• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.2219_2220
• /
• 2009

The characteristics of the Superconducting Magnetic Energy Storage (SMES) system are faster response, longer life time, more economical, and environment friendly than other Uninterruptible Power Supply (UPS) using battery. Fast charge and discharge time of SMES system can provide powerful performance of improving power quality in the grid. In order to demonstrate the effectiveness of SMES, the authors make a 10kJ SMES system for connection with RTDS (Real Time Digital Simulator). Because the characteristics of superconducting magnet are very important in SMES system, the necessary items such as thermal characteristic, mechanical stress and protection circuit should be considered. In this paper, the authors experimented thermal characteristics of the 10kJ SMES system. The experiment was accomplished using a simulation coils made of aluminium. It has same dimension of the 10kJ class HTS SMES coil. The coil was cooled with GM (Gifford -McMahon) cryocooler through the OFHC (Oxgen Free High thermal Conductivity) conduction bar. The test results of cool down and heat loads characteristics of the simulation coils are described in detail.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.1118-1119
• /
• 2015

본 논문에서는 2세대 고온초전도 선재를 이용하여 영구전류 모드 운전이 가능한 상전도 접합부가 없는 초전도 모델 코일을 제작하고, 영구전류 인가를 위해 플럭스 펌프형태의 소규모 초전도 전원장치를 제작 77 K 운전 온도에서 영구전류 충전 시험을 진행하였다. 플럭스 펌프는 영구자석을 이용한 회전 자속형으로 제작되었고, 2세대 고온초전도 선재를 이용한 영구전류 마그넷의 적용에 필요한 초전도 전원장치의 기초 특성연구를 수행하였다.

• Progress in Superconductivity and Cryogenics
• /
• v.24 no.4
• /
• pp.46-49
• /
• 2022

Since CORC^®(Conductor on Round Core) is made of multiple strands of a superconducting tape to conduct a large current, it is difficult to measure the critical current due to the limitation of a capacity of a power supply. The magnetization loss of a superconductor is dependent on the full penetration field. The full penetration field corresponds to the inflection point of the magnetization loss graph with respect to the external magnetic field. We propose a method to predict the critical current of CORC^® indirectly. This method uses the measured magnetization losses of various CORC^® samples for the prediction of the critical currents.

• Progress in Superconductivity
• /
• v.8 no.1
• /
• pp.81-86
• /
• 2006

We investigated resistance development in $Au/YBa_2Cu_3O_7(YBCO)$ thin film meander lines during high-power faults. The meander lines were fabricated by patterning 300 nm thick YBCO films coated with 200 nm thick gold layers into meander lines. A gold film grown on the back side of the substrate was also patterned into a meander line. The front meander line was connected to a high-power fault-test circuit and the back line to a DC power supply. Resistance of both lines was measured during the fault. They were immersed in liquid nitrogen during the experiment. Behavior of the resistance development prior to quench completion could be understood better by comparing resistance of the front meander lines with that of the back. Quench completion point could be determined clearly. Resistance and temperature at the quench completion point were not affected by applied field strength. The experimental results were analyzed quantitatively with the concept of heat transfer within the meander lines/substrate and to the surrounding liquid nitrogen. In analysis, the fault period was divided into three regions: flux-flow region, region prior to quench completion, and region after quench completion. Resistance was calculated for each region, reflecting the observation for quench completion. The calculated resistance in three regions was joined seamlessly and agreed well with data.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1975-1977
• /
• 2000

In this study, a relationship between AC discharge progress and the radiated electromagnetic waves were investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum of the radiated electromagnetic waves was measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progress in nonuniform electric field depend on AC power supply. From this results, it was confirmed that when partial discharge was produced in liquid nitrogen, the signal of partial discharge was detected by frequency spectrum of the radiated electromagnetic waves. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on superconducting and cryogenic power equipments.

• Progress in Superconductivity and Cryogenics
• /
• v.19 no.2
• /
• pp.38-43
• /
• 2017

The role of current lead in high-temperature superconducting synchronous machine (HTSSM) is to function as a power supply by connecting the power supply unit at room temperature with the HTS field coils at cryogenic temperature. Such physical and electrical connection causes conduction and Joule-heating losses, which are major thermal losses of HTSSM rotors. To ensure definite stability and economic feasibility of HTS field coils, quickly and smoothly cooling down the current lead is a key design technology. Therefore, in this paper, we introduce a novel concept of a cooling anchor to enhance the cooling performance of a metal current lead. The technical concept of this technology is the simultaneously chilling and supporting the current lead. First, the structure of the current lead and cooling anchor were conceptually designed for field coils for a 1.5 MW-class HTSSM. Then, the effect of this installation on the thermal characteristics of HTS coils was investigated by 3D finite element analysis.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.1
• /
• pp.143-148
• /
• 2013

