bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical Treeing Characteristics in Epoxy under Electro-magnetic Coupled Field
Authors: Wang M Y , Du B X , Han X T , Li Jin , Li Z L , Xing Y Q 
Published: June 2020

Abstract
Epoxy resin is a kind of material used as electrical insulation in superconducting magnetic devices. The dielectric properties of the epoxy resin directly affect the safety and stable operation of the whole magnet. While operating, the epoxy resin faces the challenges of complex electric field and strong magnetic field. Researches on the effects of harmonic superimposed dc voltage and magnetic field on the electrical treeing behaviour in epoxy resin were carried out. Experimental results show that low-order harmonics are more likely to lead to the extension of electrical tree branches, which mainly results from the higher energy generated by partial discharge under low-order harmonic voltages. Meanwhile, the addition of dc voltage can result in more sever partial discharge because of the asymmetric charge accumulation, and eventually accelerates the degradation process. Zeeman effects were taken into account while considering the effect of magnetic field. More shallow traps are generated under strong magnetic field, thus charges are more easily to migrate under the action of magnetic field and gain enough energy to break the molecular chain. Besides, Lorenz force leads charges to hit the molecular chain more frequently. The above results in the more serious damage in epoxy resin under electro-magnetic coupled field.
Basic research of HTS coil cooling assist technology by magnetic refrigeration
Authors: Hirano Naoki , Nagai Setsura , Xie Yunzhi , Okamura Tetsuji 
Published: June 2020

Abstract
The fundamental research of HTS coil cooling assist technology by magnetic refrigeration has been studied. Using magnetic refrigeration technology, we are focusing on numerical analysis to see if the cooling efficiency around 20 K of high-temperature superconducting coils can be enhanced. The feature of the proposed cooling method is that it utilizes the leakage magnetic field from the HTS coil. Magnetic refrigeration technology needs to apply a change of magnetic field to a certain type of magnetic material, and the configuration of applying a change of magnetic field to the material in the cryostat is the point of the proposed cooling assist method. We confirm a system that uses a magnetic refrigerator in combination with a refrigerant circulation cooling system by utilizing the leakage magnetic field generated when using a superconducting coil and producing a magneto caloric effect has higher refrigeration performance than the refrigerant circulation cooling system alone.
Thermal Transport Properties of Multiple Oscillating Heat Pipes under Simultaneous Operation
Authors: Nagamoto Naohiro , Kawagoe Akifumi , Mito Toshiyuki , Onodera Yuta , Takahata Kazuya , Yanagi Nagato , Hamaguchi Shinji , Hirano Naoki 
Published: June 2020

Abstract
In this paper, it is shown that the results of experiments on which four oscillating heat pipes (OHP) were simultaneously operated. The OHP is formed into board shape and the four OHPs were put radially. Two FRP disks as dummy winding held the OHPs. Stainless steel sheet heaters were inserted between OHPs and FRP disks, to simulate heat generation in the winding. This equipment was cooled by circulation helium gas. The helium gas flowed in the copper pipe. The copper pipe was soldered to copper plates mounted to cooling edge of the OHPs. Four buffer tanks were connected to each OHP to control the pressure of each OHP individually. The working fluid of the OHPs was Neon. It was demonstrated that all OHPs were simultaneously operated.
Directional control of arcs in liquid nitrogen using externally biased magnetic fields
Authors: Junaid Muhammad , Gao Lei , Li Hongxu , Liu Zhiyuan , Geng Yingsan , Wang Jianhua 
Published: June 2020

Abstract
Arc quenching process inside the liquid nitrogen (LN2) can be accelerated by controlling the shape, size and direction of arc plasma through the controlled magnetic fields. This paper demonstrates the experimental investigations of controlling the arcs in specific directions through NdFeB based permanent magnets. The electrodes were shorted by fuse wires to initiate arc plasmas in LN2. The effects of magnetic fields on the arcs inside LN2 were observed for the very first time. The results show that arc plasma can be stretched, lengthened and thinned in the upward and downward directions through the North-South and South-North magnetic fields approach. These findings are good news that arcs can be controlled inside the LN2 environment and several important achievements such as increasing the life time of electrodes, reduction in LN2 consumption, reduction in bubbles formation, reduction in arcing times and getting a regular cylindrical shape, can be obtained through magnetic fields.
Refrigerant circulation system for cooling a HTS coil
Authors: Xie Y , Nagai S , Okamura T , Hirano N 
Published: June 2020

