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 Post subject: Determining Temperature rise during arc eventPosted: Fri Mar 25, 2016 2:12 am

Joined: Thu Mar 24, 2016 3:34 am
Posts: 2
Good morning all,
I am currently investigating the damage caused to a fully sealed enclosure as a result from an arc event.
I am looking to find if there is a general equation relating to an arcing temperature rise to the increase in pressure within an enclosure.
I am aware of Ralph Lees method:
Lbs/ft² = ((11.5 x I_a/1000 ))/〖(Distance in Ft)〗^0.9
But looking for any information on how to determine the temperature rise due to an arc flash, and then in turn i can calculate the pressure rise and simulate the damage using a FEA software .
Any help would be greatly appreciated!!!
Thanks guys

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 Post subject: Re: Determining Temperature rise during arc eventPosted: Mon Mar 28, 2016 4:37 am
 Plasma Level

Joined: Tue Oct 26, 2010 9:08 am
Posts: 2174
Location: North Carolina
Nothing on temperature rise. Ralph Lee's equation is based on open air arcs so is not applicable. All sealed box models are linear with time and for the most part are linear with arcing current. Look at the CIGRE. modelling work for arc resistant gear and a few other places. There is one paper that duplicates what you are looking for but is specific to motor termination enclosures (peckerheads). There is also existing research on the amount of material burned/melted by arcs in air.Temperature is quite variable even in an open air arc. You can't reliably measure temperature above about 2000 K so it's all theoretical measurements. Above 4000-6000 K air dissociates so it absorbs a lot of energy which makes simple Boyles Law stuff worthless. The arc column itself is very small...1 mm and pure plasma. It is surrounded by a cloud of plasma and that's where most of the energy goes. So the models are mostly based on pressure and a few look at internal energy which gives you temperature indirectly (PV=nRT for ideal gases) and many dispense with this and assume adiabatic conditions to remove temperature/real gas energy conversions.

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 Post subject: Re: Determining Temperature rise during arc eventPosted: Tue Mar 29, 2016 9:54 am

Joined: Thu Mar 24, 2016 3:34 am
Posts: 2

I have had a look at your suggested papers and have helped.

Thanks again

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