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3-phase 10k MP - Problems turning on the grid on AC In

I run a 3-phase system with 3 Multiplus 10000 and a 50kW storage from 16 x Pylontech US3000C.

The system has been online since December 17th, 2022 and since February 5th, 2023 we no longer draw electricity from the grid. We have been feeding the surplus into the grid since February.

On April 27, 2023, the three Multiplus lost the grid and try to switch it back on and lose it again. Only a red tile can be seen on the Cerbo Display, with no heading "AC Grid".

If the grid is switched off and the system is in isolated backup system, the system works without any problems.

If I switch the 4-pin Hager 1-0-2 load switch to "grid only" and switch on the grid, this also works without problems.

If, on the other hand, I switch the grid on to the Victron system, the system tries to switch the grid to AC IN after the relay test, but the relay drops out again immediately. The Gavazzi Power Meter shows 230V on all three phases. Then the system switches on again, holds the grid, synchronizes the Fronius inverters, but the Gavazzi Power Meter shows L1 160V, L2 240V and L3 290V. The Multiplus then open the relay and 230V is again displayed in the Gavazzi Power Meter.

I have an external NA protection in front of the Multiplus, but it does not trigger.

The process or situation is difficult to describe, I made a video of it and put it here:

https://drive.google.com/file/d/18SHZxT_6cY9fPjppfuWSu9gogGOPub6Y/view?usp=drivesdk

Please watch to the end.

We checked everything and found no error. There were no changes to the wiring of the system prior to the failure.

Can anyone give me a tip? I'm completely helpless after a week of troubleshooting?

Multiplus-II
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janieronen avatar image janieronen commented ·

Loose contact or broken relay on L1 or neutral bond issue? Have seen similar case where one pole from relay showed full voltage without current but under current voltage dropped. In you case looks that ground and neutral bond is not made same kind that we have as there should not be over voltage on other lines. How your MPs stay on when 290V on L3 or is it separated already at that point? That's out of all limits and system should drop down. What grid code is used? Wiring diagram? And if you export data from VRM advanced page about that time it could give better picture about situation.

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3 Answers
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Mike Dorsett answered ·

, but the Gavazzi Power Meter shows L1 160V, L2 240V and L3 290V.

this is indicative of a neutral fault, and is severe enough to turn the multi's off. Check all neutral connections thoroughly.

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vici avatar image vici commented ·

I had the suspicion too and therefore had all neutral conductors and their connections checked by the electrician. It couldn't find any error. The direction of rotation of the phases was also checked again.

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vici avatar image vici commented ·

The Gavazzi Meter only shows this when the Multiplus switch through. This problem does not occur in isolated operation and also not when I am only in network operation.

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vici answered ·

Here the wiring diagram


2023-05-04-architektur-pvspeicher-fehr.jpg


2023-05-04-architektur-pvspeicher-fehr.jpg (205.8 KiB)
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vici avatar image
vici answered ·

Short question to the wiring diagram.

Is there anything wrong?

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