Overfrequency occurs when the total electrical generation on a power grid exceeds the total load, causing the synchronous generators to spin faster than their target speed. Grid operators must correct this imbalance quickly by curtailing generation or shutting down plants. If left unchecked, the excessive speed can cause severe mechanical damage to turbine rotors and generator shafts.
The sudden loss of the aluminum smelter load caused an overfrequency event that tripped two wind farms off the grid.
Related terms
Load shedding
Deliberate disconnection of blocks of customer load to stop frequency or voltage from collapsing.
SCADA
Supervisory control and data acquisition: the system that lets a control room watch and switch remote plant.
Islanding
Condition where part of a network stays energised by local generation after being cut off from the main grid.