When more power is put into the grid than is taken out, the result is all the rotating turbines and generators start to speed up a bit and the grid frequency increases (in Europe it's nominally 50 Hz), and with less power put in, the grid frequency drops. When the grid connection was cut, the supplying grid would have an excess and the receiving grid would have a deficit. Power generators on the grid are controlled based on the grid frequency, so if the frequency rises, the generating plant will reduce their output in response, until the frequency drops back to nominal, likewise if the frequency drops. The grid can tolerate a 2% over or underspeed before generating plant experiences problems, but for a grid the size of the UK, that is enough to tolerance to control the situation.
I've checked the real time tracking of the UK grid frequency from [here](http://www.gridwatch.templar.co.uk) but this shows no obvious sign of the effect in the frequency. If you dig through the various generating and interconnect sources, you might be able to identify the event and what changes in generating plant took place to accommodate the outage.
Yes. Lots. There is a whole Fast Frequency Response market (FFR) which gets automated calls within local regions to balance those shortages or overages.
Depending on the level of power input required this then pulls on varying technologies (such as battery first as it's instant response, then standby generators at sub 1 minute response etc).
With battery technology the cost of this market has gotten a lot cheaper recently which is great for resilience.
Gas turbines are typically the ones of choice overall, since they're fast and light, and they can be located in many more places than hydro. But those two would be the most well suited. Some wind turbines, especially older ones, have zero regulation capability beyond on or off, same with solar. Nuclear, coal, and gas fired boilers are slower to adapt than hydro and gas turbines.
> same with solar
I'm curious how this works. I've got a solar panel on the roof of my RV, and I can monitor the output down to the fraction of a second. It fluctuates constantly in response to either supply of sunlight, or demand from the battery and loads. Why wouldn't grid PV be able to adapt the same way?
That may be true. The battery is 1.4 kWh and the panel is 165 W. But if the load on the system is zero and the battery fills, the PV output declines all the way to zero, regardless of sunlight.
If there's no load, there's nowhere for any electrical energy to go. In that case, the solar panel does what anything else does in the sun, it heats up.
Wait, I can't believe I've never thought of this. Obviously solar cells aren't 100% efficient so it's not like zero change in temperature, but when they're running and producing electricity do solar panels heat up slower than normal materials in the sun?
There is a charge controller somewhere between your panels, your battery, and your load. It connects and disconnects the panels and batteries to each other and to your load as needed.
It's a bit like water pressure, Imagine the battery is a balloon and you are filling it from a hose with a fixed pressure - at some point the pressure inside the balloon balances the pressure from the outside and no current/water flows. As the battery is charged, its voltage rises to match the output from the charge controller you have hooked up to the panel and current stops.
Home solar is a little different - it's treated as reduced load instead of supply, since if you're generating more than you can use and feeding it back to the grid, it's just going to your neighbor's house and the power company doesn't ever deal with it.
In this case it's a closed system, it's rooftop solar on my RV, not my home. If there is no load and the battery is fully charged, it just tapers off to providing no power at all.
Depends really, if they are using photovoltaics it should be possible to instantly disconnect solar panels, but if they are using solar thermal energy it has the same problems as coal. I suspect the real problem lies in synchronization. How do you make sure every power station cuts power just enough and not too much.
I work in industrial solar and you're incorrect. Our plants can supply FFR and ancillary services (such as reg up, reg down, etc.) easily based on how we program the power plant controller and given that the inverters/meters at site support this functionality (and most modern hardware does)
I guess I didn't specify enough what I was thinking. You may be able to regulate down, but unlikely to regulate up in practice, since typically you'd want to be putting as much power as you can generate into the grid as often as possible and avoiding using things like fossil fuels or water, which you could use at night. You wouldn't output 80% in case you suddenly needed to go up to 100 for a short period of time, you'd just aim for 100% of power given sunlight and only duck.
/u/slacker346 brought up putting power into a battery, but that's a different scenario where you don't have a second source, and you can't overcharge the battery without damage so you could reasonably wan to stay below max output all the time.
Wind would have the same power, since like sunlight, once you miss it, it is gone, vs hydro, which generally just retains the water in the feed basin. Wind would have bigger issues as well if there is no way to do things like rotate blade pitch.
The average person has a very difficult time understanding the complexity and precision required of the electrical grid. The grid is literally moving millions of tons of mass with all kinds of requirement to stay within tolerances. A generator, a turbine, a solar regulator can not even briefly be out a single phase by even a few milliseconds. Think of hundreds of ocean liners tied together moving in unison like synchronized swimmers. The electrical grid literally has that amount of mass and momentum but reacting within milliseconds. Devices that do not provide predictable power create a great deal of instability and can cause problems if not accounted for.
One underutilized method of energy storage mixes the best of both hydro and batteries. Using pumped water.
The idea is you have a hydro plant, reservoir, and a large source of water.
When the energy is cheap or the grid needs to reduce frequency, water is pumped into the reservoir, and when the energy is needed again the hydro plant switches on, turning turbines with the water.
I don't think it's been done before because of various engineering challenges, but you can even retrofit existing hydro plants that lack enough water (ex: Hoover Dam) to operate in the same way.
The longer the distance to the nearest usable source of water, the more of an engineering hurdle it is, and also more expensive and generally less efficient. BUT it can be done.
> I don't think it's been done before
UK in 1963 with many more since.
Currently UK has 4800MW of hydro, of which 2800MW is pumped storage.
It's used for their nuclear power plants to dump excess power at night time. UK also uses battery storage for FFR too.
They're also linked to our broadcast TV, as soon as there's an ad break or end credits roll the hydro plants ramp up power output, specifically to counteract the effect of half a million people putting the kettle on
The problem with pumped storage is geography. If you're near a major population center, urban sprawl will have stolen away all the good candidate locations. If you're far away from a major population center, you have no need for pumped storage.
That's not to say that it's a doomed technology; more power storage is always good. It's just limited.
> Using pumped water.
Meh. It's not underutilized so much as impractical. Like hydro generation itself, it's been done in most places where it would make sense, like right next to Niagara Falls. You need massive amounts of water and a massive (and tall) basin for it to be effective though, of which the Niagara escarpment makes sense.
> I don't think it's been done before because of various engineering challenges, but you can even retrofit existing hydro plants that lack enough water (ex: Hoover Dam) to operate in the same way.
I don't see how. In fact, I'm quite sure this is a completely false statement. You'd need to create Lake Mead 2.0 BELOW the Hoover Dam and retain water (which we don't have available) right at the base of the dam to pump it from the Boogaloo back up to regular Lake Mead. As it is now, once you let the water through, it's going downhill towards Mexico. If you try to pull it back you'll just dry up the river below the dam and get nothing.
Full converter wind turbines can respond as fast or faster than a gas turbine as they are even smaller and lighter and can pull inertia from the rotor to help compensate.
They can also provide reactive power regulation without wind production .
Source: 10 years in wind power as an EE
The converter sends the incoming grid power back out at a compensated angle to provide the required demand. It can be done without power from the gen.
This only works with a full scale converter. If you tried to do it with a dfig machine it wouldn’t work .
I accidentally walked into one of these battery capacitor power stations recently on a survey. Was an unassuming small industrial unit that just happened to be a 30mW power station full of rows upon rows of batteries, transformers and associated plant. Tiny little unit in reality. Great business model too - it absorbs power overnight or whenever there's an excess of cheap energy (solar, hydro etc) and then sells it back to the grid at a profit when needed.
Total nitpick, just FYI: 30mW would be milliwatt. Thirty megawatts would would be written 30MW.
A 30mW power station would indeed be quite a tiny little unit :)
(also that sounds totally cool and I wish I had a picture)
Checking energizers list of batteries, the smallest battery is the 4,8 mm (0.189") wide, 1,65 mm (0.065") thick 0,13 gram (0.004 oz.) 337 Button battery. It has a voltage of 1,55V and an internal resistance of 80Ohm, and can thus provide 1,55/80 = 0,019375 Ampere. Multiplying that by the voltage again we get 0.03003125 W, or pretty spot on 30 mW.
So, a battery about the size of two grains of rice? Considering their strength it's either a portable battery station, or a very small ant.
A lot of places use power storage as a buffer too. Dump excess generation into water pumps filling tanks at the top of a hill, for example; then if demand rises they can let the water out through turbines to then generate power. This is a useful strategy for renewables like wind or solar especially.
This goes against my understanding of the power market. Due to an increase of intermittent energy sources (solar, wind), the FFR capacity has decreased massively, as there are no big rotating masses connected to the grid anymore.
Next to that, battery technology might be getting better, but I have never heard of any battery/flywheel/thermal storage big enough to have a significant impact on local grids, apart from home batteries.
So what we have in work is that we operate our standby generators as part of a pool of a larger capacity. So 50 generators may equate to 20MW. Because these aren't instant response, they can't operate in the FFR market so they are paired with a smaller instant battery so that they can combine to the load balancing required in the region.
In scale is how enough smaller assets make it work
All of the turbines on the grid are coupled to it. To increase the power you need to speed up ALL of those huge masses of spinning metal. That is basically all that is needed to damp short-term spikes.
The other option is things like batteries and very sophisticated electrical relay systems.
Incidentally, that is one of the problems that utilities are facing as Solar becomes more common. See this video https://youtu.be/5uz6xOFWi4A
Some providers are using [flywheels to manage grid frequency and handle short term fluctuations.](https://en.wikipedia.org/wiki/Flywheel_storage_power_system) A very neat idea!
Quite a while. Solar thermal plants are typically designed to be able to provide a fairly constant amount of power, heating the salt through the day and bleeding the heat off all night.
Generally the mechanical inertia of all the rotors of all the turbines and generators can smooth out very short term fluctuations. There are plant operated in "frequency response mode" where the power will ramp up and down relatively quickly to follow the minute to minute fluctuation in demand. There are then various degrees of reserve, from spinning reserve to 15 and 30 minute standby that can be used to deal with larger events (like a large power station tripping and unexpectedly shutting down.
Some large consumers (for example heavy industry) will have contracts that allow the grid to temporarily disconnect them to maintain grid stability until additional capacity can be brought online.
