Nexans has completed the installation and testing of its 445 km submarine and land mass-impregnated HVDC interconnector linking the Cepagatti converter station in Pescara, Italy, to the Kotor converter station near Budva in Montenegro.
In 2012, Nexans was awarded a €340-million contract by Terna, the transmission system operator of Italy’s power network, to supply one of the two 500 kV high-voltage direct current (HVDC) cables for the so-called MONITA interconnector.
The MONITA (MONtenegro – ITAly) project is the largest turnkey submarine project that Nexans has completed to date. The cable supplied by Nexans comprises 423 km of aluminium conductor subsea cable and 22 km of copper conductor onshore cable.
The submarine cable was transported and laid in three separate marine campaigns of approximately 160 km each by Nexans’ own cable-laying vessel Nexans Skagerrak. Around 130 km of the subsea cable was laid in water depths deeper than 700 m, of which 40 km of cable was installed at depths of 1,200 m. The subsea cable is mainly protected through trenching into the seabed by Nexans’ specialized Capjet trenching system.
The use of HVDC submarine cable with an aluminium conductor was an essential aspect of the MONITA project due to the extreme water depths at which the cable was being installed. Aluminium is around three times lighter than copper, which allows for a safer cable installation by avoiding a very large dead weight hanging below the cable-laying vessel during installation.
The land cables were delivered by Nexans Norway from Halden, Norway to Italy and Montenegro on cable reels, spooled in lengths of approximately 800 m. The cable sections were jointed on site by Nexans Norway teams.
During HVDC testing, the entire cable length, which will operate normally at 500 kV, was subjected to 700kV test voltage. The cable system including accessories were also subject to testing program which comprised, for the very first-time, earthquake testing on the terminations.