超電導ケーブル用ブッシング導体の最適熱設計

Abstract

Superconducting cable is one of the promising ways for transmitting the huge electric power in the future. In the terminal bushing of superconducting cable, huge heat influx flows from the ambient temperature region into the cold region through conductor. Huge Joule heat arises because of large electric current in the normal conducting part. To minimize the refrigerator load of terminal bushing in superconducting cable system under steady operation, the sum of Joule heat and heat influx should be minimized. In this paper we discuss the optimum thermal design of the bushing conductor for superconducting cable system.The conclusions are(1) It was shown that, to minimize the sum of Joule heat and heat influx in the terminal bushing with constant cross section along the length, it is required that heat influx is equal to the Joule heat in each part of bushing conductor.(2) We obtained the optimum cross section and optimum temperature distribution from the optimum conductor design based on the above condition. The sum of heat was compared with ones from other design to show the validity of this optimum design.(3) By the design technique combining the optimum design and simulation of temperature distribution, it is possible to take account of temperature dependences of electric resistivity and thermal conductivity, and heat transfer coefficient between gas helium and bushing conductor.(4) With regard to conductor configuration, configuration with high heat transfer coefficient, as braid conductor, makes conductor dimension and helium consumption small.