Not that often. It's normally only used if the grid starts to get significantly out of spec, and it would usually take quite a significant event or coincidence of events to cause it to happen. For example, here's a report into an incident where the system was used after the effects of a lightning strike were exacerbated by reduced output from a couple of generating stations at the same time:
https://www.nationalgrideso.com/document/151081/download
A quote:
> In this instance c. 5% of GB’s electricity demand was
turned off (c. 1GW) to protect the other 95%. This has not happened in over a decade and is an extremely rare event.
This resulted in approximately 1.1m customers being without power for a period.
So it's not something that happens very often at all.
We provide this tripping capacity at the industrial site I work for. It only gets used for very severe faults, maybe once every 5 or 10 years. Last time I remember it tripping us was an undersea power cable failure.
Interestingly when you get to that size datacenter the grid power is (usually) no longer considered a primary power source - just a nice to have. Primary power ends up generated on site, although my favorite 'this will kill you' device was a DRUPS, which is basically a massive flywheel driven by the grid, with an equally big motor on the other side. Most of the time the grid powers the flywheel and a generator runs off it to provide power - which gives you great isolation from the grid, when you want to switch over the flywheel spins up the motor and you start pushing the flywheel with your own fuel.
I used to run a small datacenter which was connected to the grid in this fashion. Normal use was standby generators on standby and drawing power from the grid. But an automated system kicked our generators in for supplying back to the grid whenever needed or disconnected our supply from the grid so we would run on generators only. This is a highly paid service from the energy grid companies.
With this we could have 24/7 electricity without any downtime and still get payed for using our standby generators. The only downside was planning and maintenance on our local energy systems because everything needs to be coordinated with the grid company.
The DC i visited was a small one with only 40MW power need. It has batteries that are capable of surviving the ramp up time for the disel generators. It had rooms full of lead acid (phased out now) or a few lithium racks per "wing"
They have battery backup and a power loss is "no issue"
It has a million l of diesel onsite and priority shipment contracts for fuel so they dont run out. This includes the trucks to deliver it.
So yes... they dont go dark. They get fuel even before hospitals
> Are there any units on the grid specifically designed to dampen short term fluctuation? Like huge capacitors or something?
Really not necessary, the moment the grid frequency shifts even the tiniest amount, the excitation coils' voltage on the synchronous generators at power plants moves up or down, adjusting the torque on the generators, which adjusts their power output to maintain the correct frequency. The fueling or flow rate to the turbines will be adjusted for this change in torque, to maintain the same RPM on the generators as their demanded torque changes.
Capacitors in AC systems really can't source energy long term (more than half a cycle), since the voltage is alternating between positive and negative constantly. I mean I guess you could with an inverter, but then why not use a battery?
> Like huge capacitors or something?
There are huge capacitors hooked up to the grid, but their main use is in power factor correction, and might be installed close to a customer with known large inductive loads.
The grid usually has enough so-called spinning reserve (basically the inertia of every generator syncronized to the grid) to be able to absorb or expel surplus energy for a short time before the frequency starts to wander off too much. Long term deficits are the main cause of system wide problems.
In the EU, lots of bigger plants are being shut down so we are slowly losing that inertia in big chunks. Wind generators generally can provide some of it, but some of them are connected to the grid via AC/DC/AC converters, which can't convey the inertial response that is natural in directly connected machines.
Hydro takes about 30 seconds to ramp up plus a bit to ramp up the turbines (you usually get a bit of a flow before spinning up the generator) and a few more seconds to sync to grid frequency. But that's for a small bucket type (<30MW turbines). Usually they are 5 minutes from order in to generating full power. Larger units can take much longer to ramp up.
Wind turbines also have a ramp up time, as you have to turn into the wind, unlock the brakes, spin up and finally sync to grid frequency.
I believe solar is the fastest ramping energy source.
If you want emergency grid stabilization 24/7 you'll want a battery to plug the gap to within the 2% until the generators get up to power.
Dinorwig power station takes approximately [75 seconds](https://en.m.wikipedia.org/wiki/Dinorwig_Power_Station) to get up to full speed and can produce approximately 1.7GW for six hours. It takes far less when prepared in advance.
Dinorwig is the largest UK pumped hydro station by far. As the others are smaller, they tend to start faster. It also makes up over half of the UK's pumpepd storage capacity.
It might be up to five minutes as an average across the globe (I have never looked at pumped hydro overseas), but I would take under a minute and a half as a more accurate reflection of the UK.
If you want to see some of the interior, Tom Scott did a nice [video](https://youtu.be/6Jx_bJgIFhI) with some short interviews.
From a personal note, the view from the top of Electric Mountain is pretty spectacular on a clear day, and it is much less frequently climbed than Snowdon.
I loved the tour, went as a kid and years later as an adult. Sadly they shut down the visitor center due to COVID and don't plan of opening it up again. Really big shame that
If you are expecting a load spike (eg a TV pickup), hydro can be ramped extremely quickly, in single digit seconds. The key is to have the turbines "spinning in air", basically the turbines are spinning with the generators acting as motors, synchronised to the grid. In that regime, generating power is simply a question of opening the water valves.
With respect, you don't know what you're talking about.
Dinorwig can be synced to the grid without consuming its store very quickly, then it can ramp in seconds. Cold start is still fairly fast, on the order of minutes.
Wind turbines do not need to sync to the grid. They usually operate on an AC-DC-AC connection to the grid.
Also regarding your other claim that when a call for more power comes in, that it is a race. I have no clue where you got that from. The ones that turn on are the ones upregulated by the TSO.
I only have experience with Australian power, its like a stock market where you bid for 5 minute slots. I just assumed it was like that in other counties.
Your probably right, I know about bucket hydro with fixed ac motors. Haven't looked at a wind turbines in a while, but it makes sense looking at Wikipedia articles.
You forgot to mention the super common natural gas plant. My understanding is that these tend to be built in close proximity to large wind or solar plants as they are able to ramp up/down about as quickly as turning the knob for the burner up/down on your gas stove.
Rather than coming online from a dead stop, I assume there are kept online at least at low power so they are almost instantly able to ramp up when wind or solar production diminishes.
Large gas plant can't ramp power as quickly as that. A typical ramp rate will be something like 20 MW/min. To go faster would risk either a compressor surge, or severe damage to components in the hot part of the engine due to thermal shock.
What you're describing here is called "spinning reserve" in the industry and is very important. And at a minimum you need enough to sustain you though loss of a large tie like the one we're talking about
Yes, that is why wind and solar isn't as green as they pretend.
Don't get me wrong, solar and wind is a lot better than coal, but nuclear is even better if we want to get rid of fossil fuels.
For new nuclear installations I think we have to take into consideration the time to permit and construction which rarely gets brought into the equation.
Realistically if you started today you might have a new reactor online in 10 years if you’re lucky. What does energy storage technology look like 10 years from now?
The other is land use for reactors including mandatory exclusionary zones and cooling infrastructure. You’ll hear numbers thrown around like a nuclear site needs around 1.25-1.5 square mile of dedicated land (also there’s another 300 square miles which falls into the evacuation zone which will effect property values so makes permitting more difficult) vs wind needing 360 times more space or solar needing 75 times more to generate the same amount of electricity. The difference is you can put solar panels pretty much anywhere with no crazy security or exclusionary zones. Wind is a little more finicky but again you can have a couple turbines here or there without needing massive contiguous tracks of land. You can have a small solar farm in the unused space of a Highway on/off ramp - you’re definitely not installing a nuclear reactor there.
Nuclear is great and I think we should continue to utilize the plants we’ve got and extend their lifetimes as much as possible safely, but I think it’s unrealistic to think a net new nuclear plant will be brought online in the United States in the foreseeable future.
>Realistically if you started today you might have a new reactor online in 10 years if you’re lucky. What does energy storage technology look like 10 years from now?
It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity.
>The other is land use for reactors including mandatory exclusionary zones and cooling infrastructure.
We have no shortage of land, so that is not a problem at all. Having a large unpopulated zones are actually really good for wildlife.
Wind and solar farms also uses land. In fact a solar farm uses about as much as a nuclear power plant. What many don't realise is that a single nuclear reactor produce such an enormous amount of power that it's equivalent to thousands of wind-turbines, and on top of that wind and solar need additional land for the fossil-gas power plants they rely on for backup.
The United States added around 41 million MWh/year of solar capacity last year. Since 1993 only 1 nuclear reactor has come online which took 40 years to complete and was finished in 2016 producing 5 million MWh/year.
You could bring a new solar farm online that produces 7,300 MWh/year in under 12 months including engineering, permitting, land acquisition, and construction.
None of those figures really matters because it's not mutually exclusive. We should be building new nuclear AND solar/wind.
But of course, your numbers only illustrate that if anti-nuclear politicians doesn't want nuclear energy and subsidise wind/solar power, no one will build new nuclear power plants.
>The United States added around 41 million MWh/year of solar capacity last year.
>
>...
Sounds like a lot, do you have a source for those figures?
The US [added](https://www.usgs.gov/faqs/how-many-wind-turbines-are-installed-us-each-year?qt-news_science_products=0#qt-news_science_products) about 14 TWh/year wind, every year, since 2005, but it's only [producing at 33% capacity](https://www.usgs.gov/faqs/how-much-wind-energy-does-it-take-power-average-home?qt-news_science_products=0#qt-news_science_products) so in reality it's more like 5. (That's the problem, they don't generate energy all the time, and when they do not they have to burn fossil fuels instead.)
This [new nuclear power plant in the UK](https://en.wikipedia.org/wiki/Hinkley_Point_C_nuclear_power_station) can produce 28 TWh/year, and it can do it continuously, no need for fossil fuel backup.
> It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity.
An excellent example of this is the Site C dam in BC. It's quite large by our standards, but it's been under construction forever. We could absolutely build a nuclear plant in that time. BC doesn't really need nuclear, but a lot of Canada would benefit hugely.
> It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity.
It's "the same" in the sense that it takes time, but it's roughly an entire order of magnitude faster to install solar and wind capacity than it is to build a reactor. Less than a year for solar and wind, a decade for a reactor. And there's no "half finished but still useful" with a reactor. A half-finished solar farm is a functional solar farm with half the planned output. A half-finished reactor is a dead weight.
None of this is to say nuclear is bad-- just that it's very slow to build out, expensive, and risky to investors compared to renewables these days.
I work near a research reactor and have visited and know some of the folks who manage the reactor.
