Also using Drakes solution, you bypass the issue with the inverter “voltage drop” causing it to go out of spec in high production times (a 5% voltage drop would really mean that the inverter would see the grid as being 5% higher than it really is when producing at full power, potentially causing a high grid voltage fault). You can then allow for more than 1% voltage drop over that distance without risking the system shutting down. You change an operational requirement constraint into a pure power production vs cost of wire issue. It might be that going with smaller wire is less expensive that the extra energy you would generate from that 1% better voltage drop.
Also you said 11.4kW inverter with 240V 1ph, which makes me think SolarEdge. If that’s true then your situation just got a even better. I believe they will communicate to optimizers up to 1000’ (I don’t like operating at the edge of a systems spec, but might be the best option here). But they operate at the same, higher voltage under power producing conditions. That only helps your power loss issues. You can run the numbers, but you usually lose about 1/2ish total annual energy compared to the calculated %voltage drop on the DC lines. So if you have the wire run designed for 5% drop at peak power, you’d really only lose roughly 2-3% total energy per year. With Regards, Daniel Young, NABCEP Certified PV Installation ProfessionalTM: Cert #031508-90 From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> On Behalf Of drake.chamber...@redwoodalliance.org Sent: Monday, September 17, 2018 1:50 PM To: RE-wrenches <re-wrenches@lists.re-wrenches.org> Subject: Re: [RE-wrenches] Step-up/Step-down Transformer question Another option would be to locate the inverters near the grid and run the DC at as high a voltage as possible. Have a separate run of wire for each of the 5 inverters. If you ran the DC at 500 V, an 11.4 kW inverter would only draw 22.8. A. Use 2/0 AL for a little over 1% VD at full power. ----- Original Message ----- From: "RE-wrenches" <re-wrenches@lists.re-wrenches.org <mailto:re-wrenches@lists.re-wrenches.org> > To: "RE-wrenches" <RE-wrenches@lists.re-wrenches.org <mailto:RE-wrenches@lists.re-wrenches.org> > Cc: Sent: Mon, 17 Sep 2018 09:42:01 -0700 Subject: [RE-wrenches] Step-up/Step-down Transformer question Wrenches, We have a PV array situated about 900' from the POI (240V 1PH). We initially spec'd (5) 11.4kW inverters and the combined output would be 238A. The wire size required for this current over that distance is cost prohibitive. A solution was to use a single 50kW 3 phase inverter at the array and then convert it to 240V... somehow? Is anyone familiar with how to go about doing this? My thought was to have a step down transformer at the POI and pull off two legs to get 240V. Is this even a thing? The other, more expensive option is to use a step up transformer at the array and a step down at the POI to get us a smaller wire size. Thanks for any input. -- Loren Ortiz Commercial PV Designer lo...@cal-solar.com <mailto:lore...@cal-solar.com> (530) 274-3671 Showroom located at: 149 E Main St. Grass Valley, CA 95945
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