Arc Flash-flooded type U.P.S. Battery strings
Arc Flash-flooded type U.P.S. Battery strings
(OP)
These (non-fused) 1.67 volt cells can each produce 14,000 amps on short circuit.
There are over 1000 battery cells in this room that require regular mtce.
What P.P.E. (arc flash)clothing would you recommend.The current standards seem to have missed this area.
There are over 1000 battery cells in this room that require regular mtce.
What P.P.E. (arc flash)clothing would you recommend.The current standards seem to have missed this area.






RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
dpc is right, nothing recognized yet for DC arc flash calcs, until then 70E is recomending using the AC equations.
RE: Arc Flash-flooded type U.P.S. Battery strings
According to C&D Tech sheets,and confirmed by their tech rep,the maximum short circuit current is 14,156 amps for model XT2LP-21 battery cell.
Question:
Is the dc voltage high enough on an individual cell to sustain an arc through air? If the answer is no, then maybe this is not an arc flash issue.We may only have to be concerned with higher dc string voltages.
RE: Arc Flash-flooded type U.P.S. Battery strings
It does not mean that the hazard does not exist, but have not been evaluated to the extent of coming up with a standard.
RE: Arc Flash-flooded type U.P.S. Battery strings
Are you sure the fault current isnt 14kA for the whole string? How is the system configured?
RE: Arc Flash-flooded type U.P.S. Battery strings
As earlier stated, each battery cell is 14 ka. short circuit.Check with your C&D rep for any further info.
Each cell is series connected into a string.
415 volts per string.
5 strings to feed 5 U.P.S. systems.
The client insists on arc flash labels for this battery system.We will have to provide interim AC based arc flash category 4 labelling.This will be very awkward during regular battery mtce. programs.
RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
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RE: Arc Flash-flooded type U.P.S. Battery strings
What is not clear is how this can be translated to short circuit calculations for a whole bank or a partial bank. It doesn't seem to make sense that a short across one cell will deliver the same fault current as the entire string. Of course the fault energy will be greater for the higher voltage.
I agree with you that arc flash calculations cannot be done on DC in accordance with any standard.
RE: Arc Flash-flooded type U.P.S. Battery strings
Same here that is why I was asking, Of course I know there isnt 3 Million+ amps of fault current, but I also knwo you wont get 14kA from a single 1.5V cell.
The best way by far is to measure your battery system impedance, fault current is battery system voltage/Z. We did a ton of these tests using an EBITE test set.
Another rule of thumb to use is fault current is 20x 3 hr discharge rate.
RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
Enclosed is this battery cel spec. sheets.
Note:the published short circuit current rating on the 2nd page (14,156 amps-max.)
RE: Arc Flash-flooded type U.P.S. Battery strings
I don't have the data sheets at home, but my best recollection is that the internal resistance of these batteries when new are in the 160 micro ohm/per cell category.
So to the questioning poster on the impedance being in the 120 micro-ohm neighborhood, yes there are batteries in internal impedances in this range..
We use an Alber CellCorder to determine the condition of our customer's batteries which measures applies a load test to each cell and computes the "metallic resistance" in microhms..
Just got back tonight from a site in Charlotte,NC that uses a smaller model of the Absolytes.. 2 stacks paralleled and with about 10 years age on the batteries.. They tested out over a 300 - 550 micro ohm range per cell.
I have not seen any documentation or practice anywhere that interprets NFPA 70 arc flash assessment to cover these DC plants and batteries.
RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
Right, my point exactly. The 14kA referenced * # of cells in the string isnt what you use for your analysis, it should be treated as a system not individual cells. Those values are for internal cell shorts.
RE: Arc Flash-flooded type U.P.S. Battery strings
RE: Arc Flash-flooded type U.P.S. Battery strings
Neglecting the impedance of intercell connections, the 14,000-amp rating for the XT battery is independant of the number of cells in a string.
However, if you have two strings in parallel, then the fault current will rougly double.