HVDC conversion of HVAC lines to provide substantial power upgrading

The feasibility of conversion of AC lines to DC lines for a substantial power upgrading is analyzed, and it is shown that increases of 3.5 times or more are feasible. The main design objective is to permit the conversion to be carried out as a simple retrofit or maintenance operation, rather than a new construction operation, thereby reducing outage times and simplifying possible new licensing procedures. Both HV and EHV double-circuit and single-circuit AC lines of average characteristics have been used as an example for conversion to both bipolar and monopolar lines respectively. In addition to the substantial increase in power transfer capability, the conversion to DC also substantially reduces the per unit losses and enhances reliability through the improved lightning performance of the converted line. HVDC operation has proven advantages in optimizing operation of the total system. The data presented provide a reference framework to facilitate preliminary evaluations, although detailed conversion studies can only be made on a case by case basis