• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.31-33
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• 2003

Power system restoration following a partial or complete blackout starts with energizing of primary transmission lines. Because system changed rapidly during early restoration process, transformer energization and load pickup is executed to maintain the power system stability. However unexpected problem such as harmonic overvoltage may be arisen during energizing transformer. The reason of harmonic overvoltage is known as transformer saturation and magnetizing in-rush current and so on, but it is difficult to estimate the condition of occurrence. This paper describes the analysis of the harmonic overvoltage while unloaded transformer is energized using PSCAD/EMTDC.

• Transactions on Electrical and Electronic Materials
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• v.15 no.1
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• pp.12-15
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• 2014

At the moment of transformer energization by the supply voltage, a high current called transient inrush current, which may rise to ten times the transformer full load current, could be drawn by the primary winding. This paper discusses a microcontroller circuit with the intention of controlling and limiting the inrush current for a transformer, by the method of ramping up the supply voltage feeding to the transformer primary. Simulations and the experimental results show a significant reduction of inrush current, when the ramping up voltage is applied to the three-phase transformer load. The inrush current could be almost eliminated if the correct switching step rate is chosen.

• Proceedings of the KIEE Conference
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• summer
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• pp.1242-1244
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• 2004

As rapid growth of energy demand in line with modem society's industrialization led to environmental pollution by fossil fuels, there are more and more interest and international research on energization of water, which is clean energy and comprising $70\%$ of earth. In offshore countries, the water is commercially used already and water has very attractive characteristics in terms of economy and efficiency compared to the existing gas welder. In this paper, the result from operating characteristic improvement of Gas Generator and Current-Controlled converter is to be considered into design in electrode, source and controller, standized into level of whole system design base.

• Journal of the Korean Institute of Rural Architecture
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• v.18 no.1
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• pp.67-74
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• 2016

Establishing a renewal plan and practical use of Jungam temple, which exists natural monuments, including national treasures and Gangwondo cultural materials, at Jungseon is as important as anything else. To discuss the renewal plan and the practical use of Jungam temple, this thesis is composed with the next series of processes. First, this thesis presents examining a relationship between Jajang, who was a buddhist monk and caused a departure point of foundation of the temple, and Jungam temple is necessary; thus, the relationship of his architectural consciousness and Jungam temple was showed in this thesis. Second, this thesis demonstrates present conditions for extant facilities and features of the space structure for Jungam temple to look into architectural characteristics of Jungam temple. Third, this thesis shows preservation of Jungam temple because this temple is the historic cultural resource; in addition, this thesis explains restoring of lost elements for points, repairing shipments regarding the whole area of preservation targets, expansion of the area nearby historic cultural resources to make plans for maintaining Jungam temple. Finally, this thesis concludes the final result of Jungam temple to work towards becoming the contemporarily historic cultural resource by designating Jungam temple as the historic site and suggesting energization by public participation and experience programs to continuously manage Jungam temple.

• BMB Reports
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• v.38 no.4
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• pp.468-473
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• 2005

The energetics of nitrate uptake by intact cells of the halotolerant cyanobacterium Aphanothece halophytica were investigated. Nitrate uptake was inhibited by various protonophores suggesting the coupling of nitrate uptake to the proton motive force. An artificially-generated pH gradient across the membrane (${\Delta}pH$) caused an increase of nitrate uptake. In contrast, the suppression of ${\Delta}pH$ resulted in a decrease of nitrate uptake. The increase of external pH also resulted in an enhancement of nitrate uptake. The generation of the electrical potential across the membrane ($\Delta\psi$) resulted in no elevation of the rate of nitrate uptake. On the other hand, the valinomycin-mediated dissipation of $\Delta\psi$ caused no depression of the rate of nitrate uptake. Thus, it is unlikely that $\Delta\psi$ participated in the energization of the uptake of nitrate. However, $Na^+$-gradient across the membrane was suggested to play a role in nitrate uptake since monensin which collapses $Na^+$-gradient strongly inhibited nitrate uptake. Exogenously added glucose and lactate stimulated nitrate uptake in the starved cells. N, N'-dicyclohexylcarbodiimide, an inhibitor of ATPase, could also inhibit nitrate uptake suggesting that ATP hydrolysis was required for nitrate uptake. All these results indicate that nitrate uptake in A. halophytica is ATP-dependent, driven by ${\Delta}pH$ and $Na^+$-gradient.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.873-878
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• 2009

When the transmission lines are initially energized for power system restoration, the power system suffers the various overvoltages that can be classified as steady-state, transient, and dynamic overvoltages. For the accurate analyses of these overvoltages, many researchers utilize different simulation tools such as Power System Simulator for Engineering(PSS/E). Although PSS/E provides good solutions in steady-state and dynamic overvoltages, it is not suitable for transient overvoltages. Therefore, transient overvoltages are simulated by using Electro-Magnetic Transients Program(EMTP) developed for the analysis of transients in the power system. Recently, EMTP can be also used to simulate dynamic behavior of the system. In order to analyze the transient overvoltages with steady-state and dynamic overvoltages, the authors adopt EMTP as the simulation tool for the analysis of overvoltages. This paper presents the simulation results for the analyses of various overvoltages, and the possibility of EMTP to be used for these types of analyses.

