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2025 Iberia Blackout Report [pdf]

193 points by leymed 1y ago

deleted 1y ago
[deleted]
fuoqi 1y ago
[flagged]
- matsemann 1y ago
  But the quote literally spells out it was market forces, not some instability in solar generation? Your other comment probably got flagged because it started with a huge straw man and had multiple unwarranted jabs in it.
  - fuoqi 1y ago
    Temporary negative prices have been caused by the renewable generation which exceeded the grid demand at the time, which then evolved into the nasty feedback loop caused by the reaction of renewable generation to those conditions. You simply do not get such situation with traditional generation, it's the direct consequence of the intermittent nature of renewables and its high ratio in the total generation. Also, have you read after the market part? Please watch this video https://www.youtube.com/watch?v=7G4ipM2qjfw https://www.youtube.com/watch?v=7G4ipM2qjfw if the last quote is gibberish to you. It discusses somewhat different issues, but the point still stands.
    - pkilgore 1y ago
      Where is the market for someone to get paid to pump water into a reservoir and let it fall down later for $$$?
      - pdpi 1y ago
        That market exists, but the window of time here is like twenty minutes. Pumps have inertia and take time to spin up, you can't HFT load and generation.
        gusgus01 1y ago
        I'm not fully informed about pumped storage, but twenty minutes is more than enough for most hydroelectric plants to go from 0 to full power, and that's probably the case for pumped storage as well. Eg, In the case of Cruachan Power Station: “It takes just two minutes for a turbine to run up from rest to generate mode,” says Martin McGhie, Operations and Maintenance Manager at the power station. “It takes slightly longer for the turbines to run down from generate to rest, but whatever function the turbines are performing, they can reach it within a matter of minutes.” https://www.drax.com/power-generation/in-energy-storage-timing-is-everything/ https://www.drax.com/power-generation/in-energy-storage-timi...
      - plorg 1y ago
        If you read the report there was a significant amount of solar being produced at low prices and being pumped for storage. Further, the pumped hydro is the first load to be disconnected to balance demand on their system.
      - ncruces 1y ago
        Partly the neighboring country. Between Spain and Portugal there's 10 GW (~20% or peak load) and 100 GWh of storage (enough for a day's worth of consumption). But that takes time and requires some rebalancing, because much of that capacity is not closest to the producers. It also requires water, which becomes scarcer in the autumn (not the case here). So the price can and does become negative for a window. “High frequency trading” the spot prices probably contributed to the problem.
    - eldaisfish 1y ago
      you are correct, but your analysis is not popular here. You will soon be presented with several reasons as to why renewable energy is not the problem and how batteries are the one true solution to these problems. The reality is that electricity is complex and that renewable energy presents a new set of problems, problems to which we do not yet have complete solutions.
    - floatrock 1y ago
      So an incredibly cheap source of supply exceeded the demand, and the market rules and some trips caused cascading failures. Why is the problem the cheap source of supply rather than the market rules and incentives that made everything act the way it did? Your comment suggests move back to good ol' expensive fossil generation instead of looking at how to bring the market rules up to date with evolving technologies.
      - martinald 1y ago
        Because the only reason that solar is still generating power at negative prices is because they are getting subsidies to do it. Otherwise they would disconnect themselves apart from in extreme scenarios (control system down or something), and I bet when you are paying many tens of thousands of euro an hour you'd get someone to fix/manually turn it off sharpish. Looks like there are a multitude of schemes of various vintages in Spain, which tl;dr basically give you a guaranteed price per MWh you generate. So imagine you get a 100eur/MWh subsidy for a (legacy) solar plant. The market price is €-20/MWh. You will still continue to produce power until the price reaches -100MW/h. Even worse are some contracts for difference (poorly thought through) which give you a guaranteed price regardless of what the market is at. So even if the price was -1,000eur/MWh the government or grid operator would still give you your €50/MWh (and the subsidy would be 1,050/MWh!). The problem is if you reform this (and it is happening worldwide) solar is much, much less appealing. Because suddenly your solar plant which was getting (say) a guaranteed 70/MWh all year round suddenly does not make money for 6 months of the year at least at peak sun hours. On top of all this, you have a lot of domestic solar in places like Spain. The grid operator _cannot_ control these assets in nearly all circumstances. They will continue to dump power into the grid regardless of the market price. This again will change but it requires an awful lot of work to retrofit invertors with remote control capability OR a lot of public backlash for charging end customers who bought solar in "good faith" now getting hit with peak time negative prices (so they change their behaviour). I think my core message would be _any_ negative power prices is a sign of market failure. Acceptable in rare extreme occurrences, but the fact most of europe has highly negative prices very frequently is telling you the grid and market design is not able to handle what is going on.
        1y ago
    - jakewins 1y ago
      > caused by the reaction of renewable generation to those conditions No, that is not what the report says. It says, just like you say, that renewables reacted to market prices, causing a generation drop. It then says explicitly that synchronous generation caused oscillation, while PV plants showed a flat non-oscillating pattern. From your comments I worry there are emotional factors clouding how you're reading the report - this was a systemic failure involving many separate technologies: - Market signals - negative prices - caused a drop in PV generation (as frequently occurs) - Synchronous plants caused oscillations as a side effect - Plants procured to dampen exactly those oscillations did not deliver as requested - TSO then took measures using interconnections to stabilize via other balance area - This caused - presumed - overvoltages in distribution grids - PV inverters then shut off, as mandatory by regulatory requirement in response to over voltage You're absolutely right that PV played a large role here, but that point is diminished by making it out that PV is both the source of the initial generation drop and the source of the oscillations; it is neither. The market design caused the generation drop, synchronous generators caused the oscillations, TSO action caused distribution overvoltages and regulatory requirements on PV firmware design in response to overvoltage caused the final blackout.
  - shakow 1y ago
    True, but the market moves fast because renewables (or, more precisely, wind & solar) move fast. There is not much fast trading to be done on a nuke/gas/coal/hydro powerplant ramping up or down, but there is a lot of instability (and thus market volatility) to be found in fast varying solar/wind conditions.
    - stephen_g 1y ago
      That's inaccurate on the whole though, because while those big generators can't move fast, demand can move fast! Which is a difficult problem to manage in baseload grids. Renewables just change one set of challenges for another set, at the end of the day it's all manageable.
      - mlyle 1y ago
        > because while those big generators can't move fast, demand can move fast! Which is a difficult problem to manage in baseload grids. Don't forget rotational inertia. This gives the system a high-frequency response mode: it can resist sudden demand changes through stored kinetic energy, effectively acting as a low-pass filter with a fast dominant pole. As you get a smaller share of generation with rotational inertia, you need a lot more buffering on short to medium timescales. And, of course, it doesn't help for longer timescales that in many places renewable production slopes off in the late afternoon right when demand slopes upwards for cooling.
        _aavaa_ 1y ago
        > in the late afternoon right when demand slopes upwards for cooling. Demand rises because that's how people have their system set up. That cooling load can be shifted earlier in the day by using a slightly smarter thermostat to precook your house when the electricity is plentiful.
        mlyle 1y ago
        > Demand rises because that's how people have their system set up. That cooling load can be shifted earlier in the day by using a slightly smarter thermostat to precook your house when the electricity is plentiful. You can do this a bit, but the insides of houses don't have that much thermal mass and the best insulated houses add a pretty large phase delay that makes the quickest rise in internal temperatures during the late afternoon as framing in the attic heats up. I don't have a lot of luck in accomplishing meaningful precooling in my house. My best plan is to suffer until the late afternoon, turning on the AC at the end of the peak demand period when at least outside temperatures are lower, my AC units are shaded, and the cooling is more efficient.