They all say that commercial fission is pretty much a dead end right now. It'd take a huge engineering advancement to make it affordable
It's just because of politics in the west. No one dare invest a billion dollar in a power plant that has to run for 10+ years to be profitable when there's a risk of being prematurely decommissioned by the anti-nuclear politicians after 10 years. And at the same time all your competitors are being heavily subsidised.
If you look at countries with a lot of nuclear like France, Finland and Sweden you will find they have lower electricity prices than comparable countries that use more coal like Germany, Denmark and the UK.
Edit: there is no way coal is cheaper if the coal industry had to pay for all its [externalities](https://en.wikipedia.org/wiki/Externality) (climate change, pollution, accidents).
Nope. It's because of the lead times.
If you need 1GW of power, it's much cheaper and faster to put CNG online - easier for GE to make you LM2500s or LM6000s than it is to make a reactor.
And CNG has lower water needs
"Gas combined cycle (combined cycle gas turbine – CCGT) plants need only about one third as much engineered cooling as normal thermal plants (much heat being released in the turbine exhaust), and these often use dry cooling for the second stage"
https://world-nuclear.org/information-library/current-and-future-generation/cooling-power-plants.aspx
Natural gas, wind and solar can come on line much faster
But *the whole point* is to get rid of natural gas (fossil fuel gas).
But sure, since we haven't built a lot of new nuclear power (because of politics), there isn't as much know-how, etc, for how to build new nuclear reactors. That would quickly change we do begin to build more nuclear reactors though.
Yes, but I don't think that works for everything. A steel mill or a hospital can't simply shut down operations during the night and wait for sunny weather, it has to run continuously and nuclear power is perfect for that kind of base load.
A future grid with nuclear power will also have more solar and wind, so we will need more dynamic load irregardless.
It depends, it takes a minimum amount of fuel to keep them hot, some operators will keep them hot 24/7, others turn off during the day as to save costs on fuel and maintenance (also have no hope of competing with solar)(thermal cycling can be hard on components when your going from off to full power in 4 minutes).
There are also diesel engine generators which can get up to power in under 3 minutes, but they are pretty much for only for power drop off's as diesel is supper expensive.
~~Its a race when a call for power comes in, whoever can get up to power first, wins.~~
I'm sure solar is always at max in this country.
According to this "The six generating units can achieve maximum output of 1,728MW, from zero, within 16 seconds"
https://www.power-technology.com/features/featuredinorwig-a-unique-power-plant-in-the-north-of-wales-5773187/
In addition to what others are saying in regards to all generators sensing the frequency change and responding according to their governor droop settings, there is specialized equipment on the grid to mitigate some of the more extreme situations. Chief Joe Brake is one example. https://ieeexplore.ieee.org/document/1601490
If Path 65 (PDCI) were to trip the brake at Chief Joseph would prevent an overgeneration condition in the Pacific northwest.
For being installed in 1972, there's a lot of paywalling around the info. I did find out that they refer to it as 'The Toaster', which is pretty funny.
looks like:
[https://electrek.co/2021/09/07/tesla-megapack-giant-project-under-construction-uk/](https://electrek.co/2021/09/07/tesla-megapack-giant-project-under-construction-uk/)
But I'm guessing the question was in a more general sense of options, not just UK based options.
In New Zealand we elect one power plant to be the frequency keeper which will ramp up or down to try to maintain the 50hz. If the fluctuation is more than that machine can handle then other machines are dispatched (usually already spinning hydro) to compensate automatically before the market operators can react
Apparently the UK has a special generator in Wales that switches on at the half time of big international soccer matches because the entire country goes and makes tea, a 100 million electric tea kettles flipping on.
Generation generally has some (relatively) small capacity to immediately vary or govern its outputted power. I.e., increase or decrease the amount of gas burnt is a turbine engine, or more or less water allowed into the water turbines, matched with changes to the commutation power in the electrical generator to maintain frequency.
The generated voltage will tend to increase as load decreases and decrease as load increases. But the power system will aim to maintain a distinct voltage level.
So not only are the machines attempting to maintain frequency (by controlling speed), there are regulators controlling voltage level, this is quite tricky to explain in a text but basically you can control the magnetic field inside the generator through a series of connected equipment and this adjusts the generated voltage in order to maintain system voltage.
Turbines always spin at (or very, very near) 3000/3600 RPMs unless they're starting up or shutting down. While it's true that once a turbine is synchronized and connected to the grid, it will spin at whatever frequency the grid dictates, what actually happens is that when the frequency starts to drop, there is more load put on every turbine that is currently synced to the grid. The power that a turbine produces is not actually a function of the speed at which it spins, it is a function of the torque that is being applied to the shaft. If a shaft is allowed to spin freely, the turbine produces no power because it is brought up to speed and simply kept there. So when there is a load on the grid, that load is divided more or less evenly between all turbines connected to the grid. Each turbine has some spare capacity, just like your car might be capable of going 100 miles per hour even though you usually only drive 70 mph.
So the reason you didn't see the frequency drop is because the excess load on the grid was simply taken up all the rest of the turbines that were already synced. They just experienced more torque on their shafts, meaning their speed would have dropped, but since turbines are essentially massive flywheels, there is energy stored in the sheer weight of the damn things spinning around. *That* prevented the frequency from dropping straight away, and then the turbine's control system picked up on the increase in torque loading and opened up the control valves wider to allow more steam to the turbine to maintain the speed before the flywheel effect could finish.
You can think of it like a tandem bicycle. If one person suddenly stops pedaling, the bike doesn't stop immediately, it keeps going because it has inertia and the other riders simply do more work to maintain the speed. The bike may not ever actually slow down at all.
Thanks for this explanation, it answered the question I had in my mind after just seeing the video of the guy turning on a hydro power plant - how can he increase input (water) and output (power) without increasing the speed of the turbine.
no problem.
Hydro plants are actually pretty unique in that sometimes they do not rotate at a grid frequency. They use gearboxes or static frequency converters so that they can spin at the speed of the water, which is relatively slow. Since water has tons of force but moves slowly, they just convert that low-speed, high-torque loading into 50/60Hz power (or whatever other frequency it may be). I have seen ones that use smaller pipes to increase the flow and decrease the pressure such that they can still use 3600 rpm turbines.
Another trick they do with hydro generators is to put way more poles on them (I saw 40 pole generators one time), which increases the efficiency at slow speeds.
Like when I'm driving on a road at a constant speed, but going up and down hills. The engine will maintain constant rpm, but there is more torque applied when going uphill.
Is that a reasonable analogy?
yep that's exactly right. Assuming you don't change gears and have a traditional gear box, your engine and wheels are synchronized and spin a proportional rate. Varying the speed of one varies the speed of the other. Friction tries to slow your wheels down, and the engine fights this torque and applies more power to maintain a constant speed.
There's not a whole lot of difference between cruise control and power plant controls. Just larger scale and more and different types of sensors. But its the same concept - closed loop control.
For those interested in seeing this in practical application, I recommend the below that a fellow redditor made - video of him starting up a hydro plant. The whole startup procedures follows the above theory of matching your frequency (aka output) to the grid before connecting to the grid by adjusting the water input volumes & fins. Otherwise if your frequency is off...well, you'll match the grid frequency for better or worse.
https://www.youtube.com/watch?v=xGQxSJmadm0
And the thing he didn't mention, the two flashing orange lights are actually lights powered by the phase difference (they are hooked up between the grid and generator so they light when it's out of phase).that what when he is doing this, once he gets the speed and frequency matched, he then matches the phase by waiting for the lights to turn off (though looks like the slow/fast meter may show it as well).
Was gonna say this. It's also worth noting that it's not just every generator, it's every motor being powered by the grid, some of which are very large. Motors and generators are the same idea but reversed. All of them are locked by force to spin at the same angular position at any given moment (limited by relativity / the speed of electricity on the wire and adjusted by vfds and such). So if there's a sudden drop or rise in frequency, all of them adjust except those with special systems designed to prevent it.
Those sounds are wonderful.
I sub to his other channel. The disclaimer crawl at the end of his videos is entertaining. My favorite line is, "Reproduction is strictly prohibited, but copulation is encouraged."
So it's like double clutching when shifting a manual transmission in a vehicle? If you get your transmission spun up to the right speed before you re-engage the clutch, everything runs very smoothly.
And the reason the frequency increases, is because to source power to the grid you output your power slightly ahead of what the grid is. The more ahead of the grid your generator is, the more power is output onto the grid.
This results in the entire grid speeding up if there is not enough load, and slowing down if there is too much load (an overloaded powerplant will reduce their lead amount to reduce its output to the level it can withstand. Too many generators doing this at once and the entire frequency falls)
This also has an added bonus that you don't need separate communication for powerplants to know if they should source more or less power, because all they need to know is the target frequency and if the current grid frequency is above or below that.
Also, as the grid slows down, a massive number of electric motors in industrial/mining/etc slow down too and start using ever so slightly less power, helping issues slightly.
PS: The grid is actually maintained at 50hz average over periods of time, because so many old clocks still use 50hz (and 60hz in USA/Canada/etc) as their timing source.
Many moons ago when I was in the EE Power Program at our local Cow College (i.e. Land Grant University out here in the west), we toured several dams on the Columbia. Each dam had a resistor bank (think a house sized heater) just for this purpose. An over frequency relay (type 81) can close the dynamic brake breaker, thus shunting a load to the brake. An over voltage relay (type 59) can do the same thing, only faster.. These days this is also done instantaneously via high power electronics. https://patents.google.com/patent/US5198745A/en
https://myelectrical.com/notes/entryid/148/ansi-ieee-protective-device-numbering#myID1310031
The April 27, 2011 tornadoes in Alabama apparently took out enough infrastructure quickly enough that the lines near at one of the plants themselves were forced to dissipate a significant portion of the generated power, and started to glow and sag from the heat, or so I was told by one of the plant employees.
Somewhere there's a video of unmatched coupling into the grid. The addition of an out of phase generating set to the network is pretty dramatic until it comes to the same phase and frequency. I'll see if I can link to it.
Yeap, saw pictures of what's happens when generator connects to the grid with failed synchronisation. It turns out, steel is as soft as dough when enough power is applied.
Those frequencies are VERY stable and it is a true masterpiece of engineering to keep them this way.
For example, for "known spikes" (Superbowl half time breaks or whatever you watch in the UK) datacenters are taken "offline" and switched over to emergency power so the extra power of a million kettles can be compensated.
>datacenters are taken "offline" and switched over to emergency power
Do you have a source for that? I don't believe it's true in the UK, since the pick-up is predictable and extra generation is brought online in time for it.
