What most people don't know is, according to correct standard, if you are using inverter you are suppose to use second dedicated RCCB for it, your main RCCB gets bypassed when inverter connections are made.
So when you have power your main RCCB will work to protect you, in case main power goes out, the inverter turns on, then your second RCCB will protect you, in case you touch live and ground.