My initial setup is to use burner inserters (which don't need an electrical connection to move) to feed the boilers, combined with priority splitters so that th

My initial setup is to use burner inserters (which don't need an electrical connection to move) to feed the boilers, combined with priority splitters so that the ore smelters only get whatever coal the power doesn't get. Combined with overprovisioning of steam power, it means that the factory will start shutting down before the power grid gets overheated to the point that it can't keep itself up. Later, I move to nuclear power, where fuel use is such that even glacial low-power inserters can keep the facilities fed through a power spiral. Although my massive 12-reactor facility did rely on pumps to keep the steam moving fast enough through my flowmeter to regulate power... but when you have a 12 reactor powerplant, power death spirals take long enough to occur that you will have ample time to fix them before things start needing black start.