I am working with a client on an Arc Flash study and the client asks me if I can simplify the study for the 956 DC cathodic protection systems they have.

Can I apply worse case incident energies for each rectifier type? I am not sure if this is okay by code since I am not calculating the incident energy for each case.

Is there any cutoff where there would be no risk of arc flash? About half the systems are below 100VDC.

Thanks

Kinetrics did some testing for Duke for DC battery systems. They were unable to get above 1.2 cal/cm2 (really even sustain an arc) at 130 VDC with up to 20 kA of available fault current and a 1/4" or less arc gap. That's not a normal arc gap at that voltage. And that is not a typical available fault current even for a substation 60 cell battery. At or below 28 VDC using Hertha Ayrton's equation it's not possible to have an arc at all. So those are both decent data points to use. You can find the Kinetrics/Duke information in some of the Battcon papers that are public (and free).