20 ms·

> Apparently to match the demand at given instance electricity plants rotate their turbines a bit faster or a bit slower instead of switching a complete plant o

> Apparently to match the demand at given instance electricity plants rotate their turbines a bit faster or a bit slower instead of switching a complete plant on and off, which results in slight deviations from the 50Hz standard but it is fine as long as it stays between the limits. This is slightly imprecise. It actually works the other way round: the demand is "communicated" through the network by slight changes in the frequency. This can be described best for the example of steam-based generators, as they are typical for the majority of coal/gas/oil/nuclear power plants. When demand for electricity grows, for example because a new factory is powered up, the turbines in the power plants are experiencing larger forces attempting to slow them down, starting with the power plant closest to the new factory. The speed (and thus the frequency) is constantly measured, and if it drops, the steam valve is opened just a tiny bit more to counteract the drop. If this is not possible because the power plant is already at maximum output, either other power plants have to take the load (and the electricity is then routed through the network to the factory) or additional power plants may have to be added to the network. The important thing is: the frequency change is a means of communication, it originates from demand changes, and because the entire network is kept in sync, it works to communicate demand changes across the entire network. Power plants providing energy to a sub-part of the entire network always attempt to run their turbines with the exact same speed of 50 rotations per second, which should ideally always conform to the frequency in all other sub-networks that a specific sub-network is attached to. If just one of these sub-networks does not perform its duty of re-establishing 50 Hertz by powering up their own plant output, the rest of the network must either channel enough power into this sub-network to allow its local generators to re-establish 50 rotations per second by taking some of the load off of them or - if that is not possible or decided against - must also deliberately drop their frequency (and thus the rotational speed of their generators) to match the sub-network that is deviating. The only alternative to this would be to drop off the deviating sub-network entirely, but that is usually only done in extreme cases of deviation.

