[RE-wrenches] Grid overvoltage and undervoltage issues on SMA install

[John Blittersdorf]

I agree with voltage drop,  I had two sb4000’s with this issue.  Power
company said it was on
Our side but I was sure it was the long run from the utility transformer.
They finally agreed and ran a heavier line.  Problem solved.  One
observation that was puzzling was that only one inverter would be off when
I arrived and it wasn’t always the same one.  When one shut off due to over
voltage, the voltage would drop and the second one would stay on.  Both had
the exact same upper voltage limit.

John B
On Thu, May 20, 2021 at 3:23 PM August Goers <august at luminalt.com> wrote:

> Hi James -
>
> Is there a long run between the inverters and the point of
> interconnection? As others have pointed out, it appears that the symptoms
> you describe are voltage drop related. If the wire size is too small it
> will result in voltage at the inverters going up when current starts to
> flow. The inverters match the voltage at the utility point of connection.
> If, for example, the voltage at the main service panel is 240 volts and you
> have a 10% voltage drop due to undersized wires, you'd see 240 x 1.10 = 264
> v at the inverters. Sometimes this issue is compounded if the utility
> voltage is a little on the high side, which can happen at the end of the
> distribution lines.
>
> There could be other explanations as well.
>
> Best, August
>
> On Thu, May 20, 2021 at 10:25 AM Jerry Shafer <jerrysgarage01 at gmail.com>
> wrote:
>
>> Wrenches
>> Looks like the i verter is doing what it should 269 is out of range, what
>> is the at meter voltage, libe loss or very high output voltage, 41 volts
>> increase looks like resistance issues. More info would help, distance, wire
>> size etc.
>> Jerry
>> Jerry
>>
>>
>> On Thu, May 20, 2021, 9:52 AM James Reismiller <james at abundantsolar.com>
>> wrote:
>>
>>> 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
>>>
>>> www.abundantsolar.com
>>> <http://www.abundantsolar.com/abundantsolar/Home.html>
>>>
>>>
>>>
>>> "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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