Arc Flash for DC voltage

[cousy2]

I work at a plant that has 250 Volts DC for the 52 cranes that are in the buildings here and I was wondering if anyone had any information on arc flash protection for this application.

Thanks

 

[kc8dxx]

The arc flash issue is all about identifying the incident energy and the boundary distance, so that appropriate PPE can be selected for the task to be done.

So far as I am aware, the studies that have been done and the guides that have been issued (IEEE1584 and NFPA70E in particular) are for AC only. If someone has knowledge of any standards or reports issued for the arc flash boundaries using DC, I would also be VERY interested in the references.

 

[WDeanN]

There is no "official" arc flash calculations for DC, as of today. I don't think that it arc flash requirements for DC are covered by the 70E, either.

I would suggest level 1 protection at a maximum. The DC arc is harder to maintain, and does not have as much energy as AC, in general, so it is not as dangerous as AC (from an arc flash standpoint) at the same voltage/current. Assuming same voltage AC, level 1 is the probably highest level of protection you would need.

 

[davidr43229]

I would disagree with your assumptions. I would not suggest any level, until an engineering study was preformed, or task defined. While there is no formal math for DC calculations, the NFPA states 50volts and above.
DC may mean battery back up, with 20-40 batteries used with very high Shortcircuit currents.
Because with DC you are not going through 0, I would maintain that DC would sustain an ARC,(harder to inturrupt) and be just as dangerous as AC.
Just my $.02

 

[WDeanN]

I'll concede with david. It would be safer to wait until an analysis was done.
I know I've seen papers on the DC arc, but I haven't been able to find them.