Date: 04/03/19 Dr John Constable, GWPF Energy Editor
The UK’s electricity network is likely to become significantly weaker within five years, due to falling Short Circuit Levels that reduce the reliability of protection systems designed to limit the geographical extent of supply loss during a fault, and also make it more likely that asynchronous sources of electricity such as wind, solar and High Voltage Direct Current interconnectors will disconnect during a fault. Ironically, Short Circuit Levels are falling because of a rising input from asynchronous sources. A remedy for this problem is unlikely to be cheap. Who will pay?
Electricity networks of any size are complex systems, with all the advantages and disadvantages that this implies. The uninitiated believe that the principal threat to such systems is the failure of electricity producers, the generators, to meet the demands of consumers for energy, resulting in a blackout. This is not completely mistaken, but, in fact, blackouts on a modern and developed electricity system are only rarely directly caused by shortfalls of generation resulting from poor system planning, a power station accident, or an unexpectedly high consumer demand. System operators are nearly always able, even at short notice, to call on sufficient additional resources either to increase generation or reduce demand, though of course this remedial action comes at a considerable cost.
A rather more probable cause of a system blackout is a transmission system equipment failure, at a transformer for example, or a sudden external event, such as a storm or a vehicle, a plane or a ship perhaps, damaging a transmission line. In a weak or poorly designed system such accidents will overload other transmission lines that then themselves have to shut down to avoid damage, sending a further ripple of overloading through a large part of the network, forcing generators themselves to come offline and resulting in a widespread blackout.
Apart from ensuring a high specification for the components used and a high standard for design and construction, the best protection against such accidents is to ensure that the system is sufficiently stable under stress that it can contain the loss of supply to a small part of the network, this capability usually being automatic since action must be taken in milliseconds to prevent a cascade of faults. Accidents will happen, but a strong system can prevent a local problem from becoming a regional or even a nationwide disaster.
The strength of the system must be continually monitored to ensure that it will be stable under stress, a precaution that would be necessary at any time, but has particular relevance in the UK at present due to the rapid and dramatic changes in the electricity supply industry being driven by climate change policy. It is therefore only prudent for National Grid ESO (the Electricity System Operator) to have initiated detailed work on an Operability Strategy with the aim of ensuring that its System Operability Framework is adequate to the task. The first tranche of documents was published in November and December 2018, and are available at the link above, with updates being provided in the regular Operational Forums, the most recent of which was held on the 26thof March (the presentations are all available here.
National Grid identifies five areas of concern, Frequency Control, Voltage Control, Restoration (i.e. recovery after a blackout), Stability, as discussed above, and Thermal (transmission line temperature). All are important, but to judge from the volume of commentary devoted to it, it is Stability that is giving most cause for concern. Specifically, Short Circuit Levels (SCL) in Great Britain are predicted to fall considerably over the next decade. The Short Circuit Level is the current that will flow through the system during a fault, an accident affecting a transmission line for example. It is, as National Grid explains, “a measure of strength”, and a “key parameter for protection systems” in the network itself and also in other equipment attached to it (National Grid, System Operability Framework: Impact of Declining Short Circuit Levels(December 2018), p. 1).
With low SCL the transmission system protection systems, which function to “isolate faulty equipment […] limiting the fault effect on the wider system” (National Grid, System Operability Framework: Whole System Short Circuit Levels(December 2018), p. 2), could, in National Grid’s own words “take longer to operate or not operate as designed”( National Grid, System Operability Framework: Impact of Declining Short Circuit Levels(December 2018), p. 1), meaning a loss of supply to a much larger area.
Furthermore, some generators, specifically wind and solar farms, and the protection systems of some sources of electricity such as High Voltage Direct Current (HVDC) interconnectors, may be much more likely to disconnect in the event of a fault if Short Circuit Levels are low.
As it happens, the Short Circuit Level is falling in the GB network because of declining input from synchronous, conventional generation, such as coal-fired power stations and Combined Cycle Gas Turbines, and a rising input from wind, solar, and HVDC links, which are asynchronous and do not provide support to the Short Circuit Level in their vicinity.
Consequently, areas where there is at present a great deal of wind and solar already have low SCL, and this is expected to spread to other areas as synchronous input declines and more asynchronous renewables and interconnectors are built. The following figure from National Grid’s publication on the subject shows regional Short Circuit Levels in Great Britain in 2020, 2025, and 2030.
Scotland and the West Country already have low SCL, due to high levels of wind and solar respectively, and the analysis projects a falling trend elsewhere, with the largest declines foreseen in the North East and East Midlands, probably because of the closure of coal fired generation in those areas. Only North Wales escapes, since it fortunately has a pumped storage plant, Dinorwig, with unusual design features that make it well equipped to support SCL.
As noted, low Short Circuit Level tends to increase the risk that asynchronous generators and HVDC interconnectors, may struggle to ride through a fault arising from an accident on the system. National Grid explains that this is due to the fact that such equipment uses Phased Locked Loop converters, a technology that relies on voltage waveform to provide it with information about system condition. If Short Circuit Levels are low a fault will cause the voltage waveform to become disturbed, with important consequences:
“When the Phase Locked Loop measures a more disturbed voltage waveform it might not provide the right information back to the converter and the converter might not respond in in the right way to a fault. In this situation there is a risk that the converter will lose connection to the network.” (National Grid ESO, System Operability Framework: Impact of Declining Short Circuit Levels(December 2018), p. 3.)
To put that in concrete terms, low Short Circuit Levels make it more likely that wind and solar and HVDC interconnectors will disconnect during a system fault, just when they are needed most to prevent a blackout.
