In general, an HVDC line tends to be used for specific critical and/or long-distance applications whereas an HVAC line tends to be part of a large AC network composed of many synchronized AC lines that operate at various voltages.
Part 1 of this series will look at specific applications where HVDC Transmission excels, other applications that may not be as suitable, and the geographic area in the U.S. Grid where they have and will continue to be used extensively. Part 1 will also look at the technology used to implement an HVDC line.