why not two of the same metal?


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PostPosted: Wed Mar 23, 2011 1:30 pm 

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"The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode."

Can you clarify "The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode."? Are these the arcing electrodes? Is the current passing through a copper electrode in series with an aluminum electrode? Copper and aluminum have different characteristics. Why not two of the same metal?


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PostPosted: Wed Mar 23, 2011 2:02 pm 
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ZeroSeq wrote:
"The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode."

Can you clarify "The two electrodes that make up the vertical arrangement consist of one copper and one aluminum electrode."? Are these the arcing electrodes? Is the current passing through a copper electrode in series with an aluminum electrode? Copper and aluminum have different characteristics. Why not two of the same metal?


There are two answers. The "offical" answer that we are told it this addresses both copper and aluminum with one test. Aluminum on top, copper on bottom. The test was developed by a few German people.

The "unoffical answer" that I have been told by a few European sources is more political. From what I understand, with the standard having its origins in Germany, the former West Germany used mostly copper wiring and East Germany used mostly Aluminum wiring. I'll let you draw your own conclusion.

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PostPosted: Wed Mar 23, 2011 2:25 pm 

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It's been a hard lesson to learn but politics usually trumps science.


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PostPosted: Wed Mar 23, 2011 2:44 pm 
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ZeroSeq wrote:
It's been a hard lesson to learn but politics usually trumps science.


I'm still working on that lesson. :)

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PostPosted: Wed Mar 23, 2011 8:29 pm 
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Two Electrodes

The mentality of the IEC Box standard was to use two different metals because the lines in a home meter in the EU often is AL on one side and copper on the other side so you do actually have two metals in an arc. The reasoning, and it is sound, is that if you get different metal spatter you might see if cloth has a different response. They have had to work on the shape of the electrodes quite a lot to get things stable. I believe they still drill a hole into the center of the electrodes to get a burning part to spray out better. In the ASTM standard we chose a different route after a lot of work which was published inside the committee. We found in the ASTM method that the copper cloud blocked energy and was negative for the workers. We got MORE energy from the stainless so we opted for that. If you focus the arc and you can get the metal spatter to be consistient, that gives you good info on that piece but the trade off is that you have a little nastier work environment. We chose energy over spatter since we didn't see a lot of issues from spatter on flame resistant materials. When both standards were working with testing non-FR cotton, spatter did make a difference in ignition so more spatter is better IF you are testing non-FR cotton. We switched to only testing FR materials long before the EN standard (later the IEC box method) did so we realized the spatter wasn't a better predictor or performance. Not against spatter testing but it is much more important in non-FR performance than in FR.


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