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<div class="moz-cite-prefix">Chris,<br>
<br>
Enphase has the ability to remotely adjust the voltage and
frequency operating windows. They have adjusted them as far as
they can, or will.<br>
<br>
I have some SMA Sunny Boy inverters in locations that recently
have TWACS remote reading systems installed. Most don't have
remote data monitoring. At least one does but the TWACS meter was
just installed there last week. I'll know more about that one
after I have a chance to confirm that the TWACS system has been
activated. <br>
<br>
I agree with you that the TWACS signal shouldn't be sent to the
customer, but it is generated in the utility meter so it's going
to both the customer and the substation. Also, the TWACS signal
can be adjusted if necessary to generate a bigger signal. I guess
that would be their first step in handling a site with a large
capacitive load.<br>
<br>
<pre class="moz-signature" cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a class="moz-txt-link-abbreviated" href="http://www.bluemountainsolar.com">www.bluemountainsolar.com</a>
t: 541-568-4882</pre>
On 7/9/2012 6:05 AM, Chris Mason wrote:<br>
</div>
<blockquote
cite="mid:CAG6C1qnATBqMPBNT0go-ZrLwZ0Ki4uhk3JtOLJOOekNmcFhEVg@mail.gmail.com"
type="cite">Yes, I expect they can. The greater issue is going to
be whether the other inverters are going to react also. Have you
had any experience with other inverters in this scenario?
<div>I don't undertand why the meter manufacturer can't ensure the
burst is filtered out of the load connections. They have to know
it can mess up devices behind the meter.</div>
<div>Large capacitors on the load side should not stop the utility
reading the meter. If it does, any consumer with a large UPS
will kill it.</div>
<div><br>
</div>
<div>In the SMA firmware, there is the ability to adjust some of
the parameters such as the Vmax to adjust the system to local
variations, which we often have to do here. Can you adjust the
size of the frequency window in the Enphase system settings? If
you can make the inverters look at a longer window of cycles
that may eliminate the problem.</div>
<div><br>
</div>
<div>Chris<br>
<br>
<div class="gmail_quote">On Sun, Jul 8, 2012 at 8:40 PM, Kent
Osterberg <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:kent@coveoregon.com" target="_blank">kent@coveoregon.com</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">
<div>Chris,<br>
<br>
SCRs are capable of creating voltage spikes that cause
noise well into the radio frequencies. But with TWACS
there is an inductor in series with the SCR that is
tuned such that the pulse caused when it fires is 0.5 ms
to 1.0 ms wide with very little high frequency content.
Because the frequency content is very low, it difficult
to filter out. Ferrite toroids are of no help and large
capacitors will prevent the utility from reading the
meter too. The pulse location is near the zero crossing
so it makes for a dirty looking waveform for about 8
seconds while the meter is sending data. Never-the-less,
it's actually easy to make a reliable frequency
measurement by shifting the measurement threshold off
zero far enough that the TWACS signal doesn't interfere.
The Enpase folks should be able to do that with a
firmware change.
<div class="im"><br>
<pre cols="72">Kent Osterberg
Blue Mountain Solar, Inc.
<a moz-do-not-send="true" href="http://www.bluemountainsolar.com" target="_blank">www.bluemountainsolar.com</a>
t: <a moz-do-not-send="true" href="tel:541-568-4882" value="+15415684882" target="_blank">541-568-4882</a></pre>
</div>
<div>
<div class="h5"> On 7/8/2012 4:47 PM, Chris Mason
wrote:<br>
</div>
</div>
</div>
<div>
<div class="h5">
<blockquote type="cite">Kent,
<div>I haven't any direct experience with the smart
meters tripping inverters, but the issue of SCRs
and generators is well known. I suspect you
understand the problem, but to recap it, the
problem revolves around the way SCRs make a sine
wave.</div>
<div>A motor driven generator controls the
alternator output by increasing or decreasing the
DC excitation level. It does that by sensing the
"zero crossing", or point in the sine wave at
which the voltage is zero. This happens 120 times
a second on a 60Hz system.</div>
<div>When the source of the electricity is
electronic, the waveform will sometimes be messy
around the zero crossing. That gives the voltage
control circuit problems to detect the zero
crossing We see this a lot when trying to drive a
UPS from a generator, it can drive the generator
crazy.</div>
<div><br>
</div>
<div>I suspect your problem is the same. The SCR in
the meter disturbs the waveform and the inverter
thinks it is a faulty waveform.</div>
<div> I would try a low pass filter between the
meter and the inverter. A properly sized capacitor
ought to remove any noise above 60hz and present a
clean waveform to the inverter.</div>
<div><br>
</div>
<div><br>
<div class="gmail_quote">On Sun, Jul 8, 2012 at
7:06 PM, Kent Osterberg <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:kent@coveoregon.com"
target="_blank">kent@coveoregon.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0
0 0 .8ex;border-left:1px #ccc
solid;padding-left:1ex"> Wrenches,<br>
<br>
There weren't very many replies to my question
about grid-connected inverter compatibility
with utility remote meter reading systems so
I'll explain my recent experience with hope
that this information may be of assistance
sometime.<br>
<br>
Last fall I installed an Ephase system for a
customer. Soon after it was on line he
complained that the inverters were dropping
off line frequently. Since we had a lot of
cloudy weather in northeast Oregon all winter,
it wasn't easy to see what was going on. In
the spring we had some clear days and noticed
that the inverters were dropping off line
several times a day at exactly the same time
every day. It didn't take very long for our
suspicion to turn to the utilities new remote
meter reading equipment. Because our weather
has been so cloudy it took a while to find
clear days where the utility could provide
assistance. But with their help by reading the
meter on demand and temporarily disabling the
meter communications we were able to finally
prove the remote meter reading system is
tripping the inverters offline for five
minutes every time the meter sends a data
packet.<br>
<br>
Recently the remote meter reading system has
expanded to more areas so we have now observed
this problem with both Enphase M190 and M215
inverters. The system we've observed that is
in town is seeing many more dropouts, so we
think every kWh meter on the same service
transformer and maybe some beyond it are
causing trouble too.<br>
<br>
The remote meter reading equipment is made by
Aclara and uses their TWACS technology. This
isn't new technology and with more remote
meter reading systems going in all the time
there will be more occurrences of
incompatibility. Certainly more between
Enphase and TWACS. And possibly more between
other inverters and other communications
systems.<br>
<br>
At present I'm really dissatisfied with
Enphase's support on this issue. All they've
done is point out that only a few systems have
been affected and put us in the position of
telling customers that they'll just have to
live with the lost production time. Until
Enphase comes up with a fix, I won't install
any more Enphase inverters.<br>
<br>
-- <br>
Kent Osterberg<br>
Blue Mountain Solar, Inc.<br>
<a moz-do-not-send="true"
href="http://www.bluemountainsolar.com"
target="_blank">www.bluemountainsolar.com</a><br>
t: <a moz-do-not-send="true"
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-- <br>
Chris Mason
<div>President, Comet Systems Ltd</div>
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-- <br>
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