There are different causes for loss of utility power. At one extreme your service drop is knocked down by a tree. Your inverter or generator could keep those wires hot without any significant current drawn. Someone picking it up could die.
If there is no damage in your area/town but the upstream transmission grid is what is out, you should see about the impedance of your nearest utility transformer. Unless we are talking about a solar/wind farm, it is likely all the other customers are going to overload the system. Current going too high and/or voltage going too low should ideally trip the disconnect.
Now you can monitor the utility for power restoration. But there is a new risk: someone else's power system could make it look like the utility is back.
