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The new three-terminal, extra-high-voltage, direct-current (HVDC) Suvereto-Lucciana-Codrongianos connection between Italy, Corsica and Sardinia will strengthen exchange capacity between the countries involved, guarantee service continuity and contribute to development of the European electricity grid and the energy transition towards greater use of renewables.

For this reason, in compliance with Regulation (EU) 347/2013, the project has been included in the third list of Projects of Common Interest (PCI) from 2017 (the third PCI list was published in November 2017 on the European Commission's institutional website for energy infrastructure; having obtained the opinions of the European Parliament and of the Council, the list came into effect on 7 April 2018).

This document complies with the provisions of Regulation (EU) 347/2013, which requires — specifically art. 9 “Transparency and public participation” — that the promoter of the project creates, and regularly updates, a website containing all pertinent information regarding the project of common interest (e.g. technical description of the project, its progress, information on the authorisation process undertaken, benefits of the project, etc.). 

It is understood that Terna will periodically update information regarding the progress of the project for the benefit of all stakeholders on its own website.

Overview of the project

The Sa.Co.I.3 project consists of renewal and modernisation of the current HVDC electricity connection between Sardinia and the Italian mainland, called Sa.Co.I.2, which has reached the end of its useful life. Definitive loss of the current interconnection would lead to:

  •  the lack of a fundamental tool for maintaining sufficient reliability levels for the Sardinian grid;
  •  a reduction in transport capacity between the Centre-North and Sardinia zones;
  • a significant deficit in terms of coverage of current and forecast demand in Corsica.

Regarding the last point, the Corsican grid operator (EDF) has requested an increase in energy withdrawal at the Lucciana substation situated in Corsica from 50 MW to 100 MW, requiring upgrading of the current connection.

On 11 October 2017, a Memorandum of Understanding was signed in Corsica between Terna and EDF for the realisation of the Sa.Co.I.3 project in order to improve supply security, integration and energy market competitiveness, in line with the European strategy for strengthening electricity interconnections between member states.

With this, the two operators launched a collaboration to study and plan works required to achieve the common goal of the planned upgrading of the current interconnection.

The future Sa.Co.I.3 electricity connection, maintaining the direct current operating voltage of 200 kV, will be largely created using existing assets, with modernisation of bipolar conversion stations and substitution of underground and undersea cables, and will allow the use of total transport capacity up to 400 MW.

Work for the renewal of the HVDC line between the substations of Suvereto (Tuscany), Lucciana (Corsica) and Codrongianos (Sardinia) is included in the 2018 Development Plan for the National Transmission Grid (NTG). It is also included in ENTSO-E’s TYNDP starting in 2016 and, as mentioned above, in 2017 it was included on the third list of Projects of Common Interest (PCIs) under Regulation (EU) 347/2013, code 2.4 Interconnection between Codrongianos (IT), Lucciana (Corsica, FR) and Suvereto (IT) (currently known as Sa.Co.I.3), in the context of the North-South Electricity Interconnections in Western Europe priority corridor (“NSI West Electricity”).

For further details please see the information posted on the European Commission platform at link 

Main benefits of the project

The works planned under the Sa.Co.I. 3 project will allow the useful life of the current three-terminal HVDC connection to be extended, maintaining the appropriate adequacy margins of the Sardinian electricity system and avoiding reductions in reserve margins for demand coverage beyond secure values.

It will also be possible to create the connection adopting the most recent technology, taking a step forward in terms of regulation and stability for Sardinia's intrinsically weak system.

Regarding the NTG Development Plan, the benefit analysis illustrated in Fig.1, derived from the cost-benefit analysis (CBA) has been created via simulation of two potential scenarios in the European context: a) the Sustainable Transition (ST) scenario and b) the Distributed Generation (DG) scenario. With a total cost of around € 670 million, the project carries social and economic benefits for the Italian system, represented by Social Economic Welfare (SEW), a reduction in Energy Not Supplied (ENS), and a reduction in the cost of supply on the dispatching services market (MSD).

The project has also been evaluated by ENTSO-E in its TYNDP 2018. The results of the CBA highlight that the project is essential to increase both supply security and integration of production from renewables (RES), and to reduce the spread of supply costs between connected areas of the market.

