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.