• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1403-1406
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• 2002

Environmental impact of human activities has become a great concern in most of the countries world-wide, and for years. It has recently focused on potential climate changes due to the increase of green house gases content in the atmosphere. One of these gases is $SF_6$, which is an essential material in electrical applications having excellent dielectric and arc-quenching properties. Though the actual contribution of $SF_6$ to global warming is negligible at present, the control of $SF_6$ emissions seems to be nevertheless imperative. Actually, it is listed in the Kyoto protocol that emissions should not only be duly reported but also the electrical industry which is now the major user of this gas must be able to show that it is possible to use this gas and at the same time preserve the environment. For the development of environmentally-benign electric power equipment and systems, novel gases or gas mixtures are strongly required as the alternatives of $SF_6$ gas. Until now, most research work is focused on the $SF_6/N_2$ mixed gas which is suitable for application in the electrical apparatus with slightly non-uniform fields. Recently, $SF_6/CO_2$ mixed gas also is expected to be promising as a $SF_6$ alternative, especially in highly non-uniform fields and in a gas-impregnated film insulation system. Including these results, the author reviews the research trend or reducing the environmental impact of $SF_6$ gas in this paper.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.695-697
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• 2009

지구온난화로 인한 기후변화 등의 문제점들이 국제적인 이슈화되면서 온실가스의 효과적인 처리에 많은 관심이 집중되고 있다. 절연제로 주로 사용되고 있는 $SF_6$는 이산화탄소의 23,900배의 지구온난화지수를 가지는 온실가스이다. 본 연구에서는 이 물질의 효과적인 분리/회수를 위하여 가스 하이드레이트 형성을 이용한 방법을 제안하였다. 하이드레이트 형성법을 이용할 경우 공정이 단순하고 저압에서 분리가 가능하므로 타 분리공정과의 경쟁이 가능할 것으로 예상된다. 본 실험은 275-290 K의 온도범위와 3 - 30 bar의 압력범위에서 질소 + $SF_6$ (10, 30, 50, 70%)의 혼합기체를 사용하여 각 조성에 따른 하이드레이트(H)-물($L_W$)-기상(V)의 3상 평형점을 측정하였다. 또한, 고체의 하이드레이트 내부에 포집된 혼합기체의 조성과 포집되지 않은 기상의 조성을 GC를 이용하여 분석함으로써 하이드레이트 형성을 이용한 공정에서의 기체분리효율을 파악할 수 있었다. 질소의 가스 하이드레이트 평형 압력에 비해 SF6의 평형압력이 현저히 낮았으며, 혼합기체의 $SF_6$의 조성이 증가할수록 순수한 SF6의 3상 평형점에 근접하는 것을 볼 수 있었다. 이는 하이드레이트 형성을 이용한 기체 분리 공정을 이용하여 고농도의 $SF_6$를 분리해 낼 수 있음을 나타내어 주며 이 결과는 GC분석을 통하여 확인하였다. 본 실험에서 얻어진 결과는 하이드레이트를 이용한 $SF_6$ 분리 공정의 중요한 기초 자료가 되며 다른 혼합 기체의 분리 공정에도 응용될 수 있을 것이다.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.213-215
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• 2008

최근 지구온난화가 국제적인 이슈화되면서 온실가스의 효과적인 처리에 많은 관심이 집중되고 있다. 냉매로 주로 사용되는 HFC-134a와 절연제로 주로 사용되고 있는 $SF_6$는 각각 이산화탄소의 11,700배와 23,900배의 지구온난화지수를 가지는 온실가스이다. 본 연구에서는 이 두 물질의 효과적인 분리/회수를 위하여 가스 하이드레이트 형성을 이용한 방법을 제안하였다. 하이드레이트 형성법을 이용 할 경우 공정이 단순하고 저압에서 분리가 가능하므로 타 분리공정과의 경쟁이 가능할 것으로 예상된다. 본 실험은 275-290 K의 온도범위와 3 - 30 bar의 압력범위에서 질소 + HFC-134a (20, 40, 60, 80%)와 질소 + $SF_6$ (10, 30, 50, 70%)의 혼합기체를 사용하여 각 조성에 따른 하이드레이트(H)-물($L_W$)-기상 (V)의 3상 평형점을 측정하였다. HFC-134a 또는 $SF_6$의 조성이 낮은 혼합기체의 3상 평형점은 순수 질소의 3상 평형점에 비하여 주어진 온도에서 평형압력이 현저히 낮은 것을 볼 수 있었으며 HFC-134a 또는 $SF_6$의 조성이 증가할 수록 순수한 HFC-134a 또는 $SF_6$의 3상 평형점에 근접하는 것을 볼 수 있었다. 특히 $SF_6$는 다른 기체와 달리 하이드레이트의 생성/해리에 긴 시간이 필요하다는 것을 알 수 있었다. 본 실험에서 얻어진 결과는 하이드레이트를 이용한 HFC-134a와 $SF_6$ 분리 공정의 중요한 기초 자료가 되며 다른 혼합 기체의 분리 공정에도 응용될 수 있을 것이다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.41-46
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• 2015

