Application of the world´s longest gas insulated transmission line in Japan

In this paper we describe the SF₆ gas insulated transmission line (GIL) applied to the 275 kV Shinmeika-Tokai line, which is designed to transport 2,850 MW in a 3.3 km tunnel. To transport this large electric power, two circuits are needed for GIL. GIL has four times greater current capacity than a cross-linked polyethylene (XLPE) cable line, while adoption of XLPE cables may have five circuits. The following structure and installation techniques have been developed to join as many as 1,500 GIL units together in a tunnel where space for the assembly work is limited and atmosphere is dusty. -GIL structure for easiness of installation in a long distance tunnel. -Quality control by mechanized construction of the GIL. -Partial discharges (PD) measuring system for after-laying test on site. This newly developed PD measuring system took advantage of low noise levels in the tunnel. We applied the advantage system to the after laying test on site and confirmed that the developed system was effective to verify the required performance for a long distance GIL.