The “black box” of the collapse and the system audios: the PP points to failures of the Government, REE and the CNMC in the crisis of April 28, 2025
The report proposal registered by the Popular Group in the Senate Investigation Committee on the blackout of April 28, 2025 places at the center of its analysis what it calls the “black box of the collapse”. According to its authors, this block —based on operational audios, communications between electricity companies and the system operator, and internal records— allows for the real-time reconstruction of the evolution of the electricity crisis and evidences, in their opinion, accumulated deficiencies in the planning, regulation, and supervision of the system by the Government, the operator Red Eléctrica de España, and the National Commission for Markets and Competition (CNMC).
The parliamentary document maintains that the blackout cannot be understood as a sudden or unforeseeable event, but as the outcome of a chain of technical alerts known by the operators, without —according to its interpretation— the competent institutions adopting proportional measures of reinforcement, supervision or regulatory correction.
A sequence of chain alerts in the “black box”, according to the report’s proposal
The Popular Group chronologically orders the communications registered in the DCO system of Iberdrola and Endesa during the morning of April 28, 2025, which it considers the evidentiary core of the so-called "system black box".
At 00:47 hours, Endesa contacts REE to request the reduction of voltages in the Barcelona area. According to the account gathered in the PP's proposal, the system operator responds that the available resources were already limited, with part of the 220 kV network out of service. For the authors of the report, this first exchange reveals operational restrictions in the system's control capacity.
At 09:54 hours, Iberdrola informs REE after receiving alerts of disturbances at the Almaraz nuclear power plant. REE rules out incidents in the transmission network, although it mentions a possible affectation at the Pizarroso substation (Cáceres), which the report interprets as an early indication of a systemic anomaly not yet diagnosed.
At 10:59 hours, Endesa reports “enormous oscillations” of voltage. In the conversation, the REE operator attributes these variations to the entry and exit of photovoltaic generation. The PP report maintains that at this point a structural tension is evident between the renewable generation model and the stability of the electrical system.
In that context, the operators come to mention the possibility of an “energy zero”, that is to say, a total blackout, as a risk associated with the lack of system inertia.
At 11:31 a.m., Iberdrola reports new oscillations at the Arcos power plant, attributed by REE to solar generation in Andalusia.
At 12:13 hours, the Trillo nuclear power plant reports new voltage oscillations. The REE operator relates the phenomenon to photovoltaics and the scarcity of synchronous generation, in what the document interprets as the confirmation of a structural problem. In that exchange, the off-protocol expression appears: “The thing is fucked.”
At 12:22 hours, REE contacts Iberdrola to gather information about Almaraz and the voltage regulation systems, which the report interprets as a change in the operator's position towards a more reactive management.
At 12:26 hours, Iberdrola warns of the possible automatic disconnection of Almaraz if the oscillations continue. REE requests information about start-up times for backup generation, which the document considers an emergency action.
Finally, at 12:32 hours, the collapse of the system occurs. According to the collected transcript, the REE operator reacts with non-protocolary expressions —“We are disconnecting!”— before concluding the communication. The report identifies it as the moment of the irreversible blackout.
The “black box” and the institutional responsibility of the electrical system
The Popular Group maintains that this sequence constitutes the “black box of the collapse”, by reflecting that the operators were aware of the instability prior to the blackout.
Based on this material, the report proposal extends its conclusions to the entire institutional system.
First, it points to REE for the insufficiency of inertia and stabilization resources in a context of high renewable penetration, as well as for the internal knowledge of a structural problem which, according to the document, did not translate into sufficient preventive measures.
Secondly, it attributes to the CNMC a lack of anticipation in the updating of procedures and in the supervision of risks derived from the increase in photovoltaic generation and from overvoltages, based on data that —according to the report— were public and accessible.
Thirdly, the document points to the Government for insufficiencies in planning and supervision of the electrical system during the energy transition process, especially regarding the reinforcement of the grid, synchronous generation, and stability mechanisms.