- wavefunction 1y ago
  You quoted >the most plausible explanation is that it is due to market reasons (prices) Seems to be market conditions or manipulations or inefficiencies in the market.
  - deleted 1y ago
    [deleted]
- pdpi 1y ago
  What I'm reading from that quote is that the issue wasn't renewables as such, but an issue of power generation reacting too quickly and too intensely to price fluctuations. "Renewables" only matter insofar as they're the sort of generation that, under the current regulatory regime, get to react to those pricing changes.
  - kmeisthax 1y ago
    [dead]
  - baq 1y ago
    The report goes to great lengths to avoid certain words or phrases. The market failed here, it didn’t price in risk of grid collapse correctly.
    - mslansn 1y ago
      [flagged]
      - xwolfi 1y ago
        Except to point out that it's not nice that renewables arrive at random prices in the grid and start crapping all around it until they disappear when expensive again. The stability of a nuclear plant vs the instability of a solar far when a cloud passes over.
    - Yeask 1y ago
      That is a simple and great explanation.
      - plorg 1y ago
        It's also just unfounded conspiracism and factually incorrect.
        mlyle 1y ago
- baq 1y ago
  Should’ve said ‘not enough spinning mass’ and it’d be perfectly fine for the politically correct and mean the same thing. This was highlighted as a risk for years and it finally materialized.
  - philipkglass 1y ago
    According to the operator report linked in another comment by leymed [1], the problem was not a lack of spinning mass (inertia) but voltage instability. From page 16 of the PDF: The incident was NOT caused by a lack of system inertia. Rather, it was triggered by a voltage issue and the cascading disconnection of renewable generation plants, as previously indicated. Higher inertia would have only resulted in a slightly slower frequency decline. However, due to the massive generation loss caused by voltage instability, the system would still have been unrecoverable. [1] https://news.ycombinator.com/item?id=44360052 https://news.ycombinator.com/item?id=44360052
    - baq 1y ago
      Obviously I’m as good of a grid operator as I was a stealth bomber expert on the weekend, but superficially that just doesn’t seem right. Maybe I’m underestimating how much spinning mass would be required, but that still qualifies as ‘not enough was present’.
      - eldaisfish 1y ago
        please can you explain what doesn't seem right?
        baq 1y ago
        They admit they had plants offline when they should be available and then they say it wouldn't matter and the grid would've collapsed anyway..? Either they're in a very very bad spot and stop short of saying it outright in the report or it would've averted the disaster if the not-spinning mass was spinning as it should have.
- rcxdude 1y ago
  It's worth pointing out that the worst part of the behaviour of renewables specifically in this incident (a fixed power factor for managing reactive power), is currently mandated by the regulations in Spain, even though many of them are already equipped to do voltage control.
- felipeerias 1y ago
  People are having three different conversations at the same time: – the concrete causes of this specific blackout; – how the existing grid is not prepared to deal with the current energy mix; – the energy policy of the past decades, from the nuclear moratorium in the 80s to the large subsidies for renewable generation of the past couple decades. A person's strong opinion on any one of these issues will inevitably influence their opinion on the others.
- tomhow 1y ago
  > but the fans of renewables just flagged it As moderators we can only guess why people flag things, but there are other reasons why people may have flagged that comment, the foremost being that it broke the guidelines due to its inflammatory style. On Hacker News we want to be able to discuss difficult topics involving arguments people may find counter to their assumptions, but you need to express things in a way that's persuasive rather than combative. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
  - fuoqi 1y ago
    Was the comment above also in "inflammatory style"? It's an obvious fact that flagging on HN is used by some people as a tool to censor unfavorable opinions. Even worse, AFAIK there is zero consequence for such frivolous flagging.
    - tomhow 1y ago
      Users who use flagging inappropriately (i.e., for reasons other than guidelines breaches) have their flagging powers disabled. We do that often. Same goes for unfair downvoting. If a comment of yours or any other you see is unfairly flagged, you can email us and we'll take a look. We'll explain how we see it and if we agree its unfair we'll restore it and consider action against those who flagged it. We always discourage complaining about flagging or downvoting in comments as you can never know exactly what has been done by other users or why they did it, and it’s usually a generic tangent from the discussion.
tofflos 1y ago
It's a difficult read. Cybersecurity and digital systems was not the issue but gets thirteen pages of proposed measures. I feel this could have been left out. Electric System Operation was the issue and gets seven pages of proposed measures.
- leymed 1y ago
  Check this shorter report by the operator: https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_SpanishPeninsularElectricalSystem_18june25.pdf https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_Sp...
- razakel 1y ago
  >I feel this could have been left out. It's pretty much their one and only chance to warn the authorities that there's a risk, so if they choose to ignore it, well, nobody can claim they weren't informed.
AnotherGoodName 1y ago
Reads very similar to some blackouts we had in Australia. Weakly connected grids with vast geographical distances leading to oscillations that took down the grid. https://en.wikipedia.org/wiki/2016_South_Australian_blackout https://en.wikipedia.org/wiki/2016_South_Australian_blackout Completely solved with lithium based grid storage at key locations btw. This grid storage has also been massively profitable for it's owners https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve#Revenues_from_operation https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve#Revenu... Australia currently has 4 of the 5 largest battery storage systems under construction as a result of this profit opportunity; https://en.wikipedia.org/wiki/Battery_energy_storage_system#Under_construction https://en.wikipedia.org/wiki/Battery_energy_storage_system#... You can also read numerous stories of how Australia's lithium ion grid storage systems have prevented blackouts in many cases. https://www.teslarati.com/tesla-big-battery-south-australia-3-blackouts/ https://www.teslarati.com/tesla-big-battery-south-australia-... The fact is that the batteries responsiveness is the fastest of any system at correcting gaps like this. 50/60hz is nothing for a lithium ion battery nor are brief periods of multi-gigawatt draw/dumping as needed. There's even articles that if Europe investing in battery storage systems like Australia they'd have avoided this. https://reneweconomy.com.au/no-batteries-no-flexibility-spain-could-have-avoided-blackout-with-lessons-learned-in-south-australia/ https://reneweconomy.com.au/no-batteries-no-flexibility-spai...
- londons_explore 1y ago
  > nor are brief periods of multi-gigawatt draw/dumping as needed. Actually this is typically an issue for grid batteries. Spinning generators can easily briefly go to 10x the rated current for a second or so to smooth out big anomalies. Stationary batteries inverters can't do 10x current spikes ever - the max they can get to is more like 1.2x for a few seconds. That means you end up needing a lot of batteries to provide the same spinning reserve as one regular power station.
  - AnotherGoodName 1y ago
    Collectively Australia's battery storage systems will be able to beat any single power plant for peak output in Australia once fully built out based on pure numbers. But for these sorts of grid oscillations the more important thing is the localization of generation. Which obviously favours the batteries over large centralized power stations in any case.
rcarmo 1y ago
Page 130 is where the actual human readable summary is. Although the previous pages were pretty detailed in explaining the cumulative instabilities. Sadly, some news outlets are probably only going to look at the recommendations and read "cybersecurity" and (even though they are common sense recommendations) assume there might be more to say about the matter.
- decimalenough 1y ago
  Don't worry, some news outlets will summarize this as "renewables = bad" regardless of what the report actually says. Oh wait, they already did: https://www.telegraph.co.uk/business/2025/06/18/renewable-energy-to-blame-for-spains-blackouts/ https://www.telegraph.co.uk/business/2025/06/18/renewable-en... Ed: Do I need a /s tag here or something? My point was that we shouldn't worry too much about about the presentation of the report, its actual contents will be spun to suit any narrative regardless.
  - baq 1y ago
    Flame bait journalism is one of the things you can count on in any circumstance. If you replace that ‘renewables = bad’ with ‘politicians = idiots’ OTOH… sometimes the elected representatives should listen to unelected physicists and engineers. Grid stuff is one of those things.
