RCD Tripping and Strange behavior switching from Battery to Grid.

[johanmeijer]

I replaced my 2 Growatt -S inverters (750-S and 1500-S) with a MIN 36000 TL-XE and after a couple of weeks with a MIN 3600 TL-XH with ARK HV batteries (strange? Yes but this was an opportunity I couldn't pass up).

After 2 weeks running with the XE suddenly the RCD of an other set of power groups kicked in (or out) when the solar panels started working in the morning.

The inverter has it own group with its own RCD (300ms) and nothing happens with this group.
After testing it was possible for me to deduct to problem to one group (from the 3 connected with the tripping RCD).
But I have not be able to detect what causes the problem in this group (electronic equipment or other devices like sockets, switches or lamps).

When testing with switching of and on the solar panels most of the time the problem appears.

In the meanwhile I have been able to buy a MIN TL-XH with ARH HV batteries (15Kwh) and installed the new configuration. And to my disappointment the RCD tripping problems stayed.

Also a new problem arises. When I run on batteries in the evening/morning and the Solar panels start producing power, the inverter disconnects from the Grid and the procedure to connect to the grid with solar panels starts (with the relais clicking ritual). While this happens very early in the morning, and the solar power produced by my two strings is not enough immediately, the connect to the Grid can take 15-30 minutes.

So in practice I run 15-30 from grid while the batteries are not empty and the solar panels does not produce enough power yet.

Secondary effect is that the RCD tripping still occurs occasionally, while I hoped to eliminated the problem while there is no need to disconnect / connect to the Grid when in battery operation mode.

I write RCD trips happens occasionally while it happens again 1 time this week (within 7 days). That also means that 5 days it didn't happend and that is much better then it was.

But I still do not have any clue what causes the RCD tripping on the other power circuit and have no ideas left anymore how to detect what causes this problem. Problem solving is also more difficult while the failure is not that reproducible as it was in the past.

Is there somebody which recognizes the problem and can help me with solving this:

• RCD Tripping in a secundaire power circuit (separated from the Inverter group)
• Inverter disconnecting from the grid when solar power kicks in (and running in battery operations mode)

[tabascoz]

Johan, I'll describe my issue in the morning (I'm busted for today) but may i ask you to:

• Measure voltage from ground to neutral in both situations, solar and grid. Measure it in a socket below the secondary power switch you mentioned.
• For testing purposes, would it be possible to test disconnecting ground that comes from the energy grid and see if that fixes the problem? of course it's just a test but that changed the game for me.

Cheers,

[johanmeijer]

Thanks for your reaction. I will perform some test this weekend.

[tabascoz]

So my experience so far....

Purchased new house for about two years. Installed two SPF5000es in parallel. At some point from weeks to few months, going to raining season i noticed RCD random trips both from General Grid and secondaries circuits (I have tree, protected by RCD at the entrance).

However the house electrical (and general) situation wasn't great and i started verifying everything. Found a bunch of weird stuff but the randoms disconnects diminish but were happening especially when it were raining.

I kept in this loop, trying to isolate circuits to "understand" what would be the cause. Nothing...

At some point i let it go and started to develop my automation to control inverters according to my Grid power plan etc. So i have a big automation that checks forecast generation, forecast demand and do the math IF i need to recharge the batteries overnight ( as grid energy is cheaper) or not. This happens at 10PM.

When the routine started i finally understood what was happening... some of the times when automation commanded inverters to switch to grid, sometimes Grid main RCD and Secondary RCD tripped together, sometimes just the main but never the secondary alone.

I kept one year trying to fight this thing until i gave up LOL. This issue made the house energy to go down in the evening like tree times because it switched to Grid to recharge the batteries, RCD tripped and I ran out of batteries.... I created contingency strategies to deal with the situation, sending emergency message to my mobile so i could do something about it ( rearm RCD).

One day, like 4 months ago something new happened. The RDC tripped and I was not able to turn it on, no matter what. It tripped again and again instantaneously. So I disconnected all inverters and tried, it stayed connected. BUT i was not able to connect the inverters anymore.

Than out of misery i had the idea to disconnect the ground from the inverters to general ground and everything magically started to work. (GREAT but not that much)

So i concentrated on grounds and find out that my neutral was offset by 20V. So ground-neutral was measuring 20v, but neutral-phase was normal at 235v. I know this is a common symptom of bad neutral connection but when it is the issue you wont be seeing a steady neutral-phase voltage. I'm able to draw 8KW from grid without any power or voltage fluctuation so I knew it wasn't the case.

I read in some local (Portugal) forum another guy saying this was a common issue that happened in a nearby location. I think this was the root cause, Sometimes it happens sometimes it doesn't. Now for ex. is stable.

Also i did only one change in the inverters. With the last firmware version i noticed two new options emerged:

FRST - 051 - under advanced calibration menu and
BASE - 066 - under normal menu.

After this change, i am now two months stable without any occurrences, BUT i noticed also that the neutral offset is normal... I am still unsure

Cheers,

[johanmeijer]

Maybe I missed it but what did you changed?

And the menu's are the menu's @the inverter ? Do you know if there are registers with the same purpose?

[tabascoz]

I changed the two parameters - the other "potential" change was not made by me - the Grid neutral-ground difference is now under normal values.

The two parameters are at the inverters. I am not sure about the registers, potentially there are, but these parameters are not documented. The best "guess" i have on the first "FRST" would be to prioritize export excess to the grid, but AFAIK SPF5000's aren't capable of exporting.

The second i have no wild idea.

[johanmeijer]

I did a little bit of maintenance in the group box yesterday. Replaced one 40 years old RCD (and the, also 40 year old, circuit breakers that where connect to it), added a Chint DSSU666 smart meter and did some rewiring.

Until now no RCD tripping, but I am not convinced yet. Let see what happens te coming days.

[tabascoz]

Wow... I suspect this house has a 30yo ROD ... let me know if it fixes the issue, I might consider replacing. The problem is that i need to ask for the power company to do it as I am not supposed to do (it's their equipment) , and for that I'll need to explain the issue , which will be tricky

[johanmeijer]

I saw on youtube that with the years a degradatie of the RCD can be expected (even from 30ma to 10-15).
I am not sure if that is true but better safe then sorry.

Yeah in the Netherlands the Group Box is part of the house and responsibility of the owner. But your are not allowed to do anything there if it does not have a Main Switch that can shut off the whole Box at once.
Older houses do not have a main switch, neither did mine. But now it has ;) (it was a little bit risky')

[tabascoz]

i'm on the same boat, heard i can overload the meter then it will shut off until i reset, looks it mitigates some of the risk. I'll as a friend if there's really a problem to change mine ( i mean with the power company) , but please let me know if it changes your issue... might be a light, although there are some weeks it doesn't happen here ( hope it stay like that )

[tabascoz]

HI there, any tripping activities? hope not! Spoke with the friend, he said if there's a seal fixed in the breaker i cannot do anything, otherwise i can - so no seals in my house fortunately. Given the situation is sort of "under control" here, I'll wait for your comments to invest on a new breaker.

Cheers

[johanmeijer]

No tripping since the update of the Group Box......

I am not totally convinced (Still using my phone as safety alarm in case the bedroom clock is not working because of a power failure) but start looking good.