You’ll need to either measure or calculate impedance from the inverters up to and ideally including the utility transformer. The most likely culprit are one or both are undersized.
________________________________ From: RE-wrenches <re-wrenches-boun...@lists.re-wrenches.org> on behalf of James Reismiller <ja...@abundantsolar.com> Sent: Thursday, May 20, 2021 10:52:06 AM To: re-wrenches@lists.re-wrenches.org <re-wrenches@lists.re-wrenches.org> Subject: [RE-wrenches] Grid overvoltage and undervoltage issues on SMA install Hi Folks, I’m wondering if anybody has ideas on what could be causing grid over/undervoltage errors on an install we did about a year ago that now has these issues. The site is a 24 kW DC ground mount array with (3) SMA SB7.0-1SP-US-40 inverters. I’ve checked and done the following: 1. Measured voltage min/max at inverter terminals and AC combiner. Min – 228VAC (with no inverter output) Max - 269 VAC (when inverter trying to connect)! 2. Had utility check service and transformer with load meter (with no PV running). No issues found and utility engineer stated he thinks it’s on our side. 3. Checked all AC connections including neutral (seemed like neutral issue) from inverters back to supply-side tap (fused disco). 4. Changed SMA upper voltage window in grid guard settings to 272V max and 264V reconnection. This helped for a while but now is faulting again. Have any of you ran into this issue and how did you solve it? Or what’s the next thing to check? Thanks in advance! Be Well, James Reismiller He/Him/His NABCEP Certified Solar PV Installer® Abundant Solar 541-231-8072 xt. 3 CCB#175919 [cid:image002.png@01D74D5D.CA065970] www.abundantsolar.com<https://us-west-2.protection.sophos.com?d=abundantsolar.com&u=aHR0cDovL3d3dy5hYnVuZGFudHNvbGFyLmNvbS9hYnVuZGFudHNvbGFyL0hvbWUuaHRtbA==&i=NWY3Yjg4NTEwMTMzZWYwZjc4ZDZiZjM0&t=UlRoM0ZoK3IzYnVOempNMktCUE5mRHpIU25SdTczdmlXZEFHU1p4dmJTND0=&h=3abbc334e64d4897a91541320d5af142> "Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!" ~William McDonough
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