technology gaps in arc flash study?

[cooldesign]

i have been looking through arc flash last 4 months, and i am kinda trying to figure out what is missing in arc flash calculations? in my mind, DC arc flash, single phase arc flash, etc. can you give me a few name in your mind? what is the technology gap for industry or engineer need to fill out? lets discuss and see where we lead them.

 

[zog]

Have you read the 2012 70E?

 

[cooldesign]

i havent read it yet. they address lots of technology gaps? can u address a few? do u have link to download that standard?

 

[zog]

Not sure what you mean by "technology gaps" but DC arc flash is addressed. You can download it from the NFPA website.

 

[cooldesign]

i mean what is not clear by saying technology gap. for example, single phase arc flash is not clear, but everyone comes up with their own assumption. is it any technology gap like that?

 

[iceworm]

i mean what is not clear by saying technology gap. for example, single phase arc flash is not clear, but everyone comes up with their own assumption. is it any technology gap like that?

In addition to NFPA 70E, I recomend you read IEEE 1584. It is a proprietary document, so no I don't have a link. However, you are a student. I recomend you go to a university library. I'm certain they will have access.

Now, let's look at what is not clear about this issue of "technology gap" - cause I don't know what that means either.

First:
Arc-flash calculations are based on a mathematical model derived from emperical lab test data. Like all math models, it must be applied within its limitations. The model just is not valid outside the limitations. Maybe this is what you are talking about - I can't tell from your questions.

Second:
I respectfully suggest that after you have completed your reading - come back and ask your questions again.

ice

 

[iceworm]

i have been looking through arc flash last 4 months, and i am kinda trying to figure out what is missing in arc flash calculations? ...

Another thought just occured to me that could help understand what you are looking for;

As you said, "i have been looking through arc flash last 4 months ...". What exactly have you looked through or read? That could give some clues as to what you are thinking.

ice

 

[charlie b]

I have not read the 2012 70E yet. But my understanding is that all of the information we have on arc flash came from experiments in which someone blew up a bunch of equipment, measured a bunch of stuff, and came up with equations that described what they observed. In other words, the equations used to calculate the arc flash energy are all empirical. So if nobody has yet blown up a single phase panel, then there are going to be no equations that describe the arc flash hazards of a single phase panel. If you want to call that a ?technology gap,? then go ahead.

Last I heard, there were no equations for DC systems, single phase systems, systems rated lower than 208 volts, and systems rated higher than 15,000 volts. Perhaps some additional experiments have been done recently, and additional systems are now covered by arc flash equations.

 

[cooldesign]

thanks charlie, that is what i meant by "technology gap". i already read IEEE standard. i just search through forum, and look through question people asked, i came up with DC arc flash and single phase arc flash equation is not in standard yet.(i think Dc is now). so how people make it to standard? they just test and come up with their assumptions. some thing is not make me feel comfartable. for example, when we calculate clearing time why we took %85 if fault current, why not %84 or %86? i think that these kinda questions dont have answer.

 

[charlie b]

Don't underestimate the testing process that goes into development of the arc flash equations. I may have made it sound trivial, but it is very scientific, and very expensive. As to why 85%, I heard an explanation of that once, but I forgot it. I wouldn't mind relearning the answer to that mystery.

 

[zog]

Don't underestimate the testing process that goes into development of the arc flash equations. I may have made it sound trivial, but it is very scientific, and very expensive. As to why 85%, I heard an explanation of that once, but I forgot it. I wouldn't mind relearning the answer to that mystery.

I beleieve IEEE 1584 had a $12M budget for the DC arc flash testing they recently conducted.

 

[zog]

thanks charlie, that is what i meant by "technology gap". i already read IEEE standard. i just search through forum, and look through question people asked, i came up with DC arc flash and single phase arc flash equation is not in standard yet.(i think Dc is now). so how people make it to standard? they just test and come up with their assumptions. some thing is not make me feel comfartable. for example, when we calculate clearing time why we took %85 if fault current, why not %84 or %86? i think that these kinda questions dont have answer.

Here is some good reading for you, Jim is a friend of mine and also a IEEE 1584 commitee member, he has some good info on his site regarding single phase and DC arc flash studies. You can download his 3 part series on how to perform an arc flash study from his site and I also highly recommend his book "Arc flash hazard calculations"

http://www.brainfiller.com/main/Default.aspx