Transmission loss of prospective power transmission model system integrated under superconducting environment

The authors have developed a "prospective power transmission model system integrated under superconducting environment", abbreviated to PROMISE, with a transmission capability of 6 kV-1000 kVA. The PROMISE consists of a superconducting transformer (SE-Tr), a superconducting fault current limiter (SC-FCL) and a superconducting power cable (SC-power cable). These components are cooled down at liquid helium (LHe) temperature, 4.2 K, in a cryostat with a volume of 854 l. The paper indicates a computing procedure of a total heat leak 4.2 K into the cryostat and discusses transmission losses of the superconducting electric power system, which evaporate the LHe. P/sub leak/, core loss P/sub core/ of the SC-Tr and AC loss P/sub ac/ in the superconductor were measured in the PROMISE to be 43 W, 180 W and 50 W, respectively. The measured P/sub leak/ agreed with the theoretical one. In the superconducting power transmission system, the power to operate the refrigerator for liquefying the evaporated helium must be taken as the transmission loss. If the penalty factor was 500, the transmission loss was estimated to be 137 kW and took 13.7% of the transmission capability in the PROMISE.