Just shut the main breaker off. Always the first step.
“The reason is because linemen or technicians on that line could be electrocuted. This generally requires a disconect switch from the mains.”
For a conventional generator, very true. In this case, I suspect the inverter does that job. All the inverter has to do is shut off output power for a millisecond and then see if output voltage collapses - if there’s no other source (i.e., grid power), then the output voltage will collapse, if there is a source, it stays at 120V. Do that once per second.
“The reason is because linemen or technicians on that line could be electrocuted. This generally requires a disconect switch from the mains.”
Yes feeding 120V AC back into a plug also feeds the panel and up the feed line to the transformer which turns it into 7200+ volts down the line current is small but voltage can kill.
Grid sensing inverters can avoid this without a disconnect, they sense and sync to the 60Hz grid phase angle and will not energise until they sense this waveform which means the grid is up and flowing they grid follow the phase angle not push active and reactive power using an internally generated phase source.
The consequence of this is two fold one they only run when the grid is active thus protecting the line man and two you cannot push power out of your meter only into other loads behind the meter again current flows towards a lagging phase angle think of it as a pump pushing against the incoming water main pressure. When you open a faucet the pressure on your pipes behind the meter drop slightly so flow happens if the pump behind your meter is slight above the now lower pipe pressure flow goes from the pump to the faucet but not out against the higher water main pressure it’s trapped behind the meter.
Grid sensing inverters do this by design they are only feeding your needs not net metering which most RPPs frown upon and will void a contract over it. Even if they do allow net metering it’s a the avoidance rate as in what what the cost of not buying the wholesale power they would have sold you at the full retail price, you will NEVER get the full retail price for power you send out of the meter.
For that you must own a LLC and form a VPP with megawatts worth of virtual capacity to sell to the wholesale power market, and then form an additional RPP if you want to sell yo retail sales so you need 3 legal entities a parent LLC a VPP and a RPP.