Development of coaxial type DC extruded insulation cable and factory joint

This paper describes the development of coaxial type DC extruded insulation cable and factory joint. Coaxial type cable consists of main conductor, main extruded insulation, return conductor and return extruded insulation. Adoption of the coaxial type cable has great advantages both environmentally and economically, "to omit installation of a cable or electrodes for the return circuit" and "to decrease compass error". In addition, extruded insulation cable has advantages compared other kinds of DC cable "to increase transmission capacity more than the mass impregnated cable", "not to concern oil leakage" and "no need of pumping facility for the oil-filled cable". Therefore coaxial type DC extruded insulation cable and factory joint have been developed for adopting into a long distance submarine cable.