• Fire Science and Engineering
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• v.19 no.2 s.58
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• pp.63-68
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• 2005

In this study, the arc dispersion properties were analyzed according to switching of high sensitive type Residual Current Protective Device(RCD) contacts. Arc dispersion and ignition process was taken by high speed imaging system(HSIS). In this experiment, electric lamps(60 W) and heaters(950 W) were connected in parallel as loads. In case of normal RCD, it took about 2.3(ms) from the generation of arc to the extinction of uc. When arc was dispersed in normal RCD, it did not ignite cotton. Whereas, in case of RCD deteriorated by NaCl solution, the range of arc dispersion was wider and the arc lasted for 3.3[ms] more compared to normal RCD. And the arc ignited cotton. In order to prevent accidents caused by RCD, we should be careful of environmental factors, such as dust and humidity, and the parts of RCD should be used as incombustible materials.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.191_192
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• 2009

지락고장 발생 시 재폐로 동작을 위하여 필요한 조건은 이차아크의 소호 여부이다. 본 논문에서는 1선 지락고장 발생 시 고장상의 전압 파형에 포함되는 짝수 고조파가 이차아크 소호 판단에 유용한지 분석해 보았다. 모의실험은 765kV 모의계통에 아크 지락고장 모델을 적용하여, 다양한 고장 조건하에 이루어졌다.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1904-1906
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• 1996

Transient voltage distribution tests are carried out to evaluate effects of a high frequency oscillating voltage generated in a superconducting magnet as a result of the arc discharge extinction. Especially, the effects of temperature and conduction state of the magnet conductor on surge behavior are carefully investigated. Based on the results of simulation tests, it is shown that internal voltage waveforms are influenced by its transmission along the superconducting wire and reflection at the terminal and that attenuation process of the waveforms depends considerably on the conductor resistance which decreases with lowering the temperature.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2069-2072
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• 1999

The extended 765 kV system may have severe electrical transients according to the interconnection of transmission lines and have long transmission line over 250 km. So we need to analyze the transient phenomena to confirm the insulation coordination which is designed for 765 kV project step I. In particular, this paper shows the analysis results of secondary arc extinction by HSGS (high speed ground switch) application. The EMTP/MODELS were used to simulation study of secondary arc phenomena. We had confirmed the TRV(transient recovery voltage) and rated current of HSGS which will be used in the KEPCO 765 kV system.

• Korean Journal of Microbiology
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• v.48 no.1
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• pp.42-47
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• 2012

Hydrothermal vents (HTV) provide special environments for evolution of lives independent on solar energy. HTV samples were gained from Tofua arc trench in Tonga, South Pacific. We investigated archaeal diversity enriched using combinations of various electron donors (yeast extract and $H_2$) and electron acceptors [Iron (III), elemental sulfur ($S^0$) and nitrate. PCR amplification was performed to detect archaeal 16S rRNA genes after the cultures were incubated $65^{\circ}C$ and $80^{\circ}C$ for 2 weeks. The cultures showing archaeal growth were transferred using the dilution-to-extinction method. 16S rRNA gene PCR-Denaturing Gradient Gel Electrophoresis was used to identify the enriched archaea in the highest dilutions where archaeal growth was observed. Most of cultured archaea belonged to genus of Thermococcus (T. alcaliphilius, T. litoralis, T. celer, T. barossii, T. thoreducens, T. coalescens) with 98-99% 16S rRNA gene similarities. Interestingly, archaeal growth was observed in the cultures with Iron (III) and nitrate as an electron acceptor. It was supposed that archaea might use the elemental sulfur generated from oxidation of the reducing agent, sulfide. To cultivate diverse archaea excluding Thermococcus, it would be required to use other reducing agents instead of sulfide.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.1
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• pp.73-79
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• 2013

