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The pure oxygen was introduced into the growth environment of the single crystal diamond with different contents, and the growth characteristics of single crystal diamond and the reaction dynamics in the plasma were studied in detail. As the ratio of O 2 to H 2 is up to 1.5%, the unique shaped etching pits with eight symmetric crystallographic planes appear. Optical emission spectra present typical characteristic radicals in the O 2 incorporated growth environment. With amount of O 2 increases, the growth rate decreases gradually due to the low active carbon source concentration and electron temperature. In the carbon contained hydrogen plasma, O 2 will react with CH radicals preferentially at low concentration and the dynamic equilibrium of CH and C 2 radicals was achieved at the O 2 concentration of 0.5% and 1%. Accompanying with the O 2 addition, the nitrogen and silicon related impurities have been reduced during the epitaxial growth process. Meanwhile, all of the FWHM of characteristic peaks in Raman decrease obviously after the epitaxial growth without and with O 2 addition, and FWHM of most samples are about 2.6 cm −1 , which are comparable with the natural type IIa SCD without stress. [ABSTRACT FROM AUTHOR]

The effects of local characteristics on the performance of full length Bi2223 multifilamentary tapes are investigated computationally and experimentally at 77 K and self-field. Generally the current–voltage characteristics of superconductors are described by the standard power law model with parameters such as critical current Ic and index n. By measuring the critical current {Ici} and index {ni} values of local tapes, we can get the critical current Ic and n value of full length tapes by means of statistical method. The results show that the distribution of local critical currents are non-uniform, and local critical currents have important effect on the performance of the entire tapes. The critical current of the entire tape is different from the mean value of local critical current based on Gaussian statistical distribution along the long tape. [Copyright &y& Elsevier]

Research of the resistance characteristics of YBCO tape under short-time DC large current impact is the foundation of the developing DC superconducting fault current limiter (SFCL) for voltage source converter-based high voltage direct current system (VSC-HVDC), which is one of the valid approaches to solve the problems of renewable energy integration. SFCL can limit DC short-circuit and enhance the interrupting capabilities of DC circuit breakers. In this paper, under short-time DC large current impacts, the resistance features of naked tape of YBCO tape are studied to find the resistance – temperature change rule and the maximum impact current. The influence of insulation for the resistance – temperature characteristics of YBCO tape is studied by comparison tests with naked tape and insulating tape in 77 K. The influence of operating temperature on the tape is also studied under subcooled liquid nitrogen condition. For the current impact security of YBCO tape, the critical current degradation and top temperature are analyzed and worked as judgment standards. The testing results is helpful for in developing SFCL in VSC-HVDC. [ABSTRACT FROM AUTHOR]

Recent years, voltage source converter-based multi-terminal high voltage DC power transmission (MTDC) is widely developed in the world. However, it is difficult for the existing DC breaker to cut off the fault transmission line with large short-circuit fault current. Then, it would be helpful to develop DC fault current limiter for the MTDC system. In this paper, DC superconducting fault current limiter (DCSFCL) is proposed to limit fault current. In order to study the resistance-time performance of the DCSFCL under the rapid change of fault current, a simulation model of Zhoushan MTDC system with DCSFCL is established, and the current-limiting performance of the DCSFCL at different location of the grid is studied. The simulation results show that DCSFCL can effectively limit short-circuit current and improve the operation reliability of MTDC system. [ABSTRACT FROM AUTHOR]

Superconducting fault current limiter (SFCL) is a prospective electric devices connected in series in power grid to limit short-circuit current. A 10.5 kV/1.5 kA 3-phase SFCL with HTS coil of 6.24 mH was developed at IEECAS in China in 2005, which was operated in a local power grid in Hunan province for more than 11,000 h, and integrated lately in a superconducting power substation in Baiyin city in 2011 and is still running safely and reliably. In order to reduce the fault response time and enhance the performance of the SFCL, we analyzed the structure characteristics of the SFCL and discussed the variation of currents and voltages of the HTS coil and the bridge during the fault time. The simulation and tests results of power system validate the feasibility of the fast fault identification method. [ABSTRACT FROM AUTHOR]

A 10 kA/360 m warm-dielectric high-temperature superconducting direct current (DC) power cable system (10 kA cable), supported jointly the Chinese government and industrial enterprise, was developed and has been operating as a branch circuit to transmit power for a 320 kA aluminum electrolyzing production line for more than 10 months at an industrial plant in central China. Both the 10 kA cable and its supporting system of the cable system are introduced. The cryogenic system for the 10 kA cable adopts closed loop and the sub-cooled liquid nitrogen is forced to flow inside by a pump. The design of corrugated cryogenic envelope pipe is modularized and every independent module has two standardized joints, which makes it easy to integrate with the other pipes and the terminations. The heat loss sources and the structure including both the termination and the cryogenic envelope pipe of the 10 kA cable are discussed. The total heat loss of the 10 kA cable excluding the loss of cryogenic pipe for liquid nitrogen backward flowing is designed to be less than 1698 W at 10 kA, and the heat loss was compared and discussed with that of the aluminum bar. The field test and commissioning of the cable show that the 10 kA cable performs steadily and its heat loss is less than the expected value. [ABSTRACT FROM AUTHOR]