  - kgwgk 1y ago
    That doesn’t really say “renewables bad”. The report actually says that there was a drop in solar generation.
  - rsynnott 1y ago
    I mean, that's the Telegraph; it's just not a serious newspaper these days. (Brexit really did a number on it; in the last decade or so it's gone from a right-wing but fairly normal broadsheet to just complete raving nonsense.)
- Nextgrid 1y ago
  There's been a shit-ton of misinformation about cyberattacks within the first hour of the outage, and the public were unfortunately very receptive to it, so I guess they're trying to preempt those concerns?
decimalenough 1y ago
> Non-confidential version of the report of the committee for the analysis of the circumstances surrounding the electricity crisis of the April 28, 2025 Now I'm curious about what's in the confidential version of the report.
- londons_explore 1y ago
  Based on the redacted bits, it is mostly company names and locations.
  - diggan 1y ago
    And more interestingly, the specific reasons various installations were unable to start up as they should have: > Incidents detected during equipment start-up - Firstly, there is information consistent with the fact that several installations with the obligation of autonomous start-up were finally unable to provide this service in a stable manner, joining the system only once voltage had arrived from outside (from another of the "islands", normally anchored in one of the interconnections). This slowed down the start-up of the "skeleton" of the electricity system that would later make it possible to replenish the supply to demand. The rest of the ~2 pages in that section is redacted.
londons_explore 1y ago
It doesn't look like this report really identifies the root causes... I would like to see: "We have simulated the complete 200 and 400 kV grid of the iberian peninsula and western europe, and can reproduce the situation that occurred. Any one of the following changes would have prevented the issue, and we suggest implementing them all for redundancy. This simulation will be re-run every day from now on to identify future cases similar incidents could occur"
- baq 1y ago
  The engineers knew exactly what’s going to happen, the report is politically redacted. Very unfortunate, but completely expected.
JanneVee 1y ago
When skimming through the report I got to think of the oscillation problem in RIP routing protocol. Although it isn't the same thing, but it shows the complexity of the problem to anyone who thinks there is a single solution to it.
deleted 1y ago
[deleted]
gred 1y ago
Why so many pages of "Recommendation: implement multi-factor authentication" and other IT security irrelevancies? Did they need to pad out the number of pages?
- diggan 1y ago
  > In the systems with network traffic evaluation probes, no records consistent with unauthorized activity have been observed, such as lateral movements, network traces or file movements for vulnerability exploitation or privilege escalation, among others. > However, as is common in networks and information systems in any sector, other risks have been identified, such as vulnerabilities, deficiencies or inadequate configurations of security measures, which may expose networks and systems to potential risks, for which a series of measures are proposed.
- rcxdude 1y ago
  Infrastructure in general has pretty terrible security practices, so I won't bemoan someone finding a useful soapbox to remind them to shape up a bit, even if it isn't the core cause of this particular issue (and it's probably also a reaction to various rumours/speculation about a cyberattack).
diggan 1y ago
Seems the money shot starts at page 131: > The ultimate cause of the peninsular electrical zero on April 28th was a phenomenon of overvoltages in the form of a "chain reaction" in which high voltages cause generation disconnections, which in turn causes new increases in voltage and thus new disconnections, and so on. > 1. The system showed insufficient dynamic voltage control capabilities sufficient to maintain stable voltage > 2. A series of rhythmic oscillations significantly conditioned the system, modifying its configuration and increasing the difficulties for voltage stabilization. If I understand it correctly (and like software, typical), it was a positive feedback-loop. Since there wasn't enough voltage control, some other station had to be added but got overloaded instead, also turning off, and then on to the next station. Late addition: It was very helpful for me to read through the "ANNEX X. BRIEF BASICS OF THE ELECTRIC SYSTEM" (page 168) before trying to read the report itself, as it explains a lot of things that the rest of the report (rightly) assumes you already know.
- leymed 1y ago
  I think your interpretation is correct. The voltage control is done at the high level of the grid, meaning the control covers bigger generation stations and major substations. Even if it’s small generator, rotating machinery, you won’t have strict voltage control other than its own AVR. The problem I see here is that we embed smaller individual generations at the lower level, where they pump the generated power to the grid at the medium voltage level. When you have majority of your generation at this level, you won’t have strict control over voltage and even frequency, I assume. I’m still digesting the report, but what I am after is whether they really neglected it and if it is not possible to do voltage control with 50% generation coming from renewable and through medium voltage level, aka lower level.
- amluto 1y ago
  I’m a bit mystified as to how the grid controls voltage at all. The non-renewable plants follow the rules here: https://www.boe.es/buscar/doc.php?id=BOE-A-2000-5204 https://www.boe.es/buscar/doc.php?id=BOE-A-2000-5204 7.1(b) seems to be saying that generators connected at 200kV adjust their reactive power generation/absorption in real time according to the voltage they observe, based on a lookup table provided by the grid operator. This seems sort of sensible according to my limited understanding of the theory of AC grids. You can write some differential equations and pretend everything is continuous (as opposed to being a LUT with 11 steps or so), and you can determine that the grid is stable. However, check out this shorter report from red eléctrica: https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_SpanishPeninsularElectricalSystem_18june25.pdf https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_Sp... Apparently these 220kV plants are connected to the 400kV grid via transformers in substations that are not owned by the generator operators. And those transformers have “tap changers” that attempt to keep the 220kV secondary side at the correct voltage within some fairly large voltage range on the 400kV side. Won’t this defeat the voltage control that the 220kV generators are supposed to provide? If the grid voltage is high, then absorption of reactive power is needed [0], and the generators are supposed to determine that they need to absorb reactive power (which they can do), but if the tap changer changes its setting, then the generator will not react correctly to the voltage on the 400kV side. In other words, one would like the generator to absorb reactive power according to P_reactive(primary voltage • 220/400), but the actual behavior is P_reactive(primary voltage • 220/400 • tap changer position), the tap changer position is presumably something like 400/primary voltage, and I don’t understand how the result is supposed to function in any useful way. Adding insult to injury, the red eléctrica repoet authors seem to be suggesting that a bunch of tap changers operators didn’t configure their tap changes well enough to even keep secondary voltages in range. Does anyone with more familiarity with these systems know how they’re supposed to work? [0] I can never remember the sign convention for reactive power.
robocat 1y ago
Individual generators monitor Voltage, Frequency, and reactive power (≈ how much current is out of phase with voltage) to make decisions about injecting more or less power into the network. This is just historically how they've always been doing it. Due to interactions between different generators, there can be instabilities causing voltage or frequency or reactive power to deviate outside of spec. A simple example might be two generators where one surges while the other drops back, then vice versa. The measurement (by the network operator) of these effects is poor for Spain - shown by the simple example that they have large oscillations that they couldn't explain. There's path dependent healing and correction of problems by different generators, which overall leads to network stability. However the network operator here is not actually resolving cause and effect, and does not have the insight to manage their stability properly. In this case you can see them trying a few things to inject changes that they hope will bring stability - e.g. tying many connections hoping that adding generators together into one network will resolve to a stable outcome. Are there countries that have a better design for their electricity network control systems? Disclaimer: I don't design electricity networks nor electricity markets. And the above is ignoring loads (loads are mostly less problematic for control than generation).
- scrlk 1y ago