mrtksn 9y ago
Thanks for the correction, as more you read the more interesting it gets.
- Slartie 9y ago
  It definitely does. And very interesting thoughts come up, especially when you add newer developments like non-rotational-mass-based power sources (solar power, batteries, stuff like that) into the mix. Because at the moment with the high number of traditional steam-powered generators, the rotating mass of the turbines and their inertia serve as a kind of buffer against sudden swings in electricity demand with an ultra-quick response time of "basically no time". As a second buffer stage we have the steam supplies in the plants, which can be quickly accessed just by opening a valve, thus the response time is non-zero, but still quite short. Now replace all those generators with some other power sources without those inherent balancing capabilities (that probably weren't explicitly built into them, but that just happen to be there because of their construction) and you'll get a network that is much more vulnerable to sudden changes on the demand side. Now, explicit mechanisms of storing energy in a way that can be accessed in literally zero time need to be introduced into the network, just to keep it stable and to provide other regulation mechanisms (of which a lot of them also have to be re-thought) with enough time to do their job. I wouldn't wonder if there were already plans for building large rotating masses with motors on them that are kept at network frequency, with the motors switching over to serve as generators when the frequency drops.
  - Piskvorrr 9y ago
    Well...that's essentially the pumped-storage model, except it also takes tens of seconds to spool up: http://virtualniprohlidky.cez.cz/cez-dlouhe-strane-aj/ http://virtualniprohlidky.cez.cz/cez-dlouhe-strane-aj/
  - beojan 9y ago
    > I wouldn't wonder if there were already plans for building large rotating masses with motors on them that are kept at network frequency, with the motors switching over to serve as generators when the frequency drops. Flywheels? Yes: https://en.wikipedia.org/wiki/Flywheel_energy_storage#Grid_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage#Grid_e....
  - blattimwind 9y ago
    Synchronous machines with no net shaft power are sometimes used to supply reactive power, but these also contribute a coupled rotating mass. (edit: Apparently English people call these "synchronous condenser") The question of "how can we build a large and stable grid without thousands of tons of rotating mass?" is an area of very active research I've been told.
tormeh 9y ago
If anyone's thinking of making a clock that assumes the average frequency is 50Hz: Don't do that. There is no commitment to having the average frequency be 50Hz. There is a commitment to keeping frequency close to 50Hz, but no one in the energy industry is thinking about the average. So don't build things on top of that.
- duffmancd 9y ago
  It depends where you are. I know for example that the Australian standards require an accumulated time error of less than +/-5 sec on the mainland (+/-15s in Tasmania). Looking at other comments, it seems that we're a little weird down under and most places don't track the drift.
- emiliobumachar 9y ago
  Additionally, it will be a region-locked clock by its very nature. We use 60Hz here in Brazil.
  - rowyourboat 9y ago
    When moving from the US to Europe, I had the opposite problem. I had brought along a number of devices that I powered off a transformer (230V -> 115V) here, among them an alarm clock. Which worked off the AC frequency and thus was losing 10 minutes every hour on 50Hz.
- zAy0LfpBZLC8mAC 9y ago
  Yes, there is, any accumulated phase error during the day is normally corrected at night.
- petschge 9y ago
  That is actually not true for the synchronized european power grid we are talking about here. The time that a clock that runs of the power grid is known as "Netzzeit" (grid time) and there is standards on how far that is allowed to deviate from the legal, public time. There is websites such as https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html https://www.swissgrid.ch/swissgrid/en/home/experts/topics/fr... that track and display the deviation.
Fiahil 9y ago
This is super interesting ! I have a few questions ! How does the demand affect the frequency ? Is there a logical unit, somewhere, responsible of "communicating" through the network ? Or is it a physical effect ? > When a factory is powered up, the turbines in the power plants are experiencing larger forces attempting to slow them down. How does something like a higher demand, a drop in frequency, translate to a larger force attempting to slow down the turbines ?
- tehwalrus 9y ago
  Energy conservation. You're pushing (literally) against the electrical workload of the connected circuits (places where people have plugged a device into a socket and made a loop). When there's more to push against, your steam goes less far and your turbine starts to slow. You can then apply more energy and push the system back up to speed.
- Slartie 9y ago
