押出しエチレンプロピレンゴム (EPR) 絶縁超電導ケーブルの課通電試験

抄録

The extensive use of an extruded crosslinked polyethylene insulation for the power transmission cables and the excellent insulation capabilities of polymeric materials at cryogenic temperatures allure a challenging trial of applying them to the electrical insulation of superconducting cables. Through a long and systematic survey and research on material properties, authors came to the conclusion that ethylene-propylene rubber (EPR) is highly suited for this purpose. Thus efforts were made toward the development and testing of the extruded EPR insulated superconducting cables. The superconductor is a niobium layer clad on a copper pipe. The main insulation design consists of EPR simulatneously extruded with semiconducting electrostatic shielding layers. Helium is the coolant for the superconductor and solely plays a role of cooling the cable. The complete exclusion of the vulnerable cryogenic helium from the electrical insulation structure is the specific feature of this cable. The cable is cooled down to the boiling helium temperature (4.2K) inside the copper pipe and subsequently the voltage (20kVrms) and current (2kArms) tests were carried out successfully. Ethylene-propylene rubber has proved to be the distinguished material for cryogenic electrical insulation.