How exactly is power generated by a power plant regulated to 60 Hz?
I'm not quite sure of your question. To get a 60 hertz generator output, you control is speed (rpm). If the power generation becomes greater at some point in the grid than the load, the grid frequency will tend to increase (and it's not instantanious). The reverse is true; when the power load is greater than the generation, the frequency will decrease. The way the grid frequency is maintained very close to 60 Hz is to have every area of control responsible for measuring their frequency and controlling their generators. This is usually done with the help of a computers using automatic generation control software.
I can't answer your question. I do remember hearing a teacher back in the 1970s say that power plant output frequency drifted a bit, and since so many electric customers at the time used stepper-motor clocks, the technicians at the power plant would make adjustments now and then to bring the clocks back to perfect time. In other words, if the number of cycles put out by the power plant over a 12-hour period turned out to be too great by 600, all those clocks connected to the power grid were ahead by 10 seconds, so maybe for the next hour the generators would be run slightly slow so as to lose 600 cycles. Judged over really long periods of time (years), the clocks connected to the grid managed to be extremely accurate.
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