The Available short-circuit current (SCA) of utility transformer is in the range of 100,000+ Amps. I still don't see a single phase solar installation being a large part of that so I doubt that is the issue. I (partially) understand the issue of reverse current detection in paralleled utility feeders, but it would require a detailed examination of the utility system by an a HV experienced Electrical PE to determine the possible implications of your solar system on that protective equipment. It would probably be money well spent to engage such an engineer before buying a three phase feed. Usually any reverse detection is on the three phase lines anyway.
On Thu, Mar 27, 2014 at 4:15 PM, Dave Click <davecl...@fsec.ucf.edu> wrote: > The "explanation" you quote doesn't make any sense to me. If the engineer > is concerned about fault current, the primary source is going to be through > the utility transformer, and it will be on the order of 5,000 - 10,000A > depending on the transformer's impedance. The fault current contribution > from the inverters will be much less than that (an SB8000 fault current is > all of 61.7A) and it will last for a much shorter duration. Be nice-- some > engineers think by default that all generation acts like a rotating > machine, which can contribute quite a bit of fault current. Not so for PV, > so hopefully this engineer will see the light with a bit of help from you. > > A few questions for your engineer then: > 1) These inverters will be exporting power, not drawing it; why are the > inverters not considered a negative load in this installation? [I assume > you're not installing batteries] > 2) What is the "500A fault current limit" that was taken into account in > the site design? The service size is ___A. > > A 167kVA transformer at 240V has a rated current of about 700A, which is > another reason why the "500A fault current" doesn't make sense. > > DKC > > > > > On 2014/3/27, 15:28, Karl Jaeger wrote: > > Nathan, > > The only explanation the electrical distributor provided is seen below. > They are really skirting a thorough explanation... > > *The distributor engineer does not view the inverters as a negative load, > and states they will exceed the 500A fault current limit the site is > designed for.* > > Thanks, > > Karl > > > > *From:* re-wrenches-boun...@lists.re-wrenches.org [ > mailto:re-wrenches-boun...@lists.re-wrenches.org<re-wrenches-boun...@lists.re-wrenches.org>] > *On Behalf Of *Nathan Charles > *Sent:* Thursday, March 27, 2014 2:03 PM > *To:* RE-wrenches > *Subject:* Re: [RE-wrenches] Fault Current > > > > Karl, > > > > Can you give us some more details on their concerns? I've done some very > large single phase ag installs and the only time I've had issues is when we > exceed the 80% of minimum load on the medium voltage feeder. > > > > Best, > > > > -N > > > > On Thu, Mar 27, 2014 at 2:51 PM, Karl Jaeger <kjae...@lightwavesolar.com> > wrote: > > Dave, > > We are about as rural as we can get here.... farm land. Very good document, > nonetheless. > > Karl > > > > *From:* re-wrenches-boun...@lists.re-wrenches.org [mailto: > re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Dave Click > *Sent:* Thursday, March 27, 2014 1:29 PM > *To:* re-wrenches@lists.re-wrenches.org > *Subject:* Re: [RE-wrenches] Fault Current > > > > Karl, you're interconnecting into a spot/area network, right? It's a real > concern; some solutions and background on the issue here: > http://www.nrel.gov/docs/fy09osti/45061.pdf > > DKC > > On 2014/3/27, 14:05, Karl Jaeger wrote: > > Esteemed Wrenches, > > We've recently run into an issue with a local distributor citing network > fault current on a split-phase service as a reason to prevent > interconnection of our customer's solar array. They've given us the options > of reducing our system size from 36.5kW-DC to 15kW-DC, or having the > customer upgrade to 3-phase at a soft price of $20-30K. We're looking at > 32kW of inverters on a 167kVA transformer. > > > > Does anyone have experience on circumventing the issue of network fault > current? Any experience with Fault Current Limiters? > > > > Much appreciated, > > > > *Karl Jaeger* > > *Design/Build Engineer* > > *LightWave Solar Electric LLC* > > > > > > _______________________________________________ > > List sponsored by Home Power magazine > > > > List Address: RE-wrenches@lists.re-wrenches.org > > > > Change email address & settings: > > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > > > List rules & etiquette: > > www.re-wrenches.org/etiquette.htm > > > > Check out participant bios: > > www.members.re-wrenches.org > > > > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > > > > -- > > Nathan Charles > > Engineer > > NABCEP Certified PV Installation Professional #042013-20 > > Paradise Energy Solutions > > (717) 283-2021 direct > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & > settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette:www.re-wrenches.org/etiquette.htm > > Check out participant bios:www.members.re-wrenches.org > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > -- Chris Mason President, Comet Systems Ltd www.cometenergysystems.com Cell: 264.235.5670 Skype: netconcepts
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