  The physical effect is known as the Lorentz force: https://en.wikipedia.org/wiki/Lorentz_force https://en.wikipedia.org/wiki/Lorentz_force If this was not the case, we could basically generate arbitrary amounts of power from nowhere, as there was no resistance and we could thus just spin a generator forever with zero power necessary (except for the little bit required to overcome friction) once it is set in motion. The Lorentz force makes sure that's not the case by slowing down the movement, and it slows it down more if more electric power is pulled from the generator.
- deleted 9y ago
  [deleted]
wojt_eu 9y ago
An example of how frequency is closely monitored before energy demand surge in Britain due to Tea Time: https://www.youtube.com/watch?v=slDAvewWfrA https://www.youtube.com/watch?v=slDAvewWfrA https://www.geek.com/geek-cetera/tea-time-in-britain-causes-predictable-massive-surge-in-electricity-demand-1535023/ https://www.geek.com/geek-cetera/tea-time-in-britain-causes-...
- macdice 9y ago
  Very interesting, thanks. At 1:22 "Power surges like this are unique to Britain. No other country in the world switches on so many kettles in so short a time." I'm not sure if that's true... I did some work for a power company in New Zealand about 14 years ago and this exact phenomenon was known there. Chip off the old block...
- stordoff 9y ago
  Worth noting that TV pickup mostly _isn't_ caused by electric kettles: > TV pickups [...] are a surge in demand caused by the flushing of toilets (leading to a surge at the pumping stations) and the opening of fridge doors by millions of people. There is a common misconception that the number one driver of TV pickup is the boiling of kettles. In fact, this only creates a pull on the local network for a short period of time until the water has boiled, and can therefore be managed relatively easily, whereas flushing the toilet causes a longer surge at the water and sewerage pumping stations, and opening the refrigerator lets the chilled air escape, causing the compressor to run. https://en.wikipedia.org/wiki/TV_pickup https://en.wikipedia.org/wiki/TV_pickup
CompelTechnic 9y ago
I have a question about the power grid I've never gotten a satisfactory answer to. I hope someone here can help. If the USA's power grid is about 4,000,000 meters wide, and the electric signal propagates at roughly the speed of light (3 x 10^8 m/s) (https://physics.stackexchange.com/questions/358894/speed-of-light-vs-speed-of-electricity https://physics.stackexchange.com/questions/358894/speed-of-...), then it will take roughly .013 seconds for the electrical signal to reach from one station to another. This is a lot out of phase! (the period of 60 Hz is .016 sec) How is this managed? If two generating stations on opposite ends of the country are both contributing to the electrical signal, how is this time lag accounted for? I have two guesses: 1. The power network is "mapped" such that there is one central generating station and all other generating stations are time lagged based on their graph distance from this generating station 2. All stations try to generate simultaneously, with their output signals interfering with eachother to a certain degree. This might not matter much because their local loads dampen the strength of their signal. Either way seems to introduce inefficiencies.
- ceejayoz 9y ago
  https://en.wikipedia.org/wiki/Continental_U.S._power_transmission_grid https://en.wikipedia.org/wiki/Continental_U.S._power_transmi... > The electrical grid that powers mainland North America is divided into multiple regions. The Eastern Interconnection and the Western Interconnection are the largest. Three other regions include the Texas Interconnection, the Quebec Interconnection, and the Alaska Interconnection. Each region delivers 60 Hz electrical power. The regions are not directly connected or synchronized to each other, but there are some HVDC interconnections.
- maxerickson 9y ago
  There's splits in the grid: https://en.wikipedia.org/wiki/Continental_U.S._power_transmission_grid https://en.wikipedia.org/wiki/Continental_U.S._power_transmi... So that takes care of some of it. Anyway, synchronization is actively managed, when a generator starts up, it is synchronized to the grid adaptively. https://en.wikipedia.org/wiki/Synchronization_(alternating_current) https://en.wikipedia.org/wiki/Synchronization_(alternating_c...
mcv 9y ago
I clearly understand far less about electricity grids than I thought. Isn't that 50 Hz frequency generated by the power plants? It seems hard enough to keep them all perfectly in sync. But I don't see how demand can drop that frequency, and even less why you would want to propagate such a drop in frequency across other subnetworks. Personally I'd expect a shortage to result in a lower voltage, not a lower frequency. I'm also rather surprised that the correct functioning of my clock depends on the political stability of a politically unstable part of the continent.
- gpvos 9y ago
  This just goes to show that everything is political.
- nomercy400 9y ago
