Development of 23 kV 60 MVA Class 3-Phase Concentric Superconducting Cable

Korea Power Electric Corporation (KEPCO) and LS Cable&System agreed to develop a 23 kV 60 MVA 3-phase concentric superconducting cable and jointly conducted preliminary tests to investigate its reliability. The 3-phase such as 2G HTS wires and copper wires were braided of concentric configuration as a core. Each phase has its own former and its material is copper, which is round type or rectangular shape, even copper tapes are wound in the shield layer for the ground connection. Impedance balance is calculated using a 13 x 13 inductance array to achieve a comparatively uniform current distribution between the three phases and the shielding layer. The estimated ac loss by FEM simulation is 2.87 W/m and the measured results with a short core less than 5 metres long is 3.3 W/m at rated current of 2150 A
_peak
. The fault current was applied to three phases simultaneously. During the short-circuit test, the rising temperature of each phase at approximately 77 K cooling condition is 18 K, 13 K and less than 7 K, respectively. Furthermore, the critical current of each phase before and after the short circuit test is measured by the 4-probe method at 77.3 K in an open bath cryostat. The critical current retention of 3-phase after fault test is over 95% based on IEC 63075 and KEPCO general technical standard. 23 kV/60 MVA concentric HTS cable has been developed through preliminary tests. In addition, the type test of the 3-phase concentric HTS cable system for the Munsan-Seonyu project in Korea has been completed.