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Paper Info

Presented At
CIGRE 2008 - B4 116



HVDC  links  are  becoming  an  increasingly  popular  solution  to  interconnect  previously  isolated systems or to establish new corridors within highly meshed networks. As a matter of fact, HVDC links show outstanding advantages with respect to HVAC corridors such as full controllability of power flow avoiding the creation of parallel or, even, loop flows in meshed networks. Moreover, HVDC technology is the only feasible solution when crossing long marine distances. Particularly, in the case of the Mediterranean basin linking Europe to Africa requires the adoption of HVDC technology, with the only exception of the Spain-Morocco interconnection, given the short distance across the Strait of Gibraltar.  Italy  is  especially  interested  in  establishing  new  interconnections  with  the  Maghreb countries, considering the shortfall of internal energy production and the heavy congestion across the trans-Alpine electricity corridors. Interconnecting Maghreb with Europe will offer mutual benefits in the technical, economical, environmental sectors, without forgetting the political dimension: indeed, a greater integration of North-Africa countries with the Europe has been recognised by the EU as a priority since the starting of the Barcelona process in 1995. On the wake of the mutual interests of the concerned countries, Italy and Maghrebian countries launched a series of feasibility studies aimed at identifying the most appealing solutions for trans-Mediterranean submarine electric interconnections. Since the investments are in the order of several hundreds of million of Euro for each interconnection, an appropriate methodology has been designed and tuned through the application to practical cases. The methodology is based on a two step-approach. In the first step, an accurate screening activity is carried out aiming at comparing the possible technical alternatives of the DC interconnector: location of the converter stations, sizing of the interconnector in relationship to the AC grid transfer capacities and  the  surplus/shortfall  of  power  at  both  ends,  selection  of  the  DC  technology,  preliminary configuration of the DC schemes. At this stage, the possible DC voltage levels are also examined. At the  end  of  the  screening  activity,  a  ranking  of  all  the  feasible  alternatives  is  drawn  through  a “differential” approach consisting of comparing the alternatives on the basis of a series of indexes, the values of which are “different” in the various solutions. Then, the second step of the methodology is applied to the selected solutions to identify the DC schemes, the technical measures to be adopted for the connection of the converter stations to the AC grids, the preliminary routing through a desktop study and the economic and financial indexes.
The paper presents the main outcomes of the three feasibility studies of interconnection between Italy and Algeria, Tunisia and Libya. However, the proposed methodology is valid in general to decide the feasibility of  DC links resorting to EHV or UHV for the transmission of large amount of power over long distances.

Cova Bruno
Phone:  +39 02 2125 5431


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