  I suppose other system operators might have better a state estimator and wide area monitoring system. But real-time system operation is universally an engineer sitting behind a desk, looking at their screen, and trying to make the best decision with whatever data they have. The actions that were taken did not strike me as out of the ordinary.
rocqua 1y ago
So, the problem was a local voltage oscilation, where the high voltages caused generators to shut off. How do these oscilations start? I understand that voltage isn't necessarily equal across the network, where frequency is. But that only allows oscillating, it doesn't cause it. Is this a basis inductor capacitor oscillation? Is it the small delay in inverters between measuring voltage and regulating their output? (seems unlikely, given that renewables aren't blamed) or is there some other source of (delayed) feedback. And why do generators cut off at a high voltage? Is it a signal of 'too much power'? Is it to protect the generator from some sort of damage?
- rcxdude 1y ago
  Sort of: For the oscillations, the European grid in general is large enough that the time it takes for the energy to flow (at some fraction of the speed of light!) from one side of it to the other is not negligible: it's not a case of delays at the power plant, but delays in the network itself which can cause the various natural and artificial feedback loops in the circuit to start to become unstable and oscillate. In this specific incident, there's some implication in the report that the largest oscillation was unusual and may have been generated by single plant essentially oscillating on its own, for reasons unknown. In either case, the oscillations were not the direct cause of the blackout: they were controlled, but the steps to control them put the system into a more fragile state. This is because of reactive power. The voltage in the system is due to both the 'real power', i.e. the power generated by the plants and consumed by consumers in the grid each cycle of the 50Hz AC, but also 'reactive power', which is energy that is absorbed by the consumers and the grid itself (all the power lines and transformers) and then bounced back to the generators each cycle. This is the basic 'inductor-capacitor' oscillation. This reactive power is considered to be 'generated' by capacitance and 'consumed' by inductance, though this distinction is arbitrary. So, after the grid operator had stopped the oscillations, the grid was 'generating' a lot more reactive power, because damping down the oscillations generally involves connecting more things together so they don't fight each other as much. It also _lowered_ the grid voltage on average, so various bits of equipment were essentially adjusting their transformer ratio with the high-voltage interconnect to try to adjust for it. Apart from these measures, the generators on the grid are generally supposed to contribute towards the voltage regulation, which helps with both damping these effects and reducing the change of the runaway spike that happened. But crucially, there's a difference between what they (by regulation, not necessarily technical capacity!) do. The traditional generators have active voltage control, which means they actively adjust how much reactive power they generate or absorb depending on the voltage on the lines. Renewable generators, by contrast, have a fixed ratio: they will be set to generate or absorb reactive power at a certain percentage of the real power (a few percent usually), they don't actively adjust this (they're not allowed to under the rules of the grid). So, after the oscillation, the grid is generating a lot of reactive power and the power plants are absorbing it, but there's a lot of renewables around, which can't actively control voltage, they're just passively contributing a certain amount. Then there's a fairly rapid drop in real power output, which seems to be related to the energy market as some plants decide to curtail. This is expected, but renewables can do it pretty quickly compared to conventional plants. This means that the amount of reactive power being absorbed drops, i.e., counterintuitively a plant producing less power means the voltage rises. In theory, there should be enough voltage control from conventional sources to deal with this, but in general they prove to not absorb as much reactive power as they were expected to, and the report calls out one plant which seems to just not be doing any control at all, it's more or less just doing something random. This means the voltage keeps rising, and, perhaps in part due to the adjustments in the transformer ratios, this means another plant trips off, at a lower voltage than it should (this is, basically, for protection: the equipment can only take so much voltage before it's damaged, but there's rules about what level of voltage it should withstand and, in extreme cases, for how long). This then makes the voltage rise more, and it's a fairly rapid cascade of failure from there, and many plants kick offline in a matter of seconds, and only then does the frequency of the grid start to drop significantly, but it's already too late because there's too much demand for the supply. The recommendations of the report basically boil down to: - Figure out why the plants (renewable and conventional) didn't have the capabilities the grid operator thought they did (or why they were actively causing problems), and fix them. - Fix the regulations so renewable plants are allowed to contribute to active voltage control, and incentivize them to do so. - Adjust the market rules so that plants have to give more notice before increasing or decreasing supply in response to prices - Improve the monitoring of the grid and add other tools to help with voltage control (including better interconnects with the rest of Europe)
ranguna 1y ago
What is curious to me is that there's a possibility that a single plant in conjunction with natural oscillations caused enough trouble to start a doom scenario. Oscillation -> damping -> possibly faulty equipment and possibly lack of power plants to absorve the reactive load -> 0 voltage in two countries and some neighbouring regions There's also the possibility that Portugal put too much demand on the market due to negative prices, but I'm not sure if it was explained how much that had an effect on the whole thing.
nraynaud 1y ago
An interesting detail is that the instability had warning signs in the waveforms, that probably means that an algorithmic response is possible.
icar 1y ago
It's a difficult read, so let me paste here what Claude Sonnet 4 summarised: Based on this comprehensive report on the April 28, 2025 electrical blackout in Spain, I can summarize the key reasons why it happened: ## Primary Cause: Voltage Control Crisis The blackout was fundamentally caused by *insufficient dynamic voltage control capacity* in the system, which led to a catastrophic "chain reaction" of overvoltages. Here's how it unfolded: ### The Perfect Storm of Contributing Factors *1. Inadequate Voltage Control Resources* - Only 11 thermal power plants were coupled with voltage control obligations (the lowest number recorded in 2025) - One planned voltage control plant in the southwest failed the previous evening and wasn't replaced - Several connected plants didn't provide expected reactive power absorption during critical moments *2. System Oscillations Weakened the Grid* - Multiple oscillations occurred throughout the morning (starting at 5:49 AM) - Two major oscillations at 12:03 PM (0.6 Hz) and 12:19 PM (0.2 Hz) significantly stressed the system - The first oscillation was traced to anomalous behavior at a specific photovoltaic installation - Measures taken to dampen these oscillations (increased grid meshing, reduced interconnection flows) inadvertently contributed to voltage increases *3. The Fatal Chain Reaction (Phase 2-3)* Starting at 12:32 PM: - Voltages began rising rapidly across the transmission network - Generation facilities started disconnecting due to overvoltages, beginning with renewable plants - Each disconnection removed reactive power absorption capacity and reduced line loading - This caused further voltage increases, triggering more disconnections - The process accelerated into an unstoppable cascade ### Key Timeline - *12:32 PM*: Sustained voltage increases begin - *12:32:57*: First major generation loss (355 MW at Granada) - *12:33:16*: Second major loss (730 MW at Badajoz) - *12:33:17*: Third major loss (550 MW at Sevilla) - *12:33:30*: Complete system collapse to zero voltage ### Why Couldn't It Be Stopped? Once the chain reaction began, stopping it would have required massive reactive power absorption capacity that simply wasn't available. The system's protective mechanisms (like demand disconnection) actually made the overvoltage problem worse by further reducing grid loading. ## Broader Context The report emphasizes this was a *multifactorial event* - no single failure explains it entirely. Contributing factors included: - Low electrical demand creating capacitive effects in the highly meshed grid - Quarter-hourly market changes causing rapid generation adjustments - Spain's weak interconnection with Europe (only 3% vs. 15% target) - Complex renewable evacuation infrastructure with inadequate protection settings The restoration process took until 7:00 AM the next day to reach 99.95% supply restoration, though it was considered exemplary by international standards.
hyperman1 1y ago
When the story of the 6 missing minutes broke our, I saw a map of the European grid, with real time and historic grid behaviour,showing over- and underproduction. Does someone have a link?