Abstract
When using the superconducting technology industrially, it is not always possible to install a refrigerator near a high temperature superconducting coil for cooling it. In the method using heat conduction cooling, cooling result as expected cannot be obtained due to temperature difference between a refrigerator and a superconducting coil via a heat transfer plate when the distance of the refrigerator and the coil is long. Therefore, a method of cooling a superconducting coil by circulating helium gas has been proposed. Helium gas discharged by a compressor at room temperature is cooled by a pre-cooling heat exchanger, thereafter cooled by a GM refrigerator. The cold helium gas cools the coil and current leads. In this study, the helium circulation cooling system was investigated by using one-dimensional numerical analysis and experiment at different helium gas mass flows.
Loss analysis of superconducting wireless charging for electric vehicles
Authors: Machura P , Kails K , Li Q 
Published: June 2020

Abstract
Wireless power transfer (WPT) is an emerging technology with widespread applications. It can be used for charging in multiple applications, such as wireless charging for electric vehicles (EVs), which has become a major point of interest. Conventionally, it is used for stationary charging, but also dynamic systems emerge. Key drawbacks of standard WPT systems are the limited transfer distance between the copper coils and the transfer efficiency. By employing high-temperature superconductors (HTS) as coil material these limitations can be alleviated. However, HTS coils have an interesting ac loss characteristic which will be studied. This study investigates the transport current and magnetisation loss of HTS coils in the frequency relevant to WPT for EVs. In addition, a comparison between the full anisotropic dependency of the critical current and only considering perpendicular field components is conducted. A homogenous 2D axisymmetric coil model is used to examine three of the most employed coil configurations and their loss characteristics depending on turn numbers.
A Comparative study of transport current loss in HTS coils for superconducting wireless power transfer
Authors: Chen Hongyi , Li Quan 
Published: June 2020

Abstract
This paper focuses on the transport current loss modelling for HTS coated conductor coils under high-frequency AC current, which is essential when applying superconducting technology in wireless power transfer system (WPT). The pancake coil, spiral coil and solenoid coil designs were proposed, whose study were carried out based on the Finite Element Method in 2D using H-formulation. The transport current loss in each layer for each coil when applying high-frequency AC current were simulated in the FEM platform. The variation of the transport current loss distribution from different layers of the HTS coated conductor according to changing current input was simulated and compared for different operating frequencies. Finally, the frequency and current dependence of the transport current loss in different layers was shown and compared. The simulation demonstrates that the transport current loss in copper layer could be much higher than the transport current loss in the HTS layer at high current and frequency level due to the skin effect. The results also present that the pancake coil design and spiral coil design could be applied to relatively lower frequency WPT application while solenoid coil design can achieve lowest total loss in higher frequency application. These results are essential when designing HTS coils for WPT system.
A Novel Configuration for Resistive SFCL with bifilar 2G tapes
Authors: Sotelo G.G. , dos Santos G. , Martins F. G. R. , Sass F. , Rocha L. M. M. , Bitencourt A. A. , Franca B. W. , Dias D. H. N. , de Andrade R. , Polasek A. 
Published: June 2020

Abstract
Electrical faults on medium voltage electric power distribution systems can damage transformers. This fact motivated an R&D project in Brazil to study Fault Current Limiters for a utility. In this context, innovative design with a bifilar winding was developed for the present work, aiming to reduce self-inductance and to improve cooling rate. Long length second-generation superconducting tapes were used to build the prototype, which was constructed on a fiber-glass base. The prototype module has been tested at low voltage levels. The nominal operation, fault current limitation and recovery time have been examined for prospective currents of 2700 A and reduction of about 90 % in the current level. Due to fast recovery time and good heat exchange, the proposed topology has potential to be applied in a full-scale prototype.
Quench-induced Dynamic Breakdown Characteristics of HTS Pancake Coil Model for Resistive SFCL
Authors: Hayakawa N , Mimbu M , Mori Y , Kojima H , Isojima S , Kuwata M 
Published: June 2020