National Grid provides a simplified representation of the increasing Phase Locked Loop risk in the following figure, which uses colour coding to show the percentage of the year affected for the GB regions for 2020, 2025 and 2030:
Scotland is already at significant, though moderate risk, being exposed for about 15% of the year, presumably the winter months when wind input is high, while the rest of the country is quite unaffected. By 2025, Scotland is at risk for half to three quarters of the year, and other areas are beginning to feel some degree of exposure. By 2030, only North Wales and the North East are free of risk, and in Scotland and in the East Midlands it is an almost year-round fact of life.
This is why UK is pushing users to allow installation of “smart meters”. This will allow the network managers to remotely disconnect household users virtually instantly at the flick of a bit in a database.
To combat rocketing utility bills householders are being offered contracts where they accept the possibility of being disconnected at any time and without notice if the supplier needs to do so.
As always it is the poor and most needy who will have to accept this kind of contract and next time this happens during a harsh UK winter people will die.
It is climate change policy which kills not climate change.
This is utter nonsense: nobody in the UK with a smart meter is going to be disconnected without their express consent… they may have an agreement to restrict or change use of some appliances
If you were to look at demand response in the UK you would find there’s no need for disconnection, because demand response firms have commercial contracts with firms running aircon, refrigeration and similar services, which need to run frequently, but not continuously and can be switched down or off in conjunction with similar devices to reduce demand. This might extend to dosmetic users EVs on eday…
https://www.ofgem.gov.uk/system/files/docs/2018/10/smart_systems_and_flexibility_plan_progress_update.pdf
“nobody in the UK with a smart meter is going to be disconnected without their express consent”
Of course this statement doesn’t contradict a single thing that Greg said.
That’s why they sign contracts griff, to give express consent beforehand.
As usual, griff takes the position that because nothing really bad has happened yet, this proves that nothing bad will ever happen.
Unlike me, Griff does not understand electrical power system dynamics. He also believes everything his masters tell him through their edicts and slavish reporting in the MSM.
The point is that they can isolate your house remotely via a smart meter, and if they can they will in an emergency.
The point is, Rob, that, in planning their bright new future electric system, they rely on cutting you off. Great customer service!
When I last changed supplier one of the first questions asked was “do you have a smart meter” when I said no the response was “good that makes it easier”.
As with most things politicians and bureaucrats get their hands on they have made a complete mess of the “smart meter” switch by using units that aren’t recognised by many power suppliers.
I don’t seem to be getting as many calls and letters saying I need or we’re coming to fit your wonderful power saving smart meter even had someone turn up on the doorstep saying “”Hi I’m here to fit your smart meter” to which they got the answer “Oh no your not goodbye”
James Bull
griff.
With all do respect to you, I still have to say you have not even the slightest idea or the slightest clue of what the matter or the issue is about.
Let me simplified for you.
Wind mill farms and solar farms, are not compatible at all with an electrical grid functioning and the main basic procedures of a functioning grid… regardless of the production demand factor.
A simple straightforward grid procedure could and will result in a cut off of wind and solar farms, and lead to a black out, like in the case of South AUS few years ago.
The black out then, was simply triggered by a normal simple grid procedure, the automatic reconnection to a faulty line… which not under any circumstances can or could bring down the grid,
unless a considerable power supply to the grid happens to be by means of incompatible and very unstable sources, like wind mill and solar farms…which can not stand up in such occasions.
Such incompatible, unstable and fragile power/energy sources, like wind mills and solar farms,
definitely will make the electrical grids more and more fragile and unstable, and also very expensive to manage and balance out, even in the most easier circumstances of the operations.
Very difficult and a very high risk factor involved when trying to properly manage and maintain an electrical grid operation, in the consideration of the said grid depending considerably in a power supply from incompatible, unstable and fragile sources like wind mill farms and solar.
And in the same time, for the very same reason, also very very expensive and wasteful under the consideration.
I do not think there is any possible workable way around this very real and very expensive problem…
unless completely dropping the unstable, fragile and incompatible wind mill and solar stupidity from the electrical grids.
Oh well, hopefully you get the point.
Do not worry much if it happens to be above your pay-grade.
cheers
With all do respect to you, I still have to say you have not even the slightest idea or the slightest clue of what the matter or the issue is about.
Heh, that statement applies to soooo many of griff posts here at WUWT.
If you believe that you will believe anything.
If the system goes down, everybody gets cut off, and if Venezuela is any example it could take 6 days to reboot the system.
Griff comments “nobody in the UK with a smart meter is going to be disconnected without their express consent”. And what is the percentage of households that have bothered to get these “smart meters”installed. The government has been plugging this very costly scheme for is it 2 or 3 years now and the take up has been minimal. There are issues with incompatibility between different suppliers and there’s no obvious advantage to users. The obvious advantage to suppliers it that it will allow them to introduce a demand level payment scheme.
nobody in the UK with a smart meter is going to be disconnected without their express consent
A statement that means nothing. They gave that consent when they signed the contract, so yeah no one will be disconnected without their consent, but they *will be* disconnected because they had to give their consent up front.
For the lowest electricity rate in France they have ‘not so smart’ electricity supply trip limiting the load to 3 kVA (@ 220V max 13.6A)
Demand Management has become common practice in Australia. It is most commonly applied on warm calm days when the air-conditioners are cranking but wind isn’t. The most recent example:
https://www.theaustralian.com.au/nation/nation/200000-homes-go-dark-as-heat-rises-electricity-cut-off/news-story/c451d4cad55137d967c2a36d1e10ef72
Demand Management = F-U Customer. What the customers want is ‘demand,’ what the bureaucrats/politicians want to deliver is something else. They just drive effective customer costs higher, with a lower-value product.