A 10 kV High Temperature Superconducting power substation (10 kV HTS substation), supported by Chinese State 863 projects, was developed and has been running to supply power for several factories for more than two years at an industrial park of Baiyin, Gansu province in Northwest China. The system of the 10 kV HTS substation compositions, including a HTS cable, a HTS transformer, a SFCL, and a SMES, are introduced. The SMES works at liquid helium temperature and the other three apparatus operates under liquid nitrogen condition. There are mainly four types of heat losses existing in each HTS apparatus of the 10 kV HTS substation, including AC loss, Joule heat loss, conductive heat, and leak-in heat from cryostat. A small quantity of AC loss still exists due to the harmonic component of the current when it carries DC for HTS apparatus. The principle and basis for analysis of the heat losses are introduced and the total heat loss of each apparatus are calculated or estimated, which agree well with the test result. The analysis and result presented are of importance for the design of the refrigeration system. [ABSTRACT FROM AUTHOR]

Abstract: Poloidal Field (PF) coils, made of CICC (Cable-In-Conduit Conductors), are the most important part of ITER (International Thermonuclear Experimental Reactor) superconducting magnet system. The structure of superconducting magnet system in ITER and the CICC are introduced. The main factors influenced the cabling of the superconducting cable for CICC is discussed. Analyzed the outer diameter controlling technique and the relationship between ac loss and structure parameters of the superconducting cable. The technique route of cabling has been established. Especially, the technique of dies setting for shaping+multi-rolling compacting dies+half-dies for diameter keeping is explained in detail, which can efficiently control the diameter and the cabling quality of the superconducting cable, without injury to strands line. The technical parameters for cabling is fixed and one 765m long dummy cable and one 115m long superconducting cable of CICC for PF coil is manufactured successfully for ITER the last. [Copyright &y& Elsevier]

Abstract: High temperature superconducting (HTS) DC power cable shows a wide application prospect in the field of power transmission for its nearly lossless and rather high capacity. A 360m/10kA HTS DC power cable system, which connects the rectifier output of a substation with the bus bar of an electrolytic aluminium cell, will be put into operation at Henan Zhongfu Industrial Co., Ltd. As one of the items in this project, a 5m/10kA HTS DC power cable was developed, which is used to investigate the conductor design, fabrication, current-carrying capacity and stability of the 360m/10kA HTS power cable. The HTS DC power cable core consists of five conductor layers wound with spliced Bi-2223 wires with the length of 600m. The cable core has five layers and 23 conductors in each layer with the outer diameter of 45.42mm. The superconducting power cable is fabricated and tested. The critical current is about 14.3kA at 77K. The superconducting power cable is charged to 10kA with rate of 10A/s and operates at steady-state for 30min. In this paper, the 10kA HTS DC power cable design, fabrication and test are presented. The experimental research of the performance of spliced superconducting wire and charging, steady-state operating performance of the cable was carried out. [Copyright &y& Elsevier]

Abstract: A double pancake coil was designed and manufactured with a 36-m long Bi-2223/Ag tape. The tape was insulated by 25μm thick Kapton tapes, which can stand a voltage of 400 V rms in liquid nitrogen. The whole double pancake was impregnated with epoxy resin. AC over-current experiments of the coil were performed by applying constant AC voltages to the two terminals of the coil and lasted for 3s. The experiment began first at a lower voltage of 33.6 V rms, and then the voltage stepped up till the coil was burned out at the pulse voltage of 202.7 V rms. All of the experiments were carried out with the coil dipped in liquid nitrogen. The current waveforms were measured. The impedance and resistance characters of the HTS coil with its over pulse currents were analyzed from the experiment results. At the end of this paper, some conclusions derived from the experiment results and their analyses are given, which are helpful for the safety operating of the HTS coils in power applications. [Copyright &y& Elsevier]

Abstract: The nondestructive and contact-free apparatus for measuring local critical current of long high temperature superconducting (HTS) tapes is presented. The local critical current of tape is acquired by using Hall probe array sensor to measure the remanent field after exposed to dc external magnetic field since the critical current is proportional to remanent field based on Bean critical state model. A detailed experiment on multifilamentary Bi2223/Ag tape is made to validate reproducibility, reliability, resolution, nondestructiveness and usefulness for manufacturer and user of tapes. The parameter COV (coefficient of critical current variation) is suggested for quantitatively describing the inhomogeneity and quality of practical long HTS tape based on Gaussian statistical analysis. The developed apparatus can detect HTS tape at velocity of 100m/h with resolution smaller than 3mm in liquid nitrogen. [Copyright &y& Elsevier]