Thanks @lucia I look forward to some technical facts as well as executive summaries. The foreign reports are not separate investigations just translation from El Pais. Browsing the Spanish press (looking for trade press reports) there was some speculation on the contribution from some form of corruption. Is this something you have any fact on rather than the speculation?

Here’s a little more technical detail https://cleantechnica.com/2025/06/18/inside-the-iberian-grid-collapse-what-really-went-wrong/

Posted by: @lucia

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The first press reporting is out Here's a brief synopsis from Spanish media:

The big Blackout El Apagón: 

Yes I realise I'm picking this up a week late...
... but I don't like the way in which the Spanish Minister, Sara Aagesen, has released this to the press.

1: There's too much 'apportioning of blame', which isn't helpful.

When a complex situation has resulted in a national outage, you need to encourage feedback from all those involved technically.
Attacking regulatory and technical mistakes by Red Eléctrica, will have the opposite effect.

Who, from a technical background, would now want to work with a Minister who's going to throw the mess all over you when something goes wrong in future?

2: Text-based descriptions of power surges and fluctuations are next to useless.

Any such report must be accompanied by timelines showing the relevant data.

Only when the reader sees the periodicity and level of such fluctuations is it possible to appreciate what the Grid Operator could and could not do with the tools they had available to them at the time.

3: Whyever does the Spanish Government think there's anything to be gained by issuing a press release in advance of the main technical report.

Any incorrect observations and opinions that have been made by the Minister, are now almost impossible to retract!

https://www.entsoe.eu/publications/blackout/28-april-2025-iberian-blackout/#Preliminary_Chronology_of_Events
this document extensively describes (in a non-blame, neutral manner) the WHAT of the voltage/frequency of the Spanish black-out but doesn’t begin to describe the WHY. Hence no corrective recommendations to prevent re-occurrence. It does state the black-out is the first incidence associated with an over-voltage state. 
I look forward to the WHY! @transparent may be satisfied with the time resolution but to me it just looks like symptoms collecting without (yet) understanding. But the underlying and implied regular oscillation between east and west Spain looks like an acceptance of marginal stability to me.

In the FT today, a report that heat pump take up in Europe has failed, so far, to meet expectations.

Mike

@mike-patrick Well, if Europe is stalling partly due to energy costs, what does that say about the UK with our exorbitant electricity prices?! Regards, Toodles.

Posted by: @mike-patrick

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In the FT today, a report that heat pump take up in Europe has failed, so far, to meet expectations.

Mike

European demand for heat pumps fal_ters.pdf

To unpack this a little....

1) how many of us in this forum would've paid for heat pumps without the BUS grant?

2) A big part of Europe has had air-to-air heat pumps for donkey's years but didn't call them that. Sweden is largely 'heat pumped up' (by smart early policy design) etc.,

3) A 22% drop in sales is big 

4) the lack of qualified installers is a massive problem in a large part caused by disjointed policy design AND the decimation of national training courses and qualifications (see my previous comment about the death of FE in Britain). This neoliberal thing is bad for societies... 

5) We're heading for a major gas glut which my analysts and traders predicted a year ago, gas prices are likely to drop just adding to the pressure on decarbonisation. 

6) Appearance of kit outside homes? Hang your head in shame Daikin (and Vaillant, Nibe etc.,). I love my Daikin heat pump, it is a very good piece of equipment but clearly looks were not a priority... It's not rocket science to sort this out. 

7) Maybe if this nonsense 'rearm Europe defence policy' was seen as the lobby that it is and more joined up thinking on green energy was rolled out this wouldn't be a problem but sadly our leaders are unable to actually lead. My opinion? Mediocrity Rules! [😩🤦🏻‍♀️]

8] Some of Daikin's statement is lobbying, keep this in mind, but it's true Europe is faltering and Daikin is correct to raise this. This will be on my list of Qs in Brussels next week. 

Ok, ENTSO-E's 1st report is out today.

They are blaming 'el apagón' - the blackout - on 'over voltage' - the first occurrence ever of this. But please note, a separate report on details of 'causes' will be issued further on. 

Here's a quick summary 

Meanwhile...

"Some important data, in particular related to some of the generation trips that took place before the blackout, remain missing, according to the report.

