Sadinia’s main electricity transmission network consist of a main bone line at 370 kV that interconnects the main generation sites located in the industrial sites of Fiume Santo, Sulcis and Rumianca, and a ring at 220 kV. The rest of the transmission system consist of a mesh network at 150 kV.
Sardinia is connected with Corsica and with the Italian peninsula through two submarine HVDC
power lines: SACOI and SAPEI.
SAPEI: Sardegna-Penisola Italiana
SAPEI (Sardinia-Italian peninsula) connect directly Sardinia to Italian peninsula since 2010trough 420 km of submarine cable layed down up to 1600 m under the sea level. The maximum power is 1000 MW, splitted in two cables of 500 MW. SAPEI is a 420 km long submarine cable (435 if you also consider the land section) between Sardinia and Lazio, passing 1600 meters below the Tyrrhenian Sea. It is the deepest submarine cable in the world. SAPEI is composed of two cables, with a total capacity of 1000 Megawatts. The laying of the cables was entrusted to “Giulio Verne”, the largest cable laying ship in the world.
The direct current connection SACOI (Sardinia – Corsica – Italy) is an HVDC interconnection used for the exchange of electricity between the Italian mainland, Corsica and Sardinia since 1965.
It is unusual, having more than two conversion stations as part of a single HVDC system and (as of 2012) it is one of only two multi-terminal HVDC systems in operation in the world (the other multi-terminal scheme is the Quebec transmission system -New England which connects the northeastern United States with Quebec in Canada). The scheme is a monopole that uses a combination of overhead line and submarine cable for the 200 kV high voltage conductor and return to the sea for neutral current. Overhead lines and submarine cables are duplicated, with both circuits installed on the same towers.
Until the 1990s mercury vapour rectifier where used, which have now been replaced by thyristors. The capacity is of 200 MW at a voltage of 200 kV. In 1992 a second pole was installed with a maximum power of 300MW at 200 kV. The fist cable of 200 MW have been in service for more than 40 years and is going to be dismissed in the next years because obsolescence.