Let me see: If a supplier says we will give you less, at a higher price, what does a rational customer do?
What does one do if the supplier is the government? Venezuela, anyone?
Do note that Dinorwig is NOT a backup supply for wind and solar intermittency. (Dinorwig holds 10 gwhr of power, normally dissipated over 5 hours.)
Dinorwig was designed to smooth out instantaneous changes in demand, like the morning breakfast or the end of a soccer match on TV. It can spin ip to a full 2 gw of power generation in a matter of seconds. And that is how it is used. So Dinorwig has no capacity to backup windless days, because it is already utilised in a completely different fashion.
Ralph
No, but it is used as part of smoothing ramp down of solar at end of day and/or wind ramping down. Note the National Grid claim to be able to predict wind levels up to 24 hours in advance with 95% accuracy.
There is no lie so bizarre, that griff won’t repeat it ad infinitum.
The 95% accuracy is for statements like “will tomorrow be windier than today”.
To predict the output of wind turbines, you need to be able to predict the speed of the wind down to a kph or less. They can’t do that 1 minute ahead, much less 24 hours.
When it is very windy power generation estimates are easy. Many turbines have a flat output curve between about 10m/s and 25m/s where they cut out for safety. There are some fluctuations, as the ability to adjust blade feathering to shed input doesn’t match gusts precisely, but this does average out somewhat over a whole wind farm during a medium storm. The timing of weather fronts and associated squalls will not be accurate until an hour or two out, but that is good enough to organise other generation to balance.
Output is also reasonably easy to forecast in light winds: it will be negligible, and zero or even negative below typical cut in speeds of 3m/s. Negative arises when the blades must be turned to prevent brinnelling of the bearings, and perhaps to power the yaw motors to untwist the internal cables – obviously best done when there is no wind.
I have some data on wind forecast performance in this chart:
Some of the difference is due to curtailment, but it’s a long way off 95% accuracy.
I don‘t buy that Griff. If Dinorwig is used to ramp down wind fluctuations at end of day, they will have nothing to cover the 7pm demand peak. Likewise, if end if day is late, they will have already used their power earlier in the day.
Dinorwig cannot smooth demand and supply, it simply does not have enough energy for that.
Ralph
Correct. It is used to allow other slower ramping generators time to ramp up and down, or to cover high ramp rates in demand associated with TV pickup – an ad break in a major sporting event. It is also used for peak shaving in winter evening rush hours, and to handle step changes in transmission on the interconnectors to the Continent, or as fast response in the event of a trip. It does make some income from daily arbitrage, pumping during the night when prices are low, and generating during higher priced hours, but its bread and butter comes from providing ancillary services. It is also capable of black start support.
Absolute nonsense. I record wind prediction and outturn figures and in periods of high wind they are often a couple of nuclear power stations out.
In particular very strong wind will result in windfarms being taken off line, either because the wind is approaching over-speed limits, or they are paid to do so due to there being more wind power than the cables can transmit.
Shooting from the hip:
A minor little point which really rather could de-rail this whole story..
Firstly. its usual Phase Locked Loop, not phased or even phaser
Second, as the wording explicitly says, they systems/components use the PHASE of the waveform – NOT its shape.
Phase is talking about where the zero-crossings are.
It matters NOT ONE JOT about the shape of the waveform, be it sinusoidal, square, sawtooth, pulse or even if it resembles the squashed bug on your car windscreen.
Your ‘shape’ concern may/does apply especially to solid state grid-tie-inverters. They are designed to be soooo safe and sooooo clever in order to be ultra ultra safe and are always looking to be grid tied to a sinusoid.
The solution was/is very simple.
To connect a windfarm or solar farm to A Grid you mash all the outputs from the panels/turbines down into one big phat lump of DC power and take it to a suitably phat DC motor in the corner of the field/farm.
Have that motor drive a (synchronous) grid-connected alternator – just like exist in power stations everywhere.
Cheap, reliable and off-the-shelf technology
We see now where the problem came from.
Because ‘someone else is paying (the taxpayer) – the wind farms and solar panels are connected by the Latest High Technology & (expensive) Fashion.
Just as someone thought that putting an up/down/left/right sensor from a (haha) smartphone and letting it control the flight of a jet airplane full of women and children
Yes Boeing, I’m looking at you.
Now THAT worked a real teat did it not?
Was that Male Toxicity or simply Unreasonable Behaviour?
Wait- do we have a lawyer in the house – I’d say they’re the same thing.
haha= – english language is fantastic innit – gudd jobbe I noze how too tork it innit.
xx
Not wanting to get too off topic, but the B-737 problem was caused by several factors.
a. Making ever more updates to a flight control system that was designed in the 1950s for the B-707.
b. Allowing a flight critical system to react on information from just one sensor.
c. Allowing said system to trim fully forwards, when NO aircraft would want to be trimmed fully forwards when pulling out of a dive.
d. Not fully testing the system for all contingencies.
e. Not telling the pilots such a system existed.
f. Not telling pilots that the manual trim system becomes unusable (locked) at high speeds.
g. Not fully explaining that a 737 with 1-2 degrees of trim and 340 kts is totally uncontrollable, and will inevitably plummet to the ground.
I cannot see how a sane test pilot ever thought this MCAS system was a good idea. Even under normal operation, at the stall, it has the potential to give so much forward trim, it is impossible to pull out of the dive. (As the flight recorder illustrated – they had full up elevator and the aircraft continued to pitch nose down.)
