Greenconnector is an HVDC interconnector project between Italy (Lombardy) and Switzerland (Graubünden).
The nominal power is 1000 MW, with continuous overload at 1100 MW and peak overload at 1200 MW. The DC voltage is +/- 400 kV DC.
Greenconnector uses underground and submarine cables throughout its route, rather than overhead lines. The route length is about 150 km.
Two cables will be installed in a so called "rigid bipolar" configuration, with no earth return.
One of the main driver of the project is to minimize any environmental impact: for this reason, only underground and submarine cables have been considered from the very beginning of the design. For great part of the cable route, an existing oil pipeline, a masterpiece of engineering at the time of its construction around 1960 and presently no longer in operations, will be reused, by pulling and installing the HVDC cables inside it. The steel pipeline will also protect the cables against possible external damages and the reliability of the link will be increased. The existing corridor and pipeline infrastructure (tunnels, dedicated bridges, river crossing weirs, etc.) will thus be brought back into new life: the new underground power line will therefore not require new rights of way, will preserve the natural habitats as well as the beautiful landscapes of the Alpine region. Civil works will be limited to a few locations along the route. In some locations, the existing pipeline included external components, such as stop valves and small control buildings: these will be removed during the installation of the cable, thus reinstating the original landscapes. For a length of approx. 47 km where the pipeline is no longer available, cables will be laid on the bottom of the Como Lake: cable laying in a lake is technically challenging, but this way trench excavation along roads and the related civil works and traffic disruption will be avoided.
The main objective of the project is the further debottlenecking of the congestion across the Alps, thus enabling the better integration of generation South and North of the Alps, including renewable and hydro power. The use of HVDC cables instead of an overhead line, besides the visual and environmental advantages described above, also improves the safety of the interconnection, protecting it against lightning, falling trees, snowfall, ice build-up, and similar adverse weather conditions. The line will generate a DC magnetic field only, of comparable level as the Earth's natural magnetic field: therefore no electromagnetic corridor will be needed along the line.
Further details can be found in the Ten-Year Network Development Plan 2018, published by ENTSO-E and the PCI list published by the European Commission.