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Choi, Youngjun,Kim, Dongmin,Cho, Jeonwook,Sim, Kideok,Kim, Sungkyu,Kim, Seokho The Korea Institute of Applied Superconductivity a 2019 한국초전도저온공학회논문지 Vol.21 No.4
To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.
AC Loss Analysis of HTS Power Cable With RABiTS Coated Conductor
Seokho Kim,Kideok Sim,Jeonwook Cho,Hyun-Man Jang,Minwon Park IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>Numerical analysis of AC loss for a HTS power cable is investigated using commercial FEM software package. AC loss of the HTS power cable, which is made by 2 G conductor, is hard to experimentally measure due to very small signal compared to that made by 1G conductor. The FEM model describes current distribution and AC loss inside the HTS conductor for the AC transport current through nonlinear E-J correlation. For the verification of the AC loss analysis model, the results were compared with the well known analytic solution of a single strip HTS conductor and experiments. Unlike IBAD substrate, magnetization of the RABiTS has influence on the precise estimation of the AC loss and it is also considered in the FEM model. Moreover, several conductors should be stacked to meet the large transport current because of the small critical current at present and the effect of stacking configuration is also investigated. In this paper, AC loss analysis results are presented for various HTS power cable configurations such as stacking directions. The results are compared with the experimental results of a model HTS power cable and the best configuration to minimize AC loss is suggested.</P>
Youngjun Choi,Dongmin Kim,Jeonwook Cho,Kideok Sim,Sungkyu Kim,김석호 한국초전도.저온공학회 2019 한국초전도저온공학회논문지 Vol.21 No.4
To reduce the fault current below the current capacity of a circuit breaker, researches on HTS (High Temperature Superconductor) power cables with fault current limiting (FCL) function are increasing. An FCL HTS power cable transports current with low a impedance during normal operation. Yet, it limits the fault current by an increased inductive or resistive impedance of conducting layer when quench occurs at the FCL HTS power cable by the large fault current. An inductive type FCL HTS power cable uses increased inductive impendence caused by leakage magnetic flux outside the cable core when the quench occurs at a shield layer losing the magnetic shielding effect. Therefore, it has an advantage of less resistive heating than resistive type FCL HTS power cable and temperature increase is suppressed. This paper describes an ideal circuit model for the FCL HTS power cable to investigate the effectiveness of increased inductive impedance when quench occurs at the shield layer. Then, FEM analysis is presented with a simplified model cable composed of various iron yokes to investigate the effect of the shape of yoke on the generation of the inductive impedance.
Current overshoot operation of a REBCO magnet to mitigate SCF
Lee, Changhyung,Hahn, Seungyong,Bang, Jeseok,Cho, Jeonwook,Kim, Seokho The Korean Society of Superconductivity and Cryoge 2018 한국초전도저온공학회논문지 Vol.20 No.4
Due to large in-field current carrying capacity and strong mechanical strength, a REBCO wire has been regarded as a viable high temperature superconductor (HTS) option for high field MRI and > 1 GHz (>23.5 T) NMR magnets. However, a REBCO magnet is well known to have an inherent problem of field inhomogeneity, so-called 'Screening Current induced magnetic Field (SCF)'. Recently, 'field shaking' and 'current overshoot operation' techniques have been successfully demonstrated to mitigate the SCF and enhance the field homogeneity by experiments. To investigate the effectiveness of current overshooting operation technique, a numerical simulation is conducted for a test REBCO magnet composed of a stack of double pancake coils using '2D edge-element magnetic field formulation' combined with 'domain homogenization' scheme. The simulation result demonstrates that an appropriate amount of current overshoot can negate the SCF. To verify the simulation results, current overshoot experiments are conducted for the REBCO magnet in liquid nitrogen. Experimental results also demonstrate the possible application of current overshoot technique to mitigate the SCF and enhance the field homogeneity.
Jae-Ho Kim,Minwon Park,Jeonwook Cho,Kideok Sim,Seokho Kim,In-Keun Yu IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3
<P>One of the most important issues in the design of a HTS power cable is the induced current between conducting and shield layers under fault condition. The current distribution of conducting and shield layers is changed due to the fault current. Conducting and shield layers are coupled magnetically. The analysis of current distribution in HTS power cable requires understanding of the magnetic coupling between the conducting and shield layers. In order to study the phenomenon mentioned above, a solenoid type of HTS power cable model which includes both conducting and shield layer is actually manufactured in this paper. The current distribution of conducting and shield layers is evaluated by real manufactured solenoid type of HTS power cable model. The results obtained through the experiment and analysis would provide important data for the design of HTS power cables and valid information for their installation in power system.</P>