  You can think of it like the rotor of a generator is spinning at 50Hz under a certain load. If you now reduce this load, the generator experiences less counter force, but its input is still the same, so it starts to spin faster, increasing its frequency to say 50.1Hz. The opposite is also true, if you suddenly increase the load on the generator, the generator will start spinnging less fast and the frequency drops to say 49.9Hz. This is all very carefully monitored, and there are multiple automatic (massive) power breakers throughout a power network to detect these changes. Imagine all power lines of a large part or entire country suddenly dropping away. The network outside of that country would suddenly experience a large decrease in load and its frequency would go up, while inside the country the load would have a large increse, reducing the frequency in that country. If the change is so large that the frequency goes above 52.5Hz or below 47.5Hz, then the automatic circuit breakers trigger to prevent damage to the entire network (basically adjusting the load of the network). If it can't adjust enough, more circuit breakers will trip, causing larger outages. Example of these are the 2003 Italy blackout and 2003 US/Canada Northeast blackout. Reconnecting a blacked out part to the grid isn't easy either. People tend to leave things on during a blackout, such as airconditioners and TL lights. Now when the power comes back, these things draw a low of power for a short period of time during startup. Normally this isn't bad, but when they all do it at the same time the load is massive (think of a power spikes of 7-8x the normal usage), usually tripping the same huge circuit breaker again. As for the clock deviation, apparently running below 50Hz for a longer period of time has been condoned by the people in charge of the EU power grid. Maybe for too long. There are two solutions: - generate more power in the EU, but that costs money. They could sell the power to the slackers (which I guess they don't want to pay for) - cut the slackers off (which is very drastic and does not help the EU's idea of looking out for each other). But a decision has to be made. Looks like more power is currently being generated, as the frequency is now on 50.010Hz.
stygiansonic 9y ago
The original article linked to this page[0], which provided a good analogy: "On a level road it is easy to maintain speed. On reaching a gradient, however, the rider needs to make more effort to achieve the same speed. Going downhill, the rider needs to apply the brakes to keep the same speed. In the entire European network the electrical generators are set up in such a way that they automatically and immediately respond to a change in grid frequency. Depending on the level of consumption they increase or lower their capacity. This ensures that the frequency remains stable. This automatic adjustment can be compared with the cruise control in a car." 0. https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html https://www.swissgrid.ch/swissgrid/en/home/experts/topics/fr...
elfchief 9y ago
One interesting thing about the "load changes the frequency" thing is that if you measure the frequency in enough places, you can actually see how large load changes "ripple" through the system. For example, there was a big power outage in Florida in 2008 that caused a generator to suddenly go offline, and several orgs had a couple dozen power frequency meters running on the grid at the time, so they were able to make an animation of the east coast power grid "ringing" over the course of about 10 seconds as the load changed rapidly throughout the grid. The animation for that is here: https://www.youtube.com/watch?v=bdBB4byrZ6U https://www.youtube.com/watch?v=bdBB4byrZ6U
- hexane360 9y ago
  Really interesting to see how some chunks lag more or less than would be indicated by geography alone. For example, the Chicago and Indianapolis areas seem to be much more affected from the northwest than the southeast. I wonder if this is mostly due to topology or just grid capacity. Do you know how the power plant's control loops are tuned? It seems like just tuning your plant to be properly damped isn't enough, because there's also lots of feedback from other power plants.
  - elfchief 9y ago
    I don't know for a fact how they manage it, but I bet the feedback is slow enough (those generators are heavy, and it probably takes a few cycles to even accurately measure a change) that they might not have to do much in the way of actively managing that feedback. The system will oscillate a bit (as it did in that video), but there's nothing inherently wrong with that, as long as it's within a certain set of limits. (And really, the load changes are typically more gradual. Even "everyone just got home from work" is a fairly spread out event, compared to, say, the sudden loss of a few hundred MW of generating capacity...)
- _trampeltier 9y ago
  Break time in big sport events also leave there fingerprints in the grid frequency. Everybody start to make a coffee, go to toilet (light), etc.

