<div dir="ltr">The <span style="font-family:'PT Sans',Arial,Helvetica,sans-serif;font-size:14px;line-height:15px">Available short-circuit current (SCA)</span> 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.<div>
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.</div>
</div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Mar 27, 2014 at 4:15 PM, Dave Click <span dir="ltr"><<a href="mailto:daveclick@fsec.ucf.edu" target="_blank">daveclick@fsec.ucf.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
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.<br>
<br>
A few questions for your engineer then:<br>
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]<br>
2) What is the "500A fault current limit" that was taken into
account in the site design? The service size is ___A. <br>
<br>
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.<br>
<br>
DKC<div><div class="h5"><br>
<br>
<br>
<br>
<div>On 2014/3/27, 15:28, Karl Jaeger wrote:<br>
</div>
<blockquote type="cite">
<div>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Nathan,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The
only explanation the electrical distributor provided is seen
below. They are really skirting a thorough explanation…<u></u><u></u></span></p>
<p class="MsoNormal"><i><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">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.<u></u><u></u></span></i></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Thanks,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Karl</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Nathan Charles<br>
<b>Sent:</b> Thursday, March 27, 2014 2:03 PM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Fault Current<u></u><u></u></span></p>
<p class="MsoNormal"><u></u> <u></u></p>
<div>
<p class="MsoNormal">Karl,<u></u><u></u></p>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">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.<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">Best,<u></u><u></u></p>
</div>
<div>
<p class="MsoNormal"><u></u> <u></u></p>
</div>
<div>
<p class="MsoNormal">-N<u></u><u></u></p>
</div>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><u></u> <u></u></p>
<div>
<p class="MsoNormal">On Thu, Mar 27, 2014 at 2:51 PM, Karl
Jaeger <<a href="mailto:kjaeger@lightwavesolar.com" target="_blank">kjaeger@lightwavesolar.com</a>>
wrote:<u></u><u></u></p>
<div>
<div>
<p class="MsoNormal"><span style="color:#1f497d">Dave,</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d">We are about as rural as we
can get here…. farm land. Very good document,
nonetheless.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d">Karl</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span><u></u><u></u></p>
<div>
<div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>
[mailto:<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" target="_blank">re-wrenches-bounces@lists.re-wrenches.org</a>]
<b>On Behalf Of </b>Dave Click<br>
<b>Sent:</b> Thursday, March 27, 2014 1:29 PM<br>
<b>To:</b> <a href="mailto:re-wrenches@lists.re-wrenches.org" target="_blank">re-wrenches@lists.re-wrenches.org</a><br>
<b>Subject:</b> Re: [RE-wrenches] Fault Current</span><u></u><u></u></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-family:"Helvetica","sans-serif"">Karl,
you're interconnecting into a spot/area network,
right? It's a real concern; some solutions and
background on the issue here:<br>
<a href="http://www.nrel.gov/docs/fy09osti/45061.pdf" target="_blank">http://www.nrel.gov/docs/fy09osti/45061.pdf</a><br>
<br>
DKC</span><u></u><u></u></p>
<div>
<p class="MsoNormal">On
2014/3/27, 14:05, Karl Jaeger wrote:<u></u><u></u></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="color:#1f497d">Esteemed Wrenches,</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d">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.</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d">Does anyone have
experience on circumventing the issue of
network fault current? Any experience with
Fault Current Limiters?</span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d"> </span><u></u><u></u></p>
<p class="MsoNormal"><span style="color:#1f497d">Much appreciated,</span><u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal"><b>Karl
Jaeger</b><u></u><u></u></p>
<p class="MsoNormal"><b>Design/Build
Engineer</b><u></u><u></u></p>
<p class="MsoNormal"><b>LightWave
Solar Electric LLC</b><u></u><u></u></p>
<p class="MsoNormal"> <u></u><u></u></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
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