Greece’s Independent Power Transmission Operator (IPTO) has revealed that a new grid line linking mainland Greece to Crete began operating on May 24.

The line consists of two 500 kV direct current (DC) subsea cables, each 335 km long and laid at depths of up to 1,200 meters, connecting the converter station in Koumoundouros, Attica, to the Damasta substation in Crete. Together, the cables provide 1 GW of total transmission capacity.

Ariadne Interconnection, an IPTO subsidiary established for the project, developed and owns the grid line. In November 2024, China’s State Grid International Development Ltd., a wholly owned subsidiary of State Grid Corp., acquired a 20% stake in Ariadne Interconnection.

The Ariadne Interconnection holds strategic significance for Greece and regional energy networks.

Integrating Crete into Greece’s mainland electricity grid will free about 2.5 GW of new renewable power capacity. Crete will also phase out high-cost fossil fuel units, such as diesel stations, currently used to ensure power adequacy and compensated by electricity consumers through their bills. As a result, IPTO said the new line will reduce these costs, leading to lower electricity bills across Greece.

The project will also have a significant environmental impact, cutting carbon dioxide emissions by more than 400,000 tons in its first year of operation.

Internationally, the new grid line holds broader significance, as Crete is expected to serve as the starting point for two planned submarine lines: one linking Crete to Cyprus and Israel, and another connecting Crete to Egypt.

IPTO said the project was completed in record time. The Ariadne Interconnection subsidiary was established in 2018, and construction lasted only 4.5 years. By comparison, IPTO said similar projects by European grid operators have taken more than seven years to complete.

The Attica-Crete grid line cost €1.1 billion ($1.24 billion) and received joint financing from the European Union and domestic sources.

The new Attica-Crete direct current (DC) link is distinct from a separate 174 km subsea connection from the Peloponnese Peninsula to Crete, completed in 2021. That project connected Crete to mainland Greece via a line with 2×200 megavolt-amperes (MVA) transport capacity.

The Ariadne Interconnection marks Greece’s first high-voltage direct current (HVDC) cable system. IPTO plans to apply the experience gained to develop a second HVDC link integrating the Dodecanese Islands into the mainland high-voltage grid.