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Yoo, Jaeun,Han, Young-Hee,Kim, Hey-Rim,Park, Byung-Jun,Yang, Seong-Eun,Kim, Heesun,Yu, Seung-Duck,Park, Kijun The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.2
In this study we investigated ac transport current losses in the face to face stack for the anti-parallel current flow, and compared the electromagnetic properties with those of the single SC tape as well as those of the same stack for the parallel current path. The gap between the SC tapes in the stack varied in order to verify the electromagnetic influence of the neighbors when current flows in opposite direction, and the model was implemented in the finite element method program by the commercial software, COMSOL Multiphysics 4.2a. Conclusively speaking, the loss was remarkably decreased for the anti-parallel current case, which is attributed the magnetic flux compensation between the SC layers due to the opposite direction of the current flows. As the gap between SC tapes was increased, the loss mitigation became less effective. Besides, the current density distribution is very flat cross the sample width for the narrower gap case, which is believed to be benefit for the power electric system. These results are all in good agreement with those predicted theoretically for an infinite bifilar stack.
Sangwon Han,Jaeun Ryu,Gihoon Kim,Jaeho Choi,Kunsoo Huh 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
As the autonomous driving expands to complex road environment, the importance of collision avoidance is emerging across industries and academia, and its application for passenger cars has been actively studied. Because the dynamic characteristics of low-floor buses are different from those of passenger cars, it is necessary to develop a corresponding collision avoidance and path tracking algorithms. In this paper, a novel Pure-Pursuit controller and collision avoidance trajectory planner considering vehicle stability for buses are proposed. First, in order to compensate for the shortcomings of the geometry-based Pure-Pursuit controller, yaw rate gain and yaw rate response analyzed from the actual vehicle data are considered to improve the stability of the bus. In addition, the Conditional Integration-Proportion Integral (CI-PI) controller is designed to reduce the effect of disturbances. Secondly, the trajectory planner is developed taking into account not only the surrounding object information, but also the dynamic limitation of the bus. A group of trajectory candidates including dynamic relation of the lateral motion is generated that satisfies path stability with pole-zero analysis. Then, an optimal trajectory is selected through the cost function which reflects the dynamic constraints. Finally, stability and performance of the proposed controller are verified through simulations and field tests.
Design of Post Metal Shields Through Electric Field Distribution Analysis for a 154-kV SFCL
Yoo, Jaeun,Shin, Woo-Ju,Han, Young-Hee,Lee, BangWook,Kim, Hey-Rim,Yang, Seong Eun,Kim, Heesun,Yu, Seung-Duck,Park, Kijun Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>Korea Electric Power Corporation has developed a 154-kV superconducting fault current limiter (SFCL). This report is a part of the design process of the SFCL, particularly for fixation of posts supporting the superconducting element on the cryostat wall side. For supporting the superconducting element, the use of a post insulator is inevitable; however, the post insulator and cryostat with liquid nitrogen <inline-formula> <TEX-math notation='LaTeX'><TEX>$(\mbox{L}\mbox{-}\mbox{N}_{2} ) $</TEX></tex-math></inline-formula> during operation of the SFCL form three junction points where electric field is intensified. In this study, we aim to design the metal shield in order to relax the electric field intensity at triple points (TPs through numerical analysis of electric field distribution. For the electric field distribution analysis, a commercial software based on the finite-element method was employed. Each design for the metal shield was checked whether it makes the electric field intensity at the TP sufficiently lower than dielectric strength in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> for 750-kV input and whether there is any electrically weak point on the metal. The designs of the metal shields were improved through four critical steps where thermal contraction, manufacture tolerance, and insulation distance in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> were considered. It was experimentally verified that there was no electric breakdown in <inline-formula> <TEX-math notation='LaTeX'><TEX>$\mbox{L}\mbox{-}\mbox{N}_{2} $</TEX></tex-math></inline-formula> between the metal shield and the fiber-reinforced plastic post insulator for the lightning impulse test and the ac breakdown voltage test according to the IEC 60137 standard.</P>
Development and Test of a Cooling System for a 154 kV Superconducting Fault Current Limiter
Kim, Heesun,Han, Young Hee,Yang, Seong-Eun,Yu, Seung-Duck,Park, Byung Jun,Park, Kijun,Yoo, Jaeun,Kim, Hye-Rim,In, Sehwan,Hong, Yong Joo,Yeom, Hankil Korea Electric Power Corporation 2015 KEPCO Journal on electric power and energy Vol.1 No.1
The superconducting fault current limiter (SFCL) is an electric power device that limits the fault current immediately in a power grid. Korea Electric Power Corporation (KEPCO) has been developing a 154 kV, 2 kA SFCL since 2011 to protect power grids from increasing fault current and improve the stability and quality of electric power. This SFCL adopts 2G YBCO wires and operates at 71 K and 5 bars. In this paper, a cooling system for the 154 kV SFCL and its cooling test results are reported. This cooling system uses a Stirling-type cooler to make sub-cooled liquid nitrogen ($LN_2$), which cools the superconductor modules of the SFCL. The $LN_2$ is circulated between the cooler and the cryostat that contains superconductor modules. The $LN_2$ also plays the role of a high voltage insulator between the modules and the cryostat, so the pressure was maintained at 5 bars for high insulation performance. After installation in a test site, the cooling characteristics of the system were tested. In this operation test, some important data were measured such as temperature distribution in $LN_2$, pressure change, performance of the heat exchanger, and cooling capacity of the total system. Consequently, the results indicate that the cooling system operates well as designed.