“We have a mountain of photovoltaics”: the diagnosis on the instability of the system
The report incorporates audios prior to the blackout which, according to the Popular Group, reinforce the thesis that the problem was structural.
In one of them, dated April 7, 2025, an operator warns of the lack of system inertia and of the possibility of an imminent collapse.
On April 22, another audio describes the system with the expression: “we have a mountain of photovoltaic”, in reference to the growing weight of solar generation.
On April 28 at 11:47 hours, it is noted that the oscillations were not an isolated phenomenon, but recurrent for weeks, which the report interprets as an additional sign of structural instability.
The statement of the Secretary of State and the controversy over the “prior notices”
In this context, the report proposal incorporates the statement of the Secretary of State for Energy, Mr. Jorge Sanz Groizard, who affirmed before the Investigation Commission that there was “no warning, no alert, no sign”.
For the Commission, according to the text of the Popular Group, this statement is incompatible with the accumulated documentation: the audios between operators of Red Eléctrica de España and electricity companies, the emails sent by REE to the sector on April 25, the statistical trend of overvoltages —which would have increased by 367% in two years— and the public data of the system operator itself.
The document argues that, if the Secretary of State did not have that information, this would imply either a lack of access, or a lack of search, or a lack of institutional processing, which in any of the cases would constitute —according to the report— an institutional failure of the first magnitude.
Behind Groizard: the institutional controversy on the available information and the records
The argumentative block subsequent to the intervention of the Secretary of State incorporates a direct criticism of the management of information on the part of the institutional and corporate actors involved.
According to the report's proposal, Red Eléctrica de España / REDEIA's refusal to hand over its complete communication records to the Commission, combined with the company's president, Beatriz Corredor's, assertion that “the audios do not change the technical narrative,” generates a relevant institutional contradiction: if the audios do not alter the analysis, the document asks why they were not provided when formally requested.
The text argues that the only coherent interpretation is that the company itself considers that said records do alter the technical narrative and that this effect is potentially detrimental to it. In this sense, the available audios —from Iberdrola and Endesa— would be, according to the report, indicative of the probative relevance of the information not delivered.
Likewise, the document underlines that the president's assertion that REE delivered “all possible information” is, in the opinion of the Popular Group, hardly reconcilable with the prior refusal to provide complete records, which constitutes —according to the text— an institutional tension of special gravity, aggravated by the duality of functions between the public supervision of the electricity system and the State's shareholding participation through SEPI.
The report adds that the statement by Minister Sara Aagesen Muñoz, according to which the blackout was “multifactorial, unprecedented and unpredictable”, is not sustained against the documentation provided.
The audios, testimonies and documentary evidence —according to the text— would accredit that the instability of the system had been warned about in previous years. In particular, repeated technical expressions are collected: on April 16, 2025 an operator attributed the phenomenon to the low presence of nuclear in the system; on April 26 the attribution to photovoltaic was reiterated; and on April 28 at 11:47 hours the problem was projected even during the summer.
For the report, an event described as structural and seasonal by the operators themselves cannot be qualified as unpredictable, but as a situation already in development.
The text also questions the coherence of this position with the simultaneous defense of the PNIEC and its Annex D, considering that if said planning incorporated an adequate systemic security evaluation, it should have identified the risks that REE's internal documents already reflected.
Finally, the document points out that this discussion was raised before the Senate's Investigation Commission into the interruption of electricity and telecommunications supply on April 28 and 29, underscoring the apparent incongruity between the institutional statements and the available technical records, especially considering that the presidency of the company operating the electrical system has been held by a former government minister.
Conclusion of the block according to the PP's proposal
From the set of audios, communications and institutional declarations, the Popular Group's report proposal concludes that the so-called “black box” of the system reveals the existence of repeated technical alerts, internal diagnoses about the loss of inertia and a growing instability associated with the generation mix.
The document argues that this evidence, coupled with the actions of REE, the CNMC, and the government's supervision, constitutes —according to its authors— a systemic failure of planning, regulation, and operation of the electrical system that would have contributed to the blackout of April 28, 2025.