Transport current properties of Y-Ba-Cu-O tape above critical current region

YBCO tape is highly promising as a 2nd-stage HTS conductor for power applications, and development of long tape is proceeding worldwide. Generally, HTS tape conductors have broad transition characteristics ranging from the superconducting state to the normal state, so they rarely quench just above the critical current defined for a usual electrical field or resistivity. However, such characteristics make the stability criteria complex when these tapes are considered for power applications. To estimate the stability criteria of HTS tapes, we prepared YBCO tapes with YSZ textured buffers by the IBAD method. The thickness, width and length of the YBCO layer are 1 /spl mu/m, 10 mm and about 140 mm, respectively, and tapes are coated with Ag of various thicknesses as a stabilizer and protector. Transport current properties are measured in a wide range of current above the critical current defined by 1 /spl mu/V/cm. The establishment of criteria to define the stability of HTS tapes will be necessary for their applications in power apparatuses.