Shelly plug S with Tie-inverters

[Galloz]

I have two systems generating power from tie-inverters (800W each) with two Shelly plug S on two different home power sockets

Both have the same behaviour: when I switch off Shelly Plug (locally or by app) this leads to trip the main differential breacker (30mA).

But if I remove manually the two plug no trip event. I think this is due:

I suppose Shelly Plug S has the relais contact on one only phase (so it not switch off both phases)

The Tie-converters generate a "differential power" not referred to a neutral point (if not connected).

So when both tie-converters wires are connected all is ok, but when they lost one wires (so the reference) on transient, before switch off (this is their safety work) should generate some currents that unbalance my home power grid and force differential breaker on trip.

Solutions:

I buy a Shelly snubber thinking that this can discharge this disturbance but it's not already tested.

To connect to Shelly Plug in series "in counterphase connection, so the "internal" switch off in cascade the other switch off (expensive and not approved).

Change my type AC differential breaker with a type F (expensive and not sure it will resolve).

Something else?

[thgoebel]

What is the reason for switching off the inverters? 

[tvbshelly]

Apart from thgoebel's question, you could use a contactor that disconnects both L and N. It is important that N is only disconnected after L and N is switched on again before L.

However, the RCD may still trip because there is a short time delay between L + N disconnection.

Edited July 4 by tvbshelly

[Galloz]

On 4.7.2024 at 18:59, thgoebel said:

What is the reason for switching off the inverters? 

Because I had problems to connect my four tie-inverters together (home differential breaker tripped), so having solar panels oriented differently I thought to do this.

Moreover panels production goes over home consumption plus batteries recharging rate, so not wanting to give energy to the grid (this because in summer production is greater and loads not)

But I solved my two problems (4 tie-converters together and switch-off with Shelly Plug problem by using a Shelly RC snubber. Great with 10€ cost!

[Galloz]

On 4.7.2024 at 21:26, tvbshelly said:

Apart from thgoebel's question, you could use a contactor that disconnects both L and N. It is important that N is only disconnected after L and N is switched on again before L.

However, the RCD may still trip because there is a short time delay between L + N disconnection.

I solved the problem by using a Shelly RC snubber putted in parallel with L and N lines near Shelly Plug S!