The sensible thing to have done is have a AoA comparator, and to take the system offline when a disparity in data was noted. The next sensible thing to do would be to limit the MCAS assistance to 2 degrees of trim, and not let it run full forwards.
And the next sensible thing to do would be to fit a stick-pusher, not a trim-pusher, because a stick pusher keeps the aircraft in trim for when you need to pull out of the dive. Or better still, redesign the tail surfaces, to give them more authority at the stall. But Boeing did not want to do any of that, as it would mean re-certification.
(Opinions made from an intimate knowledge of the system.)
Ralph
Don’t get me started on the airframe from 1996. I won’t get on a 737 from that age on.
interesting knowledgeable input , thanks.
+1
These fixes are likely, & the certificate will be preserved for commercial reasons. It is a bit strange that AOA has been introduced into an area of aviation where it may not be that useful. Commercial airlines have flown their flight regimes for years without them while the military had to make them a primary reference. Making them carrier optional, and not making it a typical dual-redundant-system on a take all or none basis seems silly now, but made sense as evolved. That little add-on indicator bug in the bottom right of the screen isn’t paid much attention to, I’ll wager. The Icon is the first ACI know of to make AOA primary in GA….for an amphibian it may make a little sense.
The stick pusher idea harks back to stick and rudder days (and I am not disagreeing with you). But when you start flying planes by making line entries on a screen and commanding the machine to perform, you are moving pretty far from the concept of ‘flying the airplane, something the crew did not do as a first priority (and perhaps were not so trained?).
Regardless of how the investigation turns out, it likely that Boeing will conclude (probably correctly) that the aircraft could have been controlled and landed with proper pilotage, perhaps with outside the book items such as a power reduction. If the stick inputs are accepted and the trim was completely off this is probably true in theory, as it used to be a certification standard that the flight controls be sufficient to overcomes a fully traveled and then failed trim.
It did appear to me that the final act in the drama was the failing trim system being re-energized.
I think the system will be “fixed”.
I think you are right that some of the subsystems need a complete restart with a clean sheet of paper. And it’s certainly possible that this airframe that had its low-profile geenesis in the need for an onboard air-stair has been modified past practicality.
But I take a little bit of a different lesson.
Systems can and will fail.
I want a plane with a definitive off switch and a default hand flying mode as robust as we can make it. And I want a trained and competent pilot in both seats…..who knows that his or her job is to save the airplane when the systems fail and practices this.
And neutral or negative stability unless augmented by computers is for fighter planes, not airliners.
>>But when you start flying planes by making line entries on a
>>screen and commanding the machine to perform, you are moving
>>pretty far from the concept of ‘flying the airplane, something the
>>crew did not do as a first priority.
Do remember that the 737 is as far from a computer controlled aircraft as you could possibly get. All the controls are 5mm steel cables, with some hydraulic assistance – it is almost the same as a Cessna 172. But Boe.ing have been bolting on a few computerised extras to this old system, but those extras were not clever enough to realise that the aircraft was not stalling – they had no inputs from airspeed or attitude which could have resolved the situation. So the problem with the 737 was not too much automation, but not enough automation. The simplistic box that Boeing attached was simply not integrated enough and not clever enough to know what was going on. (There is no computer central nervous system in a 737.)
As to the crew, they did disconnect the trim system very early on. But the MCAS trim system had already let its gremlins run loose already, moving the trimmer from 5 units to 2 units. But what is not generally taught to 737 pilots, is that at 2 trim units and 370 kts airspeed, the manual trim seizes up. So they were left with an aircraft that was barely flyable (it needs about 50kg of stick force to counteract the trimmer), and had no way of trimming it.
So the decision was made to reinstate the electric trimmer, to use that. But as soon as they did, the dumb MCAS system took over and trimmed forward again (they were going so fast that even the electric trim may have been seized for nose up movements, but ok for trim down). And that was the final straw. They could not trim up, and even full up elevator would not lift the nose.
Ralf
AoA has not been “introduced” it has always been there as an input to flight control systems. What do you think drives the stick-shaker? AoA, that’s what. What is optional is to have AoA indicated in the cockpit, that is unusual because it really isn’t needed, and the display is crowded enough as it is.
Civilian aircraft do not need to monitor AoA since they do not fly at the edge of the envelope like military aircraft, and if they goof they have the stick-shaker. Though AF 447 would perhaps not have crashed if they had an AoA indicator, but that was due to an idiotic stick-shaker logic.
However Boeing should of course have installed a stick pusher instead of this MCAS monstrosity. But that would have meant a fairly major redesign (the existing feel system does not have enough authority).
Indeed, angle of attack sensors have long been installed on the 737. The classics and NG also had them, for sensing the stall. This is especially useful when flying up in coffin-corner at 37,000 or 41,000 ft. Although why the sudden rash of AoA failures, I don’t know – I have not seen one fail before. Although failures have been a non-event, until MCAS was invented.
The difference with Airbus designs, is the greatly increased complexity. This A350 has four AoA vanes, for redundancy and data voting, and three Yaw vanes, for longitudinal balance. Compare that with the Max, which took information from just one vane, and acted upon it…
R
“A suitably phat DC motor in the corner of the field/farm”
I’m trying to visualise the commutator & brushes needed on a megawatt scale “conventional” DC motor, and the replacement/maintenance costs involved – and think of the (real) carbon emissions! These days, things are moving in the direction of solid state inverter drives tied to 3 phase induction motors. These should be more efficient, and have no wearing parts – other than the bearings. But then you are back to using “hi tech”, and the argument “why bother with the mechanical element?” Obviously having proper spinning inertia is preferable, but with current political interference in decisions which SHOULD be made by engineers, I can’t see that happening.
