{{main|Frequency control|Voltage control and reactive power management}}
Small mismatches between the total demand and total load are typical and initially are taken care of by the [[kinetic energy]] of the rotating machinery (mostly [[synchronous generatorsgenerator]]s): when there is too much supply, the devices absorb the excess, and frequency goes above the scheduled rate, conversely, too much demand causes the generator to deliver extra electricity through slowing down, with frequency slightly decreasing,{{sfn|NERC|2021|p=1}} not requiring an intervention form the operator. There are obvious limits to this "immediate control", so a ''control continuum'' is built into a typical power grid, spanning reaction intervals from seconds ("primary control") to hours ("time control").{{sfn|NERC|2021|p=6}}
