State authorization for new 400 kV substation in Lleida

A resolution eight years later

Red Eléctrica de España, SAU obtains the administrative construction authorization and the prior administrative authorization for modifications for the new Isona 400 kV substation and the 400 kV entry and exit line of the Sentmenat-Sallente line, in the municipality of Isona i Conca Dellà (Lleida). The resolution, dated 27 July 2026, was published on Tuesday 18 August in the Official State Gazette (No. 202, section III, p. 115.622), with reference BOE-A-2026-17911, and was signed by the Director General of Energy Policy and Mines, Manuel García Hernández.

The project belongs to the renewable integration and resolution of technical constraints axis of the 2021-2026 Electricity Transmission Grid Development Plan, approved by Agreement of the Council of Ministers on 22 March 2022 and published in the BOE No. 93, of 19 April 2022. The substation and its line connect to the primary transmission grid, consisting of lines and substations with nominal voltages equal to or greater than 380 kV, pursuant to Article 34 of Law 24/2013, of 26 December, on the Electricity Sector.

Technical characteristics of the substation

The new Isona 400 kV substation will have seven equipped bays and five reserve bays. Its main characteristics are:

Nominal voltage: 400 kV
Highest voltage for equipment (Um): 420 kV
Technology: AIS (Air Insulated Switchgear)
Installation: Conventional outdoor
Configuration: Breaker-and-a-half
Short-duration short-circuit current: 50 kA
Transformer: bank of single-phase transformers with three windings, transformation ratio 400/230 ± 15%/33-26.38-23.83 kV, and power rating of 600 MVA

The configuration includes four bays with reserved positions, one central breaker for each, and connections to the Sallente and Sentmenat lines via bay 3.

The overhead line: double circuit at 400 kV

The entry and exit line at the Isona substation from the Sentmenat-Sallente line consists of three sections. Section 1 (existing, between supports T-250 and T-252) measures 0.794 km with a thermal capacity of 780 MVA/circuit in summer and 1,300 MVA/circuit in winter, with existing AL/AC Cardinal conductors. Sections 2 and 3 (projected, new) total 1.058 km with AL/AW Tern conductors of three conductors per phase, reaching a capacity of 1,960 MVA/circuit in summer and up to 2,370 MVA in winter. The complete line affects the municipality of Isona i Conca Dellà, in the province of Lleida.

Public utility for the line, rejected for the substation

The resolution declares, specifically and individually, the public utility of the 400 kV entry and exit line, identifying four affected cadastral parcels in Isona i Conca Dellà. However, the request for public utility for the substation itself was dismissed (third operative provision of the resolution).

A procedure with institutional opposition

The file was processed by the Dependency of the Industry and Energy Area of the Sub-delegation of the Government in Lleida, in accordance with Royal Decree 1955/2000, of 1 December, and the public information process was carried out in three phases: November 2018, September 2021 and July 2024. The City Council of Isona i Conca Dellà issued an initial opposition report, alleging that the action was not duly justified, although it subsequently did not respond to the objections raised by Red Eléctrica, so its conformity was understood. The Directorate General for Energy of the Government of Catalonia maintained its opposition to the project, questioning both the competence for the authorisation and the justification for the works. The State resolved that competence lies with the General State Administration, by virtue of Article 3.13.e of Law 24/2013.

Deadlines and environmental conditions

The operating authorisation must be issued within a period of 24 months from notification of the resolution. The works are subject to the conditions set out in Annex I, which includes the obligation to comply with the project as submitted and with the applicable regulatory provisions. Likewise, the environmental conditions arising from the favourable environmental impact statement issued on 7 July 2017 by the Secretary of State for the Environment remain in force, including measures for the protection of soil, the water environment, flora and habitats of community interest, cultural heritage (including the marking of the Costa de la Serra-2 and Costa de la Serra-3 palaeontological sites), and an Environmental Monitoring Plan to be approved by the Government of Catalonia.

With this resolution, the strategic electricity transmission infrastructure for the peninsular system in northern Catalonia moves forward towards its materialisation, contributing to the connection of the region’s large renewable generation facilities with the national high-voltage grid.

Source: Official State Gazette (Boletín Oficial del Estado), No. 202, Tuesday, 18 August 2026, section III “Other Provisions”, p. 115,622 (official reference: BOE-A-2026-17911).