The wake-up for me was when I replaced my ancient, 1960s, furnace. The electronically comutated blower fan in the new furnace was much more efficient. That said, I can’t expect the new furnace to last fifty years like the old one did.
Your new fan is probably not “commutated”. It is probably a variable speed AC motor whose speed is controlled by a variable frequency driver. Bottom line – no moving parts like in a DC motor that actually has to have commutators and brushes.
There better be a moving part, or they need to stop calling it a motor… LOL
Wind farms have plenty of spinning inertia, but it does nobody any good as long as they are allowed to use (cheap) asynchronous generators, something no conventional powerplant would ever be permitted to use.
Once again, as usual, we have someone with a PhD in English writing about technical matters on which he is not a subject matter expert. The best we can hope for is that he accurately parrots what an actual expert told him.
If we put him on the spot, he won’t be able to describe the relationship between a PLL and a VCO.
On the other hand, the subject matter expert might be very poor at describing what she’s working on.
Trying to explain technical matters is always a compromise.
A number of WEC (wind energy convertor) manufacturers use DC generators in the WEC, no neodymium magnets, no gear boxes. The blades spin at an optimum speed unsynchronised to the grid frequency.
https://www.enercon.de/fileadmin/Redakteur/Medien-Portal/broschueren/pdf/EC_Netztechnologie_en_web.pdf
Each WEC has a dc to AC piece of power electronics to couple to the grid. There is NO synchronising time (within working times), they can even help restore a black grid, or help ride through a grid event.
Staying connected when grid problems occur
Most transmission networks and ever more distribution grids require wind energy converters to remain connected to the grid in the event of grid short circuits. Like conventional power plants, wind turbines are not allowed to suddenly disconnect from the grid during voltage dips or overvoltage caused by grid problems. ENERCON wind turbines with the optional ENERCON UVRT feature have this capacity. No matter what type of short circuit occurs, ENERCON wind turbines can ‘ride through’ faults for several seconds, even if they were operating at rated power before the fault. This is also possible if the wind turbine voltage completely breaks down as a result of a power system failure. These outstanding power plant properties have been certified by independent institutes during actual grid fault testing. Flexible setting options offer maximum performance according to the respective grid operator’s specifications or to the project’s framework conditions.
Depending on the selected parameters, the wind turbine can feed in either mainly active or reactive power to maintain grid voltage. If necessary, voltage-dependent reactive current can even be supplied to the grid; this current can be maximum rated current as stipulated by the latest German grid code. If desired or required, fault ride-through is also possible without power feed-in. The ENERCON wind turbine remains in operation during the fault. After the grid problem has been resolved and grid voltage has been restored, the wind turbine can immediately resume power feed-in. Thus the ENERCON Undervoltage Ride-Through feature facilitates adaptable settings in order to meet grid standards (e. g. of the German
Association of Energy and Water Industries) and to maximise the amount of installable wind farm power.
Also of note:
The cross channel link to France and all other long range connections are operated at DC to minimise losses on the path.
The AC to DC and the DC to AC at the other end are all handled electronically – no moving parts, to synchronism problems. And so far quite reliable.
Main problems has been ships dragging their anchors and breaking the under-sea cables!
Once power lines reach a certain fraction of a wavelength (λ = 5000 km at 60 Hz so problems start at 500 km) a whole new set of problems happen in addition to plain old line losses. If you do it right (ie. get it completely wrong) you can radiate all your power to space and none will be available at the other end of the line. link
Past a certain length, DC transmission is a no brainer.
Radiating your AC power shouldn’t be a major problem using balanced current in transmission lines. Other forms of transmission line losses would be an issue, and DC helps there. Keeping your long distance grid phase locked would be a problem, solved by a DC interconnect between segments with independent phase.
And of course the number of cross channel/N Sea HVDC lines is being expanded… I believe by around 7GW
Do you have any idea how much motors and generators capable of handling MW’s cost?
Let’s not even get into the additional inefficiencies of both.
That is close to the solution that has been proposed for South Australia but it can be done somewhat simpler by just powering a synchronous motor from the wind turbine inverters.
https://reneweconomy.com.au/cheap-condensers-to-displace-gas-as-renewable-energy-back-up-29544/
<blockquote.ElectraNet says it proposes to install three “synchronous condensers” in key areas of the state – at a cost of around $80 million – to ensure that gas-fired generators will no longer need to be switched on just to ensure the grid remains stable.
Will that allow retirement of the gas-fired turbines?
No, gas plant will still be required for back-up of wind and solar. But they will not be required to stay on line if there is wind and the wind generators will not be “curtailed” as often – at least initially.
At present the 2142MW of installed wind is capped at 1200MW for stability purposes – essentially to keep fault level high enough to cater for line failures. Depending on the actual demand, the minimum requirement for gas generation ranges between 200 and 300MW. With synchronous condensers it should be possible to drop that gas minimum to a lower value while increasing the allowable wind maximum. The battery provides 70MW of fast response capacity that helps system frequency control. There is also a 650MW link to Victoria that can source and sink power for wind back-up and for stability purposes.
Demand is disappearing in SA due to energy businesses closing while remaining businesses and households instal rooftop solar. Rooftop solar in SA is a viable year round source of power in SA. By 2022, weekend lunchtime demand in the State network will see periods of negative demand; meaning rooftops in SA will be exporting to Victoria.
Here is a 2018 poster giving some background and showing the missing map, the 2016/7 which is presumably based on real data.
No mention of the fact there will be a lack of Baseload as the Coal fired stations are phaseed out.
Trouble is brewing and the Government are about 10 years behind the curve.
