al report

The usual nonsense we have come to expect from 'factual' reports. Ignorant minister? Ignorant reporter? ...or both.

Does Spain not have any load dumps of last resort for grid balancing?

Typically industrial processes that can absorb large amounts of energy at short notice. Electrolytic chloralkali production, aluminium smelting and other arc furnaces being the UK's load dumps of last resort.

It is crazy to have lost control for an *over* voltage failure condition

- particularly at noon when predictably the sun is at its highest and solar PV output will be maximised. Non-renewable suppliers should have been throttled back to keep the thing stable. Why did that not happen?

You will always have a few sites that trip out prematurely if the line voltage starts thrashing around. In an ideal world the odd smaller one dropping off ought to have damped out the oscillation.

The rapid cascade failure over a 5 second period remains unexplained. They should be able to reconstruct the domino effect of which plants went down when and why the grid was unable to isolate the weakness.

The report is essentially a whitewash to disguise just how incompetent the people who defined the network operating rules are. If they can determine that some generating sites failed to obey the rules and caused the massive systems failure then they should be named and prosecuted. Otherwise it looks like a smoke and mirrors job to hide the root cause.

If you skate on sufficiently thin ice like they did on that fateful Monday then you will fall through it.

That is partly due to machine translation out of the Spanish.

Long and short of it was they didn't have enough dynamic inertia in the system and when it reached high noon something had to give.

Icarus syndrome - quite literally!

In addition the network failed to protect itself from the abnormal state and so went completely dark rather than dropping off the main offenders. I suspect that the French interconnect dropping out was the coup de grace but without the official timeline being published that is a guess.

A graph of power, frequency and line voltage minute by minute over the relevant few hours would be *very* interesting to examine.

It is odd that they don't explain why it failed so spectacularly quickly. The final grid collapse took 5s and then it was all over.

The bits I quoted were from Guy Hedgecoe, a BBC correspondent.

The report was written by a committee of experts. Fifty, I think.

The committee studying the blackout is made up of representatives of the Ministry for Ecological Transition and the Demographic Challenge (MITECO), the Presidency of the Government, the Ministry of Defence and the Ministry of the Interior. Specifically, the Department of Homeland Security, the National Intelligence Centre, the General Staff and the National Centre for the Protection of Critical Infrastructure are involved.

The blackout, which occurred on 28 April 2025, affected the Iberian Peninsula, including Spain, Portugal and Andorra, and extended as far south as France. The power outage caused disruptions to essential services such as hospitals, airports and telecommunications networks. The causes of the blackout are being investigated by this committee.

Oh dear! Is English his first language?

Until they publish a detailed explanation of how it was that a predictable surge of power from solar PV at high noon was able to bring down the *entire* Spanish grid it looks like a white wash to me.

Also exactly what order the cascade failure occurred in (and name and prosecute the companies that they claim did not follow the rules). If that claim is true then they were culpable for the failure.

Comparable UK reports name all the players involved and exactly what happened at each site and when. See for example the report on our fairly spectacular summer failure in 2023 - this is a summary:

I expect he's an arts or journalism graduate like most of the BBCs 'science experts'.

A phrase like " ...did not absorb all the voltage they were supposed to when tension was high" wasn't written by an expert.

As many as necessary. You probably can find their names if you are interested and seek it out.

...

Where does it say that was the cause? It happens every day.

That is for another stage.

You will have to wait. There is a procedure to follow.

The way I read it is that a relatively large number of relatively low power generators - presumably solar cell farms - were programmed to turn themselves off if the net voltage got higher than some preprogrammed limit.

They all seemed to have turned off at once which is presumably what pulled 3.3GW of generating capacity within thirty seconds.

Icarus died - but the Spanish network survived, as it was intended to do.

It just stopped delivering power for a couple of hours.

On the contrary, it did protect itself from the abnormal state, but at the considerable cost of a couple of hours of blackout.

The speed is perfectly explicable. If you have lots of identical controllers, all designed to turn themselves off when they see a particular situation, they are all going to turn off at once.

A more intelligent design might have delayed the turn-off by a short, randomly selected delay, so that the excessive voltage might have gone down slowly enough that the impeding turn-off could have been cancelled in the slower reacting controllers before it got put into effect.

Adding grid-battery based fast-reacting controller to the system would presumably have worked rather better.

Logically. If the voltage is too high, presumably there is excess generation. Inverters get disconnected, they risk fire.

Possibly.

A huge solar plant is being named. Well, its name has leaked.