193 points by leymed 1y ago

deleted 1y ago

[deleted]

fuoqi 1y ago

[flagged]

matsemann 1y ago
But the quote literally spells out it was market forces, not some instability in solar generation? Your other comment probably got flagged because it started with a huge straw man and had multiple unwarranted jabs in it.
- fuoqi 1y ago
  Temporary negative prices have been caused by the renewable generation which exceeded the grid demand at the time, which then evolved into the nasty feedback loop caused by the reaction of renewable generation to those conditions. You simply do not get such situation with traditional generation, it's the direct consequence of the intermittent nature of renewables and its high ratio in the total generation. Also, have you read after the market part? Please watch this video https://www.youtube.com/watch?v=7G4ipM2qjfw https://www.youtube.com/watch?v=7G4ipM2qjfw if the last quote is gibberish to you. It discusses somewhat different issues, but the point still stands.
  - pkilgore 1y ago
    Where is the market for someone to get paid to pump water into a reservoir and let it fall down later for $$$?
    - pdpi 1y ago
      That market exists, but the window of time here is like twenty minutes. Pumps have inertia and take time to spin up, you can't HFT load and generation.
      - gusgus01 1y ago
        I'm not fully informed about pumped storage, but twenty minutes is more than enough for most hydroelectric plants to go from 0 to full power, and that's probably the case for pumped storage as well. Eg, In the case of Cruachan Power Station: “It takes just two minutes for a turbine to run up from rest to generate mode,” says Martin McGhie, Operations and Maintenance Manager at the power station. “It takes slightly longer for the turbines to run down from generate to rest, but whatever function the turbines are performing, they can reach it within a matter of minutes.” https://www.drax.com/power-generation/in-energy-storage-timing-is-everything/ https://www.drax.com/power-generation/in-energy-storage-timi...
    - plorg 1y ago
      If you read the report there was a significant amount of solar being produced at low prices and being pumped for storage. Further, the pumped hydro is the first load to be disconnected to balance demand on their system.
    - ncruces 1y ago
      Partly the neighboring country. Between Spain and Portugal there's 10 GW (~20% or peak load) and 100 GWh of storage (enough for a day's worth of consumption). But that takes time and requires some rebalancing, because much of that capacity is not closest to the producers. It also requires water, which becomes scarcer in the autumn (not the case here). So the price can and does become negative for a window. “High frequency trading” the spot prices probably contributed to the problem.
  - eldaisfish 1y ago
    you are correct, but your analysis is not popular here. You will soon be presented with several reasons as to why renewable energy is not the problem and how batteries are the one true solution to these problems. The reality is that electricity is complex and that renewable energy presents a new set of problems, problems to which we do not yet have complete solutions.
  - floatrock 1y ago
    So an incredibly cheap source of supply exceeded the demand, and the market rules and some trips caused cascading failures. Why is the problem the cheap source of supply rather than the market rules and incentives that made everything act the way it did? Your comment suggests move back to good ol' expensive fossil generation instead of looking at how to bring the market rules up to date with evolving technologies.
    - martinald 1y ago
      Because the only reason that solar is still generating power at negative prices is because they are getting subsidies to do it. Otherwise they would disconnect themselves apart from in extreme scenarios (control system down or something), and I bet when you are paying many tens of thousands of euro an hour you'd get someone to fix/manually turn it off sharpish. Looks like there are a multitude of schemes of various vintages in Spain, which tl;dr basically give you a guaranteed price per MWh you generate. So imagine you get a 100eur/MWh subsidy for a (legacy) solar plant. The market price is €-20/MWh. You will still continue to produce power until the price reaches -100MW/h. Even worse are some contracts for difference (poorly thought through) which give you a guaranteed price regardless of what the market is at. So even if the price was -1,000eur/MWh the government or grid operator would still give you your €50/MWh (and the subsidy would be 1,050/MWh!). The problem is if you reform this (and it is happening worldwide) solar is much, much less appealing. Because suddenly your solar plant which was getting (say) a guaranteed 70/MWh all year round suddenly does not make money for 6 months of the year at least at peak sun hours. On top of all this, you have a lot of domestic solar in places like Spain. The grid operator _cannot_ control these assets in nearly all circumstances. They will continue to dump power into the grid regardless of the market price. This again will change but it requires an awful lot of work to retrofit invertors with remote control capability OR a lot of public backlash for charging end customers who bought solar in "good faith" now getting hit with peak time negative prices (so they change their behaviour). I think my core message would be _any_ negative power prices is a sign of market failure. Acceptable in rare extreme occurrences, but the fact most of europe has highly negative prices very frequently is telling you the grid and market design is not able to handle what is going on.
      - 1y ago
  - jakewins 1y ago
    > caused by the reaction of renewable generation to those conditions No, that is not what the report says. It says, just like you say, that renewables reacted to market prices, causing a generation drop. It then says explicitly that synchronous generation caused oscillation, while PV plants showed a flat non-oscillating pattern. From your comments I worry there are emotional factors clouding how you're reading the report - this was a systemic failure involving many separate technologies: - Market signals - negative prices - caused a drop in PV generation (as frequently occurs) - Synchronous plants caused oscillations as a side effect - Plants procured to dampen exactly those oscillations did not deliver as requested - TSO then took measures using interconnections to stabilize via other balance area - This caused - presumed - overvoltages in distribution grids - PV inverters then shut off, as mandatory by regulatory requirement in response to over voltage You're absolutely right that PV played a large role here, but that point is diminished by making it out that PV is both the source of the initial generation drop and the source of the oscillations; it is neither. The market design caused the generation drop, synchronous generators caused the oscillations, TSO action caused distribution overvoltages and regulatory requirements on PV firmware design in response to overvoltage caused the final blackout.
- shakow 1y ago
  True, but the market moves fast because renewables (or, more precisely, wind & solar) move fast. There is not much fast trading to be done on a nuke/gas/coal/hydro powerplant ramping up or down, but there is a lot of instability (and thus market volatility) to be found in fast varying solar/wind conditions.
  - stephen_g 1y ago
    That's inaccurate on the whole though, because while those big generators can't move fast, demand can move fast! Which is a difficult problem to manage in baseload grids. Renewables just change one set of challenges for another set, at the end of the day it's all manageable.
    - mlyle 1y ago
      > because while those big generators can't move fast, demand can move fast! Which is a difficult problem to manage in baseload grids. Don't forget rotational inertia. This gives the system a high-frequency response mode: it can resist sudden demand changes through stored kinetic energy, effectively acting as a low-pass filter with a fast dominant pole. As you get a smaller share of generation with rotational inertia, you need a lot more buffering on short to medium timescales. And, of course, it doesn't help for longer timescales that in many places renewable production slopes off in the late afternoon right when demand slopes upwards for cooling.
      - _aavaa_ 1y ago
        > in the late afternoon right when demand slopes upwards for cooling. Demand rises because that's how people have their system set up. That cooling load can be shifted earlier in the day by using a slightly smarter thermostat to precook your house when the electricity is plentiful.
        mlyle 1y ago
        > Demand rises because that's how people have their system set up. That cooling load can be shifted earlier in the day by using a slightly smarter thermostat to precook your house when the electricity is plentiful. You can do this a bit, but the insides of houses don't have that much thermal mass and the best insulated houses add a pretty large phase delay that makes the quickest rise in internal temperatures during the late afternoon as framing in the attic heats up. I don't have a lot of luck in accomplishing meaningful precooling in my house. My best plan is to suffer until the late afternoon, turning on the AC at the end of the peak demand period when at least outside temperatures are lower, my AC units are shaded, and the cooling is more efficient.
wavefunction 1y ago
You quoted >the most plausible explanation is that it is due to market reasons (prices) Seems to be market conditions or manipulations or inefficiencies in the market.
- deleted 1y ago
  [deleted]
pdpi 1y ago
What I'm reading from that quote is that the issue wasn't renewables as such, but an issue of power generation reacting too quickly and too intensely to price fluctuations. "Renewables" only matter insofar as they're the sort of generation that, under the current regulatory regime, get to react to those pricing changes.
- kmeisthax 1y ago
  [dead]
- baq 1y ago
  The report goes to great lengths to avoid certain words or phrases. The market failed here, it didn’t price in risk of grid collapse correctly.
  - mslansn 1y ago
    [flagged]
    - xwolfi 1y ago
      Except to point out that it's not nice that renewables arrive at random prices in the grid and start crapping all around it until they disappear when expensive again. The stability of a nuclear plant vs the instability of a solar far when a cloud passes over.
  - Yeask 1y ago
    That is a simple and great explanation.
    - plorg 1y ago
      It's also just unfounded conspiracism and factually incorrect.
      - mlyle 1y ago
baq 1y ago
Should’ve said ‘not enough spinning mass’ and it’d be perfectly fine for the politically correct and mean the same thing. This was highlighted as a risk for years and it finally materialized.
- philipkglass 1y ago
  According to the operator report linked in another comment by leymed [1], the problem was not a lack of spinning mass (inertia) but voltage instability. From page 16 of the PDF: The incident was NOT caused by a lack of system inertia. Rather, it was triggered by a voltage issue and the cascading disconnection of renewable generation plants, as previously indicated. Higher inertia would have only resulted in a slightly slower frequency decline. However, due to the massive generation loss caused by voltage instability, the system would still have been unrecoverable. [1] https://news.ycombinator.com/item?id=44360052 https://news.ycombinator.com/item?id=44360052
  - baq 1y ago
    Obviously I’m as good of a grid operator as I was a stealth bomber expert on the weekend, but superficially that just doesn’t seem right. Maybe I’m underestimating how much spinning mass would be required, but that still qualifies as ‘not enough was present’.
    - eldaisfish 1y ago
      please can you explain what doesn't seem right?
      - baq 1y ago
        They admit they had plants offline when they should be available and then they say it wouldn't matter and the grid would've collapsed anyway..? Either they're in a very very bad spot and stop short of saying it outright in the report or it would've averted the disaster if the not-spinning mass was spinning as it should have.
rcxdude 1y ago
It's worth pointing out that the worst part of the behaviour of renewables specifically in this incident (a fixed power factor for managing reactive power), is currently mandated by the regulations in Spain, even though many of them are already equipped to do voltage control.
felipeerias 1y ago
People are having three different conversations at the same time: – the concrete causes of this specific blackout; – how the existing grid is not prepared to deal with the current energy mix; – the energy policy of the past decades, from the nuclear moratorium in the 80s to the large subsidies for renewable generation of the past couple decades. A person's strong opinion on any one of these issues will inevitably influence their opinion on the others.
tomhow 1y ago
> but the fans of renewables just flagged it As moderators we can only guess why people flag things, but there are other reasons why people may have flagged that comment, the foremost being that it broke the guidelines due to its inflammatory style. On Hacker News we want to be able to discuss difficult topics involving arguments people may find counter to their assumptions, but you need to express things in a way that's persuasive rather than combative. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- fuoqi 1y ago
  Was the comment above also in "inflammatory style"? It's an obvious fact that flagging on HN is used by some people as a tool to censor unfavorable opinions. Even worse, AFAIK there is zero consequence for such frivolous flagging.
  - tomhow 1y ago
    Users who use flagging inappropriately (i.e., for reasons other than guidelines breaches) have their flagging powers disabled. We do that often. Same goes for unfair downvoting. If a comment of yours or any other you see is unfairly flagged, you can email us and we'll take a look. We'll explain how we see it and if we agree its unfair we'll restore it and consider action against those who flagged it. We always discourage complaining about flagging or downvoting in comments as you can never know exactly what has been done by other users or why they did it, and it’s usually a generic tangent from the discussion.

