Avoid bypass on Quattro ESS installation (problems with voltage drop due to distance)

Q&A and troubleshooting
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Hi all! This is my first post here. I have a query concerning a design we have done.

CONTEXT:
It’s a quite common ESS instalation with a PV coneected through mppt controllers to DC side (we have pylontech batteries) and 3 Quattros. We have a technical room wiht the batteries & electronic material (mppt controlers, batteries…) and the distance with the AC Electrical service entrance is around 100 meters. The quattros are 3 x Quattro 48/10000 in three Phase Configuration. The AC is 230V, and the cable we are using is 35mm2 so we are less than 3% of voltage drop (Considering 230V and 50A the voltage with the drop would be 223,8).

TOPIC:
As long as we use power from the PV solar and the batteries, no problem, the electricity goes 100m from the Quattro to the electrical cabinet. But in case there are no solar power and the batterries are in low SOC, then it seems that the Quattro will move to Bypass state (Passthru). See attached image of other installation (Before the sun comes there are some passthru status). And my question is: In that situation, then the AC have to move from the electrical cabinet (100m) then by bypassed by Quattro and do another 100m to the cabinet again to the loads. Then what happen with the voltage drop? if AC in arrives with a drop (223,8V) it is bypassed then I can get in the load a very low voltage. isn’t it???

We want to prioritize solar, then batteries then grid, but is there any way to avoid the bypass state? The baterries can last all the night till the sun comes, but if it is cloudy? Is there a possibility for example to use batteries from 40%-30%SOC along with the ACin grid to have a stable signal at the end? Just use the inverter/batteries at some point to stabilize the signal and not do a pure bypass.

Is there any other solution? I have something in mind, but don’t want to condition answers, and I don’t like a lot. :slight_smile: I’m a beginner on my firsts installation. Sorry if this could be stupid at some point.

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If the grid power has to do a 200m run, to and from the ESS installation, then you will need to beef up BOTH sets of AC cables, to achieve < 2.5% drop in each direction. As you already have cables installed, the easiest way to do this is to parallel another set of identical cables.

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Thanks Mike! It is not yet installed. Only the material purchased. But with 35mm2 cable, and a quattrro 48/10.000 , the current should be around 45A, so the drop is already around 2,5% per each 100m. My concern is when bypass then we will get 2,5%*2 a voltage drop around 5%. An there is still some distance from that electrical cabinet to the loads.

4

I thought of one alternative, Victron have a data sheet for wiring of an external transfer switch:

If the transfer contactor is installed close to the electrical cabinet, but controlled from the ESS, then there will be no loss of voltage when on mains. It would also be possible to install 2 such contactors, one at each end of the 2 feeds, then the feeds will also be paralleled on grid, reducing the cable loss while charging the ess.

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Thanks again Mike. It is quite interesting what you sent :slightly_smiling_face:. I need to study more quitely the flexibility. In fact, when I was saying I had something in mind, it was the use of an ATS (automatic tranfer switch) to manage this (on the cabinet side). We were planning to put this kind fo Switch, in case of Inverters/failure or whatever to bypass the Solar installation. (Input1 AC_out form solar, Input2 grid and output to loads) The idea was then to control the ATS with any extra cable. The ATS can switch base on the drop of the voltage from one entry to the other. Either the same voltage drop manage the tranfer or we could try to stop (not sure if possible) the AC_out from inverters based on %SOC of batteries and Solar power from the Pannels. What do you think?
Not sure, if in the case of inverter failure the solution you sent could work. This installation would be in Africa, and the possibilities to have problems with the system and have the system down till it is fixed are high.

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in case of inverter failure, it would be possible to arrange an external manual control for the contactor, bypassing the internal relay in the inverter. One would need to ensure that the AC out of the inverter was isolated before engaging this manual switch.