Venting of Short Circuit Arc Fumes 1

[kevd]

I am designing packaged electrical equipment for use in marine offshore or vessel applications and my client has asked me how much volume of space he should allow behind or on top of the equipment for the vented arc gases that could be released in the unlikely event of an electrical short circuit occurring and the gas relieving through the arc flaps being fitted into the equipment.
How do you calculate the volume of gas generated in an electric flashover?
What is the composition of the gas?
What is the maximum temperature of the gas?

Thanks

 

[tmahan]

Although I am not qualified to answer your question I think that you may get a faster response from those who are if you provide some additional information such as system voltage, and current as well as available fault current. This will detrmine the maximum available energy and therefore will have a large impact on the volume, and temperature and therefore composition.


That said though Idle speculation leads me to believe:
The composition of the gasses will vary on what is in the equipment experiencing the fault but will include copper, ozone and combustion byproducts of any insulation materials and any plating material such as silver or tin.

As for the rest lets hope some here is qualified to more than speculate as I have done.....

 

[mpparent]

Kevd,

Look for a paper written by Ralph E Lee, 1982 for IEEE. It answers some of your questions. It doesn't talk about the volume of gas generated. It does go into detail about temp. of gas, which is proportional to short circuit current available. Unfortunately, there is not a lot of info. on arc blast.

Good luck,

Mike

 

[busbar]

It is remotely possible that these links may useful.

http://www.arcwear.com

http://groups.yahoo.com/group/arcwear/

This work has evolved as addressing the cited RH Lee paper. Hugh Hoagland seems very dedicated to and qualified in the effects of electric arc-blast propagation.

 

[kevd]

Thanks for input so far.
As advised by tmahan, system info is
4160V, the switchboard is rated for 50kA/125kA. The theroetical fault level at the board is 20kA/110kA with all geneartors running.
I have found the late R Lee" paper as recommended by mpparent and another one from 1986 which talks about the internal pressures, maximum arc energy for a given fault level, etc. Very useful.
The main gas composition is copper oxide (or Al oxide if aluminium busbar or Iron oxide).
However, there appears to no easy calc for volume of gas released. The nearest I have gotten is copper expands 67,000 times as a gas and I have an estimate of copper loss given an exposure to an arc. How much does the air heat up and expand?
Any other tips or web-links would be appreciated.

 

[kevd]

Correction to above theoretical fault level is 40kA/110kA. I was typing in the dark!

 

[busbar]

IIRC in an informal conversation with Mr Hoagland, he has found the RH Lee assumptions and calculations to be somewhat high compared to those yielded in more recent testing.

 

[busbar]

Another related paper by RH Lee is Pressures Developed by Arcs, IEEE Transactions on Industry Applications, V23N4, pp.760-764, Jul/Aug 1987