tofflos 1y ago

It's a difficult read. Cybersecurity and digital systems was not the issue but gets thirteen pages of proposed measures. I feel this could have been left out. Electric System Operation was the issue and gets seven pages of proposed measures.

leymed 1y ago
Check this shorter report by the operator: https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_SpanishPeninsularElectricalSystem_18june25.pdf https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_Sp...
razakel 1y ago
>I feel this could have been left out. It's pretty much their one and only chance to warn the authorities that there's a risk, so if they choose to ignore it, well, nobody can claim they weren't informed.

AnotherGoodName 1y ago

Reads very similar to some blackouts we had in Australia. Weakly connected grids with vast geographical distances leading to oscillations that took down the grid. https://en.wikipedia.org/wiki/2016_South_Australian_blackout https://en.wikipedia.org/wiki/2016_South_Australian_blackout Completely solved with lithium based grid storage at key locations btw. This grid storage has also been massively profitable for it's owners https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve#Revenues_from_operation https://en.wikipedia.org/wiki/Hornsdale_Power_Reserve#Revenu... Australia currently has 4 of the 5 largest battery storage systems under construction as a result of this profit opportunity; https://en.wikipedia.org/wiki/Battery_energy_storage_system#Under_construction https://en.wikipedia.org/wiki/Battery_energy_storage_system#... You can also read numerous stories of how Australia's lithium ion grid storage systems have prevented blackouts in many cases. https://www.teslarati.com/tesla-big-battery-south-australia-3-blackouts/ https://www.teslarati.com/tesla-big-battery-south-australia-... The fact is that the batteries responsiveness is the fastest of any system at correcting gaps like this. 50/60hz is nothing for a lithium ion battery nor are brief periods of multi-gigawatt draw/dumping as needed. There's even articles that if Europe investing in battery storage systems like Australia they'd have avoided this. https://reneweconomy.com.au/no-batteries-no-flexibility-spain-could-have-avoided-blackout-with-lessons-learned-in-south-australia/ https://reneweconomy.com.au/no-batteries-no-flexibility-spai...

londons_explore 1y ago
> nor are brief periods of multi-gigawatt draw/dumping as needed. Actually this is typically an issue for grid batteries. Spinning generators can easily briefly go to 10x the rated current for a second or so to smooth out big anomalies. Stationary batteries inverters can't do 10x current spikes ever - the max they can get to is more like 1.2x for a few seconds. That means you end up needing a lot of batteries to provide the same spinning reserve as one regular power station.
- AnotherGoodName 1y ago
  Collectively Australia's battery storage systems will be able to beat any single power plant for peak output in Australia once fully built out based on pure numbers. But for these sorts of grid oscillations the more important thing is the localization of generation. Which obviously favours the batteries over large centralized power stations in any case.

rcarmo 1y ago

Page 130 is where the actual human readable summary is. Although the previous pages were pretty detailed in explaining the cumulative instabilities. Sadly, some news outlets are probably only going to look at the recommendations and read "cybersecurity" and (even though they are common sense recommendations) assume there might be more to say about the matter.

