It may be possible to do on a small installation such as a PV system, but I'm not really sure. All of the arc flash studies I've had anything to do with were in large plants, with lots of transformers, miles and miles of wire, and thousands of breakers. The task seems daunting. I can't imagine one person doing it. I do know they all used some kind of software. Some of the plants were older and all the prints only existed on paper, so I'm sure that added to the task
I've seen additions built, and I think a new facility wide arc flash study didn't have to be done.
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Yes you can calculate an arc flash value at a single point. However, you likely need information from several different source to be able to do it.
From both sources, I would assume, and it's 480/277V 3P4W.
Yes it can be done, why is a different question. It is not required by the NEC.
I have documentation for the inverters we use, but yeah, it's something like that.
With that little amount being supplied by the PV it is likely the arc flash energy would not change from when they are on the utility alone.
I have requested clarification from my client; it is possible that either they or I misunderstood what the AHJ is asking for.
There's software available BUSS and I believe Mike Holt has a calculator available.
That's interesting because 110.16 says the labels must meet the requirements of 110.21(B) which is Field-Applied labels, yet 110.16 says the labels can be field or factory applied. So yes, I could see this going both ways. I'm looking for field-applied to be the standard because I do arc flash calcs, but this could be interpreted either way!
How do you perform those calculations, and do you do them for every commercial PV installation? Do you generate those numbers for the entire electrical system or just for the PV installation?
Factory applied AF labels are possible if the AF study is supplied to the manufacturer who will be building the equipment, but I doubt this will be common. Much easier to field apply. The NEC is just providing options, even if unlikely to be used.
I can say we are doing an AF study on just about every PV and ESS project. AHJs are requiring it and a good number of clients who did not order an AF study in the initial proposal end up adding it as a change order later. We just do AF for the new equipment and we will add in any existing equipment that is part of the path back to the utility. So an existing service SWBD where we do the interconnection will be part of the study. We do not put any other existing equipment in, doing an AF study for an existing facility is not part of our services. If the client wants that we recommend they retain a firm that specializes in AF studies. Since AF studies are supposed to be renewed every 5 years they can just make it part of their 5 year maintenance program.
Can you tell me how you would go about performing an AF study on, say, a 400kW AC PV system connected via a supply side interconnection on the line side lugs of a main service disconnect?