The first to be hit will be Industry which are already requested to cut back (for price reductions) when peak times hit in the winter.
The Government and it’s quangos all live in cloud cuckoo land.
All power system resource plans that rely on load shedding are anti-consumer. Keep ignoring your consumer and you will be removed.
People like living in the dark with no services, including internet. They must. They keep DEMANDING it.
(Very interesting and informative article.)
Hey MODS, where is my post about smart meters and UK disconnection contracts which got held to moderation for no apparent reason?
Moderation seems to have an increased appetite lately…..
This is the kind of information that the public needs to hear and read about. Not the garbage vomited by liberals and conservatives, on Reddit, Facebook, CNN, or even Fox News. If only the general public were more intellectually adventurous– regularly searching for all the facts and not relying on mass media. Collapsing grid stability has a profound impact on life as a whole, and it is something that would knock the public upside the head if such information were more proliferated.
Sad times we live in when facts sit alone at the children’s table while opinions and virtue signals dine with the adults. This, intellectually– and soon physically– hell on earth.
Agenda 2030
hmm! Strange. The National Grid seem to say all OK. Are the giving fake news?
The operator of the UK’s National Grid has said that it is preparing the system to fully run on carbon-free electricity sources by 2025.
Fintan Slye, director of ESO, said the move would require fundamental changes to how the system is designed to operate, incorporating offshore wind farms, household solar panels and more management of demand.
The company will identify systems, services and products that it will need and design a competitive marketplace to deliver them, Slye said.
He added: “The new products and services we will introduce will help reduce the overall cost of operating the system, driving down costs for consumers.
“Operating a zero-carbon electricity system in 2025, whenever there is sufficient renewable generation, is a major stepping stone to full decarbonisation of the entire electricity system.
“This will enable new technologies and removes barriers to ever-increasing levels of renewables.”
https://eandt.theiet.org/content/articles/2019/04/national-grid-prepped-to-accept-100-per-cent-zero-carbon-sources-by-2025/
By 2025! WOW!
And, note the caveat – “[o]perating a zero-carbon electricity system in 2025, WHENEVER THERE IS SUFFICIENT RENEWABLE GENERATION, is a major stepping stone to full decarbonisation of the entire electricity system.”
So, we can have “zero-carbon electricity” whenever it’s possible.
“The operator of the UK’s National Grid has said that it is preparing the system to fully run on carbon-free electricity sources by 2025”
The operator of the UK’s National Grid said no such thing. This is the announcement of a *research project* to see if the National Grid could physically balance the system using only wind and nuclear. The funding has to be secured, and there are many significant challenges along the way. It is therefore an opening proposal.
GB minimum demand is around 40GW (summer time) and nuclear generation will likely be lower by 2025. In addition, the earliest wind farms will be lifetime expired by the late 2020’s and will either be replaced (at more expense to the consumer) or decommissioned.
National Grid’s project will seek to cater for periods when demand is minimum and wind is blowing very hard at the same time. It is very ,very unlikely that their ideas will ever be used in anger. It is just a pseudo-nationalised business making work for idle hands.
Common-language translation of Fintan Slye’s statement: You’ll get less and it will cost more. Also, we’re having a great time using your money (taxes and electricity rates) to fiddle with your critical electric system like a bunch of monkeys.
How come the article states that also the inverters are asynchronous?
Most style wind turbines use asynchronous motors or generators. The term asynchronous entails that the generator has what is called a slip. The slip is virtually zero during no load and will increase with load. So in terms of most wind turbines, the author is likely correct regarding the need for the wind turbine to have a stable network to synchronize against. Further more, the wind turbines need an Ir of about 20% of the current delivered to the network. The 20% Ir does not demand much power, as the voltage is 90° out of phase with the Ir, but the Ir needs to be provided from the grid in the first place. If the Ir is not delivered by a synchronous generator, you really run into trouble.
Going over to the Inverters for PV solar panels, HVDC, etc., I would regard the as dependent synchronous. Whether they PLL or any other technique to adjust their attempted frequency, they have no slip to my knowledge, the do not need an Ir, but they need an existing grid to synchronize against. Technically you could make the inverters behave exactly like the good old synchronous generators you see on ships and traditional power stations. However, this would make the electronics and control circuit more expensive. You would need the inverters to operate with an internal adjustable frequency and an addition synchronization module. Because these are 3-phase, there is a little bit more to it though.
So to summarize:
At the very, very least, you must have at 20% of the grid supplied with synchronous generated electricity.
If solar PV and HVDC is to be relied on, they must be able to perform synchronous generated electricity.
You must have generation capacity any second of the year to follow demand.
The grid dimension has to be adequate for worst case generating scenario.
Sorry if I did not get everything totally correct, it is just one of my outbursts in a rush. I need coffee now.
There are, in general, two related issues with renewables.
1. Intermittency. This requires equivalent backup capacity or load shedding, period. Imposes a significant cost beyond the necessarily subsidized (expensive by comparison to conventional generation) renewables themselves.
2. Grid inertia. This is normally supplied ‘free’ by the flywheel effect of the collective mass of the grid’s synchronized spinning turbogenerators. Renewables supply zero grid inertia. That makes the grid increasingly unstable as renewable penetration grows unless equivalent ‘MW mass’ of synchronous condenser is added. These are essentially undriven generators weighing several hundred tons each spinning in synch. Again a significant added cost.
Unsufficiently paying those two costs together guarantees grid wide blackouts as the renewable penetration increases. We already have South Australia 2016 as an example. UK has not faced up to those costs, as this report shows in more detail. It is likely next. Germany escapes both problems by coupling to Scandinavian hydro.
