Application study of a high‐temperature superconducting fault current limiter for electric power system

Using high‐temperature superconductors, a superconducting fault current limiter (SFCL) was fabricated and tested. The superconductor and a vacuum interrupter serving as a commutation switch were connected in parallel with a bypass coil. When a fault occurs and excessive current flows, the superconductor is first quenched and the current is transferred to the bypass coil because of the voltage drop of the superconductor. At the same time, since a magnetic field is generated by the current flowing in the bypass coil, the commutation switch is immediately driven by an electromagnetic repulsion plate connected to the driving rod of the vacuum interrupter (VI), and the superconductor is separated from this circuit. Using the test model, we were able to separate the superconductor from the circuit by the movement of the VI within a half current cycle and to transfer all current to the bypass coil. Since the operation of the commutation switch is included in the current limiting operation of this test model, it will be a useful circuit in the development of SFCL in the future. Moreover, since it can make the energy consumption of the superconductor small during the fault state due to the realization of a high‐speed switch with simple composition, the burden on the superconductor is reduced compared with the conventional resistive type of SFCL and it is considered that the flexibility of SFCL design is increased. Cooperation with a circuit breaker was also considered; trial calculations of the parameters and energy of operation were conducted and a discussion of the installation of the SFCL in an electric power system is presented. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(4): 20–29, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20265     

凝胶型99mTc发生器淋洗效率的测定

本文简述了凝胶型~(99m)Tc 发生器淋洗效率的测量原理、方法及结果。并给出了淋洗效率的变化。测量结果的不确定度估计小于±10%。     

Bi2Sr2CaCu2O8＋x单晶的热导率测量

介绍了有关高温超导材料的热导率性质、测试方法和测试结果。结合我们的测试经验，讨论了稳态热流法测量高温超导体热导率应注意的问题。给出了Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏ８＋ｘ单晶沿ａｂ面热导率的测试结果。     

High Tc Superconductor Theoretical Models and Electromagnetic Flux Characteristics

High Tc Superconductors (HTS) have special electromagnetic characteristics and phenomena. Effort has been made in order to theoretically understand the applied HTS superconductivity and HTS behaviors for practical applications, various theoretical models related to the HTS electromagnetic properties have been developed. The theoretical models and analytic methods are summarized with regard to understanding the HTS magnetic flux characteristic which is one of the most critical issues related to HTS applications such as for HTS magnetic levitation application.     

高温超导材料研究近况

近两年高温超导又取得了巨大的进展，特别是在：（１）新的更高温度超导体系的探索，这包括进一步提高Ｔｃ值和合成新结构、新类型的超导材料；（２）材料的应用基础研究，主要指超导块材、线材、带材、膜材料的制备和改进，包括ＳＱＵＩＤ、Ｊｏｓｅｐｈｓｏｎ结和微波无源器件；（３）对高温超导现象的解释和机理的研究方面尤为显著。本文重点介绍过去一年高温超导在材料研究方面的主要进展。     

Structure of superconducting thin films of YBa2Cu3O7−x grown on SrTiO3 and cubic zirconia

Thin films of the superconductive oxide YBa₂Cu₃O_7?x have been made by electron-beam coevaporation of the metals in an oxygen atmosphere onto single-crystal {001}-oriented SrTiO₃ and yttria-stabilized zirconia (YSZ) substrates. The oxide films were superconducting in the as-deposited state (T_c = 81–83K, J_c = 10⁶ A/cm² at 4.2K). Bright-field imaging, selectedarea diffraction (SAD), and high-resolution imaging in the transmission electron microscope were used to characterize the microstructure of these films. All of the films were polycrystalline. On SrTiO₃ the films were oriented, for the most part, with {110} parallel to the substrate surface. On YSZ, two microstructures were observed: one with smaller rectangular grains oriented with (100) or (010) parallel to the substrate surface and the other with (001) parallel to the surface (i.e., c-axis up).     