mrtksn 9y ago

Thanks for the correction, as more you read the more interesting it gets.

Slartie 9y ago
It definitely does. And very interesting thoughts come up, especially when you add newer developments like non-rotational-mass-based power sources (solar power, batteries, stuff like that) into the mix. Because at the moment with the high number of traditional steam-powered generators, the rotating mass of the turbines and their inertia serve as a kind of buffer against sudden swings in electricity demand with an ultra-quick response time of "basically no time". As a second buffer stage we have the steam supplies in the plants, which can be quickly accessed just by opening a valve, thus the response time is non-zero, but still quite short. Now replace all those generators with some other power sources without those inherent balancing capabilities (that probably weren't explicitly built into them, but that just happen to be there because of their construction) and you'll get a network that is much more vulnerable to sudden changes on the demand side. Now, explicit mechanisms of storing energy in a way that can be accessed in literally zero time need to be introduced into the network, just to keep it stable and to provide other regulation mechanisms (of which a lot of them also have to be re-thought) with enough time to do their job. I wouldn't wonder if there were already plans for building large rotating masses with motors on them that are kept at network frequency, with the motors switching over to serve as generators when the frequency drops.
- Piskvorrr 9y ago
  Well...that's essentially the pumped-storage model, except it also takes tens of seconds to spool up: http://virtualniprohlidky.cez.cz/cez-dlouhe-strane-aj/ http://virtualniprohlidky.cez.cz/cez-dlouhe-strane-aj/
- beojan 9y ago
  > I wouldn't wonder if there were already plans for building large rotating masses with motors on them that are kept at network frequency, with the motors switching over to serve as generators when the frequency drops. Flywheels? Yes: https://en.wikipedia.org/wiki/Flywheel_energy_storage#Grid_energy_storage https://en.wikipedia.org/wiki/Flywheel_energy_storage#Grid_e....
- blattimwind 9y ago
  Synchronous machines with no net shaft power are sometimes used to supply reactive power, but these also contribute a coupled rotating mass. (edit: Apparently English people call these "synchronous condenser") The question of "how can we build a large and stable grid without thousands of tons of rotating mass?" is an area of very active research I've been told.

tormeh 9y ago

If anyone's thinking of making a clock that assumes the average frequency is 50Hz: Don't do that. There is no commitment to having the average frequency be 50Hz. There is a commitment to keeping frequency close to 50Hz, but no one in the energy industry is thinking about the average. So don't build things on top of that.

duffmancd 9y ago
It depends where you are. I know for example that the Australian standards require an accumulated time error of less than +/-5 sec on the mainland (+/-15s in Tasmania). Looking at other comments, it seems that we're a little weird down under and most places don't track the drift.
emiliobumachar 9y ago
Additionally, it will be a region-locked clock by its very nature. We use 60Hz here in Brazil.
- rowyourboat 9y ago
  When moving from the US to Europe, I had the opposite problem. I had brought along a number of devices that I powered off a transformer (230V -> 115V) here, among them an alarm clock. Which worked off the AC frequency and thus was losing 10 minutes every hour on 50Hz.
zAy0LfpBZLC8mAC 9y ago
Yes, there is, any accumulated phase error during the day is normally corrected at night.
petschge 9y ago
That is actually not true for the synchronized european power grid we are talking about here. The time that a clock that runs of the power grid is known as "Netzzeit" (grid time) and there is standards on how far that is allowed to deviate from the legal, public time. There is websites such as https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html https://www.swissgrid.ch/swissgrid/en/home/experts/topics/fr... that track and display the deviation.

Fiahil 9y ago

This is super interesting ! I have a few questions ! How does the demand affect the frequency ? Is there a logical unit, somewhere, responsible of "communicating" through the network ? Or is it a physical effect ? > When a factory is powered up, the turbines in the power plants are experiencing larger forces attempting to slow them down. How does something like a higher demand, a drop in frequency, translate to a larger force attempting to slow down the turbines ?

tehwalrus 9y ago
Energy conservation. You're pushing (literally) against the electrical workload of the connected circuits (places where people have plugged a device into a socket and made a loop). When there's more to push against, your steam goes less far and your turbine starts to slow. You can then apply more energy and push the system back up to speed.
Slartie 9y ago
The physical effect is known as the Lorentz force: https://en.wikipedia.org/wiki/Lorentz_force https://en.wikipedia.org/wiki/Lorentz_force If this was not the case, we could basically generate arbitrary amounts of power from nowhere, as there was no resistance and we could thus just spin a generator forever with zero power necessary (except for the little bit required to overcome friction) once it is set in motion. The Lorentz force makes sure that's not the case by slowing down the movement, and it slows it down more if more electric power is pulled from the generator.
deleted 9y ago
[deleted]

wojt_eu 9y ago

An example of how frequency is closely monitored before energy demand surge in Britain due to Tea Time: https://www.youtube.com/watch?v=slDAvewWfrA https://www.youtube.com/watch?v=slDAvewWfrA https://www.geek.com/geek-cetera/tea-time-in-britain-causes-predictable-massive-surge-in-electricity-demand-1535023/ https://www.geek.com/geek-cetera/tea-time-in-britain-causes-...

