Sardegna-Penisola Italiana (SAPEI)

The SAPEI (Sardinia-Peninsula Italy) HVDC project is a power transmission system connecting the island of Sardinia to mainland Italy. Commissioned in 2011, it stands as the largest HVDC link in the Mediterranean Sea, playing a crucial role in Italy's power infrastructure.

Project Overview

SAPEI is a 1,000 MW bipole transmission link, designed to deliver surplus power from Sardinia to the Italian mainland, strengthening the power grid near Rome. The system consists of a 420 km submarine cable and 15 km of land cables, with converter stations located in Fiume Santo, Sardinia, and Latina on the Italian mainland.

Technical Specifications

The SAPEI HVDC system operates at ±500 kV, with each pole rated at 500 MW and a nominal current of 1,000 Amperes. The submarine cable, manufactured by Prysmian, has a diameter of 120 millimeters and lies at a depth of 1,600 meters (5,200 ft) below sea level in the Tyrrhenian Sea, making it the deepest subsea power cable in the world.

Converter Stations

The converter stations, supplied by Hitachi Energy (formerly ABB), are essential components of the SAPEI system. The Latina substation covers an area of 35,000 m², while the Fiume Santo substation extends over 48,000 m². These stations connect the HVDC link to the alternating current grids at 400 kV.

Historical Context

SAPEI is the second HVDC power transmission link from Sardinia to the Italian mainland. The first link, known as SACOI (Sardinia, Corsica, Italy), was commissioned in 1967 and utilized mercury-arc valves and HVDC control systems supplied by Hitachi Energy.

Project Timeline

The SAPEI project was launched in 2006, with initial scientific surveys and sea floor studies commencing shortly after. Cable laying began in 2008, and the first voltage tests were conducted the same year. The converter stations in Latina and Fiume Santo became operational in 2009. The second submarine cable was scheduled for completion by the end of 2010, and the entire system was inaugurated on March 17, 2011.

Environmental Considerations

Although the project did not fall under the EU EIA Directive due to its submarine and underground nature, a detailed Environmental Impact Assessment was conducted. This assessment focused on the installation of the submarine cable and its potential effects on marine life. The competent authorities confirmed the environmental compatibility of the installation, imposing several mitigating measures to be implemented during construction and operation.

Economic Impact

The SAPEI project represents a significant investment in Italy's power infrastructure, with costs exceeding €730 million. It enables the export of excess power from future wind farms and potentially from thermal power plants in Sardinia to meet the growing electricity demand on the mainland. Additionally, the link helps maintain and improve the reliability of the grid supply system in Sardinia, one of Italy's less developed regions.

Conclusion

The SAPEI HVDC project stands as a testament to advanced power transmission technology, addressing Italy's energy needs while overcoming geographical challenges. Its successful implementation has enhanced Italy's power grid stability and set new benchmarks in submarine power cable technology.