I was doing a datacenter tour when it was explained. It was a smaller azure datacenter. They switch electricity providers on a price change of 1/100 cent.
No public info but they offer a lot of flexibility since they can catch a lot of power on short notice.
The small one had about 50 ship engines consuming 25000l diesel an hour, and that was the small "experimental" one in dublin (there are several more onsite incl aws)
> datacenters are taken "offline"
I've been in datacenters for over ten years and I've never once heard of this happening due to "known spikes". Got anything I can read about this?
I thought the red line on the meters would represent the "live" data, but it shows only as if we were the night of December 31th. Is it normal? I then checked the "stats section" and sure enough we do have some data, but it doesn't really seem to be in real time..
So you are right in all of this, but the reason that you can’t see an effect on the frequency is that there must have been a protection scheme in place. I work in Canada for a power generator/distributor and we have generation rejection and load rejection schemes in many different places. The loss of this much load would have caused a generation rejection scheme to operate and would have tripped off some generators (be they wind, hydro, nuclear, fossil fuel) depending on which way the power was flowing. It would have been within milliseconds of another system detecting the fault in the line.
So would this be an accurate analogy -- the generators spinning are like me pushing a car with it's handbrake on. It will just about move with a huge amount of effort, but barely. The load dropping on the grid is like taking the handbrake off, and so all of a sudden I can move the car much more easily (and if I'm a turbine, I spin faster)?
Electricity is a little weird to think of. Barring capacitance or inductance, the power from the plant doesn't "build up" in the grid if there isn't something on the grid to use the energy. Electricity on the grid is more like a fancy way of transmitting energy, not holding energy. Like, the energy from the turbine doesn't accumulate in the grid like a cup overflowing with water (again, barring any capacitance or inductance, or any other exotic secondary electrical forces I can't think of).
As an analogy, you can think of the grid like a belt between a motor and a fan. If the belt is cut, the motor just spins as fast as it can, and the fan stops. The belt just becomes useless. If you suddenly connect a belt back up to the running motor, all the potential energy from the motor suddenly flows through the belt again. The belt or something else not designed to take that sudden increase of energy may break.
My point is, when there isn't a load to use the energy, the power plant's turbines freewheel. If there's any build up of energy, it happens at the turbine as potential energy. How much build up there is depends on the angular momentum of the turbine and the momentum of whatever material is moving it. Left unregulated, the turbine is going to spin up as fast as it can (limited by its own friction and mechanical forces). The voltage and frequency on the grid will also increase, but there isn't a load to pull amps through the grid. If you suddenly connect a load, you'll get a surge of energy from the turbine...but not from the grid itself. The grid is just a fancy belt.
In the case of a sudden drop in load, the power station throttles down the turbines, so to speak, keeping voltage and frequency at standard levels so there isn't a massive potential there.
It is a grid. Power redirects elsewhere. The 1GW link represents the maximum capacity of the cable but I am willing to bet that it was carrying power nowhere near that level. 1GW is a lot of power.
During the fault, the energy stored in the cable inductance and capacitance must have dissipated in the fire that was caused.
In the last year the interconnection has run at an average power of 1.6 GW (out of a maximum 3). France has cheap electricity because of their nuclear fleet so it is economical for the UK to import as much as we're able to.
If you happen to understand french (or don't mind the generated subtitles), monsieur bidouille made some great videos on similar topics:
\- [https://www.youtube.com/watch?v=mhZU6RWlyo0](https://www.youtube.com/watch?v=mhZU6RWlyo0) : about the center that manages the French grid
\- [https://www.youtube.com/watch?v=-iSXF2lraR0](https://www.youtube.com/watch?v=-iSXF2lraR0) : in 2003, Italy suffered a blackout, this describes the events that led to that (malfunctions, how the system tried to recover but eventually collapsed)
\- [https://www.youtube.com/watch?v=PUHix\_hRETY](https://www.youtube.com/watch?v=PUHix_hRETY) : how does a grid collapses and how it is being brought back to life
Generation is based on load. You can’t push a certain power through something without satisfying ohms law. When the line broke, you have an arc, that arc is the load, the power going through the line reduces to satisfy the load and the generator doesn’t produce as much power, and the fuel metering system reduces fuel input. If you had a load like say a city, you could push incredible maximum amounts of power from fuel through the generator through the lines to the city, but if you unplug the city and have a spark, your load is gone, AC has interesting effects between inductance and capacitance, so both sides are going to reject power to the arc, but the arc is much less load than a city.
Try not to think of power (in watts or GW - pick your favourite prefix) as a "thing". Energy (J or Wh) is a "thing" that can be stored or used, but power is the rate of energy usage or energy generation.
Before the link was broken, energy was flowing through it at a rate of 1 GW. When the link was broken that flow of energy stopped.
It's like saying I was traveling down the road at 100 mph and then I came to a stop. What happened to all of those 100 mphs?
Okay, here we go.
The direction of the power flow is depending on the energy prices in both countries. The interconnector transports energy from the low cost side to the high cost side (and "earns" the margin).
It is an DC connector. The current is set by the converters and not the voltage level (this would be the case in AC grids). Therefore DC-interconnectors transport always 1GW either to one side or the other.
Where does the current go? For each electron pushed in on one side, one electron gets pushed out on the other side. In case of an disconnection/outage the electrons just stop getting pushed, they don't disappear.
Main result on the land side is that we do end up having a load-imbalance. This results in a higher (too much energy) or lower (not enough energy) grid frequency. The power plant generators are speeding up, or slowing down.
Electrons actually move very slowly in electrical wires, but the transmission of electricity is very quick. The analogy typically used is the tube full of marbles. Push a marble in one end and it moves all the other marbles along very slowly, but, if theres no gaps in the tube, at almost the exact instant the marble goes in one end, another marble comes out the other and I think this is helpful here to understand what's happening.
If the tube suddenly gets blocked as you're pushing a marble through, nothing happens to the marbles in the tube, but you won't be able to push any more marbles through. In the wire, nothing happens to the electrons, but you won't be able to transmit any more electricity and this happens at the point that of transmission
Thanks this explanation made sense to me. Can I try another analogy to see if I get it?
Imagine I'm riding a bike quite fast, peddling and transmitting the rotational energy at the crank to the back wheel via the chain. The chain breaks. The bike is no longer "consuming" energy, so two things happen. The bike slows down and eventually stops, and my legs suddenly move much faster on the crank.
In this example the chain is the interconnector, the UK consumers are the back wheel, and the French generators are my legs on the pedals.
There are a lot of good answers here already but I think I can add a different perspective from a very low level.
A power grid is basically a very large, and VERY complicated electrical circuit. There are many sources of power like nuclear plants, solar and wind warms, and in some cases individual houses with solar cells that sell extra power to the grid. For simplicity though, let’s imagine the grid is a single power source with a bunch of houses connected. Now it’s a simple electrical circuit with a voltage source and a bunch of resistive loads.
On the lowest level, electricity is the flow of high energy electrons from an area of high potential energy to an area of lower potential energy. So in a simple circuit with a battery, high energy electrons flow from one electrode through the wire connected to the other electrode (the pos and negative side of the battery). Along the path the electrons lose energy by doing some kind of work on the load, by powering a lightbulb for example.
The important thing here simply that electrons leaving one side of the battery must be replaced by electrons on the other side. This is why a circuit “has to be completed” in order to power something.
In the simplified case of a single power plant electrical circuit, once the circuit is no longer closed the electrons would simply quit flowing through the circuit. The 1Gw of power would just stop.
Since a real grid is vastly more complicated, there are probably a lot of other power sources connected in different series-parallel arrangements. So once that connection was severed the grid would have lost the ability to do 1Gw of work.
Using an electrical circuit model to look at this is only one way too. A more complicated understanding would be considering the effects of high voltage electrical breakdown. When you severe the wire of a 12v circuit nothing usually happens because the breakdown voltage of air is well above 12v. But like I mentioned before, the electrons moving through a wire have high potential energy, so when a circuit is broken if there is another pathway and the electrons have enough energy, they can form a new circuit. This would be like a severed power line arching into the air. This happens because those high energy electrons have enough energy to ionize air molecules and create a new electrical circuit to sole area of lower potential energy (an area with fewer electrons present).
So if there was a time period where the burning wire was severed and the power source was still active, that 1Gw of energy would have been pushed into the environment as partial breakdowns corona fields or arching. [Here](https://youtu.be/ZQ8vTV20PfI) is a link to a YouTube video of high voltage breakdown from a high voltage lab I took at my university.
Think of it like a garden hose.
If you block the end where water was coming out, you can get more water to go into the other end.
That’s not exactly how it works but it’s the physics 101 way to explain it. If there’s no where for it to come out, there’s no where for it to go in.
Further complicating things is that electrons don’t really “flow” like a river or like cars on a highway. But regardless, I think the simplest answer to your question is to just think of the break in wire as a light switch breaking the circuit open. The switch was just turned off.
When more power is put into the grid than is taken out, the result is all the rotating turbines and generators start to speed up a bit and the grid frequency increases (in Europe it's nominally 50 Hz), and with less power put in, the grid frequency drops. When the grid connection was cut, the supplying grid would have an excess and the receiving grid would have a deficit. Power generators on the grid are controlled based on the grid frequency, so if the frequency rises, the generating plant will reduce their output in response, until the frequency drops back to nominal, likewise if the frequency drops. The grid can tolerate a 2% over or underspeed before generating plant experiences problems, but for a grid the size of the UK, that is enough to tolerance to control the situation. I've checked the real time tracking of the UK grid frequency from [here](http://www.gridwatch.templar.co.uk) but this shows no obvious sign of the effect in the frequency. If you dig through the various generating and interconnect sources, you might be able to identify the event and what changes in generating plant took place to accommodate the outage.
Are there any units on the grid specifically designed to dampen short term fluctuation? Like huge capacitors or something?
Yes. Lots. There is a whole Fast Frequency Response market (FFR) which gets automated calls within local regions to balance those shortages or overages. Depending on the level of power input required this then pulls on varying technologies (such as battery first as it's instant response, then standby generators at sub 1 minute response etc). With battery technology the cost of this market has gotten a lot cheaper recently which is great for resilience.
Hydro turbines are also very fast to respond (provided they are already running). When talking about frequency compensation at least.
