Continuous Deposition of YBCO Films for Coated Conductor Using PLD Method

A reel-to-reel PLD system was set up for studying YBCO coated conductor. YBCO films could be continuously grown on the CeO₂/YSZ/Y₂O₃ buffered Ni-5W tape. Some deposition parameters were investigated. XRD θ–2θ scans were employed to characterize the c-axis orientation and in-plane texture of YBCO films deposited with different laser repetition rates and tape moving speeds. We investigated the dependence of critical current I _c on laser repetition rates and tape moving speeds for YBCO films. It had been found that a-axis oriented grains appeared as YBCO layer thickness increased, which prevented the values of I _c improved.     

Electrothermal Modeling of Coated Conductor for a Resistive Superconducting Fault-Current Limiter

Coated conductors are very promising for the design of a novel and efficient superconducting fault-current limiter (SFCL). The thermal and electrical behaviors of this type of SFCL in the presence of over-critical currents need to be investigated in detail to master its performance in a power grid. In this paper, an Electrothermal Model of a Coated Conductor (ETMCC), not simulated in the literature, is implemented and introduced in the library of MATLAB software. An algorithm to solve the differential equations characterizing the superconducting material is developed using the Runge-Kutta method. In this context the ETMCC under over-critical current is performed. Different dimensions and substrate configurations of the sandwich layers are considered. In order to improve the high-temperature superconductor (HTS)-FCL design, the influence of the substrate and shunted layers (using different materials) on the thermal stability is investigated. The simulation results are generalized, thus allowing us to determine the current threshold to achieve thermal stability of the HTS-FCL at any point of the coated conductor.     

Reel-to-Reel PLD Fabrication of YBCO Coated Conductor by Single and Multi-coating Processes

YBa₂Cu₃O_7?δ (YBCO) coated conductors have been fabricated on CeO₂/YSZ/Y₂O₃ buffered Ni-5at%W tapes by pulsed laser deposition (PLD) using the reel-to-reel process. A multi-coating process for YBCO film was employed, and single and multi-coating methods for YBCO films are compared. X-ray diffraction texture measurements showed good in-plane and out-of-plane crystalline orientations for the YBCO films. Magnetic measurements were carried out on the samples, and the critical current density as a function of the magnetic field was investigated. The results showed that the superconducting properties of YBCO films fabricated by the multi-coating process were better than those prepared by the single coating process.     

Thermal and Electrical Stabilities of YBCO Coated Conductor Tapes in a Solid Argon-Liquid Nitrogen Mixed Cooling System

A new cryogen, a mixture of solid argon and a small amount of liquid nitrogen, was studied to improve thermal contact between the solid cryogen and high-temperature superconducting tapes. A feasibility study of the reference design codes and the thermal requirements was conducted to optimize the design of the mixed cryogen cooling system. Experimental results showed that thermal and electrical stabilities of YBCO coated conductor tapes were significantly improved when they were impregnated with the mixed cryogen. Dry-out problems were overcome by the mixed cryogen because the small amount of liquid nitrogen improved thermal contact between the solid cryogen and superconducting tape.     

The Influence of Temperature Distribution on YBCO Coated Conductor Deposited by Reel-to-Reel PLD Method

It is known that the tape’s temperature controlled by a close substrate heater will still deviate after the deposition process. In this work, we deposited YBa₂Cu₃O_7−δ (YBCO) films on RABiTS substrates with multilayer CeO₂/YSZ/CeO₂ buffer layers by pulsed laser deposition (PLD) under a different distribution of temperature deviation in order to improve it. Thermocouples were applied to exactly measure the temperature. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to inspect c-axis oriented crystals and surface morphology of YBCO films. Through this work, we found that the even shape is best. Under the temperature deviation with the best shape, a transport J _c of 3.2×10⁶ A/cm² and I _c =240 A was obtained for a 0.75 μm thick YBCO film on CeO₂/YSZ/CeO₂-bufferd RABiTS Ni–W alloy.     

