• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1744-1746
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• 2001

In this paper, we investigated the breakdown characteristics of Ar, Kr and $N_2$ gas in pure states with pressure range of 58.8-137.3[kPa] under uniform and non-uniform fields, and the measured values are compared with those in Ar/$N_2$ gas mixtures. From these results, the breakdown voltages of $N_2$ gas in uniform field were increased about 4.8 and 4.4 times than those of Ar and Kr gas, respectively. Breakdown voltages of Ar/$N_2$ gas mixtures were decreased with decreasing the mixture ratio of $N_2$ gas. Breakdown voltages of Ar(70%)/$N_2$(30%) gas mixtures in the pressure of 101.3[kPa] (gap length : 3[mm]) were increased 1.9 times than those of pure Ar gas.

• 한국전기전자재료학회논문지
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• 제16권2호
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• pp.151-156
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• 2003

High temperature superconductor can only be applied against an engineering specofication that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. However, in order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. Therefore, the composite insulation of double pancake coil type transformer are described and AC breakdown voltage characteristics of liquid nitrogen(LN$_2$) under HTS pancake coil electrode made by Bi-2223/Ag are studied. The Breakdown of LN$_2$ is dominated electrode shape and distance. The influence of pressure on breakdown voltage is discussed with th different electrode. For the electrical insulation design of turn-to-turn insulation for the HTS transformer, we tested breakdown strength of insulation sheet under varying pressure. And we investigated surface flashover properties of LN$_2$ and complex conition of cryogenic gaseous nitrogen(CGN$_2$) obove a LN$_2$ surface. The surface voltage of GFRP was measured as a function of thickness and electrode distance in LN$_2$ and complex condition of CGN$_2$ above a LN$_2$ surface. this research presented information of electrical insulation design for double pancake coil(DPC) type HTS transformer.

• 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).

• 한국항공우주학회지
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• 제40권4호
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• pp.346-353
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• 2012

레이저 조사 시 발생되는 플라즈마를 성분 분석에 이용하는 Laser-Induced Breakdown Spectroscopy(LIBS)는 우주 자원 탐사에 적합한 실시간 성분 분석 기술이다. LIBS 플라즈마의 특성은 주위 압력의 영향을 크게 받는다. 본 연구에서는 다양한 물성치를 갖는 일곱 가지 원소(C, Ti, Ni, Cu, Sn, Al, Zn)의 지속시간(lifetime)이 760 - $10^{-5}$ torr의 압력 범위에서 분석되었다. 압력이 낮아짐에 따라 탄소와 티타늄의 lifetime은 감소하였고, 그 밖의 원소들은 1 torr의 압력에서 가장 오랜 시간동안 검출되었다. 원소별 lifetime 결과를 통하여 낮은 압력 하에서 플라즈마의 특성과 원소별 끓는점 및 전기음성도의 관계를 규명하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1099-1101
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• 1999

PJB(Prefabricated Joint Box) is consisted of three major components ; an epoxy unit, a stress relief cone and a spring unit. The insulation structure of PJB is maintained by the interfacial pressure, and the dielectric performance at the interface depends on the interfacial pressure which is regarded as the most important factor for preventing breakdown failure. This experiment was performed to investigate breakdown voltage characteristic and partial discharge patterns under the controlled pressure conditions at the simulated interface. Finally, this paper presents the optimal pressure conditions at the interface by analyasing the PD patterns.

• 한국초전도ㆍ저온공학회논문지
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• 제14권3호
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• pp.38-42
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• 2012

Fixtures such as bushings in terminations of high temperature superconducting(HTS) power cable systems are subjected to high voltages, which have to transition from ambient to cryogenic temperatures. As such it is imperative to ensure the integrity of the dielectrics under all operating conditions, including thermal aspects brought about by the passage of current. Gaseous helium(GHe) at high pressure is regarded as a potential coolant for superconducting cables. The dielectric aspects of cryogenic helium gas are both complex and demanding. In this experimental study we looked at the interface between a smooth epoxy surface and high pressure helium gas in a homogeneous electric field. The alternating current(AC) flashover voltages of epoxy samples are presented. The results have been analyzed by using Weibull statistics. In addition to the behavior of the epoxy in gaseous helium as a function of pressure and temperature we also present data of the characteristics of the epoxy in mineral oil and in liquid nitrogen($LN_2$). The breakdown characteristics of a uniform field gap in gaseous helium as a function of pressure and temperature under AC, direct current(DC) and lightning impulse voltages are also given. Electric field calculations have been made for one of the experimental geometries in an attempt to explain some of the anomalies in the experimental results.

