Improvement of Current Limiting Device Consisting of Thin Film Superconductor with Thermal and Magnetic Effect

为了建立一个可靠、灵活的配电/输电系统，对故障限流器有着强烈的需求。磁屏蔽型超导故障限流器被认为是6.6 kV输电线路中有应用前景的器件之一。作者曾提出并研制了一种高性能磁屏蔽型故障限流器。然而，近年来，由于公用事业方面对66kv级故障限流器的需求日益强烈，因此，由YBCO薄膜组成的高性能故障限流器正在国际上进行研究和开发。YBCO薄膜J_c在77 K和自场下的临界电流密度可达3x10^6 A/cm^2以上。虽然在如此高的J_c下，只要有几倍于J_c的电流流过薄膜，薄膜就有望快速过渡到正常状态，从而表现出优异的限流特性，但在故障处多抽动，就可能出现热点问题，导致薄膜损坏。为了建立由YBCO薄膜组成的故障限流器的设计准则，本研究研究了YBCO薄膜的各种特性，如快速信噪比转换。我们提出了一种先进的故障限流器，当超导膜发生故障时，通过自动施加脉冲宽度为1 ~ 2ms的脉冲磁场来主动淬灭超导膜。利用该故障限流器研究了从信噪比转变开始到淬火的瞬态行为和限流特性。明确了在整个薄膜面积上实现均匀S/N过渡的要求。开发了模拟该瞬态行为的计算机代码，并分析了其限流、超导恢复等特性。据此，提出了高性能故障限流器的设计准则。少

There are strong needs for fault current limiters in order to establish a reliable and flexible power distribution/transmission system. A magnetic shield type superconducting fault current limiter is thought to be one of the promising candidates for application to 6.6 kV power line. The authors have proposed and developed a high-performance magnetic shield type fault current limiter before. Recently, however, the fault current limiters of 66 kV class are being strongly required from the utility side and accordingly, the high performance fault current limiters composed of YBCO thin film are under research and development in the world. The critical current density of YBCO thin film, J_c amounts to the value as large as 3x10^6 A/cm^2 or more at 77 K and self field. Although the thin film of such a high J_c is expected to exhibit a quick transition to a normal state provided that a current of a few times J_c will flow in the film and hence exhibit the excellent current limiting characteris … More tics at a fault, the hot spot problem may occur and lead to the damage of the film. In the present study, the various characteristics such as a quick S/N transition was studied in order to establish the design criteria for a fault current limiter composed of YBCO thin film. We proposed an advanced fault current limiter in which the superconducting film will be actively quenched by applying a pursed magnetic field of the pulse width of 1〜2ms to it automatically when a fault occurs. The transient behaviors from the onset of S/N transition to quenching and the current limiting characteristics were studied by using the proposed fault current limiter. And the requirements for the homogeneous S/N transition over the whole film area were clarified. The computer codes simulating such a transient behavior was also developed and the various characteristics such as current limiting ones, superconducting recovery and so on were analyzed. In consequence, the design criterion for a high performance fault current limiter was developed. Less