生物矿化法制备平片状 YBCO 粉末及导体

介绍了一种全新的制备YBCO超导粉末的方法,通过加入右旋糖酐采用生物矿化的方法,可以使制备的 YBCO 粉末晶粒均呈现出平片状,其典型尺寸为5μm ×5μm ×1μm, TEM显示这些平片状晶粒本身亦呈现层片状结构。同时在一定的区域内,这些平片状YBCO晶粒会自发聚集形成具有相似生长方向的晶粒簇。在这些晶粒簇内部首次在 YBCO内部发现存在有自发超导连接现象。超导连接区域平均包含3～5个平片状晶粒。由于这种YBCO粉末具有特殊的微观结构,所以具有很好的超导性能,其Jc 值在77 K自场下达到了0.1 MA· cm -2,比同等条件下的商业 YBCO 粉末高出10倍以上。用这种具有特殊结构的YBCO粉末可以制备出可以实际承载超导传输电流的 YBCO导体,结果表明此方法有望成为一条全新且廉价又高效的制备YBCO导体的新路线。     

Development,Updating and Long-Term Operations of a 10.5 kV HTS Fault Current Limiter

There are many irreplaceable advantages of high temperature superconducting (HTS) fault current limiter, applying in electric utilities. It is expected to be able to solve excessive fault current problems and to enhance safety and stability of power systems. In this paper, the R and D of an improved bridge-type 10.5 kV three-phase superconducting fault current limiter (SFCL) was present. Each phase adopted a HTS coil with inductance of 6.2 mH. The three coils wound with 8,571 m Bi2223/Ag tapes totally. After installation at a 110 kV/10.5 kV substation in Hunan Province of China, the performances of the whole SFCL were tested, including a three-phase-to-ground short circuit experiment at the pre-setup short circuit point. And then, the SFCL was put into operations in the 10.5 kV power grids for more than 11000 h. About 3 years later, the SFCL was moved, reinstalled, and put into operation again since February 16 of 2011 at a 10.5-kV superconducting power substation located in Baiyin, Gansu Province of China. In this paper, the redesigned and manufactured cryostats with nonmagnetic stainless steel, tests, and long-term operations of the SFCL in 10.5 kV power grids were also described in detail.     

Current Distribution in YBCO Coated Conductors of Toroidal Coil Composed of Multiple Double Pancake Coils

We should prevent non-uniform current distribution due to manufacturing errors of tape size, coil size, and conductor deformation in the toroidal coil composed of multiple YBCO double pancake coils. This is because the non-uniform current distribution causes the increase of AC losses and the decrease of critical current in the YBCO tapes. Therefore, we analytically investigated the relationship between the manufacturing error and the current distribution in the toroidal coils composed of the eight series-connected double pancake coils composed of the transposed conductor with two parallel-connected YBCO tapes and the eight sets of two parallel-connected double pancake coils composed of single YBOC tape conductor connected in series. The parallel-connected multiple double pancake coils composed of single tape conductor is much more effective for preventing the non-uniform current distribution than the double pancake coil composed of the transposed conductor with parallel-connected multiple tapes. The non-uniformity of current distribution can be improved by increasing the length of parallel-connected current path by increasing the number of series-connected double pancake coils in each current path.     

Experimental and Numerical Study of Co-ordination of Resistive-Type Superconductor Fault Current Limiter and Relay Protection

Superconducting fault current limiter (SFCL) has become one of the most ideal current limiting devices to solve the problem of increasing short-circuit current in high-voltage power grid. This paper presents a resistive-type SFCL model developed using simulation software PSCAD/EMTDC. After being verified by finite-element model and experimental results, the model is used to study the impact of SFCLs on the power grid and the co-ordination between SFCL and relay protections in 10 kV distribution network. A series of simulations are carried out to find appropriate parameters of SFCL model to cooperate with relay protection devices. The final result in this paper could provide important quantitative basis of parameters for SFCL to be applied in a real power system.     

Quench and Recovery Characteristics of Solid Nitrogen (SN2) Cooled YBCO Coated Conductor (CC) Tapes with Different Stabilizers

Recently, a cooling system using solid nitrogen (SN2) as a cryogen was suggested to enhance the thermal and electrical stabilities of high temperature superconductor (HTS) magnet applications, due to its large heat capacity. For the successful application of the SN2 cooling system to HTS devices, it is necessary to obtain sufficient data about the thermal and electrical characteristics of the SN2-cooled YBCO coated conductor (CC). Therefore, this study examined the thermal and electrical properties of YBCO CC tapes with different stabilizers in the presence and absence of SN2. The results clearly showed that the thermal and electrical stabilities of the YBCO CC tapes were drastically improved in the presence of the SN2, regardless of the stabilizer materials. Furthermore, copper was found to be more suitable as a stabilizer of YBCO CC tape in the SN2 cooling system than stainless steel.     