SA was caused by an extreme weather event taking out power lines and an incorrect trip setting on the wind farms (and issue identified in Germany and corrected there in 2006)
Apparently you didn’t read the part of the report where they showed that the system had repeatedly weathered similar-sized disturbances in the past due to having larger spinning inertia. This time there was not enough time (=inertia) for automatic partial load-shedding to take effect, so the whole grid crashed.
Another problem with intermittency is that the unpredictability of renewable input translates into unpredictability of fuel requirements from balancing generators. Dieter Helm made this point a couple of years ago.
National Grid boasts it can predict wind input to some 95% standard at the day-ahead stage. But replacement fuel needs to be purchased 3-4 weeks ahead to handle delivery risk.
When the coal stations are all gone, GB needs to be able to predict weather pattern 3-4 weeks ahead to some acceptable standard, otherwise it will face serious issues in securing gas supplies for power generation (gas being the only option left according to government policy).
“Germany escapes both problems by coupling to Scandinavian hydro”
Doubtful. Germany already needs more hydro than is available in Scandinavia to weather a major grid problem.
Worth a look at this page to see the reliability of nuclear thermal stations in the UK
by the end of this year 4 stations will have had a down time of over a year (25% loss of nuke capacity)
There have been a number of unexpected trips where 400Mw to 1Gw of power is lost for a few days.
as of 5th April only 11 out of 16 generators are online
hunterston offline for 1 year
Dungeness will have been offline for 1 year assuming return to service date is correct
https://www.edfenergy.com/energy/power-station/daily-statuses
See also:
http://gridwatch.co.uk/
These are stations nearing the end of their life. Let’s see how wind farms are doing after 30-40 years.
The EFR (enhanced Frequency Response) programme is already in place and being expanded with these issues in mind. There is not going to be any problem from this, given the issues are already being examined and provided for. This is alarmism…
https://www.nationalgrid.com/sites/default/files/documents/Product%20Roadmap%20for%20Frequency%20Response%20and%20Reserve.pdf
Well, I worked my way through the waffle. What it says is that they need suppliers that can provide power on demand within 1 second and for one to thirty minutes. Not a word on where it is coming from….
tty, these suppliers are in place and supplying power from diesel generators. They must of course be none carbon diesel generators if some organisations claims around carbon free by 2025 are to be believed 😉
Actually they signed up 201MW of battery capacity split between several installations – the largest is 49MW. Some details here:
https://www.nationalgrid.com/sites/default/files/documents/8589937157-06_EFR.pdf
Actually, NG have stalled the EFR programme, as they found initial trials to be less useful than they had hoped. They have concluded that other approaches are needed to ensure stability. Your document dates from 2017.
Gee: Reality intrudes on bureaucratic/political wishful thinking.
Manhattan project used AC to DC motor generators to make megawatts of DC for each of the calutron racetracks.
If the PLL in an inverter is locked in phase with the grid it will deliver no power to the grid. In the vector math of a synchronous grid it’s phase that determines power flow. The PLL has to lead (predict) the grid in order to move power to the grid. In a transient situation a big chunk of rotating iron and copper can trade energy for inertia while an inverter cannot.
The UK grid is not necessarily synchronised to the European grid allowing for frequency response power control independent of the continent – there have been a few frequency excursions recently on the continent. These are being investigated.
These DC links to a few local countries have helped to stabilise the grids – usually French nukes supply to the UK (you cannot control nuke generation quickly) but in the last couple of years when the French nukes were turned off due to possible metallurgical problems the Uk was often feeding the French grid with 2Gw of power.
It should also be noted that the grids of many (all??) European countries are hard wired (no DC) and this allows for more stability. Also worth a note is that the so called “failing” grid of Germany feeds France with frequently 6GW of power.
the uk – france 2Gw link:
wiki
2000 MW system (1986)[edit]
Because the first installation did not meet increasing requirements, it was replaced in 1975–1986 by a new HVDC system with a maximum transmission rating of 2,000 MW between France and Great Britain, for which two new converter stations were built in Sellindge, between Ashford and Folkstone in Kent (UK) and in Bonningues-lès-Calais (Les Mandarins station), near Calais, (France). Unlike most HVDC schemes, where the two converter stations are built by the same manufacturer, the two converter stations of the 2,000 MW scheme were built by different manufacturers (although both have subsequently become part of the same parent company, Alstom). The Sellindge converter station was built by GEC[4] and the Les Mandarins converter station was built by CGE Alsthom.
This HVDC-link is 73 kilometres (45 mi) long in route, with 70 kilometres (43 mi) between the two ends. The undersea section consists of eight 46 kilometres (29 mi) long 270 kV submarine cables, laid between Folkestone (UK) and Sangatte (France), arranged as two fully independent 1,000 MW Bipoles, each operated at a DC voltage of ±270 kV. Cables are laid in pairs in four trenches so that the magnetic fields generated by the two conductors are largely cancelled. The landside parts of the link consist of 8 cables with lengths of 18.5 kilometres (11.5 mi) in England, and 6.35 kilometres (3.95 mi) in France.[5]
In common with the 1961 scheme, there is no provision to permit neutral current to flow through the sea. Although each station includes an earth electrode, this is used only to provide a neutral reference, and only one of the two electrodes is connected at a given time so that there can be no current flow between them.
