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 Post subject: Dynamic Arc ModelingPosted: Sat Feb 04, 2012 9:38 am

Joined: Sat Feb 04, 2012 9:21 am
Posts: 1
I'm trying to study arc flash in the time domain, seeing the arc as a variable impedance. I don't really know where to start... I read a little bit on the subject, and the Cassie-Mayr model seems to be the only one which was developed for electric arc flash.

Do you know of any other model? What are their advantages/limitations? For now, I want my model to work for voltages below 1 kV.

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 Post subject: Posted: Mon Feb 06, 2012 5:14 pm
 Plasma Level

Joined: Mon Sep 17, 2007 5:00 pm
Posts: 1635
Location: Scottsdale, Arizona
For now we look at the model as more of a steady state condition. It really isn't of course but the arc is so erratic, especially at the beginning. We have a lot to do before we move on to a time domain model. About the only dynamic aspect right now has to do with multiple sources tripping sequentially and motor contribution / decay.

Good luck and we would all love to hear your progress!

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Jim Phillips, P.E.
Brainfiller.com

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 Post subject: Posted: Tue Feb 07, 2012 7:23 pm
 Plasma Level

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
R. Wilkins published a time domain model recently. It does not start from the theoretical (Cassie-Mayr) model but is essentially just taking the general shape of an equation and fitting it to the same data set that IEEE 1584 derives from. The result is that it fits the data set better but since there are more parameters, I'm sure that this is to be expected. Not sure what the confidence intervals are on the model at this point.

There are also some strange artifacts in the model that Wilkins points to, but it does at least avoid all the anomalies in the IEEE 1584 models.

The only theoretically derived model in popular use is Lee's 1984 model. This one has a glaring error that voltage and current are treated as interchangeable when clearly it is not the case since voltage drop across the arc is almost constant relative to system voltage. I know the real phenomena is more complex but this is as I said a rough approximation.

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