The world´s first long-distance 500 kV-XLPE cable line. 2. Joints and after-installation test

For pt. 1 see ibid., vol. 18, no. 2, p. 65-67 (2002). In this second part of a three part series introducing the Shin-Keiyo/Toyosu underground transmission line using a 500-kV XLPE cable, the authors describe the specially developed extrusion-molded joints and after-installation test procedures. Based on the results of basic research extensively done to design the 500-kV extrusion-molded joints, the insulation thickness was determined to be 36 mm through careful considerations of various design parameters obtained. As in the case of the cable, the main factors that determine the performance of the joints are contaminants and voids, and their permissible levels are determined. Unlike cables, it is impossible to conduct sampling inspections for the extrusion-molded joints after they were assembled. Therefore, particular emphasis has to be placed on supervision and inspection of conditions during the assembly process.