Kent, Typically the manufacturer is not to anxious to change the parameters outside those set out in the UL 1742 standard. However, for this, I suspect that is what is needed. They will probably need you to sign a waiver first, which is what we had to do with SMA.
Do you have a scope to look at the waveform of the signal? With a scope and a few capacitors, you could see what it took to clean up the waveform reaching the inverters. On Mon, Jul 9, 2012 at 10:46 AM, Kent Osterberg <[email protected]> wrote: > Chris, > > Enphase has the ability to remotely adjust the voltage and frequency > operating windows. They have adjusted them as far as they can, or will. > > 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. > > 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. > > > Kent Osterberg > Blue Mountain Solar, Inc.www.bluemountainsolar.com > t: 541-568-4882 > > On 7/9/2012 6:05 AM, Chris Mason wrote: > > 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? > 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. > 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. > > 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. > > Chris > > On Sun, Jul 8, 2012 at 8:40 PM, Kent Osterberg <[email protected]>wrote: > >> Chris, >> >> 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. >> >> Kent Osterberg >> Blue Mountain Solar, Inc.www.bluemountainsolar.com >> t: 541-568-4882 >> >> On 7/8/2012 4:47 PM, Chris Mason wrote: >> >> Kent, >> 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. >> 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. >> 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. >> >> I suspect your problem is the same. The SCR in the meter disturbs the >> waveform and the inverter thinks it is a faulty waveform. >> 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. >> >> >> On Sun, Jul 8, 2012 at 7:06 PM, Kent Osterberg <[email protected]>wrote: >> >>> Wrenches, >>> >>> 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. >>> >>> 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. >>> >>> 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. >>> >>> 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. >>> >>> 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. >>> >>> -- >>> Kent Osterberg >>> Blue Mountain Solar, Inc. >>> www.bluemountainsolar.com >>> t: 541-568-4882 >>> >>> _______________________________________________ >>> List sponsored by Home Power magazine >>> >>> List Address: [email protected] >>> >>> Options & 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 >> >> >> >> _______________________________________________ >> List sponsored by Home Power magazine >> >> List Address: [email protected] >> >> Options & >> 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: [email protected] >> >> Options & 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 > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: [email protected] > > Options & > 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: [email protected] > > Options & 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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