MKEEET wrote:

For the most part they are all for 3 phase systems, except for D.8.

I don't recall exactly where I've seen it but the results are very similar and the recommendation is to use the same formulas. Assuming the arcing fault never advances to a 3 phase bolted fault condition (this can happen with low level arcing faults), then the formulas would be identical.

The actual source for the calculations regardless of how you go about it is IEEE 1584. 70E is supposed to produce the same results but on occasion in the past the formulas in the appendix of 70E have been different from those in IEEE 1584. In the past if IEEE 1584 changed, then there would be a delay before NFPA 70E changed. That is why for instance they "removed" the 125 kVA transformer exception in the 2012 version.

**Quote:**

Again that was using a 3 Phase calculation, and I can see some resistance with the validity of my numbers at the different distances. Now that I have access to the code, I can say if I am under 4cal/in2 I don’t have to worry about the arc, it’s just using the right formula at this point.

You most certainly do have something to worry about. At 1.2 cal/cm^2 using the generally accepted 2 second cutoff then there is a 50% chance of a second degree burn. There is no accepted engineering data showing what happens above that point (there is no "fatality threshold") but some rough geometric calculations I've done and posted in the general discussion section of this forum show that it is not very much of an increase over the second degree burn threshold.

That being said, working in PPE that gives adequate protection up to 4 cal/cm^2 isn't a big deal. We have an entire division of several thousand people at my company that wear this stuff as everyday work wear, and many utilities require this.