Third day without water now. You can get bored with this.
I'll have none tomorrow, but I'm confident it'll be back on by 1600 ish. This is only because we will have no electricity because they are cutting down trees that are in the way, all day. Its a very rural area, and we don't have mains water, but its pumped from our borehole. Not a real problem for us, as there will be some storage, but its an ideal excuse to go out and do some vital shopping, and have lunch out. biggest downer? no electricity supply means no solar PV generation either. Whoever decided that domestic PV installations couldn't have automatic disconnect, and therefore couldn't run in island mode, needs a kick in the bollocks.
I presume that is to avoid having to add controller circuitry that would handle synchronising with the grid (while devices are drawing power), when connection is reestablished.
So, with your current (sic) setting, I guess the incoming grid power is used to drive the frequency.
I think it's just a safety feature to avoid back-feeding ostensibly 'dead' cables and electrocuting line workers, in the absence of proper isolation.
I don't think re-synchronising an inverter is particularly tricky; it's not like there's a rotating machine that needs its speed slewed. At worst you can just drop the output for a cycle or two and come back in sync, and let the load cope with the glitch. I have a UPS that switches back and forward between dual-conversion and bypass mode when the mains voltage is wibbly, and I think it just switches a relay. DC power supplies cope fine, and mains loads are unlikely to care.
No reason you couldn't have an island-capable inverter with appropriate changeover switching, but most people don't want to pay for that. I think it tends to be a feature of battery storage systems, because a pure-solar supply becomes quite unpredictable. (Perhaps in a non-combined system the battery inverter does the islanding, and a standard PV inverter can just tie to that?)