Disengage from the grid and do what with the vast amount of power that suddenly has no place to go? That kind of power tends to break things. Powerplants have big cooling towers because disposing of heat is problematic.
And you're assuming that there is a throttle setting that lets the plant produce so little power that it only runs itself. Think of the Falcon 9--the landing is hairy because it's impossible for it to produce less thrust than it weighs. The engine will go out if you try to throttle it too much.
And you're assuming that there is a throttle setting that lets the plant produce so little power that it only runs itself. Think of the Falcon 9--the landing is hairy because it's impossible for it to produce less thrust than it weighs. The engine will go out if you try to throttle it too much.