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

为了建立可靠和灵活的配电/输电系统，对故障电流限制器的需求很大。磁屏蔽型超导限流器被认为是6.6kV输电线路上最有前途的限流器之一。作者提出并研制了一种高性能的磁屏蔽式故障限流器。然而，近年来，电力系统对66kV级故障限流器的需求越来越大，世界各国都在研究和开发由YBCO薄膜构成的高性能故障限流器。在77K和自场作用下，YBCO薄膜的临界电流密度J_c达到3×10~(-6)A/cm~2以上。尽管这种高J_c的薄膜有望快速转变到正常状态，但前提是几倍J_c的电流将在薄膜中流动，从而表现出优良的限流特性…一个故障抽动较多时，可能会出现热点问题，导致胶片的损坏。为了建立由YBCO薄膜组成的故障电流限制器的设计准则，本文研究了YBCO薄膜的各种特性，如快速的S/N转变。我们提出了一种改进的故障限流器，当故障发生时，通过向超导薄膜施加脉冲宽度为1~2ms的脉冲磁场来自动对超导薄膜进行主动猝灭。利用所提出的故障限流器，研究了从S/N过渡到猝灭的暂态行为和限流特性。明确了在整个膜区实现均匀的S/N跃迁的要求。编制了模拟这种暂态行为的计算机程序，并对其限流、超导恢复等特性进行了分析。在此基础上，提出了高性能故障限流器的设计准则。较少

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