By agreement of Estonia's Elering, Latvia's Augstsprieguma tīkls (AST) and Lithuania's Litgrid, an attempt will be made on 8 June or alternatively 29 June 2019 to desynchronise the three countries' power grids from the Russian electricity system, Elering said on Monday.

"In order to achieve the capability by 2025 for the stable long-term functioning of the electricity systems of the Baltic countries as a separate frequency band and be prepared for synchronisation with the Central European frequency band, the Baltic states must test various aspects of the independent work of the electricity system still on several occasions," said Elering CEO Taavi Veskimägi.

During the desynchronisation attempt to be carried out next June, the power grids of the Baltic countries will be separated from the Russian frequency band for 12 hours while remaining connected to the Nordic countries and Poland via direct current connections.

In order to desynchronise the Baltic power grids from the Russian network, all nine power lines that connect the Baltic states with the main territory of Russia and Belarus will be switched off one by one. Unlike previous similar attempts, the power lines between Lithuania and Russia's Kaliningrad region will also be switched off this time, and similarly to the Baltic states, the Kaliningrad power grid will also function as a separate frequency band during the test. The lines will be switched back on at the end of the test.

During the test, the focus will be on testing the operational management processes of the frequency of the power grid. Several subtests will be carried out in the framework of the desynchronisation test and the impact of the shutdown of a sufficiently large production device on the frequency will be simulated, among other things.

During the desynchronisation test, the power of the direct current connections between the Baltic and Nordic countries must be limited in order to reduce the risk originating from a possible failure of the power grid's largest element. In order to increase the flexibility of the power grid, more production capacities than usual will be launched in the Baltic states for conducting the test. In addition, production units must maintain a greater than usual reserve capacity in order to be prepared for the operational and automatic increase or decrease in production, in order to respond to changes in frequency in the power grid.

Tests to desynchronise the Estonian power grid from the neighboring systems have previously been conducted in November 2006 and April 2009. The last desynchronisation attempt, in which three Baltic power grids along with Kaliningrad were separated from the Russian system, took place in April 2002.