decimalenough 1y ago
Don't worry, some news outlets will summarize this as "renewables = bad" regardless of what the report actually says. Oh wait, they already did: https://www.telegraph.co.uk/business/2025/06/18/renewable-energy-to-blame-for-spains-blackouts/ https://www.telegraph.co.uk/business/2025/06/18/renewable-en... Ed: Do I need a /s tag here or something? My point was that we shouldn't worry too much about about the presentation of the report, its actual contents will be spun to suit any narrative regardless.
- baq 1y ago
  Flame bait journalism is one of the things you can count on in any circumstance. If you replace that ‘renewables = bad’ with ‘politicians = idiots’ OTOH… sometimes the elected representatives should listen to unelected physicists and engineers. Grid stuff is one of those things.
- kgwgk 1y ago
  That doesn’t really say “renewables bad”. The report actually says that there was a drop in solar generation.
- rsynnott 1y ago
  I mean, that's the Telegraph; it's just not a serious newspaper these days. (Brexit really did a number on it; in the last decade or so it's gone from a right-wing but fairly normal broadsheet to just complete raving nonsense.)
Nextgrid 1y ago
There's been a shit-ton of misinformation about cyberattacks within the first hour of the outage, and the public were unfortunately very receptive to it, so I guess they're trying to preempt those concerns?

decimalenough 1y ago

> Non-confidential version of the report of the committee for the analysis of the circumstances surrounding the electricity crisis of the April 28, 2025 Now I'm curious about what's in the confidential version of the report.

londons_explore 1y ago
Based on the redacted bits, it is mostly company names and locations.
- diggan 1y ago
  And more interestingly, the specific reasons various installations were unable to start up as they should have: > Incidents detected during equipment start-up - Firstly, there is information consistent with the fact that several installations with the obligation of autonomous start-up were finally unable to provide this service in a stable manner, joining the system only once voltage had arrived from outside (from another of the "islands", normally anchored in one of the interconnections). This slowed down the start-up of the "skeleton" of the electricity system that would later make it possible to replenish the supply to demand. The rest of the ~2 pages in that section is redacted.

londons_explore 1y ago

It doesn't look like this report really identifies the root causes... I would like to see: "We have simulated the complete 200 and 400 kV grid of the iberian peninsula and western europe, and can reproduce the situation that occurred. Any one of the following changes would have prevented the issue, and we suggest implementing them all for redundancy. This simulation will be re-run every day from now on to identify future cases similar incidents could occur"

baq 1y ago
The engineers knew exactly what’s going to happen, the report is politically redacted. Very unfortunate, but completely expected.

JanneVee 1y ago

When skimming through the report I got to think of the oscillation problem in RIP routing protocol. Although it isn't the same thing, but it shows the complexity of the problem to anyone who thinks there is a single solution to it.

deleted 1y ago

[deleted]

gred 1y ago

Why so many pages of "Recommendation: implement multi-factor authentication" and other IT security irrelevancies? Did they need to pad out the number of pages?

diggan 1y ago
> In the systems with network traffic evaluation probes, no records consistent with unauthorized activity have been observed, such as lateral movements, network traces or file movements for vulnerability exploitation or privilege escalation, among others. > However, as is common in networks and information systems in any sector, other risks have been identified, such as vulnerabilities, deficiencies or inadequate configurations of security measures, which may expose networks and systems to potential risks, for which a series of measures are proposed.
rcxdude 1y ago
Infrastructure in general has pretty terrible security practices, so I won't bemoan someone finding a useful soapbox to remind them to shape up a bit, even if it isn't the core cause of this particular issue (and it's probably also a reaction to various rumours/speculation about a cyberattack).

diggan 1y ago

Seems the money shot starts at page 131: > The ultimate cause of the peninsular electrical zero on April 28th was a phenomenon of overvoltages in the form of a "chain reaction" in which high voltages cause generation disconnections, which in turn causes new increases in voltage and thus new disconnections, and so on. > 1. The system showed insufficient dynamic voltage control capabilities sufficient to maintain stable voltage > 2. A series of rhythmic oscillations significantly conditioned the system, modifying its configuration and increasing the difficulties for voltage stabilization. If I understand it correctly (and like software, typical), it was a positive feedback-loop. Since there wasn't enough voltage control, some other station had to be added but got overloaded instead, also turning off, and then on to the next station. Late addition: It was very helpful for me to read through the "ANNEX X. BRIEF BASICS OF THE ELECTRIC SYSTEM" (page 168) before trying to read the report itself, as it explains a lot of things that the rest of the report (rightly) assumes you already know.

leymed 1y ago
I think your interpretation is correct. The voltage control is done at the high level of the grid, meaning the control covers bigger generation stations and major substations. Even if it’s small generator, rotating machinery, you won’t have strict voltage control other than its own AVR. The problem I see here is that we embed smaller individual generations at the lower level, where they pump the generated power to the grid at the medium voltage level. When you have majority of your generation at this level, you won’t have strict control over voltage and even frequency, I assume. I’m still digesting the report, but what I am after is whether they really neglected it and if it is not possible to do voltage control with 50% generation coming from renewable and through medium voltage level, aka lower level.
amluto 1y ago
I’m a bit mystified as to how the grid controls voltage at all. The non-renewable plants follow the rules here: https://www.boe.es/buscar/doc.php?id=BOE-A-2000-5204 https://www.boe.es/buscar/doc.php?id=BOE-A-2000-5204 7.1(b) seems to be saying that generators connected at 200kV adjust their reactive power generation/absorption in real time according to the voltage they observe, based on a lookup table provided by the grid operator. This seems sort of sensible according to my limited understanding of the theory of AC grids. You can write some differential equations and pretend everything is continuous (as opposed to being a LUT with 11 steps or so), and you can determine that the grid is stable. However, check out this shorter report from red eléctrica: https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_SpanishPeninsularElectricalSystem_18june25.pdf https://d1n1o4zeyfu21r.cloudfront.net/WEB_Incident_%2028A_Sp... Apparently these 220kV plants are connected to the 400kV grid via transformers in substations that are not owned by the generator operators. And those transformers have “tap changers” that attempt to keep the 220kV secondary side at the correct voltage within some fairly large voltage range on the 400kV side. Won’t this defeat the voltage control that the 220kV generators are supposed to provide? If the grid voltage is high, then absorption of reactive power is needed [0], and the generators are supposed to determine that they need to absorb reactive power (which they can do), but if the tap changer changes its setting, then the generator will not react correctly to the voltage on the 400kV side. In other words, one would like the generator to absorb reactive power according to P_reactive(primary voltage • 220/400), but the actual behavior is P_reactive(primary voltage • 220/400 • tap changer position), the tap changer position is presumably something like 400/primary voltage, and I don’t understand how the result is supposed to function in any useful way. Adding insult to injury, the red eléctrica repoet authors seem to be suggesting that a bunch of tap changers operators didn’t configure their tap changes well enough to even keep secondary voltages in range. Does anyone with more familiarity with these systems know how they’re supposed to work? [0] I can never remember the sign convention for reactive power.

robocat 1y ago

Individual generators monitor Voltage, Frequency, and reactive power (≈ how much current is out of phase with voltage) to make decisions about injecting more or less power into the network. This is just historically how they've always been doing it. Due to interactions between different generators, there can be instabilities causing voltage or frequency or reactive power to deviate outside of spec. A simple example might be two generators where one surges while the other drops back, then vice versa. The measurement (by the network operator) of these effects is poor for Spain - shown by the simple example that they have large oscillations that they couldn't explain. There's path dependent healing and correction of problems by different generators, which overall leads to network stability. However the network operator here is not actually resolving cause and effect, and does not have the insight to manage their stability properly. In this case you can see them trying a few things to inject changes that they hope will bring stability - e.g. tying many connections hoping that adding generators together into one network will resolve to a stable outcome. Are there countries that have a better design for their electricity network control systems? Disclaimer: I don't design electricity networks nor electricity markets. And the above is ignoring loads (loads are mostly less problematic for control than generation).

