General trends in the development of +-400 kV to +-1200 kV HVDC systems and areas of application

General trends in the development of hvdc systems are discussed, with specific reference to actual projects as indicators of such trends. Present systems rated +-250 kV to +-400 kV and potential future projects rated up to +-1200 kV are considered. Signigicant improvements achieved in both equipment design and system design concepts have had and will continue to have a very real impact on such trends and these improvements are also discussed.