Load shedding is the planned dropping of load when generation cannot meet demand, either automatically by underfrequency relays set in stages such as 49.0, 48.8 and 48.6 Hz on a 50 Hz system, or manually by the system operator during a sustained shortage. Rotating schedules spread the outages across areas in blocks of one to a few hours. It sacrifices some customers so the rest of the system stays synchronised and a total blackout is avoided.
Frequency hit 49.2 and kept falling, first stage of underfrequency load shedding took out 300 MW before it turned around.
Also heard as
- load shed
- rolling blackouts
- rota disconnection
Related terms
Brownout
Sustained drop in supply voltage, caused by overload or applied on purpose to cut demand during a shortage.
Black start
Restarting a power system from total shutdown using generators that can start without any outside supply.
N-1 criterion
Planning rule that a grid must stay within limits after losing any single major element such as a line or generator.