Development of low- lossAg-sheathed superconducting tapes based on electromagnetic design and their application to AC power cables

基于电磁设计的低损耗银套超导带材的研制及其在交流电力电缆上的应用研究，从2005-2007财政年度开始，历时三年。(1)交流损耗测量系统的构建搭建了测量系统，测量了超导带材在交流工作状态下，通过任意方向的交流传输电流和交流电外加磁场到达带材表面时产生的交流损耗。在改变频率、传输电流幅值和磁场幅值的情况下，我们可以得到交流损耗的总和。(1)银芯阻挡层高T_c超导带材的制备和表征我们成功地制备了具有阻挡层…的银套高温超导带材并对其在电力电缆中的应用进行了研究。在胶带制造中，我们使用了两种方法来引入Banier。一种是使用阻挡层浆料涂覆的方法，另一种是使用具有良好机械性能的金属进行内氧化的方法。特别是用Ca_2CuO_3粉末和30wt%Bi2212粉末混合作为势垒材料制备的银包层带材，其长度在几米量级，具有相当好的均匀的J_(77K，OT)分布，远高于10^4A/cm~2(最大为1.8×10~(-4)A/cm~2)。此外，这种势垒的引入使横向电阻率提高了数倍，交流损耗比未引入势垒时降低了1/3。(2)银套超导带圆柱形导线电缆的电场和交流损耗根据电磁场理论，阐明了银套超导带圆柱形导线电缆附近的电场分布，这对交流损耗的测量误差估计有重要作用。在交流操作下，电缆附近的电场表现出复杂的变化，取决于电缆的结构，并且在离开磁带表面大约磁带宽度时，电场几乎是恒定的。结果表明，电缆导线的交流损耗测量应在远离磁带表面至少小于磁带宽度的距离处进行

Studies on development of low-loss Ag-sheathed superconducting tapes based on electromagnetic design and their application to AC power cables have been conducted for three years between fiscal 2005 and 2007. Main results through the study am summarized as follows:(1) Construction of AC loss measurement systemWe constructed the measuring system to obtain the AC losses generating in superconducting tape under AC operation, in passing through AC transport current and AC external magnetic fields at arbitrary directions to tape surface. Using this, we can obtain total values of AC losses obtained by a sum of AC transport losses and AC magnetization losses in the tapes and/or wires, while changing frequency, transport current amplitude and magnetic field amplitude.(1) Fabrication and characterization of Ag-sheathed high-Tc superconductiong tapes with interfilamentary resistive barriersWe successfully fabricated Ag-sheathed high-Tc superconducting tapes with interflamaaary resistive barriers … More and investigated their electromagnetic properties toward applications to electric power cables. We used two methods for banier introduction in tape fabrication. The one is the coating method using paste of resistive barriers and another the inner oxidization method using metals with nice mechanical properties. In particular the tape fabrication using mixture of Ca_2CuO_3 powder and 30 wt%Bi2212 powder as barrier materials produces Ag-sheathed tapes on the order of several meter lengths, which have considerable nice and homogeneous J,(77K, OT) distribution well above 10^4 A/cm2 (1.8 x 10^4A/cm2 at maximum). In addition, this barrier introduction causes several-times enhancement in transverse resistively and lowers the AC losses up to 1/3 compared to the tapes without barrier introduction.(2) Electric fields andAC losses for cylindrical conductor cables composed of Ag-sheathed superconducting tapesWe elucidate the electric-field distribution near cylindrical conductor cables composed of Ag-sheathed superconducting tapes based on the electromagnetic theory, which plays an important role in the error estimation for AC losses from measurements. The electric field under AC operation shows complicated variations in the vicinity of cables depending upon the cable structures and it becomes nearly constant in going away from the tape surface by about tape width. The result shows that AC loss measurements for cable conductors should be made at the distance far from the tape surface by at least tape width Less