Abstract
Quench-induced dynamic breakdown (BD) characteristics of LN2 under transient bubble disturbance at the quench of HTS tapes are crucial to the reliable and rational insulation design of resistive superconducting fault current limiters (RSFCL). We have been investigating the dynamic BD characteristics using a nichrome pancake coil model for RSFCL using bifilar nichrome tapes as a heater. In this paper, we fabricated an HTS pancake coil model for RSFCL using GdBCO tapes and discussed the dynamic BD characteristics as a function of heat flux generated from the actually quenched HTS tapes.
Experimental AC loss analysis of braid type non-inductive coil for superconducting fault current limiter
Authors: Song W , Pei X , Xi J , Xiang B , Liu Z 
Published: June 2020

Abstract
Resistive superconducting fault current limiter (SFCL) plays a key role to realise the stability and safety of power grid and the future electric aircraft. This paper presents the design and test of a braid type non-inductive coil for SFCL. One inner coil and one outer coil were wound around a G10 tube using 4 mm-wide SuperPower wires. Two configurations of the braid type non-inductive coil were achieved by connecting the inner coil and outer coil in series and in parallel, respectively. AC loss results of these two non-inductive coils were measured and compared to investigate the AC loss dependency on coil configuration and current distribution. It has been concluded that braid type non-inductive coil has low AC loss due to magnetic field cancellation. Serial connection of the inner and outer coils leads to a good degree of field cancellation, which results in higher critical current and lower AC loss of the non-inductive coil, compared to parallel connection.
Study on the Alliance between SFCL and Hybrid DC Circuit Breaker for Protecting HVDC Grid
Authors: Ayachi Amor Yacine , Didier Gaëtan , Leveque Jean , Hamoudi Farid 
Published: June 2020

Abstract
Breaking the DC fault in HVDC grid is the greatest challenge for DC grid protection system. Although there are many scientific researches investigating the high voltage DC breakers, yet, there is still always a trade-off between the interruption time and the breaking capability. Therefore, combining between the superconducting fault current limiter (SFCL) technology with a fast DC circuit breaker could bring a solution to this limitation. In this work, an accurate model of resistive-type SFCL (r-SFCL) considering the electro-thermal behaviour, is proposed to be placed in series with ABB proactive hybrid DC circuit breaker (PHCB). To test the viability of the system, a pole-to-pole DC fault scenario was imposed in a HVDC grid. The numerical analysis was undertaken with (EMTP-RV®) software, while the simulation results show how effectively the SFCL can reduce the fault current below the maximum breaking capability. Also, it is concluded that there is a positive interaction between the r-SFCL and PHCB.
Analysing Faults and SFCL Response in Electric Aircraft
Authors: Alafnan H , Zeng X , Pei X , Khedr M , Zhang M , Yuan W 
Published: June 2020

Abstract
Aircraft technology moves towards electrification in order to achieve environmentally friendly goals. However, one of the main challenges facing the electrification of aircraft technology is the weight of the electric devices necessary for operating a fully electric aircraft. The National Aeronautics and Space Administration (NASA) proposed the use of the superconductive technology in electric aircraft (EA) to overcome this challenge in addition to its other benefits. The proposed EA is called N3-X and it has an on-board DC superconducting network including a superconducting fault current limiter (SFCL). The SFCL is a self-mechanism device that very effectively limits the current within a few milliseconds, thus improving the stability of the system. As the grounding of this network is different from traditional networks, analysing the behaviour of different fault types and how to manage them becomes critical. In this paper, one set of the EA’s systems (one generator, AC/DC rectifier and four motors with their DC/AC variable frequency drives) has been modelled in MATLAB/Simulink environment to carry out the fault analysis and to demonstrate the effect of the SFCL on this network under different types of faults.
Experimental investigation of current limiting characteristics for a novel hybrid superconducting fault current limiter (SFCL) with biased magnetic field
Authors: Zhu Jiahui , Zhang Huiming , Chen Panpan , Zhao Yongqing , Qin Hanyang , Wei Defu , Lu Kun , Dong Yujun , Zhang Ke , Du Qingqin 
Published: June 2020