Electrochemically reduced titanocene dichloride as a catalyst of reductive dehalogenation of organic halides

We have studied a reaction between the reduced form of titanocene dichloride (Cp₂TiCl₂) and a group of organic halides: benzyl derivatives (4-XC₆H₄CH₂Cl, X = H, NO₂, CH₃; 4-XC₆H₄CH₂Br, X = H, NO₂, PhC(O); 4-XC₆H₄CH₂SCN, X = H, NO₂) as well as three aryl halides (4-NO₂C₆H₄Hal, Hal = Cl, Br; 4-CH₃O-C₆H₄Cl). It has been shown that the electrochemical reduction of Cp₂TiCl₂ in the presence of these benzyl halides leads to a catalytic cycle resulting in the reductive dehalogenation of these organic substrates to yield mostly corresponding toluene derivatives as the main product. No dehalogenation has been observed for aryl derivatives. Based on electrochemical data and digital simulation, possible schemes of the catalytic process have been outlined. For non-substituted benzyl halides halogen atom abstraction is a key step. For the reaction of nitrobenzyl halides the complexation of Ti(III) species with the nitro group takes place, with the electron transfer from Ti(III) to this group (owing to its highest coefficient in LUMO of the nitro benzyl halide) followed by an intramolecular dissociative electron redistribution in the course of the heterolytic CHal bond cleavage.The results for reduced titanocene dichloride centers immobilized inside a polymer film showed that the catalytic reductive dehalogenation of the p-nitrobenzyl chloride does occur but with a low efficiency because of the partial deactivation of the film due to the blocking of the electron charge transport between the electrode and catalytic centers.     

Improvement of epitaxy and crystallinity in YBa2Cu3Oy thin films grown on silicon with double buffer of ECO/YSZ

A novel double buffer of Eu2CuO4 （ECO）/YSZ （yttrium-stabilized zirconia） was developed for growing YBa2Cu3Oy （YBCO） thin films on Si substrates. In these films, the severe reaction between Si and YBCO is blocked by the first YSZ layer, whereas, the degradation of crystallinity and superconductivity in the grown YBCO is greatly improved by the second ECO layer. Such an ECO material possesses a very stable 214-T＇ structure and excellent compatibilities with YBCO and YSZ. The result shows that the epitaxy and crystallinity of YBCO deposited on Si could be considerably enhanced by using the ECO/YSZ double buffer. The grown films are characterized by high-resolution X-ray diffraction, grazing incidence X-ray reflection, and transmission electron microscopy （TEM）, respectively. It is found that well defined interfaces are formed at YBCO/ECO/YSZ boundaries. No immediate layer could be seen. The defect density in all grown layers is kept at a lower level. The YBCO film surface turns out to be very smooth. These films have full superconducting transitions above 88 K and high current carrying capacity at 77 K. The successful growth of highly epitaxial YBCO thin films on silicon with ECO/YSZ buffer, demonstrate the advantages of such a double buffer structure.     

加速器质谱法测量99Tc

99Tc is a fission product, and it has high fission yield (6%) and very long half-life (2.1×105 a). With the movement of nucleus, the concentration of 99Tc is increasing in the circumstance. So it's important to measure the concentration of 99Tc in the circumstance, and accelerator mass spectrometry (AMS) might be the best method for 99Tc measurement. The 93Nb is used for AMS instrument normalization, sample matrix. And we used the difference of energy loss and deducting the isotope to measure the 99Tc in a series of standard samples. And the results show that the AMS is the feasible measurement method.     

高Tc超导材料正常态与超导态热导率的研究

研究高Ｔｃ超导材料在正常态与超导态的热导率,对于开拓高Ｔｃ超导材料新的应用,以及对于确保高Ｔｃ超导体稳定运行措施的制定等都是至关重要的。本文从微结构的角度来研究超导材料在正常态和超导态的热导率随温度的变化情况。