Arc flash spreadsheet
Arc flash spreadsheet
(OP)
Anyone try using the spreadsheet that came with IEEE 1584. I just tried it for a 69kV 9.2KA bus and the PPE requirement is off the chart. Same data input into flux.exe gives 9 cal/cm^2, while the spreadsheet gives 700. Double checked all my input values, and there's still 25.4 mm in an inch and 60 cycles in a second if I'm not mistaken. The 9 value is also more in line with the tabulated values in the NESC preprint proposals that came from Arcpro. Anyone find the error in this spreadsheet?






RE: Arc flash spreadsheet
Mike
RE: Arc flash spreadsheet
Further testing should be done in my opinion; specifically at higher voltage and longer clearing times.
RE: Arc flash spreadsheet
So I tried using a shorter clearing time. One right off the NESC proposal chart under the 5-cal system chart. IEEE says 212 cal/cm^2.
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
I must have fat-fingered a button, cause when I ran my program on my handy-dandy calculator again, I came up with the same results as you. You're right though, Lee's method is a bit ridiculous for HV calculations.
Mike
This has been an interesting discussion. Definitely more work needs to be done to iron out the issues w/ Arc Flash Analysis.
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
1) For liability reasons we have chosen to use IEEE formulation, but also determined terrible results. In some cases the calculated Arc Flash Boundary around a 480V pad mount was over a quarter mile. To preserve credibility, we placarded such locations :"Do not work energized".
2) I am reluctant to not use IEEE as an industry standard, what is "ArcPro" and how much of an industry standard would it be seen as in court?
RE: Arc flash spreadsheet
It's basically a glorified, overpriced MathCAD template, IMO. But it may be that the results given are more reasonable for high-voltage outdoor applications than the IEEE-1584 equations.
I don't think you want to use it for 480V.
RE: Arc flash spreadsheet
The lowest tabulated value from NESC/OSHA proposals is 4kV Certainly a 480V fault is more likely to go three phase. The IEEE method for lower voltages also takes into account the energy focusing that occurs within an enclosure. ArcPro is for open air only.
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet
I looked at the OSHA Table 9. Using ArcPro, I tried a couple of different data points and a couple were right on.
72.5kV, 20kA, 10.6 cyc; I got 2.55 cal/cm2 instead of 5.
145kV, 20kA, 12.2 cyc; I got 5.1 cal verses tables 5
362kV, 20kA, 28.3 cyc; I got 5.04 verses tables 5
So, is the table totally wrong, or did they just miss the boat at the lower voltages. Looking at Table V-2 AC Live line work minimum approach distance in the subject document,there are some problems: ie for 41.6-72.5kV they have 3' 3" instead of 3' 2". Not a big deal, but just one example.
RE: Arc flash spreadsheet
I confirmed your results except for the last. Inputting 20kA, 209001V, 28.3 cycles, 20.9" gap and 60.2" distance I get 5.5 cal/cm^2.
The above referenced MAD is 3'3" per NESC 2002. It includes a 1" adder for inadvertent movement not used at the higher voltages. So the MAD is 3'2" for 72.6 to 121kV. Seems odd, but the MAD drops an inch as voltage increases across this transition. I believe OSHA is intending to match the NESC on this.
RE: Arc flash spreadsheet
You are right, I copied the wrong number for the 363kV level. By the way, and you probably know this, but ArcPro only uses the voltage to ensure the arc is sustained. Whether you run the study at 362kV or 209kV, you get the same answer.
As far as the table values, if what you say is correct, there is an error in NFPA 70E. Table 130.2(C) has the values for 72.5kV and 121kV reversed from the OSHA tables:
46.1 to 72.5kV = 3' 2"
72.6 to 121.kV = 3' 3"
RE: Arc flash spreadsheet
RE: Arc flash spreadsheet