Regarding service security and continuity, the new interconnection will guarantee better distribution of power flows across lines, supporting greater system adequacy. Operational security will also increase, with greater system stability and more operational flexibility.
The transport capacity between Italy and Corsica enabled by the project will contribute to electricity exchanges, allowing Italy to approach its target of 10% of total interconnection capacity by 2020 in relation to installed generation capacity.

Authorisation process

In the context of the Sa.Co.I.3 project, in compliance with Regulation (EU) 347/2013 applicable to “projects of common interest” including the one in question, a phase for informing the public is required (see article 9 of said European Regulation. 

Therefore, in compliance with the provisions of the Regulation a project has been outlined for participation and consultation of the public with the aim of providing exhaustive information about the project.
Following this public-consultation phase, Terna will send the Ministry of Economic Development (MED) and the Ministry of the Environment and the Protection of Land and Sea (MATTM) requests for authorisation of the SA.CO.I.3 project together with a report on the outcome of the consultation. 

Upon receipt of this documentation, the Ministry of Economic Development will launch the pre-assessment phase, verifying that the documentation sent is complete, and will call a Preliminary Service Conference. Following its successful completion, this will allow the Ministry to announce the launch of the process to the competent Bodies and Authorities for issue of relative opinions. 

Terna, will then launch the Environmental Impact Assessment (EIA) procedure with MATTM and the Ministry of Cultural Assets and Activities (MiBAC). It will also publish a Public Notice for the EIA Procedure in newspapers and on official noticeboards, regarding participation in the administrative procedure and the application of power line easements and declaration of public interest. 

Furthermore, Terna will request opinions, consents and approvals from the competent Bodies and Administrative Authorities, including Municipalities, Architectural, Environmental and Archaeological Superintendencies (environmental and archaeological restrictions), the Ministry of Health (MH) (electromagnetic fields); other requested opinions regarding Implication Assessments, Hydrological restrictions, hydrological risk, etc.; finally, other affected Bodies will be involved (ENEL Distribuzione, RFI, ANAS, SNAM RETE GAS, etc.). 

Upon completion of the procedural phase of the EIA, with the issue of an environmental compatibility decree from the competent Ministries, MISE will call a Service Conference, in which all subjects involved in the works are invited to express their opinion, including bodies managing infrastructure which may be involved in relation to that under authorisation. Once the service conference is successfully completed and with the formal Agreement of the Regions of Sardinia and Tuscany, the competent Ministries will proceed to issue Terna with the authorisation for project construction and operation.

Below is a flow chart of activities included in the authorisation procedure

Description of public consultation process

As indicated in the previous paragraph, for the Sa.Co.I 3 project, Terna will implement the public-consultation plan. With the aim of providing the fullest disclosure and allowing the widest possible public participation, Terna will inform the press to announce the beginning of the activities set out in the public disclosure and consultation plan and the schedule of the 5 “Terna Meets...” events aimed at the Municipalities involved in the project.

The Terna Meets... events will see direct dialogue with citizens in a public venue to provide accurate information on the works and at the same time clarify any queries regarding the entire project. 

The event will be open to the public and organised in collaboration with the Municipalities involved. 

Those attending will be guided through the technical details of the works with a series of informational panels dealing with various topics (energy scenario, reasons for the works, authorisation procedure and role of Municipalities, project and work-site details, environmental and territorial aspects related to the realisation of the project, procedure for collecting observations and queries). 

Participants will be able to ask questions along the way and make notes of their observations on printed sheets from a specific stand at the end of the presentation. 

A dedicated web page will be available online at with a non-technical overview, information brochure and project chorography. Contact information will also be available for sending observations and objections during public consultation.

The Terna Meets... events will be held as follows:


  • 25 September, from 15:00 to 20:00, Sala Consiliare, Torre di San Vincenzo, San Vincenzo (Livorno)
  • 26 September, from 11:00 to 20:00, Museo di Arte Sacra, Piazza Vittorio Veneto 1, Suvereto (Livorno)
  • 27 September, from 11:00 to 20:00, Sala Comunale, Quartiere Salivoli, Lungomare Guglielmo Marconi 280, Piombino (Livorno)


  • 2 October, from 11:00 to 20:00, Sala Consiliare del Comune, Via Roma 6, Codrongianos (Sassari)
  • 3 October, from 11:00 to 20:00, Sala Consiliare del Comune, Piazza Villamarina 1, Santa Teresa di Gallura (Olbia-Tempio)

Observations can be sent from the date of presentation to the press for a period of 30 days, in writing to a specially created email address., for Requests may also be written by all parties that participate in the Terna Meets... events and who leave their email address. Every single request will be replied to via email within 15 days. 

