Residual Current Detection in inverters

[Radian]

I understand that Solar PV inverters have residual current detection built-in, e.g.

 

But what is the primary reason for this? Is it to disconnect the generation if a leak to Earth fault occurs within the inverter or solar panel array - or is it to disconnect if a leakage to Earth fault happens in the AC wiring connecting the inverter to the incoming mains? I.e. if the inverter was providing the current to a Live circuit in the home which was accidentally touched then the inverter generated current would be shut off?

 

While this latter case would be desirable I can't see how the residual current detection in the inverter could accomplish this as it's Neutral is not referenced to its Earth the unlike with the incoming mains. All current flowing out of L can only be matched exactly by current coming back into N as there is no internal link between N and E.

 

I can see how the current path being completed through the TN connection back at the meter might trip the main RCD in the consumer unit but the inverter will only disconnect for anti-islanding purposes which have a different set of criteria to RCD protection.

[Radian]

Path of inverter generated current flowing through fault from Live to Earth, returning via TN. Balanced current seen in inverter, unbalanced in CU RCD:

 

 

Of course this is for a temporary plug-in style grid-tie inverter, a 'proper' installation would make the connection the other side of the main breaker X1, X2. Then that would provide Earth leakage protection for the house circuits but not for the separate connection to the inverter.

 

'Proper' installations would have circuit breaker protection for this separate cabling to the inverter but do these also combine RCD protection as well?

[Radian]

Permanent installations connecting back at the meter tails (Henley blocks or inside CU) via MCB/isolators (not shown) are referenced to TN so residual current protection for inverter sourced currents is maintained:

 

 

Just getting this 'straight' in my head and putting it somewhere for when I next forget it. 📌 in about a week's time