• Transactions on Electrical and Electronic Materials
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• 제13권4호
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• pp.200-203
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• 2012

Epoxy/mica composite was synthesized, in order to use it as an impregnation resin in a vacuum pressure impregnation (VPI) process, for manufacturing a high voltage rotary machine. The average particle size of the mica was 5~7 ${\mu}m$ and its content was 0, 20, 30 and 40 wt%. A plasticizer or a low molecular aliphatic epoxy was also used, to decrease the viscosity of the composite. The AC electrical breakdown strength was estimated in sphere-to-sphere electrodes, and the electrical breakdown data were estimated by Weibull statistical analysis. The electrical breakdown strength became higher with the addition of mica; and that of the system with 20 wt% mica was highest. The electrical breakdown strength of the system with an aliphatic epoxy was higher than that of the system with a, plasticizer.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권3호
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• pp.152-158
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• 2000

This paper deal with the experimental discussion about the impulse and AC dielectric strength of SF6 gas insulated transformer. Test sample is measured the dielectric breakdown voltage about modeling of the first and second section which is the weakest for surge voltage. The AC breakdown voltage is appeared 1.4 times than impulse breakdown voltage, so we can estimate that the impulse breakdown voltage is severe to AC breakdown voltage, and when the impulse is applied, in case of lmm tapping with Nomex paper, the characteristics of dielectric breakdown voltage is same to that in oil immersed transformer when SF6 gas pressure is 2.2kg/$cm^2$G.

• 조명전기설비학회논문지
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• 제15권5호
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• pp.20-27
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• 2001

본 연구에서는 평등 및 불평등 전계하에서 58.8~137.3[kPa]의 가스 압력변화에 따른 순수 Ar 및 $N_2$가스의 교류절연파괴 특성을 조사하였다. 그리고 가스 압력 변화에 따른 Ar/$N_2$ 혼합 가스의 교류절연파괴 특성과 비교하였다. 실험 결과를 요약하면, 평등 및 불평등 전계하에서 순수 $N_2$가스의 압력 변화에 따른 교류절연파괴 특성은 순수 Ar 가스에 비해 약 4.8배 1.1배 증가된 것으로 나타났으며, 압력이 증가됨에 따라 교류절연파괴전압은 증가되었다. Ar/$N_2$혼합 가스의 절연파괴전압은 순수 $N_2$가스의 혼합비가 적을수록 감소되었으며, 혼합 가스 압력이 101.3[kPa]일 때, 순수 Ar 가스에 비해 Ar 가스 혼합 비율이 각각 85[%] 및 70[%] 인 경우, 교류절연파괴전압은 평등 전계하에서는 약 1.5 및 2.1배 증가되었으며, 불평등 전계하에서는 약 1.1 및 1.3배 증가되었다. 또한 불평등 전계하에서 Ar(70%)$N_2$(30%) 혼합 가스의 코로나개시전압은 순수 Ar 가스에 비해 약 1.5배 증가되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.306-309
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• 1995

This paper describes the dielectric characteristics of $SF_{6}$ gas in a non-uniform electric field under overvoltages. The breakdown voltage-time characteristics and the breakdown voltage-gas pressure characteristics are measured within a gas pressure range extending from 0.1 to 0.5 [Mpa] for the plane electrode system with a needle-shaped protrusion. The curvature radius of the needle protrusion is 0.5[mm]. Also, the growth process of the predischarge are simultaneously observed. As a result, it is found that the breakdown mechanism and predischarge phenomena are closely associated with the polarity and waveforms of the testing voltage.