@lucia I look forward to reading the full report it’s a rainy weekend!

is there any more in the Spanish reports which has not rippled through?

@lucia Point 1: Yes, I think that I would still have ‘plumped for a pump’ - even if I hadn’t been granted the £5,000 BUS. I feel very strongly about going green and very annoyed by the way the ‘people in charge’ are making it nigh on impossible to go green without stumping up a great deal more money than it would cost to carry on being dirty and to hell with the world’s future.

Point 6: Yes, my Daikin, like yours is very much enjoyed and loved, it would not win any beauty contests, nor is it small - but it lives at the back of the house and just does its’ job! Regards, Toodles.

Posted by: @lucia

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Ok, ENTSO-E's 1st report is out today.

Thanks Lucia. I'll set aside some time to go through this.

For others to note, over-voltage is more common that one might suppose.

Here's an area-wide voltage-rise which took my Brown Monitor outside the upper limit.
Peach and Grey Monitors were similarly affected, but didn't exceed 253v because there was less solar-generation in their locations at that time.

When assets are switched in/out of grid supply on the 33kV or 132kV levels, there is no monitoring at the lower 11kV and LV levels to see the effect.

NESO issues the instruction, and the Generation Operator is working blind.

When the over-voltage lasts longer than the odd minute, then G98/G99 certified inverters detach themselves from the grid.
Here's a domestic solar inverter doing just that:

At 12:50 the inverter decoupled itself.
Although the connected solar-panels were still capable of generation (yellow), no electricity was exported (red) nor stored in the home battery (blue) for around an hour.
Generation re-started once the local grid voltage had again fallen below 253v.

Very few home owners know that this occurs.
They too don't monitor the grid.

The grid parameters in GB are set by the Electricity Regulations, Section 27

Note that generation sites connected at the 132kV level must keep within plus or minus 10% of that voltage.

Below that, the 33kV and 11kV levels must be within plus or minus 6%

So it's all too easy for a large generation site, connecting at 132kV or 400kV to swing the 33kV and 11kV levels outside their permitted range.

Unless this is corrected†, inverters at lower voltage levels respond to the over-voltage by ceasing to export.
Thus an over-voltage is followed by an under-voltage due to the sudden loss of embedded generation.

It's these sudden fluctuations which occurred in Spain on 28th April.

What I now need to find in the ENTSO report is why an over-voltage occurred in the first place.

† It's usually frequency rather than voltage which the grid operator would respond to in order to make the correction.

An over-supply results in the 50Hz frequency rising.
NESO measures the Rate of Change of Frequency (RoCoF) and thus gets a few seconds warning in which to act.

If they measured the raw frequency itself, then it could rise to 50.5Hz (plus 1%) before action is taken.
At that point it's no longer possible to connect/disconnect grid assets.
A collapse is inevitable.

I'm still going through the latest ENTSO-E report on the Iberian blackout of 28apr25, but I need to draw a paragraph on p.10 to the attention of members here.

This is very start of the actual blackout, and the Technical Committee are identifying two simultaneous events.

The second of these is a probable loss of power from (domestic) rooftop solar!

Our small solar installations are contributing sufficiently to the energy-mix, that Spain's RE had to supply an additional 317MW of electricity when a collection of domestic-level inverters went off-line.

Based on the Demand Forecasts for Spain, the grid demand at that time was about 25.5GW
which means that the 'embedded generation' being referred to accounted for around 1.2% of the total.

We don't yet know what grid parameter caused those solar inverters to go off-line;
It could be the supply voltage or 50Hz frequency going outside of the statutory limits,
or perhaps a surge.

But it was a large-enough loss to create a catastrophic Cascade Effect, which brought down the entire Iberian electricity supply system.

For comparison, it was the loss of just 150MW of embedded generation around north London in August 2019 which instigated the East Coast outage
in which 1 million people found themselves in blackout.

In the British case, the initial cause was a lightning strike on the 400kV transmission line just outside Stevenage.
The small-scale inverters in the area complied with their G98/G99 certification and detached themselves from the grid.

There is no part of our electricity supply system which is 'too small to matter'.

A Cascade Effect can rapidly spread across the country as one inverter after another ceases to supply power.