*The photovoltaic plant at the origin of the blackout is Iberdrola's Núñez de Balboa mega-plant.*

As confirmed by elDiario.es, it was this plant which, half an hour before the outage, when it was generating 250 MW, began to produce anomalous oscillations which Red Eléctrica has asked to investigate and attributes to ‘a malfunction of an internal control’ or ‘an internal anomaly (...) to be clarified by the owner’ - Red Eléctrica places the start of the blackout in the ‘malfunction’ of a photovoltaic plant in Badajoz

The photovoltaic plant in the province of Badajoz that triggered the historic blackout on 28 April, when it caused a series of anomalous oscillations in the grid, is Iberdrola's Núñez de Balboa mega-plant. This was confirmed to elDiario.es by several sources familiar with the confidential reports of the Government's commission of experts and the system operator, Red Eléctrica, which asked to investigate the ‘malfunctioning’ of this installation, one of the largest solar parks in the country.

The government has concluded, after 49 days of investigation, that the Iberian blackout was a ‘multifactorial’ event without a single cause that would explain a combination of factors: insufficient capacity in the system to regulate voltage as expected, failures in REE's programming (which the company denies), malfunctioning of the voltage control systems of generation facilities and plants that were disconnected ‘improperly’.

It was, according to the governmental opinion, ‘a combination of conditions’ that led to ‘a chain reaction of overvoltage, with no single fault having been identified that could alone explain the outage’.

This ‘chain reaction’ started, according to REE, half an hour before the blackout. Until midday on Monday ‘nothing could have foreshadowed or even remotely predicted the events that occurred’, according to the system operator. But at 12:03, an anomalous oscillation reduced the voltage in the system and forced urgent measures to be taken.

As REE's Director of Operations, Concha Sánchez, explained at a press conference on Wednesday, this ‘very significant’ fluctuation lasted almost five minutes and required “immediate” action as it was a ‘dangerous’ situation: the way in which the interconnection with France operates had to be changed, as it stopped operating on alternating current and switched to fixed set-point, and the grid meshing was increased, which complicated voltage control.

The origin is in what the report released Wednesday by REE calls ‘Photovoltaic Plant A’, which according to sources consulted by elDiario.es corresponds to the Núñez de Balboa plant. At that time, the facility generated about 250 megawatts (MW), according to the REE report. The Government's report (in its confidential version, instead of the one published with numerous crossings out and the names of plants and companies erased, as the electricity companies had demanded), points to ‘anomalous oscillatory behaviour in the output of active and reactive power’ of this Iberdrola plant.

"In a few seconds, the plant's generation oscillates with a peak-to-peak amplitude of around 70% of the output it had immediately before the oscillation. This behaviour contrasts with that of other plants of the same technology connected at the same node or nearby nodes," says the document published by the government on Tuesday night.

According to the report, this oscillation is ‘more typical of synchronous technologies’, such as nuclear or gas, which ‘modify their power factor to maintain a constant voltage’, than of a photovoltaic plant, ‘which is subject to a fixed power factor’ and in which ‘the output power value, especially the active power, should be constant’.

According to the committee's opinion, "during this disturbance there are strong voltage oscillations, not only in frequency and power, mainly in the south and west of the Iberian Peninsula. Unlike previous voltage fluctuations detected on the same morning or on previous days, in this case there are repetitive oscillations of voltage rise and fall in the space of seconds, which follow a specific pattern coinciding with the oscillation in frequency, in the form of a seesaw".

According to the REE report, ‘no fluctuations were observed in the plant's active power’, but ‘in reactive power’, which is needed to operate the electricity grids. This second oscillation of Núñez de Balboa comes shortly before another less atypical one originating in the centre of Europe at 12.19 pm, a prelude to the succession of overvoltages that will begin at 12.22 pm, which the system will not be able to absorb and will end up leading to the blackout.

REE points to a malfunction at Núñez de Balboa as an explanation for this anomalous behaviour: ‘The grid conditions at the connection point, short-circuit power and voltage level were analysed, and both were correct, so it is likely that the oscillation was caused by a malfunction of an internal control or by an internal anomaly of the plant, which should be clarified by the owner of the plant’.

The document, which REE is obliged to publish by regulation, given the seriousness of the blackout, calls for an ‘investigation into the cause of the appearance of the forced oscillation originating in the photovoltaic plant in the province of Badajoz and to implement corrective actions to avoid its repetition’.

"Before, during and after

When asked by elDiario.es, Iberdrola does not comment on this matter. On Wednesday, sources from the electricity company told Europa Press that its behaviour was ‘impeccable’, in contrast to the ‘reckless and negligent’ management of REE, and expressed their “astonishment” at the statements made by those responsible for Redeia, ‘who seem to confuse the consequences of the blackout with its causes’.