• Journal of Power Electronics
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• v.5 no.4
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• pp.305-311
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• 2005

Throughout the world, studies on the water energization are currently under way. Of those, Brown gas, which is generated through the electrolyzation of water and is a mixed gas of the constant volume of 2 parts hydrogen to 1 part oxygen, has better characteristics in terms of economy, energy efficiency, and environmental affinity than those of acetylene gas and LPG (Liquefied Petroleum Gas) used for existing welding machines. This paper analyzes the characteristics of Brown gas and presents methods for increasing the generating efficiency of Brown gas by designing a power supply to deliver power to a water-electrolytic cell and designing a cylindrical electrode to improve the efficiency of the electrolyzer needed for water electrolyzation. Based on the above the methods, a welding machine using Brown gas is developed. And the generation efficiency of Brown gas is measured tinder different conditions (duty ratio, frequency and amplitude) of supplied power.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.82-85
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• 2004

EPDM 봉인물질을 가진 SOV의 작동실패 사례 및 원인을 분석해보면 많은 SOV 고장(SOV failures)은 결국 EPDM 봉인물질이 원인인 것으로 나타났다. SOV 고장은 SOV가 그것의 설계 범위를 초과하는 주위 온도(ambient temperature)에 노출되어 있었기 때문에 발생되었다. 그러한 SOV 고장은 증기누설, 주위 온도의 부정확한 평가 등의 원인에 의해 발생되었다. 또한 SOV 고장은 연속적인 coil의 여기시 발생하는 가열(heatup from energization)로 인해 수명이 단축되는 영향이 서비스 수명 기간에 적절하게 포함되지 않았기 때문에 발생되었다 많은 발전소 운용자는 이러한 사실을 알고 있지 못하였으며 결과적으로 서비스 수명 기간이 과도 예측되는 결과가 초래되었다 SOV의 또 다른 연성(Soft) 봉인물질로, 열저항 특성이 EPDM에 비해 약 $50^{\circ}C$ 정도 우수한 Viton 봉인물질에 대한 특성이 제시되었다. 더불어 현재 많은 국외 솔레노이드구동밸브 전문 생산업체들이 Viton 재료를 옵션으로 채택하고 있는 추세이다. 그러나 고온주변에서 지속적으로 노출되어 있는 환경에서 Viton이 EPDM의 문제점을 어느 정도 해결할 수 있는 지의 여부는 현재 결론 내리기 어려울 것으로 판단되며, 향후 이를 채택한 SOV의 운전경험을 계속 주시할 필요가 있을 것으로 판단된다.

• Proceedings of the KIEE Conference
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• summer
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• pp.48-50
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• 2004

The energization of high voltage transmission lines and transformers, that is an inevitable process in most countries as the first restorative action for wide-area blackout, may induce overvoltages such as sustained overvoltage, transient overvoltage and harmonic resonant overvoltage. And these may cause damages to power system equipments or failure of surge arresters. The harmonic resonant overvoltage originates in switching operations and nonlinear characteristics of equipments. Actually it is difficult to predict the occurrence of harmonic overvoltage, since they result from nonlinear characteristics of transformers and other equipments. This paper describes the analysis of domestic primary restorative transmission system using PSCAD/EMTDC. The harmonic resonance is verified and the solution to prevent harmonic resonance is proposed in this paper. As a result, the PSCAD/EMTBC simulation showed slightly conflictive results that had been presented by IEEE Power System Restoration Working Group report.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.49.1-49.1
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• 2019

Giant radio relics in the outskirts of galaxy clusters have been observed and they are interpreted as synchrotron emission from relativistic electrons accelerated via diffusive shock acceleration (DSA) in weak shocks of Ms < 3.0. In the DSA theory, the particle momentum should be greater than a few times the momentum of thermal protons to cross the shock transition and participate in the Fermi acceleration process. In the equilibrium, the momentum of thermal electrons is much smaller than the momentum of thermal protons, so electrons need to be pre-accelerated before they can go through DSA. To investigate such electron injection process, we study the electron pre-acceleration in weak quasi-perpendicular shocks (Ms = 2.0 - 3.0) in an ICM plasma (kT = 8.6 keV, beta = 100) through 2D particle-in-cell simulations. It is known that in quasi-perpendicular shocks, a substantial fraction of electrons could be reflected upstream, gain energy via shock drift acceleration (SDA), and generate oblique waves via the electron firehose instability (EFI), leading the energization of electrons through wave-particle interactions. We find that such kinetic processes are effective only in supercritical shocks above a critical Mach number, $Ms{\ast}{\sim}2.3$. In addition, even in shocks with Ms > 2.3, energized electrons may not reach high energies to be injected to DSA, because the oblique EFI alone fails to generate long-wavelength waves. Our results should have implications for the origin and nature of radio relics.