macdice 9y ago
Very interesting, thanks. At 1:22 "Power surges like this are unique to Britain. No other country in the world switches on so many kettles in so short a time." I'm not sure if that's true... I did some work for a power company in New Zealand about 14 years ago and this exact phenomenon was known there. Chip off the old block...
stordoff 9y ago
Worth noting that TV pickup mostly _isn't_ caused by electric kettles: > TV pickups [...] are a surge in demand caused by the flushing of toilets (leading to a surge at the pumping stations) and the opening of fridge doors by millions of people. There is a common misconception that the number one driver of TV pickup is the boiling of kettles. In fact, this only creates a pull on the local network for a short period of time until the water has boiled, and can therefore be managed relatively easily, whereas flushing the toilet causes a longer surge at the water and sewerage pumping stations, and opening the refrigerator lets the chilled air escape, causing the compressor to run. https://en.wikipedia.org/wiki/TV_pickup https://en.wikipedia.org/wiki/TV_pickup

CompelTechnic 9y ago

I have a question about the power grid I've never gotten a satisfactory answer to. I hope someone here can help. If the USA's power grid is about 4,000,000 meters wide, and the electric signal propagates at roughly the speed of light (3 x 10^8 m/s) (https://physics.stackexchange.com/questions/358894/speed-of-light-vs-speed-of-electricity https://physics.stackexchange.com/questions/358894/speed-of-...), then it will take roughly .013 seconds for the electrical signal to reach from one station to another. This is a lot out of phase! (the period of 60 Hz is .016 sec) How is this managed? If two generating stations on opposite ends of the country are both contributing to the electrical signal, how is this time lag accounted for? I have two guesses: 1. The power network is "mapped" such that there is one central generating station and all other generating stations are time lagged based on their graph distance from this generating station 2. All stations try to generate simultaneously, with their output signals interfering with eachother to a certain degree. This might not matter much because their local loads dampen the strength of their signal. Either way seems to introduce inefficiencies.

ceejayoz 9y ago
https://en.wikipedia.org/wiki/Continental_U.S._power_transmission_grid https://en.wikipedia.org/wiki/Continental_U.S._power_transmi... > The electrical grid that powers mainland North America is divided into multiple regions. The Eastern Interconnection and the Western Interconnection are the largest. Three other regions include the Texas Interconnection, the Quebec Interconnection, and the Alaska Interconnection. Each region delivers 60 Hz electrical power. The regions are not directly connected or synchronized to each other, but there are some HVDC interconnections.
maxerickson 9y ago
There's splits in the grid: https://en.wikipedia.org/wiki/Continental_U.S._power_transmission_grid https://en.wikipedia.org/wiki/Continental_U.S._power_transmi... So that takes care of some of it. Anyway, synchronization is actively managed, when a generator starts up, it is synchronized to the grid adaptively. https://en.wikipedia.org/wiki/Synchronization_(alternating_current) https://en.wikipedia.org/wiki/Synchronization_(alternating_c...

mcv 9y ago

I clearly understand far less about electricity grids than I thought. Isn't that 50 Hz frequency generated by the power plants? It seems hard enough to keep them all perfectly in sync. But I don't see how demand can drop that frequency, and even less why you would want to propagate such a drop in frequency across other subnetworks. Personally I'd expect a shortage to result in a lower voltage, not a lower frequency. I'm also rather surprised that the correct functioning of my clock depends on the political stability of a politically unstable part of the continent.

