[jleahy]

That’s not correct. The frequency provides an indication of how much power is being drawn. If the frequency is low then generators supply more power to bring it back to 60 Hz.

If there was not a well known fixed frequency it would be impossible to evenly distribute load over power stations. All generators have a %load vs frequency delta curve built into them which is precisely calibrated.

[applied_heat]

I think the parent is more correct than you are?

The frequency does not provide an indication of load. The frequency can be 60.00Hz with 20,000 MW load in Ontario or with 10,000MW.

Changes in frequency provide a measure of changes in the balance between generation and load.

The generator’s prime mover’s governor has a droop function set so that typically a 5% change in frequency will result in a 100% change in output. This is how most generators on the grid arrest changes in frequency, but they would not restore the frequency to 60Hz. The droop allows for a steady state frequency error.

A handful of special generators are used to restore the frequency to 60Hz or balance the generation and load in an area.

The precise frequency does not matter, if one generator thinks the frequency is 59.99 and another thinks it is 60.01 their outputs will only be a little higher and lower than their load setpoint. It does not matter if they share changes in load perfectly evenly, so long as generators on the system in bulk respond according to their capabilities.

[jleahy]

The point is that they need to be synchronised in order to respond to changes in load.