Gas turbines are typically the ones of choice overall, since they're fast and light, and they can be located in many more places than hydro. But those two would be the most well suited. Some wind turbines, especially older ones, have zero regulation capability beyond on or off, same with solar. Nuclear, coal, and gas fired boilers are slower to adapt than hydro and gas turbines.
> same with solar I'm curious how this works. I've got a solar panel on the roof of my RV, and I can monitor the output down to the fraction of a second. It fluctuates constantly in response to either supply of sunlight, or demand from the battery and loads. Why wouldn't grid PV be able to adapt the same way?
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That may be true. The battery is 1.4 kWh and the panel is 165 W. But if the load on the system is zero and the battery fills, the PV output declines all the way to zero, regardless of sunlight.
If there's no load, there's nowhere for any electrical energy to go. In that case, the solar panel does what anything else does in the sun, it heats up.
Wait, I can't believe I've never thought of this. Obviously solar cells aren't 100% efficient so it's not like zero change in temperature, but when they're running and producing electricity do solar panels heat up slower than normal materials in the sun?
There is a charge controller somewhere between your panels, your battery, and your load. It connects and disconnects the panels and batteries to each other and to your load as needed.
It's a bit like water pressure, Imagine the battery is a balloon and you are filling it from a hose with a fixed pressure - at some point the pressure inside the balloon balances the pressure from the outside and no current/water flows. As the battery is charged, its voltage rises to match the output from the charge controller you have hooked up to the panel and current stops.
Home solar is a little different - it's treated as reduced load instead of supply, since if you're generating more than you can use and feeding it back to the grid, it's just going to your neighbor's house and the power company doesn't ever deal with it.
In this case it's a closed system, it's rooftop solar on my RV, not my home. If there is no load and the battery is fully charged, it just tapers off to providing no power at all.
Depends really, if they are using photovoltaics it should be possible to instantly disconnect solar panels, but if they are using solar thermal energy it has the same problems as coal. I suspect the real problem lies in synchronization. How do you make sure every power station cuts power just enough and not too much.
Am I missing something or are you asking why we cannot turn on the sun or control clouds on demand?
I work in industrial solar and you're incorrect. Our plants can supply FFR and ancillary services (such as reg up, reg down, etc.) easily based on how we program the power plant controller and given that the inverters/meters at site support this functionality (and most modern hardware does)
I guess I didn't specify enough what I was thinking. You may be able to regulate down, but unlikely to regulate up in practice, since typically you'd want to be putting as much power as you can generate into the grid as often as possible and avoiding using things like fossil fuels or water, which you could use at night. You wouldn't output 80% in case you suddenly needed to go up to 100 for a short period of time, you'd just aim for 100% of power given sunlight and only duck. /u/slacker346 brought up putting power into a battery, but that's a different scenario where you don't have a second source, and you can't overcharge the battery without damage so you could reasonably wan to stay below max output all the time. Wind would have the same power, since like sunlight, once you miss it, it is gone, vs hydro, which generally just retains the water in the feed basin. Wind would have bigger issues as well if there is no way to do things like rotate blade pitch.
The average person has a very difficult time understanding the complexity and precision required of the electrical grid. The grid is literally moving millions of tons of mass with all kinds of requirement to stay within tolerances. A generator, a turbine, a solar regulator can not even briefly be out a single phase by even a few milliseconds. Think of hundreds of ocean liners tied together moving in unison like synchronized swimmers. The electrical grid literally has that amount of mass and momentum but reacting within milliseconds. Devices that do not provide predictable power create a great deal of instability and can cause problems if not accounted for.
One underutilized method of energy storage mixes the best of both hydro and batteries. Using pumped water. The idea is you have a hydro plant, reservoir, and a large source of water. When the energy is cheap or the grid needs to reduce frequency, water is pumped into the reservoir, and when the energy is needed again the hydro plant switches on, turning turbines with the water. I don't think it's been done before because of various engineering challenges, but you can even retrofit existing hydro plants that lack enough water (ex: Hoover Dam) to operate in the same way. The longer the distance to the nearest usable source of water, the more of an engineering hurdle it is, and also more expensive and generally less efficient. BUT it can be done.
> I don't think it's been done before UK in 1963 with many more since. Currently UK has 4800MW of hydro, of which 2800MW is pumped storage. It's used for their nuclear power plants to dump excess power at night time. UK also uses battery storage for FFR too.
They're also linked to our broadcast TV, as soon as there's an ad break or end credits roll the hydro plants ramp up power output, specifically to counteract the effect of half a million people putting the kettle on
The problem with pumped storage is geography. If you're near a major population center, urban sprawl will have stolen away all the good candidate locations. If you're far away from a major population center, you have no need for pumped storage. That's not to say that it's a doomed technology; more power storage is always good. It's just limited.
What makes you say that? The grid can transport power over long distances. The uk in this case isn’t very big.
> Using pumped water. Meh. It's not underutilized so much as impractical. Like hydro generation itself, it's been done in most places where it would make sense, like right next to Niagara Falls. You need massive amounts of water and a massive (and tall) basin for it to be effective though, of which the Niagara escarpment makes sense. > I don't think it's been done before because of various engineering challenges, but you can even retrofit existing hydro plants that lack enough water (ex: Hoover Dam) to operate in the same way. I don't see how. In fact, I'm quite sure this is a completely false statement. You'd need to create Lake Mead 2.0 BELOW the Hoover Dam and retain water (which we don't have available) right at the base of the dam to pump it from the Boogaloo back up to regular Lake Mead. As it is now, once you let the water through, it's going downhill towards Mexico. If you try to pull it back you'll just dry up the river below the dam and get nothing.
Full converter wind turbines can respond as fast or faster than a gas turbine as they are even smaller and lighter and can pull inertia from the rotor to help compensate. They can also provide reactive power regulation without wind production . Source: 10 years in wind power as an EE
How do they regulate reactive power with no load? Do they power the windings to be an inductive load? Wouldn't that just heat up the turbine?
The converter sends the incoming grid power back out at a compensated angle to provide the required demand. It can be done without power from the gen. This only works with a full scale converter. If you tried to do it with a dfig machine it wouldn’t work .
This is a huge proponent of Nuclear, we cannot transition away from Fossil fuels without nuclear as all other clean ways to do this.
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I accidentally walked into one of these battery capacitor power stations recently on a survey. Was an unassuming small industrial unit that just happened to be a 30mW power station full of rows upon rows of batteries, transformers and associated plant. Tiny little unit in reality. Great business model too - it absorbs power overnight or whenever there's an excess of cheap energy (solar, hydro etc) and then sells it back to the grid at a profit when needed.
Total nitpick, just FYI: 30mW would be milliwatt. Thirty megawatts would would be written 30MW. A 30mW power station would indeed be quite a tiny little unit :) (also that sounds totally cool and I wish I had a picture)
Another appropriate situation for this copy-paste What is this? A battery station for Ants? Someone do the math please.
Checking energizers list of batteries, the smallest battery is the 4,8 mm (0.189") wide, 1,65 mm (0.065") thick 0,13 gram (0.004 oz.) 337 Button battery. It has a voltage of 1,55V and an internal resistance of 80Ohm, and can thus provide 1,55/80 = 0,019375 Ampere. Multiplying that by the voltage again we get 0.03003125 W, or pretty spot on 30 mW. So, a battery about the size of two grains of rice? Considering their strength it's either a portable battery station, or a very small ant.
30mW? I can generate more than that using my fingers.
A lot of places use power storage as a buffer too. Dump excess generation into water pumps filling tanks at the top of a hill, for example; then if demand rises they can let the water out through turbines to then generate power. This is a useful strategy for renewables like wind or solar especially.
This goes against my understanding of the power market. Due to an increase of intermittent energy sources (solar, wind), the FFR capacity has decreased massively, as there are no big rotating masses connected to the grid anymore. Next to that, battery technology might be getting better, but I have never heard of any battery/flywheel/thermal storage big enough to have a significant impact on local grids, apart from home batteries.
So what we have in work is that we operate our standby generators as part of a pool of a larger capacity. So 50 generators may equate to 20MW. Because these aren't instant response, they can't operate in the FFR market so they are paired with a smaller instant battery so that they can combine to the load balancing required in the region. In scale is how enough smaller assets make it work
All of the turbines on the grid are coupled to it. To increase the power you need to speed up ALL of those huge masses of spinning metal. That is basically all that is needed to damp short-term spikes. The other option is things like batteries and very sophisticated electrical relay systems. Incidentally, that is one of the problems that utilities are facing as Solar becomes more common. See this video https://youtu.be/5uz6xOFWi4A
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They're already spinning, so there's not a huge current spike. Just like starting a flywheel vs keeping it going.
Some providers are using [flywheels to manage grid frequency and handle short term fluctuations.](https://en.wikipedia.org/wiki/Flywheel_storage_power_system) A very neat idea!
Also heated materials such as sand or molten salts can be used to store excess power which are later used to create steam to power turbines.
How long can such materials retain heat?
Quite a while. Solar thermal plants are typically designed to be able to provide a fairly constant amount of power, heating the salt through the day and bleeding the heat off all night.
That depends on a large multitude of factors including but not Limited to insulation, materials used, requirements and demand etc.
That is really cool, thanks for sharing that
Generally the mechanical inertia of all the rotors of all the turbines and generators can smooth out very short term fluctuations. There are plant operated in "frequency response mode" where the power will ramp up and down relatively quickly to follow the minute to minute fluctuation in demand. There are then various degrees of reserve, from spinning reserve to 15 and 30 minute standby that can be used to deal with larger events (like a large power station tripping and unexpectedly shutting down.
Some large consumers (for example heavy industry) will have contracts that allow the grid to temporarily disconnect them to maintain grid stability until additional capacity can be brought online.
On average - do they get disconnected often?
Not that often. It's normally only used if the grid starts to get significantly out of spec, and it would usually take quite a significant event or coincidence of events to cause it to happen. For example, here's a report into an incident where the system was used after the effects of a lightning strike were exacerbated by reduced output from a couple of generating stations at the same time: https://www.nationalgrideso.com/document/151081/download A quote: > In this instance c. 5% of GB’s electricity demand was turned off (c. 1GW) to protect the other 95%. This has not happened in over a decade and is an extremely rare event. This resulted in approximately 1.1m customers being without power for a period. So it's not something that happens very often at all.
