Development and test results of a double 0.5 MJ coil SMES system

The design and test results of a SMES system built for the Korea Electrical Power Company are described. The system consists mainly of two superconducting (SC) coils, two cryostats, a primary power supply and a DC-AC-DC power converter to transfer the stored energy from one coil to another and vice versa. Each of two almost identical coils can store more than 0.5 MJ at about 1.55 kA. Minimum energy transfer time is about 2 s. The conductor is made by cabling of several SC, copper and stainless steel strands around a copper core. At 2 s transfer time mode, the AC losses in each coil are about 500 J. The cryostats are manufactured mainly of thin-walled stainless steel. Their eddy current losses at liquid helium temperatures are lower than AC losses in the coils. After preliminary tests in Moscow, the system was delivered to Republic of Korea and successfully tested at Korea Electrotechnology Research Institute.