This study was conducted to discover a substitute of $SF_6$ gas. $SF_6$ gas is widely used across the industries. Thanks to superior electrical properties, in particular, it has been commonly used in electrical industry. However, there have been a lot of studies on its serious effect on global warming. As a substitute of this synthetic gas, a mixture of dry air and $N_2/O_2$ was chosen in this study. In case of $N_2/O_2$, dielectric strength differs depending on the mixing ratio. This study examined dielectric breakdown and flashover after adjusting oxygen percentage in the dry air. This test was conducted in a quasi-uniform electric field depending on pressure, oxygen concentration and gas mixtures. The test results found that dielectric voltage and flashover voltage were the highest at a certain oxygen concentration. It is the results of this photoionization and electron attachment of oxygen.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1734-1737
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• 2015

Insulating characteristics of Cl₂-He mixture gases in gas discharges were analysed to evaluate ability of these gases for using in medium voltage and many industries. These are electron transport coefficients, which are the electron drift velocity, density-normalized longitudinal diffusion coefficient, and density-normalized effective ionization coefficient, in Cl₂-He mixtures. A two-term approximation of the Boltzmann equation was used to calculate the electron transport coefficients for the first time over a wide range of E/N (ratio of the electric field E to the neutral number density N). The limiting field strength values of E/N, (E/N)_lim, for these binary gas mixtures were also derived and compared with those of the pure SF₆ gas.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.49-57
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• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2403-2409
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• 2014

Absolute isotope ratio is a critical constituent in determination of atomic weight. To measure the absolute isotope ratio using a mass spectrometer, mass discrimination factor, $f_{MD}$, is needed to convert measured isotope ratio to real isotope ratio of gas molecules. If the $f_{MD}$ could be predicted, absolute isotope ratio of a chemical species would be measureable in absence of its enriched isotope pure materials or isotope references. This work employed gravimetrically prepared isotope mixtures of argon (Ar) to obtain $f_{MD}$ at m/z of 40 in the magnetic sector type gas mass spectrometer (gas/MS). Besides, we compare the nitrogen isotope ratio of nitrogen trifluoride ($NF_3$) with that of nitrogen molecule ($N_2$) decomposed from the same $NF_3$ thermally in order to identify the difference of $f_{MD}$ values in extensive m/z region from 28 to 71. Our result shows that $f_{MD}$ at m/z 40 was $-0.044%{\pm}0.017%$ (k = 1) from measurement of Ar artificial isotope mixtures. The $f_{MD}$ difference in the range of m/z from 28 to 71 is observed $-0.12%{\pm}0.14%$ from $NF_3$ and $N_2$. From combination of this work and reported $f_{MD}$ values by another team, IRMM, if $f_{MD}$ of $-0.16%{\pm}0.14%$ is applied to isotope ratio measurement from $N_2$ to $SF_6$, we can determine absolute isotope ratio within relative uncertainty of 0.2 %.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.69-74
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• 2018

With the increasing development of industrial society and the availability of high quality electrical energy, the simplification of operation and maintenance procedures is required, in order to ensure the reliability and safety of electrical systems. In this paper, the dielectric breakdown characteristics of $N_2-O_2$ mixed gas solid insulation, which is used as an alternative to SF6 in various electric power facilities, are verified. When the gas mixture has a composition ratio similar to that of the atmosphere, the dielectric breakdown characteristics are relatively stabilized. It was confirmed that the breakdown voltage of the gas in the electrode near an equal electric field increased with increasing pressure according to Paschen's rule. The breakdown voltage of the surface increased linearly with increasing pressure, and the difference was caused by the mixing ratio of $O_2$ gas. This change in the surface insulation breakdown voltage was caused by the influence of the electrically negative $O_2$ gas and the intermolecular collision distance. In this study, the influence of the intermolecular impact distance was larger (than that in the absence of the electrically negative $O_2$ gas). The breakdown voltage relation applicable to Teflon according to the surface insulation characteristics was calculated. The characteristics of the surface insulation properties of Teflon, which is used as a solid insulation material, were derived as a function of pressure. It is thought that these results can be used as the basic data for the insulation design of electric power facilities.