• 조명전기설비학회논문지
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• 제24권7호
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• pp.41-46
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• 2010

With the improvement of industrial society, high quality electrical energy, simplification of operation and maintenance, and ensuring reliability are being required. Also we request an urgent change from $SF_6$ gas to an environment-friendly gas insulation material. In this paper, the experiments of breakdown characteristics by pressure and gap change of $N_2/O_2$ mixture gas through a GIS (Gas Insulated Switchgear) model were described. This paper reviews basic data of the surface discharge characteristics for Teflon resin in not only pure $N_2$, $N_2:O_2$ mixture gas as being focused on environmentally-friendly insulating gas, but also $SF_6$. Also, insulation characteristics by breakdown voltage and surface discharge voltage of $N_2:O_2$ mixture gas in the experimental chamber were studied.

• 한국전산구조공학회논문집
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• 제29권1호
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• pp.53-60
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• 2016

본 연구는 NO96 화물창의 BOG(boil off gas), BOR(boil off rate)을 감소시키기 위한 노력으로 단열재료 및 단열층을 변화시켜서 개발된 NO96-GW, NO96-L03의 방열구조에 대해서 BOG, BOR 값을 계산하고 단열성능을 비교 평가하였다. 두가지의 변형된 NO96 모델을 기존의 NO96 방열과 단열층 및 단열재료의 차이점을 비교하고, 각각의 열저항 및 BOG/BOR 값의 비교 결과를 제시하였다. 열저항 값은 유한요소해석법을 이용하여 계산되었으며, 준정적 열평형 상태를 가정하여 열유속과 온도분포를 통하여 단열성능을 비교하였다. 계산에 사용된 화물창의 모든 재료물성치는 온도 의존값으로서 반영하여 $-163^{\circ}C$에서의 극저온 상태에서 특성을 반영되었다. 각 화물창의 BOG, BOR 계산은 국부 열전달 해석을 통해 방열판에서 발생하는 열유속을 계산하고, 등가모델을 적용하여 계산하는 과정으로 수행되었으며, 그 결과를 각 화물창의 단열성능을 비교 평가하기 위해서 검토하였다.

• 조명전기설비학회논문지
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• 제21권2호
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• pp.20-27
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• 2007

정보화 시대로 변화함에 따라 고품질 전력의 중요성이 강조되고 있으며 이를 보장하기 위한 전력기기 운전의 신뢰성 향상이 선결과제로 대두되었다. 특히 대용량 전력기기 중 개폐기와 차단기의 성능을 일정 수준 이상으로 유지하기 위한 예방진단기술이 발달되어 왔다. 개폐기와 차단기에서 많이 사용되는 $SF_6$ 가스의 절연성능을 검출하여 유지보수 여부를 결정하는 것이 매우 중요하다. 본 연구에서는 이러한 $SF_6$ 가스의 절연성능을 검출하기 위해 사용되는 여러 가지 방법 중에 전기방전에 의해 나타나는 여러 현상을 검출하는 센서들의 기초특성을 확인하고 파악된 특성을 통해 복수의 검출센서를 사용할 것을 제안하였다. 즉 코로나 방전이나 아크방전 시에도 사용할 수 있는 UHF 센서와 방전전류 검출기를 병용하는 것이 $SF_6$ 가스의 절연성능 확인에 유리할 것으로 판단되었다. 이외에도 가스센서를 이용한 $SF_6$ 가스의 절연상태 검출을 시도해 그 가능성을 시험해 보았다.

• 한국가스학회지
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• 제20권6호
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• pp.50-57
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• 2016

배관은 석유화학플랜트에서 가장 많은 구성요소이며, 주요설비들에서 생산된 물질을 수송하는 매우 중요한 역할을 수행한다. 특히, 저온 또는 고온의 물질을 수송하는 배관들의 경우 물질의 온도변화를 최소화하기 위해 보온재를 배관의 외면에 덮어 사용하는 경우가 다수이다. 그러나 이러한 보온재에 덮인 배관들에서 부식이 발생할 경우 보온재를 제거하지 않고서는 확인하기 어렵기 때문에 현장검사시 유도초음파를 이용한 비파괴적 방법이 사용되고 있다. 본 논문에서는 보온재 내부에서 발생하는 보온재하 부식(CUI : Corrosion Under Insulation)을 유도초음파를 사용하여 효과적으로 검출하기 위해서 유도초음파의 위상속도 분산선도와 파형구조의 이론적 해석을 통해 최적 발생조건을 선정하고자 하였다. 본 연구의 결과는 다양한 석유화학플랜트 배관의 보온재하 부식에 대한 유도초음파를 이용한 현장검출에 적용할 경우 매우 유용할 것이다.

