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Analysis of Wave Propagation of HTS Cables for Compensation of Thermal Loss on Connectors
Yeong Ho Lee,Su Sik Bang,Gu-Young Kwon,Geon Seok Lee,Gyeong Hwan Ji,Song-Ho Sohn,Kijun Park,Yong-June Shin Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4
<P>High temperature superconducting (HTS) cable operates under relatively low temperature and its unique operating condition brings new challenges in the area of maintenance and diagnostics of the cable. As an example, a temperature difference occurs on connection systems between instruments on room temperature and HTS cables which eventually leads to thermal energy loss. The thermal energy loss affects frequency characteristics of the cable which are critical aspects for simulation and maintenance of the HTS cable systems. In this paper, an attempt to reduce thermal loss is introduced with an improved connector applying a Peltier module. The performance of the designed connector is verified with analysis of electromagnetic wave propagation properties of HTS tapes and a cable. The investigation of S -parameters and the proposed connection method is expected to be further applied to various HTS systems in future.</P>
Lee, Geon Seok,Kwon, Gu-Young,Bang, Su Sik,Lee, Yeong Ho,Sohn, Song-Ho,Park, Kijun,Shin, Yong-June Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4
<P>A high-temperature superconducting (HTS) cable system with the 22.9 kV, 50 MVA, and 410 m length is installed and operated at 154 kV Icheon substation of Korea Electric Power Corporation (KEPCO). Unfortunately, it is a difficult task to diagnose and monitor electrical and thermal characteristics of the HTS cable system in a real-time manner. In order to protect operational failures of grid-connected HTS cable systems, this paper proposes time-frequency domain reflectometry (TFDR) and analysis techniques, i.e., time-frequency cross correlation and instantaneous frequency estimation. To verify the performance of the proposed method, the temperature is changed via the cryogenic refrigeration system and the status of the grid-connected HTS cable is monitored via TFDR in a real-time manner.</P>
Geon Seok Lee,Gu-Young Kwon,Su Sik Bang,Yeong Ho Lee,Seung Jin Chang,Song-Ho Sohn,Kijun Park,Yong-June Shin Institute of Electrical and Electronics Engineers 2016 IEEE transactions on applied superconductivity Vol.26 No.4
<P>For the electrical insulation of a high-temperature superconducting (HTS) cable, wrapped polypropylene laminated paper (PPLP) tape is typically used. Unfortunately, it is possible that unexpected faults at insulation layers will be present in the cables as a result of either a problematic manufacturing process or an incomplete installation procedure. In order to protect against operational failures of grid-connected HTS cable systems, this paper proposes a nondestructive diagnostic technique, i.e., time-frequency domain reflectometry (TFDR), and focuses on the characteristic of HTS cable that caused the local insulation defects. To verify the performance of the proposed method, detection and localization of local insulation failure via TFDR are compared with traditional time-domain reflectometry. The experiments are conducted at room temperature and under liquid nitrogen in order to check the efficacy of the proposed method in varieties of HTS cable's conditions. In addition, to improve the accuracy of detection and localization, a methodology to analyze incident signals, which are composed of upchirp and downchirp signals, is presented.</P>
Lee, Geon Seok,Ji, Gyeong Hwan,Kwon, Gu-Young,Bang, Su Sik,Lee, Yeong Ho,Sohn, Song-Ho,Park, Kijun,Shin, Yong-June Institute of Electrical and Electronics Engineers 2018 IEEE transactions on applied superconductivity Vol.28 No.4
<P>In this paper, we propose a new time-frequency based analysis method that monitors the state of the high temperature superconducting (HTS) cable system in a real-time manner and detects the current imbalance of HTS cable system. The new time-frequency-based method utilizes the cross Wigner–Ville distribution to analyze the time-frequency localized phase difference of the reflected signal, which varies depending on the insulation characteristics of the HTS cable system. Also, a real-world AC 22.9 kV 50 MVA HTS cable system and a current source are used to validate the performance of the new monitoring method in order to detect current imbalance phenomenon.</P>
Intae Whoang,Chinkwan Cho,Jin Hee Hong,Dong Hee Son,Byung Yoon Lim,Jin Pyung Kim,Kijun Bang 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.5
At SK hynix Wafer Level Package (WLPKG) line, there are plenty of measuring and inspection steps to ensure the quality of High Bandwidth Memory (HBM). Although most of the measuring and inspection steps are handled automatically, some of the steps still need confirmation from line operators with their naked eye and skills. Since the operators' skills are different, sometimes it causes human errors, and these risks become chronic problems for the company. To solve this problem, Package & Test (P&T) group at SK hynix has been steadily promoting the inspection automation system using deep learning. However, deep learning has the disadvantage of not providing interpretation information, such as which area is actually defective in the target image and its shape for the ‘Excellent’ result of outputs. In this paper, we will introduce cases in which defect patterns are automatically extracted from inspection images taken during the SiN / SiO2 film deposition process by using two deep-learning segmentation models. The performance of the technology to be introduced was demonstrated by comparing the Mean IoU value between the extracted defect image and label mask. Through the proposed technology, we intend to contribute to unmanned inspection verification tasks in the future and accelerate the realization of Industry 4.0.