The agreement was signed in Brussels on Tuesday.
Harmony Link is part of the planned synchronization, estimated to cost 1.6 bn euros in total, of the Baltic power grids with the Continental European system.
The agreement was signed by the CEOs of Lithuania's Litgrid and Poland's PSE, and officials from the European Commission's Innovation and Networks Executive Agency (INEA).
In October, the EU approved 50% co-funding, the maximum possible amount, under the Connecting Europe Facility (CEF) for Harmony Link preparatory projects estimated to cost 20 mln euros in total, including 8 mln euros in Lithuania.
The Baltic grids are still part of the post-Soviet BRELL ring, which also includes Russia and Belarus, and remain dependent on the control center in Moscow and the Russian electricity system.
Lithuania, Latvia and Estonia aim to desynchronize from the post-Soviet IPS/UPS system and synchronize their grids with Continental Europe by 2025.