Abstract
High temperature superconducting fault current limiter (SFCL) is widely considered as an effective protection for power system when the short-circuit fault currents occur. This paper proposes a novel design of a hybrid SFCL with biased magnetic field which has two-stage current limiting characteristics. This kind of SFCL limits the short current using non-inductive superconducting coil at the first stage, and then by the double-split reactor at the second stage, usually 10 ms later. The advantage of this type of SFCL is saving the amount of superconducting tapes, and it is especially attractive in large current and high voltage occasions. A prototype hybrid SFCL with biased magnetic field is designed and constructed in China Electric Power Research Institute (CEPRI) using YBCO coated conductor. A high speed Data Acquisition (DAQ) System based on LABVIEW is established to monitor and control the SFCL. The current limiting ratios for this prototype SFCL have been investigated experimentally under the operating temperature of 77 K. The experimental results show that the current limiting ratio reaches to 89.66% which validates the design and proves the potential application of this hybrid SFCL.
Detailed Review of a Novel Model SFCL for Grid
Authors: Kosa Janos A , Shao Qing , Zhu Huiyun , Yu Yueyue , Vajda Istvan 
Published: June 2020

Abstract
Our paper shows an RL-Indirect SFCL model (RL-I-SFCL). The applied superconducting tape is SF 12100 (Furukawa Electric Group). In the case of the operational current of a grid, the superconducting wire is in a serial connection with the grid as in a resistive SFCL. If we have a short circuit current on the grid, the RL-I-SFCL protection includes an extra inductance. This inductance is in a serial connection with the short circuit current. The change of the resistance of the superconducting wire creates an extra impedance in the main circuit without delay. It is an advantage. We have measured our SFCL and developed a simulation program by using MATLAB program. Hence, we could test our real measured results using a simulation program. We examined only the steady state in fault. Our checking was successful. We can protect the grid, switchgears and the superconducting wire effectively with this solution. We would like to contribute with this novel model solution to the development of an SFCL in industry because this technology is very simple and it can work safely.
Estimation of performance of Nb3Sn CICC with thermal strain distribution
Authors: Wesche R , Sedlak K , Bruzzone P 
Published: June 2020

Abstract
In the last few years, the critical temperature (T
c) of several ITER cable-in-conduit conductors (CICC) was determined by magnetization measurements at zero current. The distribution of the critical temperatures (T
c), caused by variation of strain in the Nb3Sn strands, was found to vary with the number of load cycles. A comparison with mechanical modelling requires the strain distribution, while the T
c distribution is sufficient to determine the CICC performance. The current sharing temperature (T
cs) is calculated supposing that the measured distribution of T
c is representative of its variation along a single strand and that the current is uniformly distributed among the strands. The T
cs values, found for background and peak magnetic field, are compared with the results of the DC test in the SULTAN facility. The presented estimation techniques lead to an overestimation of T
cs. The differences of the estimated and measured T
cs values are discussed including the effect of different current-voltage characteristics of single strands and CIC conductors.
Topology optimization for superconducting magnet system in helical fusion reactor
Authors: Tamura H , Goto T , Miyazawa J , Tanaka T , Yanagi N 
Published: June 2020

Abstract
In magnetic-confinement-type fusion reactors, the strong electromagnetic force generated by the superconducting coil is of the order of several tens of MN/m. To support this huge force, a strong and heavy coil support structure is required. The total weight of each magnet designed for conventional fusion reactors or experimental devices is several times greater than the ideal value. In recent years, structural optimization has advanced, owing to improvements in computer-aided design and finite-element analysis. For instance, the topology optimization method contributes novel designs that overturn common sense. In the present study, topology optimization is applied to the design of the magnet system used in a helical fusion reactor to reduce the weight of the magnet while maintaining the mechanical soundness of the component. A weight reduction of more than 25% from the conventional design could be achieved.
Development of the quench protection system for the CFETR CS model coil
Authors: Ma Y Y , Wu Y , Xu L W , Wu Y N , Li J , Mao H F 
Published: June 2020

