• 대한전기학회논문지
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• 제36권11호
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• pp.796-805
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• 1987

The flashover voltages have been investigated for spacer and unbridged-gap in SF6-N2 gas mixtures up to the value of 760(torr. cm), The gap was stressed by DC source The results obtained are as follows` 1) The flashover voltages for an unbridged gap and for a spacer in SF6, N2 and SF6-N2 gas mixtures follow the Paschen's curve. 2) The polarity effects was not observed in both unbridged gap and a spacer which had per ect contact with an electrode. The flashover voltages for negative polatity are lower than those for positive polarity in case of imperfect contact. 3) 3%flashover voltage is decreased by putting a spacer which had perfect contact with an electrode. The spacer which has a gap void shows the lowest flashover voltage. 4) The lowest spacer efficiency was obtained with higher gas pressure & large amount of N2 content. The flashover voltages depend on the gas pressure rather than the spacer efficienty at low value of pd. 5) The flashover voltages of gas mixtures of N2 with SF6 are relatively high, even though the amount of SF6 gas content is small.

• 전기의세계
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• 제28권4호
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• pp.39-46
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• 1979

The effective ionization coefficient in $SF_{6}$/$N_{2}$ mixtures was attempted to derive from the pure gases. Measurements of static breakdown voltage were made under the uniform field at pressures up to 4 bar in order to compare with the results obtained from this assumption. The relative performance of $SF_{6}$/$N_{2}$ mixtures to pure $SF_{6}$ was also investigated. The effect of surface roughness on discharge thresholds in $SF_{6}$/$N_{2}$ mixtures was calculated employing the simplified model and mesurements of breakdown voltages for a gap with an artificial protrustion were also made. The experimental results show that the effective ionization coefficient in gas mixtures can not be reliably estimated from the values measured for the pure gases. Therefore, basic parameters for $SF_{6}$/$N_{2}$ mixtures must be measured by investigation of the mixtures themselves. The relative performance of mixtures to pure $SF_{6}$ could be considered with the values of pR.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1262-1263
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• 2011

Sulfur hexafluoride is the most commly used insulation gas in electrical systems. Gas insulated systems are widely used in the electric power industry for transmission and distribution of electrical energy. When $SF_6$ was first discovered, the potential application was only considered for insulation because of good dielectric properties. But the widespread use of $SF_6$ gas by electric power and other industries has led to increase concentrations of $SF_6$ gas in the atmosphere. This concern as to possible effects on global warming because $SF_6$ is a potent greenhouse gas. That's why firstly we studied uniform and nonuniform field property by mixing $SF_6$ and N2 gas. This paper presents the dielectric strength and insulating property for particle contamination under $SF_6/N_2$ mixtures. Two types of mixed gases(50% $SF_6$_50%$N_2$, 20% $SF_6$_80%$N_2$) were applied. We performed tests for the length and shape of particle. Test gas pressure is from 0.3 to 0.7 Mpa. The study was conducted to develop environment-friendly insulating material for GIS that can reduce $SF_6$ gas and make a design criteria for mixtures.

• 전기학회논문지
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• 제59권8호
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• pp.1416-1422
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• 2010

$SF_6$ is the most commonly used insulating gas in electrical systems. But In these days $SF_6$ mixtures and alternative gas has been studied because of global warming. so although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/N_2$ mixtures. At present study the breakdown characteristics of $SF_6/N_2$ mixtures in Non-uniform field was performed. In this paper, The simulation value are compared with experiment values. Streamer breakdown criterion was used for predicting breakdown voltage. For accurate simulation this simulation apply utilization factor using CST(computer simulation technology) EM $studio^{tm}$ program. AC breakdown experiments in non-uniform field was performed to compare with the breakdown simulation values. The pressure range of gas mixtures was 0.4 MPa to 0.7 MPa. The rod-plane was used and mixture ratio is $SF_6$ 20% : $N_2$ 80%. The gap lengths are 10mm to 70mm. As the pressure increase, this simulation value does not correspond to the experiment value. So this simulation need surface roughness factor. As a result of applying surface roughness factor this simulation decrease a relative error (|experiment value - simulation value| /simulation value).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.17-21
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• 2000

A Study on the electron energy distribution function in $SF_6+Ar$ mixtures gas used by MCS-BE algorithm, the electron swam parameters in the 0.5% and 0.2% $SF_6+Ar$ mixtures are measured by time of flight method over the E/N(Td) range from 30 to 300(Td). A two-term approximation of the Boltzmann equation analysis and Monte Carlo simulation have been also used to study electron transport coefficients. The electron energy distribution function has been analysed in $SF_6$ gas and $SF_6+Ar$ mixtures at E/N : 200(Td) for a case of the equilibrium region in the mean electron energy. The measured results and the calculated results have been compared each other.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.339-340
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• 2006

AC spark discharge voltage of SF6/CO2and SF6/N2 containing various mixed rate in volume percent (1, 5 and 10%) of SF6 in non-uniform fields are investigated. The needle to plane electrode gap spacing was 5 and 10 mm, and the gas pressure was varied within the range of 0.1~0.7 MPa. We have observed a N-characteristic typical for the electronegative gases even in gas mixtures of 1% SF6 with CO2 and N2 as buffer gases. Especially, the materials of the needle electrode affect the insulation properties of the gas mixtures drastically. On the contrary to the case of needle electrodes made by mild steel or high carbon steel, the N-characteristics are hardly perceived in the case of stainless steel needle in this experiment.