When the fault occurs in power system, the fault-current exceeds breaking capacity of the circuit breaker. So, reliablity of the power system is decreased sharply. Superconducting fault-current limiter (SFCL) is operated without impedance in normal state. The fault-current is limited by its impedance during the fault condition. However, the SFCL has several weak points such as huge size, high-price, liquid-nitrogen operation for the real power system. In this paper, We suggested the high-speed interrupter to limit the fault-current in case of the single line-to-ground fault. In addition, we compared the high-speed interrupter with the SFCL to ensure the operation reliability. The proposed interrupter detected the fault-current through the CT, and the power was supplied by operation of the SCR control system. In this experiment, the power of high-speed interrupter was applied after the 4.8[msec] from fault instant. The on-off operation of the interrupter was started after half-cycle from the fault. The fault-current was flowed into the impedance element by the switching operation of the high-speed interrupter. So, the fault current was limited within one cycle, and then it didnt exceed the capacity of a circuit breaker. We confirmed that there was slight difference between the SFCL with high-speed interrupter in terms of limiting-time of the fault-current and switching speed of the SCR. The high-speed interrupter was considered to be more efficient than the SFCL in size, cost or reliability.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.11
• /
• pp.5879-5884
• /
• 2013

With the rapid industrialization and economical development, the electricity demands of the industrial facilities and densely populated large cities are continuing to increase in Korea. The increase in the power consumption requires the extension of power facilities, but it is difficult to secure spaces for equipment installation in the limited space of urban areas. In addition, the 154 kV or 345 kV transmission systems in Korea has a short transmission distance, and are connected to one another in network structures that ensure the high reliability and stability of power supply. This structure reduces the impedance during the fault in power system, and increases the magnitude of in the short circuit fault current. The superconducting fault current limiter (SFCL) was devised to effectively address these existing problems. The SFCL is a new-concept eco-friendly protective device that ensures fast operation and recovery time for the fault current and does not need additional fault detection devices. Therefore, many studies are being conducted around the world. In this paper, based on the wiring method the initial fault current characteristics, current limiting characteristics, according to the incident angle and the change in inductance current limiting characteristics were analyzed in a multifaceted methods.

• Journal of the Korean Vacuum Society
• /
• v.17 no.1
• /
• pp.58-66
• /
• 2008

The KSTAR Current Lead System(CLS) with network based real-time distributed control system is implemented using an EPICS as a middle-ware software. The current lead system transfers current from magnet power supplies to superconducting magnet system and simultaneously supply the coolant to maintain superconducting state. To control the CLS at main control room an EPICS IOC server is installed in local control area. Using this server, it is able to be controlled and monitored the system in main control room through operator interface(OPI) which uses "caget" to read status and "caput" to write command with a unique name called PV. The EPICS IOC is developed using "ether-ip" driver to communicate with PLC. Also we achieved satisfactory results in operation and stability aspects from a long period commissioning test.

• Nuclear Engineering and Technology
• /
• v.36 no.4
• /
• pp.357-363
• /
• 2004

A prototype long pulse ion source was developed, and the beam extraction experiments of the ion source were carried out at the Neutral Beam Test Stand (NBTS) of the Korea Superconducting Tokamak Advanced Research (KSTAR). The ion source consists of a magnetic bucket plasma generator, with multi-pole cusp fields, and a set of tetrode accelerators with circular apertures. Design requirements for the ion source were a 120kV/65A deuterium beam and a 300 s pulse length. Arc discharges of the plasma generator were controlled by using the emission-limited mode, in turn controlled by the applied heating voltage of the cathode filaments. Stable and efficient arc plasmas with a maximum arc power of 100 kW were produced using the constant power mode operation of an arc power supply. A maximum ion density of $8.3{\times}10^{11}\;cm^{-3}$ was obtained by using electrostatic probes, and an optimum arc efficiency of 0.46 A/kW was estimated. The accelerating and decelerating voltages were applied repeatedly, using the re-triggering mode operation of the high voltage switches during a beam pulse, when beam disruptions occurred. The decelerating voltage was always applied prior to the accelerating voltage, to suppress effectively the back-streaming electrons produced at the time of an initial beam formation, by the pre-programmed fast-switch control system. A maximum beam power of 0.9 MW (i.e. $70\;kV{\times}12.5\;A$) with hydrogen was measured for a pulse duration of 0.8 s. Optimum beam perveance, deduced from the ratio of the gradient grid current to the total beam current, was $0.7\;{\mu}perv$. Stable beams for a long pulse duration of $5{\sim}10\;s$ were tested at low accelerating voltages.