Development of 250kV HVDC XLPE cable system in Korea

HVDC transmission systems are being employed in many projects all over the world. In particular, the demand for long-distance HVDC power transmission lines is increasing to interconnect power grids between main land and island or wind farm grid connection. With such an increasing demand, it was required to develop new insulation materials suitable for the DC cables. The extruded insulation material for AC power cable can't be used for DC operation because of space charge accumulation in the material. Thus many researchers have been conducted to find an effective solution, which decrease the space charge accumulation in the materials: For example, addition of conductive inorganic fillers or polarized inorganic fillers to cross-linked polyethylene (XLPE). This paper describes the development of 250kV HVDC XLPE cable in Korea. The research on HVDC power cable system has been carried out for last 6 years. In early stage of the research, a nano-composite compound was developed for HVDC XLPE cable insulation by adding nano sized inorganic filler. The volume resistivity of developed nano-DC XLPE is higher than those of conventional AC and DC XLPE. HVDC 80kV XLPE cable with 325mm² conductor and termination was developed using nano-composite filled insulation material. The excellent performance of the cable system was confirmed by the mechanical and electrical type test according to the CIGRE recommendations. In addition, HVDC 250kV XLPE cable system was developed and successfully passed a type test in accordance with CIGRE TB 496.