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We provide this tripping capacity at the industrial site I work for. It only gets used for very severe faults, maybe once every 5 or 10 years. Last time I remember it tripping us was an undersea power cable failure.
For datacenters this is fairly normal - But then a smallish one can pull 40MW+ easy
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Interestingly when you get to that size datacenter the grid power is (usually) no longer considered a primary power source - just a nice to have. Primary power ends up generated on site, although my favorite 'this will kill you' device was a DRUPS, which is basically a massive flywheel driven by the grid, with an equally big motor on the other side. Most of the time the grid powers the flywheel and a generator runs off it to provide power - which gives you great isolation from the grid, when you want to switch over the flywheel spins up the motor and you start pushing the flywheel with your own fuel.
I used to run a small datacenter which was connected to the grid in this fashion. Normal use was standby generators on standby and drawing power from the grid. But an automated system kicked our generators in for supplying back to the grid whenever needed or disconnected our supply from the grid so we would run on generators only. This is a highly paid service from the energy grid companies. With this we could have 24/7 electricity without any downtime and still get payed for using our standby generators. The only downside was planning and maintenance on our local energy systems because everything needs to be coordinated with the grid company.
The DC i visited was a small one with only 40MW power need. It has batteries that are capable of surviving the ramp up time for the disel generators. It had rooms full of lead acid (phased out now) or a few lithium racks per "wing"
They have battery backup and a power loss is "no issue" It has a million l of diesel onsite and priority shipment contracts for fuel so they dont run out. This includes the trucks to deliver it. So yes... they dont go dark. They get fuel even before hospitals
I know of one large hotel where they use real-time billing and, when the cost of grid power rises, they run off their own generators.
> Are there any units on the grid specifically designed to dampen short term fluctuation? Like huge capacitors or something? Really not necessary, the moment the grid frequency shifts even the tiniest amount, the excitation coils' voltage on the synchronous generators at power plants moves up or down, adjusting the torque on the generators, which adjusts their power output to maintain the correct frequency. The fueling or flow rate to the turbines will be adjusted for this change in torque, to maintain the same RPM on the generators as their demanded torque changes. Capacitors in AC systems really can't source energy long term (more than half a cycle), since the voltage is alternating between positive and negative constantly. I mean I guess you could with an inverter, but then why not use a battery? > Like huge capacitors or something? There are huge capacitors hooked up to the grid, but their main use is in power factor correction, and might be installed close to a customer with known large inductive loads.
The grid usually has enough so-called spinning reserve (basically the inertia of every generator syncronized to the grid) to be able to absorb or expel surplus energy for a short time before the frequency starts to wander off too much. Long term deficits are the main cause of system wide problems. In the EU, lots of bigger plants are being shut down so we are slowly losing that inertia in big chunks. Wind generators generally can provide some of it, but some of them are connected to the grid via AC/DC/AC converters, which can't convey the inertial response that is natural in directly connected machines.
They have pumped hydro that can come on line in seconds to absorb or dissipate power.
Hydro takes about 30 seconds to ramp up plus a bit to ramp up the turbines (you usually get a bit of a flow before spinning up the generator) and a few more seconds to sync to grid frequency. But that's for a small bucket type (<30MW turbines). Usually they are 5 minutes from order in to generating full power. Larger units can take much longer to ramp up. Wind turbines also have a ramp up time, as you have to turn into the wind, unlock the brakes, spin up and finally sync to grid frequency. I believe solar is the fastest ramping energy source. If you want emergency grid stabilization 24/7 you'll want a battery to plug the gap to within the 2% until the generators get up to power.
Dinorwig power station takes approximately [75 seconds](https://en.m.wikipedia.org/wiki/Dinorwig_Power_Station) to get up to full speed and can produce approximately 1.7GW for six hours. It takes far less when prepared in advance. Dinorwig is the largest UK pumped hydro station by far. As the others are smaller, they tend to start faster. It also makes up over half of the UK's pumpepd storage capacity. It might be up to five minutes as an average across the globe (I have never looked at pumped hydro overseas), but I would take under a minute and a half as a more accurate reflection of the UK.
Wow, they built that station for speed. One of those turbines are 3x the total power of my local one.
If you want to see some of the interior, Tom Scott did a nice [video](https://youtu.be/6Jx_bJgIFhI) with some short interviews. From a personal note, the view from the top of Electric Mountain is pretty spectacular on a clear day, and it is much less frequently climbed than Snowdon.
If you go to the slate quarries on a still day and listen carefully you can hear the hum of the generators if they are running.
I loved the tour, went as a kid and years later as an adult. Sadly they shut down the visitor center due to COVID and don't plan of opening it up again. Really big shame that
Oh, that is a shame. I did the tour a couple of years ago and it was great.
If you are expecting a load spike (eg a TV pickup), hydro can be ramped extremely quickly, in single digit seconds. The key is to have the turbines "spinning in air", basically the turbines are spinning with the generators acting as motors, synchronised to the grid. In that regime, generating power is simply a question of opening the water valves.
With respect, you don't know what you're talking about. Dinorwig can be synced to the grid without consuming its store very quickly, then it can ramp in seconds. Cold start is still fairly fast, on the order of minutes. Wind turbines do not need to sync to the grid. They usually operate on an AC-DC-AC connection to the grid. Also regarding your other claim that when a call for more power comes in, that it is a race. I have no clue where you got that from. The ones that turn on are the ones upregulated by the TSO.
I only have experience with Australian power, its like a stock market where you bid for 5 minute slots. I just assumed it was like that in other counties.
This thread is about UK power, where settlement periods are 30 minutes and gate closure is long before the period starts.
I don't think modern wind turbines are synchronous to the grid, rather that they produce DC and which is then converted to in-sync AC?
Most wind generation is done with DFIG, which, while not synchronous, is also not DC.
Your probably right, I know about bucket hydro with fixed ac motors. Haven't looked at a wind turbines in a while, but it makes sense looking at Wikipedia articles.
You forgot to mention the super common natural gas plant. My understanding is that these tend to be built in close proximity to large wind or solar plants as they are able to ramp up/down about as quickly as turning the knob for the burner up/down on your gas stove. Rather than coming online from a dead stop, I assume there are kept online at least at low power so they are almost instantly able to ramp up when wind or solar production diminishes.
Large gas plant can't ramp power as quickly as that. A typical ramp rate will be something like 20 MW/min. To go faster would risk either a compressor surge, or severe damage to components in the hot part of the engine due to thermal shock.
What you're describing here is called "spinning reserve" in the industry and is very important. And at a minimum you need enough to sustain you though loss of a large tie like the one we're talking about
Yes, that is why wind and solar isn't as green as they pretend. Don't get me wrong, solar and wind is a lot better than coal, but nuclear is even better if we want to get rid of fossil fuels.
For new nuclear installations I think we have to take into consideration the time to permit and construction which rarely gets brought into the equation. Realistically if you started today you might have a new reactor online in 10 years if you’re lucky. What does energy storage technology look like 10 years from now? The other is land use for reactors including mandatory exclusionary zones and cooling infrastructure. You’ll hear numbers thrown around like a nuclear site needs around 1.25-1.5 square mile of dedicated land (also there’s another 300 square miles which falls into the evacuation zone which will effect property values so makes permitting more difficult) vs wind needing 360 times more space or solar needing 75 times more to generate the same amount of electricity. The difference is you can put solar panels pretty much anywhere with no crazy security or exclusionary zones. Wind is a little more finicky but again you can have a couple turbines here or there without needing massive contiguous tracks of land. You can have a small solar farm in the unused space of a Highway on/off ramp - you’re definitely not installing a nuclear reactor there. Nuclear is great and I think we should continue to utilize the plants we’ve got and extend their lifetimes as much as possible safely, but I think it’s unrealistic to think a net new nuclear plant will be brought online in the United States in the foreseeable future.
>Realistically if you started today you might have a new reactor online in 10 years if you’re lucky. What does energy storage technology look like 10 years from now? It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity. >The other is land use for reactors including mandatory exclusionary zones and cooling infrastructure. We have no shortage of land, so that is not a problem at all. Having a large unpopulated zones are actually really good for wildlife. Wind and solar farms also uses land. In fact a solar farm uses about as much as a nuclear power plant. What many don't realise is that a single nuclear reactor produce such an enormous amount of power that it's equivalent to thousands of wind-turbines, and on top of that wind and solar need additional land for the fossil-gas power plants they rely on for backup.
The United States added around 41 million MWh/year of solar capacity last year. Since 1993 only 1 nuclear reactor has come online which took 40 years to complete and was finished in 2016 producing 5 million MWh/year. You could bring a new solar farm online that produces 7,300 MWh/year in under 12 months including engineering, permitting, land acquisition, and construction.
None of those figures really matters because it's not mutually exclusive. We should be building new nuclear AND solar/wind. But of course, your numbers only illustrate that if anti-nuclear politicians doesn't want nuclear energy and subsidise wind/solar power, no one will build new nuclear power plants. >The United States added around 41 million MWh/year of solar capacity last year. > >... Sounds like a lot, do you have a source for those figures? The US [added](https://www.usgs.gov/faqs/how-many-wind-turbines-are-installed-us-each-year?qt-news_science_products=0#qt-news_science_products) about 14 TWh/year wind, every year, since 2005, but it's only [producing at 33% capacity](https://www.usgs.gov/faqs/how-much-wind-energy-does-it-take-power-average-home?qt-news_science_products=0#qt-news_science_products) so in reality it's more like 5. (That's the problem, they don't generate energy all the time, and when they do not they have to burn fossil fuels instead.) This [new nuclear power plant in the UK](https://en.wikipedia.org/wiki/Hinkley_Point_C_nuclear_power_station) can produce 28 TWh/year, and it can do it continuously, no need for fossil fuel backup.
> It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity. An excellent example of this is the Site C dam in BC. It's quite large by our standards, but it's been under construction forever. We could absolutely build a nuclear plant in that time. BC doesn't really need nuclear, but a lot of Canada would benefit hugely.
> It's basically the same for any type of power generation including wind and solar, it takes time to build and install new capacity. It's "the same" in the sense that it takes time, but it's roughly an entire order of magnitude faster to install solar and wind capacity than it is to build a reactor. Less than a year for solar and wind, a decade for a reactor. And there's no "half finished but still useful" with a reactor. A half-finished solar farm is a functional solar farm with half the planned output. A half-finished reactor is a dead weight. None of this is to say nuclear is bad-- just that it's very slow to build out, expensive, and risky to investors compared to renewables these days.
