If your electrical interconnect fails it could be weeks before power is restored. Skip to about 10 minutes for the part about restarting a blacked out power grid.
I have no idea what black start capabilities may attach to solar or wind, but in all cases I know of on fossil fuel (literally dozens) and nuclear plants there are electrically isolated gensets on sites that can bring the plants to life. It MAY take a while due to the stepwise nature that must be taken. Grid down is not necessarily a long term deal, tho' locally parts of the grid may be disabled longer than the rest.
Solar needs about a 60.1 to 59.8 grid signal to connect to the power grid. Big wind can actually be set run at a range of frequency like 60.1 to 59.3. Grid tird solar is really horrible at handeling any kind of start up surge.
That is why Hydro makes up the West Coast Base loading... If you gots the Head, you gots the Power...
We have frequency high/low shut-downs for years in stand alone locations along with a multitude of other safety devices Voltage, vibration, temperatures safety highs, Even the cooling fans are covered, Overspeed, Under-speed, Oil pressure. Gas freezing up,All that is nothing new. Been there,Done that and got a T shirt
Yep, if you have a source of field current if the generator breakers get dumped on fault and the generators don't have an exciter on the same shaft. Usually, absent a same shaft exciter, that field excitation will be a small fossil fueled gennie. But hydro is GOOD stuff, too bad the greenies are actively trying to get the dams taken out to restore the original conditions of the streams. That would include flooding ----
Yeah improper shut down can cause loss of residual magnetism. Any new gem set should flash the field with 12v on start up because they just assume the Gen set is likely to be shut down under load, such as running out of fuel.