The deepest link

2011-03-18 - As Italy celebrates unification and 150 years of nationhood, the Italian power transmission operator, Terna SpA, is celebrating the unification of the mainland grid with Sardinia, thanks to ABB high-voltage direct current (HVDC) technology and a record-breaking undersea power link.

By ABB Communications

With a capacity of 1,000 megawatt (MW), the Sapei interconnection enables electricity transfers in either direction between the Italian mainland and the island of Sardinia 435 km away. Its voltage rating of 500 kilovolts (kV) improves transmission efficiency and is the highest ever in Italy’s transmission system. Electricity is delivered via the world's deepest undersea power cables 1,640 meters below the surface of the Tyrrhenian Sea.

Nearly 140,000 MW of HVDC transmission capacity is either in operation or under construction in some 145 projects around the world. ABB has been entrusted with orders for more than 70 of these projects, with an installed transmission capacity of about 60,000 MW.

ABB designed and built the sophisticated high-voltage converter stations at either end of the link - one at Fiume Santo on Sardinia, and one at Latina on the Italian mainland near Rome.

Here, electricity is converted into direct current (DC) and transmitted by cable to the converter station at the other end of the link. It is then converted back into usable alternating current (AC), and fed into the AC grid.

The link significantly increases Terna's flexibility and options in terms of managing its power transmission network in central Italy, and removes a power bottleneck between Sardinia and the Italian mainland.

Sardinia normally produces more power than it needs, while the Italian mainland must import power. By creating the means of transferring surplus power, the Sapei interconnection is the equivalent of building new power generating units, minus the expense and impact of building a new power plant. It is a strategically important infrastructure project that will allow Sardinia to export surplus power to users on the mainland and reduce the cost of energy. The Italian energy bill will therefore become cheaper for everyone. Both the private and public sectors will benefit from this.

It is also in line with Italy's national energy strategy, a key part of which is construction of infrastructure that will help the country diversify its energy supply. The Italian government plans to provide 25 percent of the country’s energy through renewables by 2020.

A windy island, Sardinia is already dotted with wind power turbines, and more wind generating projects are planned. Earlier this year, Enel Green Power announced it will construct Italy's largest wind farm to date on Sardinia at Portoscuso - a 90 MW power plant that will generate enough energy to power 70,000 households.

The company already operates three wind farms on the island with a combined capacity of 161 MW.

Sapei is the third HVDC link delivered by ABB to Italy. The most recent interconnection between Italy and Greece was completed in 2001.

The ABB-built Latina HVDC converter station

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    The valve hall at Fiume Santo converter station in Sardinia. ABB high-voltage transmission technology is helping to support the latest addition to Italy's power infrastructure - the Sapei HVDC transmission interconnection between Sardinia and the Italian mainland.

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