While the groundwork is being prepared to determine who is responsible for the blackout, with a view to the millions in compensation that will have to be paid to those affected in the future, Iberdrola has been pointing the finger at REE, as the electricity system operator, as being responsible for the incident for weeks.

Its executive chairman, Ignacio Sánchez Galán, said a few weeks ago that ‘Iberdrola's actions before, during and after the incident always responded to the protocols and regulations established by the competent ministry and by the system operator, which is Red Eléctrica, which is ultimately responsible for keeping the lights on in the country’. The day before, the CEO of Iberdrola España, Mario Ruiz-Tagle, stressed that ‘the responsibility for controlling overvoltages lies with Red Eléctrica’.

The malfunctioning of Núñez de Balboa is not the only cause of the blackout, but it is the beginning of the events that led to this unprecedented Iberian zero, according to REE, which fixes its origin in the previous half hour.

But the vice-president and minister for Ecological Transition, Sara Aagesen, pointed on Tuesday to ‘poor planning’ on the eve of the blackout by REE in the reserve power (gas and nuclear) in the so-called technical restrictions market, which the company denies: the planned power was at annual minimums, and also a plant was declared unavailable and was not replaced.

The government has also pointed out (this analysis is shared by REE) that this reserve market did not work as it should: the three nuclear reactors and the six combined cycle gas plants that were supposed to operate under technical restrictions (a mechanism with which electricity companies pocket billions every year) ‘were not regulating voltage’ as they should when these surges began. One gas plant in southern Spain stands out as doing the opposite of what it should have done: it injected reactive power instead of absorbing it.

According to REE's Director of Operations, if these plants had done their job by controlling the voltage, ‘we would not have had a blackout’. ‘The incident would have been avoided,’ said the non-executive president of REE, Beatriz Corredor. The former socialist minister insists on denying any responsibility for the company and rules out resigning.

The third cause of the blackout, according to the government's report, is an ‘undue’ disconnection of installations: a ‘cascading tripping of renewable generation plants’, says REE, which does not identify which ones because the companies in the sector have asked to anonymise all the information that affects them. REE has agreed to publish the information that affects it.

It is likely that this information will emerge with the report being prepared by the sector regulator, the National Markets and Competition Commission (CNMC).

In the background of the blackout is also the lack of mechanisms to allow renewables to regulate voltage. This possibility is included in an operating procedure that is already 25 years old. Its update, as the REE report reminds us, ‘has been pending approval since 2021’ by the CNMC.

The experts' report urges it to be implemented now. So does REE. In its report it calls for it ‘so that all generation that has the capacity to control voltage in real time must activate this control and also establish penalties for possible non-compliance’. A few weeks ago, when elDiario.es revealed that Competition had been analysing it for years, the CNMC assured that it would probably approve this new service in May. So far it has not done so.

Haphazard existence

Spain's largest electricity company owns just over 25% of Spain's installed capacity, some 31,800 MW. In 2020 it inaugurated the huge Núñez de Balboa photovoltaic plant in Usagre (Badajoz). With a capacity of 500 MW and the only Iberdrola facility in that province, it was presented in 2019 as the largest photovoltaic plant in Europe, with the capacity to supply energy to 250,000 homes. In 2022, it was surpassed as the largest on the continent by another Iberdrola mega-plant in Cáceres, the Francisco Pizarro (590 MW).

La Núñez de Balboa has had an eventful existence. The Supreme Court has yet to confirm the ruling that three years ago the High Court of Justice of Extremadura (TSJE) annulled the expropriation of the 525 hectares it occupies. Last summer, the European Public Prosecutor's Office opened an investigation into the 145 million euro loan granted to the plant by the European Investment Bank (EIB). Emma Navarro, now a director of Iberdrola Spain, was vice-president of the EIB until 2020.

At the end of last year, Antonio Luna, former mayor of Usagre, was acquitted of an alleged crime of administrative malfeasance linked to the building permit for the facility.

------------------++-

That procedure appears to be prevaricate and obfuscate.

I expect some randomly chosen scapegoat will be blamed rather than a system which manifestly was intrinsically vulnerable to such a failure.

Politicians will invariably blame the scientists and engineers when their policies cause such a mess - that is how these things play out.

That is the sort of detail that should be in the report and isn't.

Now we are getting somewhere... Thank heavens for unauthorised leaks in corrupt political administrations.

It was only multifactorial in the sense that the way the Spanish grid was designed and managed a single installation of 250MW misbehaving could bring the whole thing tumbling down.