The system was built with solid-state semiconductor thyristor valves from the outset. Initially these were air-cooled and used analogue control systems but in 2011 and 2012 respectively, the thyristor valves of Bipole 1 and Bipole 2 were replaced by more modern water-cooled thyristor valves and digital control systems supplied by Alstom.[6]
This system remains the world’s largest-capacity submarine cable HVDC system.[7]
In November 2016 during Storm Angus a ship dragging an anchor cut four of the eight cable components, reducing capacity by 50%.[8] Repairs were completed by the end of February 2017.
a better document from the national grid
https://web.archive.org/web/20100206093023/http://nationalgrid.com/NR/rdonlyres/E19B4740-C056-4795-A567-91725ECF799B/32165/PublicFrequencyDeviationReport.pdf
Jay-sus! You’ve got monkeys designing critical electrical systems using wishes and government propaganda.
Thinking people, at least in the U.S., used to mistrust government activities. We’ll see what happens to the Obama-era Deep State operatives.
One of the biggest power outages in the UK was in fact caused by 2 thermal (longannet 350Mw and a nuke sizewell 1.2Gw stations tripping loosing 1.6Gw of generations, followed by all the supposed backups (private diesel generators etc. failing or refusing to start) this caused load shedding of industries which accepted this for lower cost electricity, and then followed load shedding of large areas which did not have low costs.
https://www.ofgem.gov.uk/ofgem-publications/41426/nationalgrid-systemeventsof27mayfordswg16july.pdf
The grid stability can be maintained against windless and sunless power loss as these are slow events. the loss of a few Mw from wec failure is not significant.
The lack of wind or sun means there must be enough backup – slow start is ok – to handle it. I assume the NG knows what it is doing!
Do the politicians directing the NG with their edicts know what they are doing ?
Partial load-shedding is all very well, if you have time to do it. Even completely automatic control systems are not quite instantaneous, and large high-voltage circuit-breakers can’t be instantaneous unless you want to destroy the whole system.
The South Australia debacle shows that in a system with much wind-power there may not be enough inertia/time to do partial load-shedding before the whole grid crashes.
Longannet no longer in existence so no need to worry about it failing again, or the reliable energy it used to produce.
When the author talks about high levels of solar in the south west he is talking relatively, compared to say northern Norway.
In truth the sunniest part of the south west where I live has around 1700 hours of solar per annum which of course means the rapidly expanding solar industry in this neck of the woods is not viable without large subsidies.
Disturbingly, places with even less solar are being subsidised even more. It is not a viable industryb in the uk in the conventional sense
Unfortunately our biggest asset, wave/tidal power remains unexploited even though we are an island with nowhere more than 70 miles from the sea
Tonyb
Neither wave nor tidal power are economically exploitable in any serious quantities around the UK. All the wave and tidal stream projects have been heavily subsidised, and run into operating problems with damaged and limited life equipment. The Swansea Bay tidal barrage was canned because it was going to cost well over £1bn to produce a highly intermittent supply (fluctuations every tide at 12 hour 20 minute intervals, amplified by fluctuations between spring and neap tides every lunar month) averaging about 60MW. Even greenie BEIS minister Greg Clark said:
“The same power generated by the lagoon, over 60 years, for £1.3 billion, would cost around £400 million for offshore wind even at today’s prices, which have fallen rapidly, and we expect to be cheaper still in future. At £1.3 billion, the capital cost per unit of electricity generated each year would be 3 times that of the Hinkley Point C nuclear power station.”
When the author talks about high levels of solar in the south west he is talking relatively, compared to say northern Norway.
In truth the sunniest part of the south west where I live has around 1700 hours of solar per annum which of course means the rapidly expanding solar industry in this neck of the woods is not viable without large subsidies.
Disturbingly, places with even less solar are being subsidised even more. It is not a viable industryb in the uk in the conventional sense
Unfortunately our biggest asset, wave/tidal power remains unexploited even though we are an island with nowhere more than 70 miles from the sea
Tonyb
I’ve observed that people often are incapable of learning from other’s mistakes. In that case, they need to experience failure before making rational decisions.
The term “renewable”, used as a description for solar and wind generators, is incorrect. As in:
These forms of power generation are in no way renewable. They consume more energy during their manufacture and installation than can ever be recovered from them over their lives. The description is inappropriate.
Have a look at New Zealand ,
Most of our electricity is generated by Hydro and a number of large wind farms have been built .
There are a few small geothermal stations with the biggest being Wairakei near Taupo .
The system works well and a large amount of power generated in the South Island is sent to Auckland via the Cook Strait undersea cable .
With fluctuating wind hydro stations can be automatically turned on or off as required from a central control base .
All that said just last month Vector Power (formerly Auckland Electric Power Board ) was fined $3.575 million NZ dollars as they had too many power outages in the last two years.
The judge said thy had breached the network Quality standard due to a high number of power outages .
Vector under estimated the risk of managing vegetation ( trees in lines ] and the life cycle of certain ageing assets.
This is a ridiculous fine as Vector is in effect owned by its customers so that every customer will get little or no dividend as a rebate on future power bills .
The Commerce Commission and the court wanted to send a message to Vector and other Power distribution companies . but why take money effectively off the consumers who had to put up with the power outages .
Customers have to pay the cost of maintaining the system anyway, which probably will far exceed the fine which is a token of official disapproval. I have a local distribution line that passes close to my home: it is inspected by helicopter annually, flying at no more than 100ft. Last year they sent out a team to cut down trees that threatened to grow into the line, or which might get blown into it in a storm. We had a half day power outage while they did that. At least they notified us in advance.
Is there any chance, however small, that the Greeniacs pushing for windmills and solar panels could explain the difference between a synchronous machine and an induction machine? And could they explain why this difference is so crucial to the stability of the electric grid?
It’s not clear that knowledgeable people will be welcomed to the conversation by our “leaders,” but having politicians consult nobody but priests of Gaia about the grid is really asking for some kind of Armagriddon to take place.