gpvos 9y ago
This just goes to show that everything is political.
nomercy400 9y ago
You can think of it like the rotor of a generator is spinning at 50Hz under a certain load. If you now reduce this load, the generator experiences less counter force, but its input is still the same, so it starts to spin faster, increasing its frequency to say 50.1Hz. The opposite is also true, if you suddenly increase the load on the generator, the generator will start spinnging less fast and the frequency drops to say 49.9Hz. This is all very carefully monitored, and there are multiple automatic (massive) power breakers throughout a power network to detect these changes. Imagine all power lines of a large part or entire country suddenly dropping away. The network outside of that country would suddenly experience a large decrease in load and its frequency would go up, while inside the country the load would have a large increse, reducing the frequency in that country. If the change is so large that the frequency goes above 52.5Hz or below 47.5Hz, then the automatic circuit breakers trigger to prevent damage to the entire network (basically adjusting the load of the network). If it can't adjust enough, more circuit breakers will trip, causing larger outages. Example of these are the 2003 Italy blackout and 2003 US/Canada Northeast blackout. Reconnecting a blacked out part to the grid isn't easy either. People tend to leave things on during a blackout, such as airconditioners and TL lights. Now when the power comes back, these things draw a low of power for a short period of time during startup. Normally this isn't bad, but when they all do it at the same time the load is massive (think of a power spikes of 7-8x the normal usage), usually tripping the same huge circuit breaker again. As for the clock deviation, apparently running below 50Hz for a longer period of time has been condoned by the people in charge of the EU power grid. Maybe for too long. There are two solutions: - generate more power in the EU, but that costs money. They could sell the power to the slackers (which I guess they don't want to pay for) - cut the slackers off (which is very drastic and does not help the EU's idea of looking out for each other). But a decision has to be made. Looks like more power is currently being generated, as the frequency is now on 50.010Hz.

stygiansonic 9y ago

The original article linked to this page[0], which provided a good analogy: "On a level road it is easy to maintain speed. On reaching a gradient, however, the rider needs to make more effort to achieve the same speed. Going downhill, the rider needs to apply the brakes to keep the same speed. In the entire European network the electrical generators are set up in such a way that they automatically and immediately respond to a change in grid frequency. Depending on the level of consumption they increase or lower their capacity. This ensures that the frequency remains stable. This automatic adjustment can be compared with the cruise control in a car." 0. https://www.swissgrid.ch/swissgrid/en/home/experts/topics/frequency.html https://www.swissgrid.ch/swissgrid/en/home/experts/topics/fr...

elfchief 9y ago

One interesting thing about the "load changes the frequency" thing is that if you measure the frequency in enough places, you can actually see how large load changes "ripple" through the system. For example, there was a big power outage in Florida in 2008 that caused a generator to suddenly go offline, and several orgs had a couple dozen power frequency meters running on the grid at the time, so they were able to make an animation of the east coast power grid "ringing" over the course of about 10 seconds as the load changed rapidly throughout the grid. The animation for that is here: https://www.youtube.com/watch?v=bdBB4byrZ6U https://www.youtube.com/watch?v=bdBB4byrZ6U

hexane360 9y ago
Really interesting to see how some chunks lag more or less than would be indicated by geography alone. For example, the Chicago and Indianapolis areas seem to be much more affected from the northwest than the southeast. I wonder if this is mostly due to topology or just grid capacity. Do you know how the power plant's control loops are tuned? It seems like just tuning your plant to be properly damped isn't enough, because there's also lots of feedback from other power plants.
- elfchief 9y ago
  I don't know for a fact how they manage it, but I bet the feedback is slow enough (those generators are heavy, and it probably takes a few cycles to even accurately measure a change) that they might not have to do much in the way of actively managing that feedback. The system will oscillate a bit (as it did in that video), but there's nothing inherently wrong with that, as long as it's within a certain set of limits. (And really, the load changes are typically more gradual. Even "everyone just got home from work" is a fairly spread out event, compared to, say, the sudden loss of a few hundred MW of generating capacity...)
_trampeltier 9y ago
Break time in big sport events also leave there fingerprints in the grid frequency. Everybody start to make a coffee, go to toilet (light), etc.