DC Arc Flash Result Update

What timing. I just rolled out my newly devloped DC Arc Flash Calculation training module that is part of the 2 day Arc Flash Calculation Study class. There is a lot of research and testing that I have so I sifted through to come up with the module for the class. I got tired of saying "we are still waiting for an answer"

As far as NFPA 70E, I understand they may add HRC tables for DC battery systems as well as a table for the approach limits.

As far as IEEE, nothing yet. That is why I moved ahead and used what was available to help people deal with DC.

Nice to know there is an interest in DC Arc Flash

I consider DC to be about where we were in 1998-2000 with AC arc flash. Back then there were several good papers and research but no standard. Then NFPA developed the Hazard / Risk tables for protection based on "experience and opinion" in an attempt to provide some guidance. Eventually IEEE 1584 was developed for a detailed calculation assessment.

Fast forward to now. History repeats itself but I added a step. NFPA is once again going to address the issue with HRC tables so there is something out there for people to use. I have a copy of the proposed table but don't believe I am at liberty to post it yet. The proposed table is broken into 3 levels.

Battery systems up to 250V nominal - mostly HRC 0 and 1
Battery systems 250 V to 600V - mostly HRC 2 with a few at 0 and 1
Battery systems above 600V - mostly HRC 3 with a few at 1 and 2
keep in mind this is not "official" yet.

The major issue as I see it is arc duration. Many DC systems do not have much in the way of protection. My calculations show depending on the size of the battery string, DC short circuit current and duration the energy can be quite high. That should not be a surprise since that is basically what impacts the severity of an arc flash to begin with but it is important to note the energy can be high. Someday there will be a standard for calculating DC arc flash but at the present time there is only some research and also a few pretty good papers on the subject.

A few months ago after saying "we don't have anything for DC" for the zillionth time, I snapped and decided to put my arms around what I feel is the better info (subject to my own interpretation and opinion ), filled in a few blanks and came up with some information, methods and calculation worksheets. Those of you that know me probably realize this should not be too much of a surprise since I'm not known for sitting patiently waiting for something to happen.

I don't want to violate the forum's anti-commercialism policy so I won't plug the class but if you have any questions, either PM me or send an email to jphillips@brainfiller.com

I doubt it. The 2 second cut off is an IEEE thing and in a conversation I had with 1 NFPA person, they do not seem to want to embrace it.

Absolutely! Even though I doubt if 2 seconds will get listed, I would tend to use that number as you mentioned based on the IEEE 1584 reference to it.

You hit one of the most important points and that is still the missing link in much of this.

I am hopeful that by forcing the issue by bringing the calculations and the problems out in the open instead of saying "we have no information", manufacturers will begin to rethink a few things just like they have done with AC equipment. Who would have considered maintenance switches, safer designs, different protection schemes, remote operation, uv detection etc. years ago.

I sifted through all of the info above plus info from several others as well as my own additions to provide a few practical DC arc flash calculation/ applications. Hopefully it will help begin to to fill in the big hole for DC.

The papers are from IEEE conferences such as ESW and PCIC which are held every year. You can find the papers as well as loads of other good information at IEEE's on line library.