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<p><font size="4">Wouldn't the microinverters shut down if the
voltage rose? They wouldn't be able to raise voltage about
PUC/DPU limits I would think. They would shut down on high
voltage. I am saying this because of an experience this fall
where our infamous Block Island Power Company raised the taps on
a local xfmr due to their "secret heat pump program" that was
dragging down local voltage. They claimed solar was a burden,
but were quiet on the load building program they embarked upon
without any disclosure. When the cooling loads disappeared,
the voltage went above our grid tied systems set points and they
shut down. We told the utility they had a high voltage problem
and they adjusted the taps. Of course they did not acknowledge
or thank us. It seems our little coop which is now head from a
guy from the Vermont Electric Coop is taking an old utility
approach instead of cooperation, integration and maximization of
performance and economics. <br>
</font></p>
<p><font size="4">I'd think you be able to ask how the supply can
raise the voltage when there is so much diversified load on the
same device. Electricians have to do a diversity calculation,
and I know a utility has to conduct them as part of these
studies. Worse case of no load and all generation is such a low
probability that to design for it, when/if it occurred, is not a
danger and of no material consequence makes little sense. But,
we've been dealing with that ever since this person arrived in
our neck of the woods.</font></p>
<p><font size="4"><br>
</font></p>
<p><font size="4">Chris Warfel <br>
</font></p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 12/25/2022 5:21 PM, Garrison via
RE-wrenches wrote:<br>
</div>
<blockquote type="cite"
cite="mid:B3828347-26D3-4D91-B39A-D75F489C1ADF@gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="ltr">Hi William,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">One possible path forward would be to ask the
utility co what AC inverter capacity would be allowed. Maybe the
solution would be to unplug a micro or two if you are just over
the limit. Even better, maybe they would allow you set an export
limit on the micros you have installed.</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I had a recent situation where a 40kW DC system had
exceeded a utility transformer by only 2kW AC, so a simple
redesign avoided an $8k invoice from the utility. The utility
was not transparent about this option at first and only made it
clear after some persistence.</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Good luck,</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Garrison Riegel</div>
<div dir="ltr">Celestar Solar</div>
<div dir="ltr"><br>
<blockquote type="cite">On Dec 25, 2022, at 3:14 PM, Darryl
Thayer via RE-wrenches
<a class="moz-txt-link-rfc2396E" href="mailto:re-wrenches@lists.re-wrenches.org"><re-wrenches@lists.re-wrenches.org></a> wrote:<br>
<br>
</blockquote>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">
<div class="gmail_default" style="font-family:times new
roman,serif;font-size:large">It is common practice for the
utility to overload the transformer a lot for the
potential load. They expect no one will use their service
at maximum, furthermore, they expect non coincidence of
loads. Look at the transformer most have a label as to
the kW or the unit, and the utility should give you that
number along with the impedance. Note I have had area
engineers not understand that solar reduces the load on
the transformer. They have two concerns, you will
overload and you will raise the voltage
to other customers. Overload is ridiculous;
the transformer must be at least 20 kW if a 15 kW concern
is valid. However, raising the voltage is not. If all
the customers shut off their power, the voltage would rise
to the inverter limit,and/or feed current back on the
distribution line raising up/downstream customers
voltage. I have had this problem, on three occasions
discussions with the utility upper engineering, not local
engineer, i prevailed, one case I did not. In one cast
utility allowed connection and put a voltage monitor on
secondary voltage, then later allowed
permanent connection.. Good luck </div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Dec 25, 2022 at
1:16 PM William Miller via RE-wrenches <<a
href="mailto:re-wrenches@lists.re-wrenches.org"
moz-do-not-send="true" class="moz-txt-link-freetext">re-wrenches@lists.re-wrenches.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
<div class="msg7831789815957074960">
<div lang="EN-US">
<div class="m_7831789815957074960WordSection1">
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">Wrenched:</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">Merry
Christmas to those of you that observe such
traditions, or substitute the winter festivity
of your choice.</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">I
helped a previous employee install an Enphase
IQ8 system on his home. He applied for the
utility approval concurrently with his building
permit The day he got his final inspection the
utility contacted him and claimed "The aggregate
generation exceeds the identified transformer
rating" and refused him a Permission to Operate
letter.</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">Adding
up the service ratings of the homes on his
secondary we get about 336 kW of potential
consumption. Adding the grid-tied systems on
his secondary we get about 16.5 kW. How is it
that the back-feed exceeds the transformer
rating?</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">I
would appreciate any insight on how to consider
this situation and how to fight it.</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">Sincerely,</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif"">William
Miller</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Verdana,"sans-serif""> </span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Arial,"sans-serif"">Miller
Solar</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Arial,"sans-serif"">17395
Oak Road, Atascadero, CA 93422</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Arial,"sans-serif"">805-438-5600</span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Arial,"sans-serif""><a
href="http://www.millersolar.com/"
target="_blank" moz-do-not-send="true">www.millersolar.com</a></span></p>
<p class="MsoNormal"><span
style="font-size:12pt;font-family:Arial,"sans-serif"">CA
Lic. 773985</span></p>
<p class="MsoNormal"> </p>
<p class="MsoNormal"> </p>
</div>
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<font face="PMingLiU-ExtB">
Christopher Warfel</font><br>
<font face="PMingLiU-ExtB"> ENTECH
Engineering, Inc.</font><br>
<font face="PMingLiU-ExtB">PO Box 871, Block Island, RI
02807</font><br>
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401-466-8978</font><br>
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