Conversion of AC distribution lines into DC lines to upgrade transmission capacity

Nowadays it is difficult to find corridors for building new overhead lines in industrialized countries. In many cases it is simply impossible. For that reason, new solutions for the upgrading of existing overhead lines are required. The conversion of existing AC lines into DC lines represents an alternative to upgrading the power carrying capability for the existing rights of way ( ROW). Thus, this paper presents a comparison between AC and DC technologies for power transmission and distribution. The underlying technology is reviewed and different conversions are analyzed, for simple and double circuit lines. Also, increased power carrying capability and loss reduction are studied. Finally, an example of the conversion of a 66 kV double circuit AC distribution line into a DC line is included. (C) 2011 Elsevier B.V. All rights reserved.