Abstract
The Central Solenoid (CS) model coil, which is responsible for developing and verifying the larger-scale superconducting magnet technology of China Fusion Engineering Test Reactor (CFETR), has been designed and is currently being manufactured at ASIPP. The energy storage of the CS model coil is 407MJ, so a reliable quench protection system is needed to ensure the safety of the coil when a quench occurs. This paper describes the progress of the quench protection system. The two-stage commutating current technique is used to solve the difficulties that the breaker cannot directly break the high DC current. For the key components in the circuit, the prototype of the breaker was manufactured and the performance test was carried out. The engineering design and manufacture of the discharge resistor were carried out. An experimental study of the quench protection circuit was carried out to verify the feasibility of the design. Besides, the reliability of the quench protection control system is qualitatively analyzed based on the fault tree.
Investigation of trade-off solution in mechanical edge joint of STARS conductors
Authors: Sato S , Ito S , Hashizume H 
Published: June 2020

Abstract
Mechanical edge joints of stacked tapes assembled in rigid structure (STARS) conductors have been proposed to be applied to remountable high-temperature superconducting fusion magnets. Our previous study showed the joint resistance decreases with an increase in stabilizer thickness and joint pressure. However, this induces a trade-off between joint resistance and critical current due to increasing strain in the REBCO tape during bending (winding) for the conductors. Furthermore, an appropriate joint surface structure has not been discussed about taking into account a remountable joint. Based on the above background, this study first numerically evaluated the joint resistance depending on the structure of REBCO conductors with copper jackets. The results showed the copper jacket does not efficiently decrease the joint resistance compared to a copper stabilizer. Furthermore, to make strains lower than irreversible strain limit, the joint length should be longer than 500 mm. In addition, the joint surface structure was investigated based on joint testing and observing the surface, from which it was proposed that protective layer on the joint surface is needed to remove the remaining indium and keep the flatness of the joint surface. Therefore, a new structure for the issue was proposed for a remountable joint and the reattaching performance was evaluated experimentally.
Development of an inductive noise cancellation method for quench detection of the KSTAR CS coils by introducing improved plasma modeling
Authors: Kim Jinsub , Jeon Youngmu , Yonekawa Hirofumi , Kim Kwang-pyo , Chu Yong 
Published: June 2020

Abstract
An inductive noise cancellation method, CDA+MIK, has been developed for better performance of KSTAR (Korea Superconducting Tokamak Advanced Research) CS (Central Solenoid) coils’ quench detection. The CDA+MIK method was evaluated in real operations of the KSTAR superconducting coils. An analysis of this evaluation considering mutual inductances only among CS and PF (Poloidal Filed) coils showed insufficient reduction of the inductive noise in the quench detection signal. On the other hand a supplementary analysis taking into account of eddy currents induced on conductive structures and dynamic plasma evolutions capable to induce voltages showed better reduction even though the inductive noise was under-estimated. This paper describes an improved plasma modelling by considering plasma’s volume and shape, and also application of the model to the experimental results
Development of a superconducting transformer for high current conductor testing
Authors: Ma H J , Liu H J , Shi Y , Liu F , Chen H , Zhang X T , Lei L 
Published: June 2020

Abstract
Critical current (Ic) tests on superconducting conductors require currents on the order of tens of kilo-amperes in combination with sub-microvolt resolution voltage measurements. Instead of traditional expensive DC power supply and complicated current leads, a superconducting transformer has been developed to feed the test sample with current up to 30 kA. The transformer consists of two concentric layer-wound superconducting solenoids with the primary coil inside the secondary. In order to reduce the influence by stray field of background magnet and transformer, a hall array with two hall sensors symmetrically distributed around the secondary conductor is used to achieve accurate secondary current measurement. This paper describes the design and manufacturing of transformer, including accurate secondary current measurement method. The first test results are also presented. The superconducting transformer system enables fast, high resolution, economic and safe tests of high current conductors.