Power Cable Insulation

The history of the development of power cables in Japan is introduced in this paper, focusing the technical progress of three types of cables: OF cable, XLPE cable, and GIL (Gas-Insulated transmission Line). Researchers have been seeking an increase of the transmitting capacity, which can be realized by increasing voltage and/or current. For this purpose, various types of insulation have been developed. Namely, deionized water-washed Kraft paper, synthetic paper, XLPE, and SF6 insulation have been developed to reduce the dielectric loss. GIL and strand-insulated larger conductors have been developed in order to permit a larger current. As for XLPE cable, various manufacturing techniques such as dry curing, three-layer simultaneous triple extrusion, etc. have been developed. Applications of metal-laminated water-impervious layers and water-tree-retardant XLPE have been studied to avoid the water-tree deterioration of XLPE cable. The techniques concerning GIL also have progressed rapidly. GIL has been utilized in cases where extremely large transmitting capacity is required.