4 ms·

In general, slowing frequency is an indicator of a heavily loaded grid. I don't have an appreciation how much the frequency can practically be off the nominal 5

In general, slowing frequency is an indicator of a heavily loaded grid. I don't have an appreciation how much the frequency can practically be off the nominal 50 Hz (in Europe) before it indicates grid failure.

cookieswumchorr 6y ago
does this happen if the heavy load is at region scale? because at small scale (within a village in my experience) the voltage would drop. I didn't measure the frequency though.
foobarian 6y ago
This is fascinating to me. What is the mechanism by which this happens? The added load causes an average slow down across the population of actual spinning generator bits?
- gefh 6y ago
  Yes, the generators literally have to push harder and slow down.
  - deleted 6y ago
    [deleted]
- thatcherc 6y ago
  That's exactly right. Extra electrical draw on the grid (or a loss of electrical production elsewhere) causes the turbines in power plants to physically spin slower due to increase load on each turbine. An (imperfect) analogy would be if you and a friend were biking up a hill on a tandem bike. If a third person hopped on the handle bars (or your friend stopped pedaling) the bike's wheels would slow down, assuming you are putting a constant amount of power into the pedals.
  - jonsen 6y ago
    Tangentially (or maybe tandemially :) this illustrates the problem of synchronizing an e.g. solar power unit delivering to the net. The person jumping on a multicycle in speed must synchronize their feet to the rotating pedals to actually add power.
- nabla9 6y ago
  Most power generators are rotating engines (there are exceptions like solar and and batteries that use power inverters). Increasing load decreases frequency exactly the same way as anything rotating slows down when you increase load. Electric grid is like chain in a bike. Generator producing power leads a little. Loads follow little behind. They are not exactly matched. Like bike chain is tighter to one direction and looser to other under load. Mass of rotating generators provide kinetic inertia into the grid so it reacts very little to small variations in the load. But if the load becomes too high and turbines can't speed up, frequency of the grid slows down.
fennecfoxen 6y ago
In practice it depends a lot on how a bunch of specific power equipment is set up. Remember that the A/C power grid needs to be synchronized across the entire continent, so each A/C generator that makes A/C power and runs at 50Hz needs to have the position of a physical object (the rotors) match the position in the current power cycle. If it's badly wrong, you have power-plant sized energy feeds fighting each other — imagine a train wreck, two massive oversized freight trains smashing right into each other. It's like that, but with electricity instead of a physical collision. This can obviously cause major damage, so once you start deviating from the reference frequency by enough, it's safer to just cut off the interconnects and go offline.
posix_me_less 6y ago
Under 49Hz they start disconnecting consumers. If that does not stabilize the dropping, under 47.5 Hz they disconnect the power plants and the network fails. [1] [1] https://www.netzfrequenzmessung.de/abschaltung.htm https://www.netzfrequenzmessung.de/abschaltung.htm

cookieswumchorr 6y ago

does this happen if the heavy load is at region scale? because at small scale (within a village in my experience) the voltage would drop. I didn't measure the frequency though.

foobarian 6y ago

This is fascinating to me. What is the mechanism by which this happens? The added load causes an average slow down across the population of actual spinning generator bits?

gefh 6y ago
Yes, the generators literally have to push harder and slow down.
- deleted 6y ago
  [deleted]
thatcherc 6y ago
That's exactly right. Extra electrical draw on the grid (or a loss of electrical production elsewhere) causes the turbines in power plants to physically spin slower due to increase load on each turbine. An (imperfect) analogy would be if you and a friend were biking up a hill on a tandem bike. If a third person hopped on the handle bars (or your friend stopped pedaling) the bike's wheels would slow down, assuming you are putting a constant amount of power into the pedals.
- jonsen 6y ago
  Tangentially (or maybe tandemially :) this illustrates the problem of synchronizing an e.g. solar power unit delivering to the net. The person jumping on a multicycle in speed must synchronize their feet to the rotating pedals to actually add power.
nabla9 6y ago
Most power generators are rotating engines (there are exceptions like solar and and batteries that use power inverters). Increasing load decreases frequency exactly the same way as anything rotating slows down when you increase load. Electric grid is like chain in a bike. Generator producing power leads a little. Loads follow little behind. They are not exactly matched. Like bike chain is tighter to one direction and looser to other under load. Mass of rotating generators provide kinetic inertia into the grid so it reacts very little to small variations in the load. But if the load becomes too high and turbines can't speed up, frequency of the grid slows down.

fennecfoxen 6y ago

In practice it depends a lot on how a bunch of specific power equipment is set up. Remember that the A/C power grid needs to be synchronized across the entire continent, so each A/C generator that makes A/C power and runs at 50Hz needs to have the position of a physical object (the rotors) match the position in the current power cycle. If it's badly wrong, you have power-plant sized energy feeds fighting each other — imagine a train wreck, two massive oversized freight trains smashing right into each other. It's like that, but with electricity instead of a physical collision. This can obviously cause major damage, so once you start deviating from the reference frequency by enough, it's safer to just cut off the interconnects and go offline.

posix_me_less 6y ago

Under 49Hz they start disconnecting consumers. If that does not stabilize the dropping, under 47.5 Hz they disconnect the power plants and the network fails. [1] [1] https://www.netzfrequenzmessung.de/abschaltung.htm https://www.netzfrequenzmessung.de/abschaltung.htm