An important milestone for the national electricity supply system is the completion, last week, of the construction of the Crete-Attica Electric Interconnection which, after the necessary tests have been carried out, is expected to be put into operation in the spring of 2025, i.e. at the beginning of the tourist season.

Island interconnections have multiple positive benefits for consumers (reduction of costs), the national economy (reduction of fuel imports), the environment (reduction of pollutant emissions and increase in the utilization of renewable energy sources). These apply to a greater extent to the interconnection of Crete, due to the size of the island and the volume of electricity demand that increases in the summer with tourist traffic.

With the interconnection in operation, the electricity generation units in Crete, which operate with liquid fuels, will be “turned off”, burdening the account of the Public Welfare Services that are financed by consumers through their electricity bills. The benefit from the reduction of ICOs is estimated at 300 million. euros per year. At the same time, the emission of 500,000 tons will be avoided. of carbon dioxide annually produced by the units in Crete and the further development of RES units in Crete will be allowed.

The Crete-Attica interconnection, with a budget of over 1.1 billion euros and with a capacity of 1000 megawatts started in 2020 with the signing of the contracts with the contractors, while in the meantime the small interconnection (Chania – Peloponnese) was completed and put into operation in 2021, which made a decisive contribution to ensuring the island’s electricity supply in the last three years.

According to the ADMIE data:

The Crete-Attica electrical interconnection is the largest and most complex Electricity Transmission project in Greece, with a budget exceeding 1.1 billion Euros, using state-of-the-art direct current technology of bipolar design and rated power (2x500MW) as well as Voltage Source Converter (VSC) at the Conversion Stations. Its special technical characteristics rank it among the top interconnection projects in the world, as it is located in the 3 deepest interconnections worldwide and at the top in terms of power transmission capacity in an island system (1000MW) together with the Sardinian interconnection.

The Crete-Attica Interconnection is the second phase of interconnection of the Crete System with the Continental System and in combination with the AC interconnection will remove the electrical isolation of the island and ensure its energy security. At the same time, through the permanent shutdown of the conventional production units, a significant reduction in CO2 emissions will be achieved that exceeds 500,000 tons per year, while a significant financial benefit will arise for consumers through the reduction of GHGs.

Finally, the strengthening of the Electricity grid will contribute to the further economic development of Crete (new jobs, Industry, RES).

Brief description of the project:

The nominal voltage of the link is 525 kV with a transmission capacity of 1,000 MW using VSC (Voltage Source Converter) technology on both sides, Attica and Crete.

The Conversion Station (CM) of Attica, AC/DC (400kV / 500kV), of bipolar design and nominal power of 2×500 MW, is located north of the existing 400 kV Ultra High Voltage substation of Koumoundourou. The other end of the link on the Crete side is the SM (150kV / 500kV) located in the area of ​​Damasta. In Crete, a GIS 150 kV AC high voltage substation has also been built to connect the Damastas substation with the existing 150 kV Electricity Transmission System of Crete.

The two (2) SMs are connected to the cable system, which is divided into the following main sub-projects:

â–ª 2 525kV Mass Impregnated HVDC submarine cables of 335 km length each.

â–ª 2 underground cables of Mass Impregnated HVDC 525kV length 32 + 11 km (Attica and Crete respectively) each.

â–ª 2 submarine and 2 underground optical fiber cables with a total length of 378 technology each.

The Contractors of the project are among the largest companies in the world, while at the same time, the 2 most modern ships in the world were used to lay the submarine cables.

Project progress

The construction phase of the project was completed in December 2024 and it is expected to be operational in the spring of 2025.

In particular, the following have been completed: the installation of the equipment at the Conversion Stations (Conversion Valves, Transformers, primary and secondary equipment), the installation of the entire 500kV cable system (335km x2 underwater cables, underwater optical fiber cables, 32km x2 underground cables in Attica and 11km x 2 underground cables in Crete) from the Attica Transfer Station to the Station Conversion in Crete.

The tests of the project, which have already started since the beginning of Autumn with the preliminary equipment tests (pre-commissioning) and functional tests of the subsystems, are in full progress. Soon, with the completion of the above tests, the system acceptance tests will follow, which are the final and most critical control before the start of the trial operation of the Conversion Stations.

According to the integration decision of the Ministry of Development and Investments, the interconnection of Crete with the ESMIE Phase II will be financed with an amount of up to 313.2 million. euros from the Operational Program of the NSRF “Transport Infrastructures, Environment and Sustainable Development 2014-2020” for the work of the 1st stage of the project (until 31/12/2023), thus drawing significant resources and reducing, to a very large extent, the cost of the project of major importance for the Greek consumer. The 2nd stage of the project was included in the NSRF Operational Program 2021 – 2027 “Environment and Climate Change” according to the decision of the Ministry of National Economy and Finance and will be financed with an amount of up to 222.3 million. euro.