That is down to bad engineering pure and not so simple to fix.

I suspect the distribution of electricity production and consumption in Spain also played a part much like in the shorter and better contained UK power fail. It upset all those living in the consumer zones of London and the SE but left those in the electricity producer zones untouched.

As Christine Keeler so aptly put it "they would say that wouldn't they".

"stopped operating on AC" does that mean it can switch to DC operation to allow Spain to freewheel its grid frequency?

If it was operating in "DC mode" why did it disconnect?

How grid meshing being increased complicates voltage control needs explaining. It looks a lot like technobabble word salad to me.

It sounds a lot like some sort of latent instability in the control system software led to it going crazy and chasing its own tail.

Is that a triangle wave in more scientific language?

Did some of the classical turbine generator systems drop off grid prematurely to save themselves from the frequency going out of bounds? That could partially explain the loss of damping (or was there almost no spinning reserve making power at the peak of solar PV output).

The fluctuation "originating" in the "centre of Europe" sounds more like a reaction to Spain injecting fluctuations into the continental grid.

Power plants do malfunction from time to time. They are supposed to leave gracefully when that happens - not bring down the whole grid!

Indeed. But it is unlikely to happen or have anything done about it.

It will become a finger pointing game and only the fat slimly lawyers defending their clients will win in the end. Decade long legal battle...

They have had enough warnings that something like this would happen if they cut their spinning reserves right to the bone.

It must also surely be the responsibility of *all* the generating systems not to continue to push full power into an already over voltage and over frequency grid.

That is the influence of bean counters. Spinning reserves cost money.

If that is true then they should be prosecuted for it. They helped to bring down the grid. It doesn't bode well when the investigators have their hands tied by government and the energy companies to anonymise who was guilty of what! Better to pretend it was multifactorial and completely unforeseeable than try to find and fix the actual root cause.

Why am I not surprised?

It wasn't undue if they were left holding the baby and the grid was in catastrophic collapse. Serious damage can result to their output stages.

The sector regulator seems to have totally failed to regulate.

Perhaps now they might pull their finger out and do it. Don't hold your breath.

"Spinning reserve" is just stored energy. As the South Australian Hornsdale Reserve has been demonstrating since 2017, a grid scale battery stores quite enough energy to do the same job, if connected to the grid by properly programmed inverters.

It looks as if some of the generating systems discharged their responsibilities by simply turning themselves off.

And providing "grid inertia" with a grid scale battery does seem to be a cheap alternative to rotating lumps of metal in turbines and generators.

The Australian example might get drawn to their attention, but I doubt it.

And maybe it is. The actual report is many pages, not what the press published.

...

This is not corruption. Secrets can not be maintained from the press when there are hundreds of people having the data.

...

I'm not clear in their actual meaning.

...

Yes.

Which is impossible if the connection was DC. So it can not be DC but some other meaning.

...

Notice that Iberdrola has generation of all kinds, from ancient turbines to state of the art solar.

...

The names are not published now, they will be named later, at another stage.

...

In time.

Indeed, that report includes a detailed timeline of the grid collapse caused by the near simultaneous failure of the Hornsea wind turbine farm due to improper control settings (-737 MW) and the Little Barford Combined Cycle Gas Turbine plant caused by EMI on a tach signal tripping the steam turbine (-244 MW) and a steam bypass valve failure tripping both gas turbines (-387 MW), both of these events triggered by grid voltage transients from the lightning induced phase to ground fault.

The wind farm failure was interesting, from the report:

"The wind turbine settings were standard settings from the manufacturer. During the incident, the turbine controllers reacted incorrectly due to an insufficiently damped electrical resonance in the sub-synchronous frequency range, so that the local Hornsea voltage dropped and the turbines shut themselves down.

Orsted have since updated the control system software for the wind turbines and have observed that the behaviour of the turbines now demonstrates a stable control system that will withstand any future events in line with Grid Code and CUSC requirements."

(IOW they finally called the wind turbine manufacturer and got the optimal control settings, as they should have done before powering up for the first time.)

Note that the waste heat recovery boilers on 387 MW of gas turbines at Little Barford produced 244 MW steam turbine power, a nice indication of just how inefficient gas turbines are unless used in a combined cycle configuration.

Solar clearly played no significant role, operating exactly as designed with the possible minor exception of 200 MW reportedly tripping at 49 Hz rather than 48.8 Hz. If true the utilities screwed up letting 200 MW of inverters connect to the grid with incorrect protective relay settings, but 200 MW was not enough to prevent the ~1 GW load dump.

The utilities learned from this event and have/are taking corrective action without input from any politician, as usual.

Glen