Superconducting power transmission system

Abstract

In a thermally insulated double pipe, a structure is provided in which an inner pipe may be prevented from being appreciably offset relative to an outer pipe due to thermal contraction. The structure includes an inner pipe 101, within which a superconducting cable is mounted, an outer pipe 103 within which the inner pipe is housed, with the inner and outer pipes constituting a thermally insulated double pipe, and an inner pipe support member 104 supporting the inner pipe. The inner pipe support member 104 is secured to the inner and outer pipes.

What is claimed is: 
     
         1 . A method for evacuation to vacuum for a thermally insulated double pipe, comprising:
 introducing a pre-set sort of gas into a region defined between an inner pipe and an outer pipe composing a thermally insulated double pipe, thereby effecting gas replacement, with a superconducting cable being installed within the inner pipe, with the inner pipe being housed within the outer pipe; evacuating said region to vacuum; and   subsequently cooling the inner pipe.   
     
     
         2 . The method for vacuum evacuation for a thermally insulated double pipe according to  claim 1 , wherein,
 the pre-set sort of gas comprises a carbon oxide gas.   
     
     
         3 . The method for vacuum evacuation for a thermally insulated double pipe according to  claim 1 , wherein,
 the pre-set sort of gas is a gas that solidifies at a temperature higher than a liquid nitrogen temperature, having a low saturated vapor pressure upon solidification, that is gaseous at ambient temperature and ambient pressure, that is relatively low in viscosity and in dipolar moment, and that has a relatively high mass number.   
     
     
         4 . The method for vacuum evacuation for a thermally insulated double pipe according to  claim 1 , wherein,
 the pre-set sort of gas is   a rare gas comprising argon and xenon, excerpt for neon,   a chlorofluorocarbon (CFC) gas,   a hydrocarbon-based gas, or   a mixture(s) thereof.