Development of Extrusion Molded Joint for 500kV XLPE Cables

In recent yesrs, the demand of electric power in urban area has been increasing more and more in Japan. In order to realize long-distance underground power transmission lines, we need cable joints with enough electrical performance. We carried out basic research from 1989 to 1992 and determined a joint type and the design values. This paper reports on the electric performance of fabricated 500kV joints based on the design. We carried out various breakdown tests for the purpose of evaluating the performance. And it was found that design values, degradation coefficient, temperature coefficient, and EL were appropriate. Also it was found that the approaches to design EL, factors governing the performance, thickness dependence of breakdown stress, and the improved ratio of the perfoprmance at treatment portion of cable screen, were appropriate. Through evaluation we found that it should be possible to apply the Extrusion Molded Joints to 500kV XLPE cable lines.