• 한국수소및신에너지학회논문집
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• 제32권6호
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• pp.585-591
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• 2021

Liquefied hydrogen have advantage which reduces the volume by about 800 times or more compared to hydrogen gas, so it is possible to increase the storage density. However, liquefied hydrogen produced by cryogenic cooling of 20 K or less at normal pressure has a problem of maximizing the insulation effect that blocks heat introduced from the outside. Representative insulation technologies include vacuum insulation and multi-layer insulation materials and in general, heat blocking is attempted by combining insulation technologies. Therefore, in this study, the pressure of the internal vacuum layer was changed to 10^-1, 10^-2, 10^-3 and 10^-4 Torr to confirm the thermal insulation performance of the vacuum jacket valve for transporting liquefied hydrogen. As a result, it was confirmed that the insulation performance improved as the degree of vacuum increased.

• 전기학회논문지P
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• 제58권1호
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• pp.44-47
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• 2009

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. $SF_6$ gas is widely used in industrial of insulation field. In this paper, $N_2$ is mixed to improve pure $SF_6$ gas characteristics. Electron transport coefficients in $SF_6-N_2$ mixture gases are simulated in range of E/N values from 70 to 400 [Td] at 300K and 1 Torr by using Boltzmann equation method. The results of this method. which are ionization coefficient, attachment coefficient, effective ionization coefficient, and critical E/N, can be important data to present characteristic of gas for insulation. Specially critical E/N is a data to evaluate insulation strength of a gas and is presented in this paper for various mixture ratios of $SF_6-N_2$ mixture gases.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권3호
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• pp.115-121
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• 2001

This paper deals with the electrical insulation design of a gas insulated power transformer based on extra turns method satisfying the impulse test performed in the worst condition. The calculation of electrical strength in insulation structure was done by 2D finite element method. The gas insulated power transformer was manufactured by selecting the optimum arrangement among design results. the validity of the design result is verified by the impulse test of manufactured machine.

• 한국안전학회지
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• 제7권3호
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• pp.14-21
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• 1992

The smouldering combustion of cellulose insulation treated with boric acid-borax-alum as combustion retardants are examined by Candle type combustibility tester. This sequence was examined quantitatively for longitudinal cylinder bed of cellulose insulation. Two configuration are possible, downward and upward smoulder spread ; both were investigated exprimentally. The smoulder spread velocity of cellulose insulation was 2.5cm/s -5.0cm/s in smoulder region. As results of critical oxygen content measurement, the effectiveness of alum as third combustion retardant are acceptable for flaming retardant effect. The phenomena of combustion transition are governed by quantity of commbustible gas generation In heating zone of cellulose insulation. The critial oxygen content are decreased with the increase of gas flow rate.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1783-1786
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• 2016

The paper investigates the insulation properties of the supercritical $CO_2$ ($SCCO_2$) fluid as an insulating medium for electrical apparatuses. The insulating material is crucial for electrical apparatuses and $SF_6$ gas has been widely used for high power electrical apparatuses. There have been many research efforts to develop substituents for $SF_6$ gas because of high global warming potential. We obtained above 350 kV/mm insulation strength with 12.0 MPa $SCCO_2$. The positive and negative IEC standard pulses are applied between two 10 mm diameter spherical electrodes. The insulation strength of $SCCO_2$ is at least 2.5 times higher than that of $CO_2$ gas at 6.0MPa. The insulation strength of $SCCO_2$ fluid is about 10 times higher than that of $SF_6$ at 0.5MPa which is the ordinary operating pressure of electrical switchgears. Using the result, we expect that the time for switching and dielectric recovery could be reduced using $SCCO_2$ fluid as an insulating medium.

• 전기학회논문지P
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• 제59권2호
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• pp.197-201
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• 2010

$SF_6$ gas would be used in power transformer, GIS (Gas insulated switchgear) and so on because of its electrically superior insulation and chemically stable structure. Recently, the reduction of $SF_6$ is required to avoid global warming and the researches on the dilution of $SF_6$ with other gases have been carried out. $SF_6$ mixture gases with $N_2$ and $C_xF_y$ have drawn attention to the synergy effect. However, in order to understand the mechanism of the synergy effect, it is important to analyze and evaluate properties of mixture gases quantitatively. In this paper, we investigated the mechanism of synergy effect from electron collision processes and electron energy distribution by solving Boltzmann equation with propagator method. Three kinds of gases for dilution of $SF_6$ ($SF_6/N_2$, $SF_6/CF$4 and $SF_6/C_4F_8$) are considered in this simulation. On the properties of $SF_6/N_2$ mixture gas, the variation of reduced electric field was shown highly within 0%~40% mixtures of $SF_6$. And the more low-level electron energy has been distributed, the higher insulation capability has appeared.