Progress in high temperature superconductor coated conductors and their applications

Abstract

Second generation (2G) high temperature superconductor (HTS) wires are based on acoated conductor technology. They follow on from a first generation (1G) HTS wireconsisting of a composite multifilamentary wire architecture. During the last couple ofyears, rapid progress has been made in the development of 2G HTS wire, which is nowdisplacing 1G HTS wire for most if not all applications. The engineering critical currentdensity of these wires matches or exceeds that of 1G wire, and the mechanical propertiesare also superior. Scale-up of manufacturing is proceeding rapidly, with several companiesalready supplying the order of 10 km annually for test and demonstration. Coils ofincreasing sophistication are being demonstrated. One especially attractive application,that relies on the specific properties of 2G HTS wire, is fault current limitation. Byincorporating a high resistivity stabilizer in the coated conductor, one can achieve highresistance in a quenched state during a fault event and at the same time providesignificant heat capacity to limit the temperature rise. A test of a 2.25 MVA singlephase system at 7.5 kV employing such wire by the Siemens/AMSC team hasdemonstrated all the key features required for a cost-effective commercial system. A novelapproach to providing fault current limiting functionality in HTS cables has also beenintroduced.