scrlk 1y ago
I suppose other system operators might have better a state estimator and wide area monitoring system. But real-time system operation is universally an engineer sitting behind a desk, looking at their screen, and trying to make the best decision with whatever data they have. The actions that were taken did not strike me as out of the ordinary.

rocqua 1y ago

So, the problem was a local voltage oscilation, where the high voltages caused generators to shut off. How do these oscilations start? I understand that voltage isn't necessarily equal across the network, where frequency is. But that only allows oscillating, it doesn't cause it. Is this a basis inductor capacitor oscillation? Is it the small delay in inverters between measuring voltage and regulating their output? (seems unlikely, given that renewables aren't blamed) or is there some other source of (delayed) feedback. And why do generators cut off at a high voltage? Is it a signal of 'too much power'? Is it to protect the generator from some sort of damage?

rcxdude 1y ago
Sort of: For the oscillations, the European grid in general is large enough that the time it takes for the energy to flow (at some fraction of the speed of light!) from one side of it to the other is not negligible: it's not a case of delays at the power plant, but delays in the network itself which can cause the various natural and artificial feedback loops in the circuit to start to become unstable and oscillate. In this specific incident, there's some implication in the report that the largest oscillation was unusual and may have been generated by single plant essentially oscillating on its own, for reasons unknown. In either case, the oscillations were not the direct cause of the blackout: they were controlled, but the steps to control them put the system into a more fragile state. This is because of reactive power. The voltage in the system is due to both the 'real power', i.e. the power generated by the plants and consumed by consumers in the grid each cycle of the 50Hz AC, but also 'reactive power', which is energy that is absorbed by the consumers and the grid itself (all the power lines and transformers) and then bounced back to the generators each cycle. This is the basic 'inductor-capacitor' oscillation. This reactive power is considered to be 'generated' by capacitance and 'consumed' by inductance, though this distinction is arbitrary. So, after the grid operator had stopped the oscillations, the grid was 'generating' a lot more reactive power, because damping down the oscillations generally involves connecting more things together so they don't fight each other as much. It also _lowered_ the grid voltage on average, so various bits of equipment were essentially adjusting their transformer ratio with the high-voltage interconnect to try to adjust for it. Apart from these measures, the generators on the grid are generally supposed to contribute towards the voltage regulation, which helps with both damping these effects and reducing the change of the runaway spike that happened. But crucially, there's a difference between what they (by regulation, not necessarily technical capacity!) do. The traditional generators have active voltage control, which means they actively adjust how much reactive power they generate or absorb depending on the voltage on the lines. Renewable generators, by contrast, have a fixed ratio: they will be set to generate or absorb reactive power at a certain percentage of the real power (a few percent usually), they don't actively adjust this (they're not allowed to under the rules of the grid). So, after the oscillation, the grid is generating a lot of reactive power and the power plants are absorbing it, but there's a lot of renewables around, which can't actively control voltage, they're just passively contributing a certain amount. Then there's a fairly rapid drop in real power output, which seems to be related to the energy market as some plants decide to curtail. This is expected, but renewables can do it pretty quickly compared to conventional plants. This means that the amount of reactive power being absorbed drops, i.e., counterintuitively a plant producing less power means the voltage rises. In theory, there should be enough voltage control from conventional sources to deal with this, but in general they prove to not absorb as much reactive power as they were expected to, and the report calls out one plant which seems to just not be doing any control at all, it's more or less just doing something random. This means the voltage keeps rising, and, perhaps in part due to the adjustments in the transformer ratios, this means another plant trips off, at a lower voltage than it should (this is, basically, for protection: the equipment can only take so much voltage before it's damaged, but there's rules about what level of voltage it should withstand and, in extreme cases, for how long). This then makes the voltage rise more, and it's a fairly rapid cascade of failure from there, and many plants kick offline in a matter of seconds, and only then does the frequency of the grid start to drop significantly, but it's already too late because there's too much demand for the supply. The recommendations of the report basically boil down to: - Figure out why the plants (renewable and conventional) didn't have the capabilities the grid operator thought they did (or why they were actively causing problems), and fix them. - Fix the regulations so renewable plants are allowed to contribute to active voltage control, and incentivize them to do so. - Adjust the market rules so that plants have to give more notice before increasing or decreasing supply in response to prices - Improve the monitoring of the grid and add other tools to help with voltage control (including better interconnects with the rest of Europe)

ranguna 1y ago

What is curious to me is that there's a possibility that a single plant in conjunction with natural oscillations caused enough trouble to start a doom scenario. Oscillation -> damping -> possibly faulty equipment and possibly lack of power plants to absorve the reactive load -> 0 voltage in two countries and some neighbouring regions There's also the possibility that Portugal put too much demand on the market due to negative prices, but I'm not sure if it was explained how much that had an effect on the whole thing.

nraynaud 1y ago

An interesting detail is that the instability had warning signs in the waveforms, that probably means that an algorithmic response is possible.

icar 1y ago

It's a difficult read, so let me paste here what Claude Sonnet 4 summarised: Based on this comprehensive report on the April 28, 2025 electrical blackout in Spain, I can summarize the key reasons why it happened: ## Primary Cause: Voltage Control Crisis The blackout was fundamentally caused by *insufficient dynamic voltage control capacity* in the system, which led to a catastrophic "chain reaction" of overvoltages. Here's how it unfolded: ### The Perfect Storm of Contributing Factors *1. Inadequate Voltage Control Resources* - Only 11 thermal power plants were coupled with voltage control obligations (the lowest number recorded in 2025) - One planned voltage control plant in the southwest failed the previous evening and wasn't replaced - Several connected plants didn't provide expected reactive power absorption during critical moments *2. System Oscillations Weakened the Grid* - Multiple oscillations occurred throughout the morning (starting at 5:49 AM) - Two major oscillations at 12:03 PM (0.6 Hz) and 12:19 PM (0.2 Hz) significantly stressed the system - The first oscillation was traced to anomalous behavior at a specific photovoltaic installation - Measures taken to dampen these oscillations (increased grid meshing, reduced interconnection flows) inadvertently contributed to voltage increases *3. The Fatal Chain Reaction (Phase 2-3)* Starting at 12:32 PM: - Voltages began rising rapidly across the transmission network - Generation facilities started disconnecting due to overvoltages, beginning with renewable plants - Each disconnection removed reactive power absorption capacity and reduced line loading - This caused further voltage increases, triggering more disconnections - The process accelerated into an unstoppable cascade ### Key Timeline - *12:32 PM*: Sustained voltage increases begin - *12:32:57*: First major generation loss (355 MW at Granada) - *12:33:16*: Second major loss (730 MW at Badajoz) - *12:33:17*: Third major loss (550 MW at Sevilla) - *12:33:30*: Complete system collapse to zero voltage ### Why Couldn't It Be Stopped? Once the chain reaction began, stopping it would have required massive reactive power absorption capacity that simply wasn't available. The system's protective mechanisms (like demand disconnection) actually made the overvoltage problem worse by further reducing grid loading. ## Broader Context The report emphasizes this was a *multifactorial event* - no single failure explains it entirely. Contributing factors included: - Low electrical demand creating capacitive effects in the highly meshed grid - Quarter-hourly market changes causing rapid generation adjustments - Spain's weak interconnection with Europe (only 3% vs. 15% target) - Complex renewable evacuation infrastructure with inadequate protection settings The restoration process took until 7:00 AM the next day to reach 99.95% supply restoration, though it was considered exemplary by international standards.

hyperman1 1y ago

When the story of the 6 missing minutes broke our, I saw a map of the European grid, with real time and historic grid behaviour,showing over- and underproduction. Does someone have a link?