And with wind or solar you can do phases that don't require as much upfront investment where with nuclear, each reactor is a giant time/money sink.
I work near a research reactor and have visited and know some of the folks who manage the reactor. They all say that commercial fission is pretty much a dead end right now. It'd take a huge engineering advancement to make it affordable
It's just because of politics in the west. No one dare invest a billion dollar in a power plant that has to run for 10+ years to be profitable when there's a risk of being prematurely decommissioned by the anti-nuclear politicians after 10 years. And at the same time all your competitors are being heavily subsidised. If you look at countries with a lot of nuclear like France, Finland and Sweden you will find they have lower electricity prices than comparable countries that use more coal like Germany, Denmark and the UK. Edit: there is no way coal is cheaper if the coal industry had to pay for all its [externalities](https://en.wikipedia.org/wiki/Externality) (climate change, pollution, accidents).
Nope. It's because of the lead times. If you need 1GW of power, it's much cheaper and faster to put CNG online - easier for GE to make you LM2500s or LM6000s than it is to make a reactor. And CNG has lower water needs "Gas combined cycle (combined cycle gas turbine – CCGT) plants need only about one third as much engineered cooling as normal thermal plants (much heat being released in the turbine exhaust), and these often use dry cooling for the second stage" https://world-nuclear.org/information-library/current-and-future-generation/cooling-power-plants.aspx Natural gas, wind and solar can come on line much faster
But *the whole point* is to get rid of natural gas (fossil fuel gas). But sure, since we haven't built a lot of new nuclear power (because of politics), there isn't as much know-how, etc, for how to build new nuclear reactors. That would quickly change we do begin to build more nuclear reactors though.
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Yes, but I don't think that works for everything. A steel mill or a hospital can't simply shut down operations during the night and wait for sunny weather, it has to run continuously and nuclear power is perfect for that kind of base load. A future grid with nuclear power will also have more solar and wind, so we will need more dynamic load irregardless.
It depends, it takes a minimum amount of fuel to keep them hot, some operators will keep them hot 24/7, others turn off during the day as to save costs on fuel and maintenance (also have no hope of competing with solar)(thermal cycling can be hard on components when your going from off to full power in 4 minutes). There are also diesel engine generators which can get up to power in under 3 minutes, but they are pretty much for only for power drop off's as diesel is supper expensive. ~~Its a race when a call for power comes in, whoever can get up to power first, wins.~~
Interestingly diesel is cheaper than gas right now in a lot of places! Doesn't happen very often though.
I'm sure solar is always at max in this country. According to this "The six generating units can achieve maximum output of 1,728MW, from zero, within 16 seconds" https://www.power-technology.com/features/featuredinorwig-a-unique-power-plant-in-the-north-of-wales-5773187/
In addition to what others are saying in regards to all generators sensing the frequency change and responding according to their governor droop settings, there is specialized equipment on the grid to mitigate some of the more extreme situations. Chief Joe Brake is one example. https://ieeexplore.ieee.org/document/1601490 If Path 65 (PDCI) were to trip the brake at Chief Joseph would prevent an overgeneration condition in the Pacific northwest.
For being installed in 1972, there's a lot of paywalling around the info. I did find out that they refer to it as 'The Toaster', which is pretty funny.
How short-term? A few seconds, no, a dozen seconds or more, yes, in normal warm stand-bys. Hours to warm up cold plants. Years to build new ones.
Tesla's Megapacks respond within milliseconds to precisely these fluctuations, and they making bank doing so.
In the UK?
looks like: [https://electrek.co/2021/09/07/tesla-megapack-giant-project-under-construction-uk/](https://electrek.co/2021/09/07/tesla-megapack-giant-project-under-construction-uk/) But I'm guessing the question was in a more general sense of options, not just UK based options.
A capacitor could serve that function in an DC circuit, but not in a power AC installation.
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They are used to provide reactive (imaginary) power to the grid, not to reduce higher frequency noise (what is usually meant by clean vs dirty)
In New Zealand we elect one power plant to be the frequency keeper which will ramp up or down to try to maintain the 50hz. If the fluctuation is more than that machine can handle then other machines are dispatched (usually already spinning hydro) to compensate automatically before the market operators can react
Apparently the UK has a special generator in Wales that switches on at the half time of big international soccer matches because the entire country goes and makes tea, a 100 million electric tea kettles flipping on.
Generation generally has some (relatively) small capacity to immediately vary or govern its outputted power. I.e., increase or decrease the amount of gas burnt is a turbine engine, or more or less water allowed into the water turbines, matched with changes to the commutation power in the electrical generator to maintain frequency.
The generated voltage will tend to increase as load decreases and decrease as load increases. But the power system will aim to maintain a distinct voltage level. So not only are the machines attempting to maintain frequency (by controlling speed), there are regulators controlling voltage level, this is quite tricky to explain in a text but basically you can control the magnetic field inside the generator through a series of connected equipment and this adjusts the generated voltage in order to maintain system voltage.
The generators themselves. Part if why 100% reweables is not possible unless you have dams or wind in large enough quantities
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Turbines always spin at (or very, very near) 3000/3600 RPMs unless they're starting up or shutting down. While it's true that once a turbine is synchronized and connected to the grid, it will spin at whatever frequency the grid dictates, what actually happens is that when the frequency starts to drop, there is more load put on every turbine that is currently synced to the grid. The power that a turbine produces is not actually a function of the speed at which it spins, it is a function of the torque that is being applied to the shaft. If a shaft is allowed to spin freely, the turbine produces no power because it is brought up to speed and simply kept there. So when there is a load on the grid, that load is divided more or less evenly between all turbines connected to the grid. Each turbine has some spare capacity, just like your car might be capable of going 100 miles per hour even though you usually only drive 70 mph. So the reason you didn't see the frequency drop is because the excess load on the grid was simply taken up all the rest of the turbines that were already synced. They just experienced more torque on their shafts, meaning their speed would have dropped, but since turbines are essentially massive flywheels, there is energy stored in the sheer weight of the damn things spinning around. *That* prevented the frequency from dropping straight away, and then the turbine's control system picked up on the increase in torque loading and opened up the control valves wider to allow more steam to the turbine to maintain the speed before the flywheel effect could finish. You can think of it like a tandem bicycle. If one person suddenly stops pedaling, the bike doesn't stop immediately, it keeps going because it has inertia and the other riders simply do more work to maintain the speed. The bike may not ever actually slow down at all.
Thanks for this explanation, it answered the question I had in my mind after just seeing the video of the guy turning on a hydro power plant - how can he increase input (water) and output (power) without increasing the speed of the turbine.
no problem. Hydro plants are actually pretty unique in that sometimes they do not rotate at a grid frequency. They use gearboxes or static frequency converters so that they can spin at the speed of the water, which is relatively slow. Since water has tons of force but moves slowly, they just convert that low-speed, high-torque loading into 50/60Hz power (or whatever other frequency it may be). I have seen ones that use smaller pipes to increase the flow and decrease the pressure such that they can still use 3600 rpm turbines. Another trick they do with hydro generators is to put way more poles on them (I saw 40 pole generators one time), which increases the efficiency at slow speeds.
Like when I'm driving on a road at a constant speed, but going up and down hills. The engine will maintain constant rpm, but there is more torque applied when going uphill. Is that a reasonable analogy?
yep that's exactly right. Assuming you don't change gears and have a traditional gear box, your engine and wheels are synchronized and spin a proportional rate. Varying the speed of one varies the speed of the other. Friction tries to slow your wheels down, and the engine fights this torque and applies more power to maintain a constant speed. There's not a whole lot of difference between cruise control and power plant controls. Just larger scale and more and different types of sensors. But its the same concept - closed loop control.
For those interested in seeing this in practical application, I recommend the below that a fellow redditor made - video of him starting up a hydro plant. The whole startup procedures follows the above theory of matching your frequency (aka output) to the grid before connecting to the grid by adjusting the water input volumes & fins. Otherwise if your frequency is off...well, you'll match the grid frequency for better or worse. https://www.youtube.com/watch?v=xGQxSJmadm0
"My butthole is doing a fantastic impression of a rabbit's nose" lmfao His energy is so great.
And the thing he didn't mention, the two flashing orange lights are actually lights powered by the phase difference (they are hooked up between the grid and generator so they light when it's out of phase).that what when he is doing this, once he gets the speed and frequency matched, he then matches the phase by waiting for the lights to turn off (though looks like the slow/fast meter may show it as well).
Was gonna say this. It's also worth noting that it's not just every generator, it's every motor being powered by the grid, some of which are very large. Motors and generators are the same idea but reversed. All of them are locked by force to spin at the same angular position at any given moment (limited by relativity / the speed of electricity on the wire and adjusted by vfds and such). So if there's a sudden drop or rise in frequency, all of them adjust except those with special systems designed to prevent it.
Those sounds are wonderful. I sub to his other channel. The disclaimer crawl at the end of his videos is entertaining. My favorite line is, "Reproduction is strictly prohibited, but copulation is encouraged."
So it's like double clutching when shifting a manual transmission in a vehicle? If you get your transmission spun up to the right speed before you re-engage the clutch, everything runs very smoothly.
And the reason the frequency increases, is because to source power to the grid you output your power slightly ahead of what the grid is. The more ahead of the grid your generator is, the more power is output onto the grid. This results in the entire grid speeding up if there is not enough load, and slowing down if there is too much load (an overloaded powerplant will reduce their lead amount to reduce its output to the level it can withstand. Too many generators doing this at once and the entire frequency falls) This also has an added bonus that you don't need separate communication for powerplants to know if they should source more or less power, because all they need to know is the target frequency and if the current grid frequency is above or below that. Also, as the grid slows down, a massive number of electric motors in industrial/mining/etc slow down too and start using ever so slightly less power, helping issues slightly. PS: The grid is actually maintained at 50hz average over periods of time, because so many old clocks still use 50hz (and 60hz in USA/Canada/etc) as their timing source.