• 한국조명전기설비학회지:조명전기설비
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• 제7권1호
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• pp.21-29
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• 1993

본 연구는 전력계통의 절연에 가장 가혹한 영향을 미치는 뇌충격 전압에 대한 50% FOV와 V-t 특성 및 코로나 진전 과정을 불평등 전계중에서 순수 $SF_6, N_2, SF_6-N_2$혼합가스 분위기에서 연구하여 SF6-N2 혼합가스의 파괴과정과 경제적 실용 가능성에 대해서 검토하였다. 실험결과 $SF_6$ 50%-$N_2$ 50% 혼합가스의 50% FOV는 순수 $SF_6$의 80%보다 높다. 또 V-t 특성의 측정치와 등면적 법칙으로 계산된 곡선은 각 경우에 일치했다. 따라서 순수 $SF_6$에 대한 경제적 대체가스로서 SF6 50%-$N_2$ 50% 혼합가스가 사용되어질 수 있다는 것을 알 수 있었다. 또한 방전 도형을 이용한 코로나 진전과정 분석으로 이를 입증했다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.37-37
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• 2010

In these days $SF_6$ mixtures and alternative gas has been studied because of global warming. so although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/N_2$ mixtures. In this paper, breakdown experiment values and breakdown simulation value are compared. Streamer theory was used for predicting breakdown voltage. For accurate simulation, this simulation apply utilization factor using CST program. AC breakdown experiments in non-uniform field was performed to compare with the breakdown simulation values. But with gap lengths increasing, the breakdown voltage is saturated. So simulation need surface roughness factor.

• 전기학회논문지
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• 제57권2호
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• pp.245-251
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• 2008

Although many studies have been carried out about binary gas mixtures with $SF_6$, few studies were presented about breakdown characteristics of $SF_6/CF_4$ mixtures. At present study the breakdown characteristics of $SF_6/CF_4$ mixtures in non-uniform field was performed. The experiments were carried out under AC voltage and standard lightning impulse(SLI) voltage. Breakdown characteristics were investigated for $SF_6/CF_4$ mixtures when AC voltages and standard lighting impulse voltage was applied in a needle-plane. The needle-plane electrode whose gap distance was 3 mm were used in a test chamber. $SF_6/CF_4$ mixtures contained from 0 to 100% $SF_6$ and the experimental gas pressure ranged from 0.1 to 0.5 MPa. The breakdown characteristics of $SF_6/CF_4$ mixtures in non-uniform field may be influenced by defects like needle-shaped protrusions. In case of slowly rising SLI voltage and AC voltage it is enhanced by corona-stabilization. This phenomena caused by the ion drift during streamer development and the resulting space-charge is investigated. In non-uniform field under negative SLI voltage the breakdown voltage was increase linearly but under positive SLI voltage the breakdown voltage increase non-linearly. The breakdown voltage in needle-plane electrode displayed N shape characteristics for increasing the content of $SF_6$ at AC voltage. $SF_6/CF_4$ mixture has good dielectric strength and arc-extinguishing properties than pure SF6. This paper presents experimental results on breakdown characteristics for various mixtures of $SF_6/CF_4$ at practical pressures. We could make an environment friendly gas insulation material with maintaining dielectric strength by combing $SF_6\;and\;CF_4$ which generates a lower lever of the global warming effect.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1102-1105
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• 2003

Energy distribution function for electrons in $SF_6$-Ar mixtures gas used by MCS-BEq algorithm has been analysed over the E/N range $30{\sim}300[Td]$ by a two term Boltzmann equation and by a Monte Carlo Simulation using a set of electron cross sections determined by other authors, experimentally the electron swarm parameters for 0.2(%) and 0.5(%) $SF_6$-Ar mixtures were measured by time-of-flight(TOF) method, The results show that the deduced electron drift velocities, Electrons Drift Velocities for a rang of E/N values. As a consequence, it was known that the spatial growth rates and the dielectric behaviors in $SF_6$-Ar mixtures are strongly dependent on the addition rate of $SF_6$ gas but the transport coefficients of electrons are insensitive to the addition rate of $SF_6$ gas. The results obtained from Boltzmann equation method and Monte Carlo simulation have been compared with present and previously obtained data and respective set of electron collision cross sections of the molecules.