Trial ops underway: Greece’s €1B subsea electricity interconnection weeks away from start-up

Ariadne Interconnection, a subsidiary of Greek transmission system operator (TSO) Independent Power Transmission Operator (IPTO or ADMIE), has confirmed the beginning of trial operations at a subsea interconnection development between the island of Crete and the Greek mainland, described as the largest electricity transmission project in Greece.

IPTO underlines that the final tests and equipment checks are being completed at the Damasta Converter Station in Heraklion, marking the start of the trial operation of the Crete–Attica electricity interconnection, which IPTO portrays not only as “the largest and most complex” electricity transmission project ever implemented in Greece but also as one of the three deepest marine interconnections worldwide.

Following the wrap-up of the site acceptance test (SAT) for the cable system in January 2025, after the electrical interconnection in December 2024, the management of IPTO and Ariadne Interconnection inspected the facilities, which are scheduled to be energized this week with the injection of reactive power into Crete’s system.

Simultaneously, a trial electrification of the 400 kV cable system is taking place on the Attica side between the Koumoundouros Converter Station and the adjacent Extra High Voltage Center, which is the connection point of the electrical interconnection with the mainland system. In addition, the system tests of the operation as a whole will also begin within the month.

Manos Manousakis, Chairman and CEO of IPTO, highlighted: The Crete-Attica electrical interconnection project is counting down to being plugged in. Crete will now be doubly interconnected with the mainland electrical system, enjoying greater energy security and will not depend exclusively on local production.

“The next milestone is the start of the test operation of the interconnection from the end of May with the transfer of active power from Attica to Crete, followed by commercial operation.”

Given the gradual start of the trial operation, the transmission of active power from Attica to Crete is set to kick off at the end of May. With a budget exceeding €1.1 billion, this project is co-financed by the operational program ‘Transport Infrastructure, Environment and Sustainable Development’ of NSRF 2014–2020 and the ‘Environment and Climate Change’ program of NSRF 2021–2027, up to the amount of €535.5 million.

The Crete-Attica electricity interconnection, in IPTO’s view, is drawing significant European and national resources and reducing, to a very large extent, the cost of the project of major importance for the Greek consumer.

Manousakis emphasized: “Another important development directly linked to the project and the island’s energy security is the approval by AEPO for the new high-voltage line between Chania and Damasta, which is necessary for the two interconnections of Crete, via Attica and the Peloponnese, to operate optimally.”