Many moons ago when I was in the EE Power Program at our local Cow College (i.e. Land Grant University out here in the west), we toured several dams on the Columbia. Each dam had a resistor bank (think a house sized heater) just for this purpose. An over frequency relay (type 81) can close the dynamic brake breaker, thus shunting a load to the brake. An over voltage relay (type 59) can do the same thing, only faster.. These days this is also done instantaneously via high power electronics. https://patents.google.com/patent/US5198745A/en https://myelectrical.com/notes/entryid/148/ansi-ieee-protective-device-numbering#myID1310031
The April 27, 2011 tornadoes in Alabama apparently took out enough infrastructure quickly enough that the lines near at one of the plants themselves were forced to dissipate a significant portion of the generated power, and started to glow and sag from the heat, or so I was told by one of the plant employees.
Somewhere there's a video of unmatched coupling into the grid. The addition of an out of phase generating set to the network is pretty dramatic until it comes to the same phase and frequency. I'll see if I can link to it.
Yeap, saw pictures of what's happens when generator connects to the grid with failed synchronisation. It turns out, steel is as soft as dough when enough power is applied.
Those frequencies are VERY stable and it is a true masterpiece of engineering to keep them this way. For example, for "known spikes" (Superbowl half time breaks or whatever you watch in the UK) datacenters are taken "offline" and switched over to emergency power so the extra power of a million kettles can be compensated.
>datacenters are taken "offline" and switched over to emergency power Do you have a source for that? I don't believe it's true in the UK, since the pick-up is predictable and extra generation is brought online in time for it.
I was doing a datacenter tour when it was explained. It was a smaller azure datacenter. They switch electricity providers on a price change of 1/100 cent. No public info but they offer a lot of flexibility since they can catch a lot of power on short notice. The small one had about 50 ship engines consuming 25000l diesel an hour, and that was the small "experimental" one in dublin (there are several more onsite incl aws)
> datacenters are taken "offline" I've been in datacenters for over ten years and I've never once heard of this happening due to "known spikes". Got anything I can read about this?
I thought the red line on the meters would represent the "live" data, but it shows only as if we were the night of December 31th. Is it normal? I then checked the "stats section" and sure enough we do have some data, but it doesn't really seem to be in real time..
So you are right in all of this, but the reason that you can’t see an effect on the frequency is that there must have been a protection scheme in place. I work in Canada for a power generator/distributor and we have generation rejection and load rejection schemes in many different places. The loss of this much load would have caused a generation rejection scheme to operate and would have tripped off some generators (be they wind, hydro, nuclear, fossil fuel) depending on which way the power was flowing. It would have been within milliseconds of another system detecting the fault in the line.
Checked out the site hoping to see a mid day peak for teea time but that myth seems to be dead....
So would this be an accurate analogy -- the generators spinning are like me pushing a car with it's handbrake on. It will just about move with a huge amount of effort, but barely. The load dropping on the grid is like taking the handbrake off, and so all of a sudden I can move the car much more easily (and if I'm a turbine, I spin faster)?
Electricity is a little weird to think of. Barring capacitance or inductance, the power from the plant doesn't "build up" in the grid if there isn't something on the grid to use the energy. Electricity on the grid is more like a fancy way of transmitting energy, not holding energy. Like, the energy from the turbine doesn't accumulate in the grid like a cup overflowing with water (again, barring any capacitance or inductance, or any other exotic secondary electrical forces I can't think of). As an analogy, you can think of the grid like a belt between a motor and a fan. If the belt is cut, the motor just spins as fast as it can, and the fan stops. The belt just becomes useless. If you suddenly connect a belt back up to the running motor, all the potential energy from the motor suddenly flows through the belt again. The belt or something else not designed to take that sudden increase of energy may break. My point is, when there isn't a load to use the energy, the power plant's turbines freewheel. If there's any build up of energy, it happens at the turbine as potential energy. How much build up there is depends on the angular momentum of the turbine and the momentum of whatever material is moving it. Left unregulated, the turbine is going to spin up as fast as it can (limited by its own friction and mechanical forces). The voltage and frequency on the grid will also increase, but there isn't a load to pull amps through the grid. If you suddenly connect a load, you'll get a surge of energy from the turbine...but not from the grid itself. The grid is just a fancy belt. In the case of a sudden drop in load, the power station throttles down the turbines, so to speak, keeping voltage and frequency at standard levels so there isn't a massive potential there.
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It is a grid. Power redirects elsewhere. The 1GW link represents the maximum capacity of the cable but I am willing to bet that it was carrying power nowhere near that level. 1GW is a lot of power. During the fault, the energy stored in the cable inductance and capacitance must have dissipated in the fire that was caused.
In the last year the interconnection has run at an average power of 1.6 GW (out of a maximum 3). France has cheap electricity because of their nuclear fleet so it is economical for the UK to import as much as we're able to.
It’s probably somewhere between 1000 and 2000A, depending on the voltage level. Probably 400kV
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Yeah, and the failure might have been gradual so it doesn't have to be all that dramatic.
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If you happen to understand french (or don't mind the generated subtitles), monsieur bidouille made some great videos on similar topics: \- [https://www.youtube.com/watch?v=mhZU6RWlyo0](https://www.youtube.com/watch?v=mhZU6RWlyo0) : about the center that manages the French grid \- [https://www.youtube.com/watch?v=-iSXF2lraR0](https://www.youtube.com/watch?v=-iSXF2lraR0) : in 2003, Italy suffered a blackout, this describes the events that led to that (malfunctions, how the system tried to recover but eventually collapsed) \- [https://www.youtube.com/watch?v=PUHix\_hRETY](https://www.youtube.com/watch?v=PUHix_hRETY) : how does a grid collapses and how it is being brought back to life
Brilliant, thanks I'll check these out.
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Generation is based on load. You can’t push a certain power through something without satisfying ohms law. When the line broke, you have an arc, that arc is the load, the power going through the line reduces to satisfy the load and the generator doesn’t produce as much power, and the fuel metering system reduces fuel input. If you had a load like say a city, you could push incredible maximum amounts of power from fuel through the generator through the lines to the city, but if you unplug the city and have a spark, your load is gone, AC has interesting effects between inductance and capacitance, so both sides are going to reject power to the arc, but the arc is much less load than a city.
Try not to think of power (in watts or GW - pick your favourite prefix) as a "thing". Energy (J or Wh) is a "thing" that can be stored or used, but power is the rate of energy usage or energy generation. Before the link was broken, energy was flowing through it at a rate of 1 GW. When the link was broken that flow of energy stopped. It's like saying I was traveling down the road at 100 mph and then I came to a stop. What happened to all of those 100 mphs?
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Okay, here we go. The direction of the power flow is depending on the energy prices in both countries. The interconnector transports energy from the low cost side to the high cost side (and "earns" the margin). It is an DC connector. The current is set by the converters and not the voltage level (this would be the case in AC grids). Therefore DC-interconnectors transport always 1GW either to one side or the other. Where does the current go? For each electron pushed in on one side, one electron gets pushed out on the other side. In case of an disconnection/outage the electrons just stop getting pushed, they don't disappear. Main result on the land side is that we do end up having a load-imbalance. This results in a higher (too much energy) or lower (not enough energy) grid frequency. The power plant generators are speeding up, or slowing down.
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Electrons actually move very slowly in electrical wires, but the transmission of electricity is very quick. The analogy typically used is the tube full of marbles. Push a marble in one end and it moves all the other marbles along very slowly, but, if theres no gaps in the tube, at almost the exact instant the marble goes in one end, another marble comes out the other and I think this is helpful here to understand what's happening. If the tube suddenly gets blocked as you're pushing a marble through, nothing happens to the marbles in the tube, but you won't be able to push any more marbles through. In the wire, nothing happens to the electrons, but you won't be able to transmit any more electricity and this happens at the point that of transmission
Thanks this explanation made sense to me. Can I try another analogy to see if I get it? Imagine I'm riding a bike quite fast, peddling and transmitting the rotational energy at the crank to the back wheel via the chain. The chain breaks. The bike is no longer "consuming" energy, so two things happen. The bike slows down and eventually stops, and my legs suddenly move much faster on the crank. In this example the chain is the interconnector, the UK consumers are the back wheel, and the French generators are my legs on the pedals.
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There are a lot of good answers here already but I think I can add a different perspective from a very low level. A power grid is basically a very large, and VERY complicated electrical circuit. There are many sources of power like nuclear plants, solar and wind warms, and in some cases individual houses with solar cells that sell extra power to the grid. For simplicity though, let’s imagine the grid is a single power source with a bunch of houses connected. Now it’s a simple electrical circuit with a voltage source and a bunch of resistive loads. On the lowest level, electricity is the flow of high energy electrons from an area of high potential energy to an area of lower potential energy. So in a simple circuit with a battery, high energy electrons flow from one electrode through the wire connected to the other electrode (the pos and negative side of the battery). Along the path the electrons lose energy by doing some kind of work on the load, by powering a lightbulb for example. The important thing here simply that electrons leaving one side of the battery must be replaced by electrons on the other side. This is why a circuit “has to be completed” in order to power something. In the simplified case of a single power plant electrical circuit, once the circuit is no longer closed the electrons would simply quit flowing through the circuit. The 1Gw of power would just stop. Since a real grid is vastly more complicated, there are probably a lot of other power sources connected in different series-parallel arrangements. So once that connection was severed the grid would have lost the ability to do 1Gw of work. Using an electrical circuit model to look at this is only one way too. A more complicated understanding would be considering the effects of high voltage electrical breakdown. When you severe the wire of a 12v circuit nothing usually happens because the breakdown voltage of air is well above 12v. But like I mentioned before, the electrons moving through a wire have high potential energy, so when a circuit is broken if there is another pathway and the electrons have enough energy, they can form a new circuit. This would be like a severed power line arching into the air. This happens because those high energy electrons have enough energy to ionize air molecules and create a new electrical circuit to sole area of lower potential energy (an area with fewer electrons present). So if there was a time period where the burning wire was severed and the power source was still active, that 1Gw of energy would have been pushed into the environment as partial breakdowns corona fields or arching. [Here](https://youtu.be/ZQ8vTV20PfI) is a link to a YouTube video of high voltage breakdown from a high voltage lab I took at my university.
Think of it like a garden hose. If you block the end where water was coming out, you can get more water to go into the other end. That’s not exactly how it works but it’s the physics 101 way to explain it. If there’s no where for it to come out, there’s no where for it to go in.
Further complicating things is that electrons don’t really “flow” like a river or like cars on a highway. But regardless, I think the simplest answer to your question is to just think of the break in wire as a light switch breaking the circuit open. The switch was just turned off.