Iberien Peninsular Blackout

The next report from ENTSO-E on the Iberian blackout has now been published:

Grid Incident in Spain and Portugal on 28 April 2025 » ICS Investigation Expert Panel » Factual Report » 3 October 2025

This suggests that the cause was a large quantity of various renewables going off line.

'Several important generation trips occurred from 12:32:00 onwards. Between 12:32:00.000 and 12:32:57.000, there was a loss of 208MW identified distributed wind and solar generators in northern and southern Spain, as well as an increase in net load in the distribution grids of approximately 317MW, which might be due to the disconnection of small embedded generators​ <1MW (mainly rooftop​​ PV) or to an actual increase in load or to a combination of both. The reasons for these events are not known. From 12:32:57.000 until 12:33:18.020, major disconnection events occurred in the regions of Granada, Badajoz, Sevilla, Segovia, Huelva, and Cáceres, which resulted in an additional loss of generation of at least 2GW (the effects of frequency deviation suggest a loss of even 2.2GW).'

The reasons for ​for the trips are not stated.

Thanks for this Roger

However, I disagree: It doesn't suggest that renewables were the cause.

The document is a factual report describing the sequence of events; it explicitly states that the root cause analysis (including determining whether the network operators' actions contributed) is a next step i.e. the cause is not addressed in this report.

Instead the report defines the event as starting at the time that things started tripping. The first things to go were indeed embedded generators. These were mostly renewables, and the actual cause of the trip is not explicitly known, but subsequent trips were due to overvoltage then overfrequency and RoCoF. Because distribution network voltages tend to flap around more than transmission, it is perhaps unsurprising and likely by design that they went first. This does not mean that they were the cause.

(Disclaimer: Obviously I haven't had the chance to read the report in full as it is very dense detail and it was only released today)

Thanks for this Roger

However, I disagree: It doesn't suggest that renewables were the cause.

The document is a factual report describing the sequence of events; it explicitly states that the root cause analysis (including determining whether the network operators' actions contributed) is a next step i.e. the cause is not addressed in this report.

Instead the report defines the event as starting at the time that things started tripping. The first things to go were indeed embedded generators. These were mostly renewables, and the actual cause of the trip is not explicitly known, but subsequent trips were due to overvoltage then overfrequency and RoCoF. Because distribution network voltages tend to flap around more than transmission, it is perhaps unsurprising and likely by design that they went first. This does not mean that they were the cause.

(Disclaimer: Obviously I haven't had the chance to read the report in full as it is very dense detail and it was only released today)