지역사회에서의 아동참여 활성화를 위한 실천 가이드라인 제안
문성호(Moon, Sung Ho),한지연(Han, Ji Yeon),노자은(Roh, Jaeun),노지혜(Noh, Ji Hye) 한국지역사회복지학회 2021 한국지역사회복지학 Vol.- No.76
본 연구의 목적은 지역사회에서의 아동참여 활성화를 위해 기본원칙 준수 방안, 실천 과정에 따른 핵심내용, 그리고 실천가의 역량을 중심으로 실천 가이드라인을 제안하는 것이다. 이러한 목적을 달성하기 위해 문헌분석, 설문조사, 델파이조사, FGI를 활용하였다. 설문조사 결과, 아동과 성인 모두 우리나라의 아동참여가 낮은 수준에 머물러 있고, 가정과 학교보다 사회에서 아동의 참여가 덜 보장된다고 인식하였다. 또한, 참여활동에 대한 정보 부족과 참여방법의 어려움도 한계로 나타났다. 델파이조사에서는 기획 및 개발, 실행, 모니터링 및 평가의 각 과정별로 포함되어야 할 주요 내용과 고려할 사항이 도출되었다. 특히, FGI 분석결과, 실천가가 퍼실리테이터로서 조력자 및 촉진자의 역할을 수행해야 한다는 점이 강조되었다. 이와 같은 결과를 종합적으로 반영하여 본 연구에서는 아동참여의 전 과정에서 9대 기본원칙의 준수 방안을 제안하였다. 그리고 아동참여의 과정별 핵심적인 내용과 필요한 역량을 바탕으로 실천가가 활용할 수 있는 가이드라인을 구체적으로 제시하였다. 실천 가이드라인은 향후 지역단위에서 아동참여 사업을 수행하는 실천가가 전문성을 확보하고 아동참여를 활성화하는데 광범위하게 활용될 것으로 기대된다. The purpose of this study was to suggest practical guidelines focusing on compliance with basic principles, the main contents of each process, and the competence of practitioners in local community. For this, the literature review, the self-report survey, the Delphi survey and the focus group interview were conducted. The results confirm that both children and adults perceived child participation in Korea as a low level and recognized that it is less guaranteed in society than at home and at school. In addition, the finding shows that it is difficult to participate due to the lack of information and not knowing how to participate, suggesting that the efforts to promote child participation in consideration of these points were necessary. Through the Delphi survey, the contents and considerations for practitioners were derived at each process of the planning and development, implementation, monitorization and evaluation process. In particular, according to the FGI analysis results, the role of practitioners as facilitator was especially emphasized. Incorporating these findings, this study proposed a plan to comply with the nine basic principles throughout the entire process of child participation. Also, the guidelines for practical application based on the main contents and necessary competencies for each child participation process were presented. These guidelines can be widely used to secure expertise and activate child participation in the future.
Development and Grid Operation of Superconducting Fault Current Limiters in KEPCO
Hye-Rim Kim,Seong-Eun Yang,Seung-Duck Yu,Heesun Kim,Byung-Jun Park,Young-Hee Han,Kijun Park,Jaeun Yu Institute of Electrical and Electronics Engineers 2014 IEEE transactions on applied superconductivity Vol.24 No.5
<P>Development and grid operation of superconducting fault current limiters (SFCLs) have been carried out in Korea Electric Power Corporation (KEPCO), as a possible measure to handle the increasing fault current in Korea. A 22.9 kV SFCL has been successfully operated unmanned on a distribution line of Icheon Substation. It has been very stable throughout the operation of more than 1.5 year. Temperatures and level of liquid nitrogen that cools the superconducting element have been maintained constant. Performance of the SFCL maintained the initial level. The SFCL was modified so that it can limit the fault current within the first half cycle. A short-circuit test on the modified SFCL showed it started limiting the current within 2 ms. In parallel, a 154 kV SFCL has been also developed. A superconducting element was designed and fabricated. A short-circuit test was performed on a superconducting unit module, and showed that the module limited the current effectively. The element is planned to be integrated into a single-phase 154 kV SFCL together with the cooling system and other components, and tested soon.</P>