Crystalline silicon solar cells with $SiN_x/SiN_x$ and $SiN_x/SiO_x$ double layer anti-reflection coatings(ARC) were studied in this paper. Optimizing passivation effect and optical properties of $SiN_x$ and $SiO_x$ layer deposited by PECVD was performed prior to double layer application. When the refractive index (n) of silicon nitride was varied in range of 1.9~2.3, silicon wafer deposited with silicon nitride layer of 80 nm thickness and n= 2.2 showed the effective lifetime of $1,370{\mu}m$. Silicon nitride with n= 1.9 had the smallest extinction coefficient among these conditions. Silicon oxide layer with 110 nm thickness and n= 1.46 showed the extinction coefficient spectrum near to zero in the 300~1,100 nm region, similar to silicon nitride with n= 1.9. Thus silicon nitride with n= 1.9 and silicon oxide with n= 1.46 would be proper as the upper ARC layer with low extinction coefficient, and silicon nitride with n=2.2 as the lower layer with good passivation effect. As a result, the double layer AR coated silicon wafer showed lower surface reflection and so more light absorption, compared with $SiN_x$ single layer. With the completed solar cell with $SiN_x/SiN_x$ of n= 2.2/1.9 and $SiN_x/SiO_x$ of n= 2.2/1.46, the electrical characteristics was improved as ${\Delta}V_{oc}$= 3.7 mV, ${\Delta}_{sc}=0.11mA/cm^2$ and ${\Delta}V_{oc}$=5.2 mV, ${\Delta}J_{sc}=0.23mA/cm^2$, respectively. It led to the efficiency improvement as 0.1% and 0.23%.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.88.2-88.2
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• 2011

The far-ultraviolet (FUV) continuum and spectral images of C IV and H2 emission lines for the region of Orion-Eridanus Superbubble (OES) are hereby presented and compared with the maps obtained in other wavelengths. While the region shows complex structures, consisting of hot gases and cold dust, a close examination reveals that the FUV emission in this region can be understood reasonably as the result of their interactions. We confirm the origin of most diffuse FUV continuum to be starlight scattered by dust, but we also find that the ionized gas also contributes 50-70% of the total FUV intensity in the regions of H_alpha arcs. We note the bright diffuse FUV continuum in the eastern part of the northern dust-rich region, and attribute it to the bright early-type stars more abundant in this region than in the west as the amount of dust itself does not seem to be much different across 'arc A' that separates the two regions. In addition, two P Cygni-type stars are identified in this eastern region and their peculiar spectral profiles around the C IV emission line are anifested in the scattered diffuse spectrum. Besides this, the C IV emission is generally enhanced at the boundaries of the hot X-ray cavities where thin dust regions are located, confirming the thermal interface nature of the origin of this cooling emission line. The morphology of the H2 emission shows a general correlation with dust extinction features but its intensity peaks are rather located in thin dust areas, off the peak dust regions. Furthermore, H2 emission is seen to be weak in the arc A region though the arc passes through the center of the dust-rich area. Hence, the H2 emission and dust features, together with those of X-ray and ion lines emissions, show stratified structure of arc A quite well, again confirming its thermal interface nature.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1347-1352
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• 2010

This paper presents a new adaptive single-phase auto reclosure (SPAR) algorithm to discriminate between a permanent fault and a transient fault and to minimize a protection dead time. The algorithm precisely detects the extinction of the secondary arc, based on THD's profiles on the faulted phase voltage waveform. The EMTP/ATPDraw program was used to simulate the single phase grounding fault for evaluating the proposed algorithm. And the simulation results show that the proposed algorithm is performing well.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2231_2232
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• 2009

기술의 발전과 고도의 산업화로 인해 전력소비자들이 이전에 비해 더욱 고품질의 전력공급을 원하게 되었고 이에 부합하여 전력공급 신뢰도 향상과 전력품질이 현재 중요한 연구과제로 대두되어 왔다. 계통의 특성에 따라 다르지만, 대략 송전 계통에서 발생하는 전체 고장 의 75~90%는 일시고장이고 이러한 일시고장을 제거하기 위한 재폐로 과정을 수행시 계통의 신뢰도 및 안정도 향상을 위하여 적응적으로 무전압 시간을 조절하는 것이 필요하다. 본 논문에서는 아크고장에 따른 무전압시간을 최소화시켜주는 HSGS(High Speed Grounding Switches)의 기능에 대해서 검토하고, EMTP로 모델링된 765kV 송전계통에 일시 고장을 발생시켜 HSGS의 투입여부에 따른, 1선 및 2선 지락사고에서의 2차아크 소호특성을 분석하였다.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.166-168
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• 2002

This paper presents a new numerical algorithm suitable for defining recloser reclaims time and blocking automatic reclosing during permanent faults on overhead lines. It is based on terminal voltage input data processing. The decision if it is safe or not to reclose is determined from the voltage signal of faulted and tripped line phase using Total Harmonic Distortion factor calculated by Discrete Fourier Transform. The algorithm was successfully tested using signals recorded on the real power system. The tests demonstrate the ability of presented algorithm to determine the secondary arc extinction time and to block unsuccessful automatic reclosing of HV lines with permanent fault.