RCD trips when connecting 1-phase shore power to 3-phase system

Q&A and troubleshooting
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1

Hi all,

I have installed a 3-phase system for a client with Quattro 48-5000’s. I have “switch as group” turned off and when connecting only 1-phase shore power to the system, L1 Quattro goes into charger/pass-through mode and the other two stay in inverter mode, great. When switching power on to the consumer unit, the 3-phase shore power RCD trips. Sometimes immediately, sometimes after an hour. Does anyone know what good be the issue here?

Everything is grounded to a central grounding bus, neutrals of every unit are obviously connected, but AC1 in, AC2 in, AC1 out and AC2 out have there neutrals separated from each other. I have a boiler connected to AC2 out as solar dump. Don’t know if that matters at all.

EDIT: Now that I’ve thought about it for another 30 minutes, I think it must be the neutral-earth connection that excists in the other 2 units while in inverter mode. This basically provides an earth leak for the shore power. How do I deal with this?

2

Victron inverters have a ground relay that connect the neutral to the earth, it is programmable.

Check 7.4 in the wiring unlimited book for more information.

3

Hi Mac, I know about that, but it would prevent the RCD from L2 and L3 from working so that’s a big deal for safety.

I can’t imagine I’m the first one having this issue tho. Maybe I am still missing something simple?

4

Also add an isolating transformer to the system.

5

Will do. Luckily this was on the planning anyway. Will post back for future readers maybe.