REBCO涂层导体制备技术及其进展

REBCO涂层导体具有J<,c>(77K)高于10<'6>A/cm<'2>的临界电流密度和高的不可逆场H77 K),展示了在液氮温度下非常有实用前景的超导性质,从而成为目前各国竞相研究开发的焦点.简要概述了高温涂层导体薄膜的制备技术,着重介绍了脉冲激光沉积、金属有机物沉积、化学气相沉积、溶胶-凝胶、磁控溅射和液相外延等方法的特征、优缺点和最新发展情况,并对REBCO高温超导涂层导体的应用前景进行了展望.     

精密有源互感器的研制

本文介绍了精密有源电流互感器的原理和设计方法。该互感器的准确度达到０．０１级，线性度优于１×１０－５．     

用红外成像设备检测电路板中的故障元器件

在检测电路板的故障时,外观检查的方法作用有限,功能测试的方法工作量大并且在某些"软故障"(如电阻或电流超差但信号处理功能正常)中难以派上用场。文中叙述用红外成像设备检测电路板中的元器件的过程,故障器件定位准确、快速,对以后检测故障元器件具有参考意义。     

Effects of Sm-doping on Structures and Properties of YBCO Coated Conductors Fabricated by TFA-MOD Process

The Sm-doping YBCO films, Y_1−x Sm _x Ba₂Cu₃O _y and Y₁Sm _x Ba_2−x Cu₃O _y (x=0.1, 0.3), were fabricated on LAO (00l) single-crystal substrates by TFA-MOD process in order to improve the superconducting properties of YBCO films. The XRD analyses indicated that these samples have a strong c-axis texture, but the secondary phase of BaCuO₂ are found from Y₁Sm _x Ba_2−x Cu₃O _y films with Sm³⁺ substitution on Ba²⁺ sites. High quality surface, better in-plane and out-of-plane texture of the Sm-doping films have been obtained compared with that of the undoped YBCO film. The Y_0.9Sm_0.1Ba₂Cu₃O _y films showed the highest value of T _c and J _c in self-field. Superconducting properties of all Sm-doping films are better than those of the pure film. These results strongly suggest that Sm-substitution on Y or Ba sites of YBCO phase is a powerful method to efficiently improve J _c and introduce artificial pinning centers in YBCO films.     

Influence of O<Subscript>2</Subscript> Pressure on the Structure and Surface Morphology of YSZ Layer for YBCO Coated Conductor Deposited by PLD on Ni-W Tape

Yttria-stabilized ZrO₂ (YSZ) buffer layers were prepared on Ni-5%W tapes coated with CeO₂-seed layers by a pulsed laser deposition (PLD) technique. The influences of oxygen pressure on the structure and surface morphology of YSZ buffer layers for YBCO coated conductors was investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Atomic Force Microscope (AFM) were used to characterize YSZ films. It was found that the structure and surface morphology were sensitive to the oxygen pressure. When the O₂ pressure was higher than 1 mTorr, the YSZ film had mixed orientation and rugged surface. When the oxygen pressure was reduced to 0.5 mTorr, YSZ film had the pure (001) orientation. The surface became smooth as the oxygen pressure decreased. However, when the pressure was low to 0.1 mTorr, X-ray diffraction peaks form YSZ (002) were weak and the rough surface appeared again. The results could be explained either by plume stoichiometric changes, gas and ions interaction, or atomic rearrangement on the substrate.     

Simulation of the Heating of a Tungsten Conductor by a Nanosecond High-Power Current Pulse

The initial stage of explosion of a thin tungsten wire by a high-power current pulse of nanosecond duration is simulated. Radial distributions of parameters of matter are obtained for two models. According to one of the models, it is assumed that an instantaneous separation into phases occurs if the parameters of metal have reached values corresponding to the binodal; in the other model, the existence of a metastable state is allowed. Phase trajectories in the P–Tand –Tplanes are given.     

Spin-Polarized Current in a Nonmagnetic Conductor and the Role of Electron–Electron Scattering

The influence of electron–electron scattering on the efficiency of certain methods for the injection and generation of spin–polarized current states in nonmagnetic conductors is discussed. We consider the effect of electron–electron collisions on the resistance to electric transport developing at the interface between a magnetic conductor (MC) and a nonmagnetic conductor (NMC). An essentially unbounded increase of the interfacial MC/NMC magnetoresistance with temperature is predicted.