HVDC Italy–Corsica–Sardinia

HVDC Italy–Corsica–Sardinia
Pylon of the HVDC Italy–Corsica–Sardinia
Location
Country	Italy France
From	Suvereto 43°03′10″N 10°41′42″E / 43.05278°N 10.69500°E / 43.05278; 10.69500 (Suvereto HVDC converter station)
Passes through	Lucciana, Corsica 42°31′40″N 9°26′59″E / 42.52778°N 9.44972°E / 42.52778; 9.44972 (Lucciana HVDC converter station)
To	Codrongianos, Sardinia 40°39′07″N 8°42′48″E / 40.65194°N 8.71333°E / 40.65194; 8.71333 (Codrongianus HVDC converter station (Sardinia))
Ownership information
Operator	Terna
Construction information
Manufacturer of substations	Ansaldo English Electric Alstom
Commissioned	1967, 1988, 1992
Technical information
Type	overhead lines submarine cables
Type of current	HVDC
Total length	385 km (239 mi)
Power rating	300 MW
DC voltage	200 kV
No. of poles	2

The HVDC Italy–Corsica–Sardinia (also called SACOI; Sardinia–Corsica–Italy) is an HVDC interconnection used for the exchange of electric energy between the Italian mainland, Corsica and Sardinia. It is unusual, having more than two converter stations as part of a single HVDC system, and (as of 2012) is one of only two Multi-terminal HVDC systems in operation in the world (the other multi-terminal scheme being the Quebec – New England Transmission system linking northeastern United States with Quebec in Canada).

The scheme is a monopole using a mixture of Overhead line and submarine cable for the 200 kV high voltage conductor, and sea return for the neutral current. The overhead lines and submarine cables are duplicated, with both circuits being installed on the same towers.

The scheme was constructed in three phases.

When originally completed in 1968 by English Electric, the scheme comprised two converter stations, at San Dalmazio in Tuscany on the Italian mainland and Codrongianos on Sardinia. Each converter station was rated at 200 kV, 200 MW and consisted of two 6-pulse converter bridges in series. Normal operation was with both bridges in service but the scheme could be operated at 50% of rated voltage and power by bypassing one converter group at each end, to allow maintenance to be carried out.

Each 6-pulse converter bridge consisted of 6 main Mercury-arc valves plus a 7th for high-speed bypass operations. Each valve was rated at 1000 A dc and had four anode columns in parallel, with air cooling used for both the anodes and cathodes of the valve.

The original scheme was commissioned during 1967 and put into commercial operation in January 1968.

The scheme consists of three overhead line sections: one on the Italian mainland with a length of 22 kilometres (14 mi), one on Corsica with a length of 156 kilometres (97 mi) and one on Sardinia with a length of 86 kilometres (53 mi). The overhead line sections use twin conductors (each rated at 1000 Adc) connected in parallel. Each conductor has an aluminium conductor cross section of 628 mm² in Sardinia and Italy, and 755 mm² on Corsica.