I’ll start by stating that our problem is not the typical overvoltage scenario, where there are too many PV systems feeding the grid in sunny hours.
We have a three phase system, each phase with a MP2 8kva, a few battery packs totaling 40kWh and a three phase Huawei 20kW inverter on the AC out. Our system is setup as AC-Coupling, that is the grid on the IN side of the MP2 and loads + Huawei PV inverter on the AC out. Additionally, there are a couple of switches to bypass the entire solar installation (this includes batteries and all inverters). This is an industrial setup in a warehouse.
Now having some context, if the system is configured such that it bypasses the entire solar/batteries/victron/huawei installation, the grid voltages are fine. No overvoltages and everything runs smoothly.
If we then switch to enable the solar system, what the MP2 read as grid voltages are way higher. Anytime during the day (or night) regardless of whether the Huawei inverter is producing energy or not, say at 4am with the Huawei off, grid voltage readings are 251V. For example today, overcast (Huawei producing 3kW total) and pulling 15 or 20A on each phase from the grid, voltages where around 247-249V. Eventually the MP2 disconnects from the grid and the Huawei restarts.
A few minutes later, if we disable the inverters+battery pack, and just hook up directly to the grid, we’re back to 230V.
So I guess my main question is why? The installer has no clue and blames the grid, but “the grid” is obviously at 230V when we just connect to it directly. This is not the typical case where there’s surplus energy being fed to the grid in sunny days, with neighbor PV systems also feeding back to the grid or a Sunday with low demand. This was literally an overcast Tuesday morning where we were pulling 15kW from the grid at any given time (and balanced), yet it still was at 250V.
I don’t see how this could be, physically. So – what if the measurements are wrong? What are you measuring with (a good true RMS multimeter or a 10 EUR special from the big box store)? Where are you measuring? If you measure at multiple points under the same load conditions (grid, multi AC-In, AC-out, load), what are you getting?
The multimeter is from HT Instruments I believe. Besides that, I don’t think the sensor is to blame, the Victron readings matched those from the multimeter. Additionally, the CNC mills and lathes also showed overvoltage warnings when the Victrons (and myself) were measuring 250V on the grid. After the bypass was enabled and the multi readings were 230V, the machines did not show the overvoltage warnings again.
The voltage readings, with the same load conditions, had a variation of 1-2V across all the different measurement points (grid, Ac-in, Ac-out and mill).
I have to check if the meters show power factor, I don’t think they do, but will check tomorrow for sure. The output voltage of the Multis in inverter mode is 230V as well. Inverter mode is when they disconnect from the grid and are in “islanding” correct?
Ok, if you have mills and lathes your load is very inductive, you might need a compensator, the voltage is probably shown too high because of waveform distortions
We have a capacitor bank that’s supposed to account for it and compensate those inductive loads. I don’t have the capacitor bank specs here with me now but could get it tomorrow. Edit: The capacitor bank also helps to keep things more stable when we turn on the 30T crane or other hefty motors.
Anyhow, why is the voltage any different with or without the multis? The loads and capacitor banks are still there, and the grid is still the same.
Yeah… only that our “specialist” installer can’t find out. It’s very frustrating that neither the installer nor another electrician can find out. It’s a significant investment and we can’t even use it.
I’m aware this is just a forum, but this is where we are at honestly.
Update: with the solar system disabled (yeah I just love to call it solar system, sue me), machines showed overvoltage warnings again this morning. Grid voltage readings were slightly higher than 230V, but nothing out of the ordinary, they were around 235-237V all three phases.
Later today, I saw some linemen working on a pole by a high voltage transformer. So maybe this is all connected, and chances are there’s a reason these workers were sent there. Maybe not, I’m just trying to be optimistic here.