Arc pressure wave

[TMD]

Can anybody offer any direction on calculating the pressure wave that would be produced by an electric arc? As an example, if I have a 10 kA fault current that is cleared in 1/2 sec, is it possible to calculate or are their general guidelines for determining what the pressure will be?

 

[Bung]

I don't think an arc would produce a significant "pressure wave". It isn't an explosive phenomenon. It could cause an explosion of other material (eg vapourised oil), and perhaps by heating other gases in a confined space to the point where the increased pressure causes rupture of whatever is confining it.

I would just treat the arc as a sustained ignition source, and see how the arc energy affects the surroundings. But it all depends a s much on the surroundings as on the arc itself.


Bung
Life is non-linear...

 

[umrpwr]

TMD

The only paper I have seen that addresses that topic was written by Ralph Lee. It offers some guidance for calculating pressures developed by arcs. The paper is titled Pressures Developed by Arcs and was published in IEEE Transactoions on Industry Applications, Vol IA-23, NO. 4, July/August 1987.

 

[PWR]

The 2004 NFPA 70E electrical safety standard does not address
working where the arc flash hazard exceeds 40 cal/cm2. One of the prinicipal reasons it does not do so is because while you can protect against greater radiated heat energy, it is unknown what damage would be done by the mechanical blast forces such arcs will produce. The NFPA Research Foundation has a task force investigating that and other related phenomenon. I don't know if there is any good source of information available at present. For your example, depending on working distance, arc electrode spacing, size of the "box" where the arc occurs, and 30 cycles duration you probably have a "blow the doors off" type situation.

 

[alehman]

The pressure wave can be quite substantial. Arc flash pressure waves have been know to throw workers many tens of feet and cause hearing injuries. IEEE 1584 and NFPA 70E don't presently address this hazard. This article discusses pressure waves.

http://www.ecmweb.com/mag/electric_putting_arcflash_calculations/

 

[TMD]

Very good information. Thanks to everybody. I've located some papers and other info which I will post later, when I'm back at work (holiday until May 3. Yoo hoo)

 

[umrpwr]

There is another article you may want to check for information. I just received my issue of IEEE Industry Applications Magazine and they have an article in the current issue that deals with topic of pressures developed from arcs as well as some additional references at the end of that article. The article is titled Shrapnel, Pressure, and Noise By Thomas Neal and Roger Parry. It is in the current issue of IEEE Industry Application May/June 2005 Vol. 11 No. 3 pp. 49-53.

 

[TMD]

The papers I mentioned in my Apr 23 post (for completeness):

A Calculation Method for Pressure Waves Due to Arc Faults, Dasbach and Pietsch (source unknown)

Pressure Waves Due to Arcing Faults in a Substation, Drouet and Nadeau, IEEE Trans. Power Apparatus and Systems, Sep/Oct 1979

The Calculation of Overpressure in Metal-Enclosed Switchgear Due to Internal Arcing, Lutz and Pietsch, IEEE Trans. Power Apparatus and Systems, Nov 1982