Operation Losses and Economic Evaluation of UHVAC and HVDC Transmission Systems

For the economic benefits of power transmission facilities during their whole life circle,we analyzed the technical and economic aspects of ultra-high voltage AC(UHVAC) and high voltage DC(HVDC) projects that have been put into operation.Based on the construction investment and operation losses,and taking several major factors into consideration,such as the line loss hours of the power transmission system,the on-grid price,the cost of the transmission line project,and so on,we calculated the economical current density levels of the lines which were used in a HVDC transmission system with long-term heavy load or in a UHVAC system with commonly light load,then the total conductor section area of the transmission lines.With further technical and economic analysis,we proposed that the economical current density levels of lines in the HVDC transmission system with long-term heavy load or in the UHVAC system with commonly light load should be around 0.5~0.6 A/mm2 and 1.9 A/mm2,respectively.Therefore,it is concluded that in order to decrease the operation losses ratio of the total system,conductors with larger cross-section on HVDC transmission projects and new diameter-expanded conductors on UHVAC transmission projects need further development.