Polymeric insulation for high-voltage dc extruded cables: challenges and development directions

High-voltage DC (HVDC) power transmission plays a key role in the global power grid today and will continue to play a key role in the future, particularly for high-voltage, large-capacity, long-distance power transmission and regional power grid interconnection [1]. HVDC was first developed in the 1930s as a reliable technology that can effectively convert AC electricity produced at the point of generation to DC electricity for transmission. In 1954 the world's first commercial HVDC project connected the Swedish mainland and the Island of Gotland with a ±100 kV mass-impregnated cable with a power rating of 20 MW [2], [3]. Since the 1960s the number of HVDC systems has grown rapidly with the maturation of thyristor and transistor technologies. Two main technologies were developed in the past half century.