rated at 1000 A dc) connected in parallel. Each aluminium conductor has a cross section of 628 mm2 in Sardinia and Italy, and 755 mm2 on Corsica. In addition to this, there are two submarine cable sections: between Italy and Corsica and between Corsica and Sardinia. The conductor cross-sections are 1080 mm2 on land and 420 mm2 for the submarine lengths. Sea electrodes The scheme was designed to export power from coal-fired power stations on Sardinia to the Italian mainland, and thus was only required to operate in one direction. Although the converter stations are inherently capable of operating in either direction of power transmission, advantage was taken of the unidirectional power-flow requirement to economise on the design of the sea electrodes. The sea return current enters the sea at the Sardinian end (anode) and leaves the sea at the mainland end (cathode). The mainland electrode consists of bare copper (a section of insulated copper cable with the insulation stripped off), which would corrode rapidly if used as an anode but suffers no degradation when used as a cathode. However, the anode electrode on Sardinia required a more sophisticated design using platinum-coated titanium pipe, subdivided into 30 sub-electrodes, in order to prevent corrosion. Corsica tap (1988) In 1988 a third converter station, rated at 50 MW, along with a reversible ground electrode, was installed at Lucciana on Corsica, making the scheme into a multi-terminal scheme for the first time. In order to allow power to be either imported into or exported from Corsica (even though the direction of power flow is always from Sardinia to Italy), the Lucciana converter station was equipped with high-speed changeover switchgear. Unlike the two original converters, the Lucciana converter station was built with air-insulated, air-cooled thyristor valves, supplied by CGE Alstom SACOI 2 - 1992 upgrade In 1992 the mercury arc converters at Codrongianos and San Dalmazio were decommissioned and two new converters stations were built, using air-cooled, air-insulated thyristor valves similar to those supplied for the connection at Lucciana. At the Sardinian end, the new converter station was built next to the existing station but at the mainland end a new converter station was built at Suvereto, as this site offered in opposite to San Dalmazio an interconnection to the 380 kV grid. At the same time, the rating of the scheme was increased to 300 MW, keeping the same voltage of 200 kV.