Finally, the questions and observations received will be published online, along with their relative replies. Meanwhile, a detailed report will be prepared for MISE on the outcomes of the whole consultation process, as well as all questions, requests, suggestions and any other elements, and a statistical analysis summary

Technical description of the project

The “Sa.Co.I.3” project consists of the renewal and modernisation of the current HVDC (high voltage direct current) electrical connection between Sardinia, Corsica and the Italian mainland, through the upgrading of underground and undersea cables and conversion stations composing the direct current interconnection. The new electrical connection will be created maintaining the current voltage level (200 kV direct current) and the current overhead power lines, already suitable for the increased power levels to be installed by the project. Specifically, the renewal of the connection will be carried out through the creation of two new conversion stations located in the vicinity of the current substations, and through the laying of new underground and undersea cables, allowing the current transport capacity to be upgraded to 400 MW and the modernisation of connection assets (created in the '60s). In the context of the renewal activities, the existing cathode in Tuscany and the relative cable line will also be replaced due to their age.

In detail, the works on the Italian side include the following:

Sardinian Side

A) One new alternating/direct current conversion station located in the vicinity of the existing Codrongianos electrical substation and relative cable connections to the existing electrical substation;
B) Two new underground cables between the current landing point of the undersea cables at Santa Teresa di Gallura (OT) and the new transition point for passage from cable to aerial line;
C) Two new undersea cables for connection between Sardinia (landing at Santa Teresa di Gallura) and Corsica;

Tuscan Side

D) Two new undersea cables for connection between Corsica and the Italian mainland (landing at Salivoli, Municipality of Piombino);
E) Two new underground cables between an area overlooking the current landing point of the undersea cables at Salivoli and the new transition point from cable to aerial line;
F) One new alternating/direct current conversion station located in the vicinity of the existing Suvereto electrical substation and relative cable connections to the existing electrical substation;
G) Two new underground electrode cables and relative aerial transition point/cable on pylon, in addition to two new undersea electrode cables and electrode (cathode) in Torraccia (Municipality of San Vincenzo, Livorno)

For the various sections, both undersea and underground, the connection is composed of a pair of cables with copper conductor for underground cables and in aluminium for undersea cables with MIND insulation (mass impregnated non draining). The laying trench for every single line will have a depth of approximately 170 cm and a width of approximately 80 cm. The cables will be suitably protected using casings, ducts or special polyethylene tubing running inside a reinforced concrete pipeline with dimensions of 70x70 cm, depending on the laying context. In the case of crossings and points with particular characteristics where it is not possible to carry out open digging, the most appropriate crossing solutions from a technical perspective will be evaluated, including possible use of remote HDD.

Landing of the undersea pole cables, both on the Tuscan and Sardinian sides, will be carried out using HDD techniques. This solution will see a single straight drilling action (for each cable), with sufficient length and depth to avoid problems related to “exposure” of the equipment caused by coastal erosion.

The route of the cable power line, entirely direct current, has been designed in compliance with the provisions of art. 121 of Italian Consolidated Law no. 1775 of 11/12/1933, comparing public utility requirements of the works with the public and private interests involved, trying in particular to:

  • reduce movement of earth from digging through the adoption of a trench-pipeline approach which minimises extraction volume, and reduces working times and work site size required;
  • minimise the number of heavy vehicles on roads, considering that excavation volumes will be notably reduced compared to those generated by excavation of tunnels;
  • reduce implementation times through adoption of the trench-pipeline approach;
  • mitigate impacts on local traffic through adoption of batch-based organisation of work sites allowing normal traffic flow and optimising the use of the roadnetwork throughout the valley;

The conversion stations, on the other hand, will be created in agricultural areas adjacent to the Codrongianos (Sassari) and Suvereto (Livorno) electrical substations, covering around 40 hectares.