Since, and unless electricity has properties I’m not aware of, it’s not possible for electric power plants to produce only and EXACTLY the amount of electricity being drawn at an given time, and not having enough electricity for everyone is a VERY bad thing, I’m assuming the power plants produce enough electricity to meet a predicted average need plus a little extra margin. So, if this understanding is correct, where does that little extra margin go? And what kind of margin are we talking about?
In: Engineering
>it’s not possible for electric power plants to produce only and EXACTLY the amount of electricity being drawn at an given time
Traditionally, this is exactly what happened. Now we have a small amount of energy storage that can act as a buffer, but it is still pretty miniscule when compared to peak load.
Generators don’t know exactly what the load is at any given time, however they are able to monitor their rotational speed (directly correlated to frequency for synchronous machines). When additional load is added, it essentially “bogs down” the grid and lowers grid frequency, which can be immediately seen and responded to by synchronous generators.
Generators have Primary Frequency Response built into their governor, so that a frequency drop or rise will bias the generator output in the right direction. PFR should kick in within a few seconds and last about a minute. Secondary Frequency Response is an automated system located at a central dispatch location that then kicks in to regulate the units up and down as necessary for longer duration correction, and tertiary frequency response would be dispatchers working with the sites to start up or shut down additional generators.
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