• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 춘계학술대회논문집
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• pp.279-282
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• 2005

Morden electronic equipments are becoming very important in information oriented society, but they are vulnerable to lightning surges. Soil resistivity in the vicinity of grounding electrodes my be affected by the current flowing from the grounding electrodes into the surrounding soil. Electrical conduction in soils depends on the grain size, compactness, and variability of the grain sizes. When a high current is injected into the soil, and the breakdown phenomenon occur. In the present work, Electrical behaviors related to discharge in soils were investigated. The breakdown voltages in soil were lower than that sparkover voltage in air. The breakdown voltage in the gravel layer is relatively low, and the breakdown was caused by the flashover through the surface of gravels

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.366-367
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• 2008

SF6 widely used as insulating gas is rising as the environment problem. For decreasing this greenhouse gas, electrical breakdown characteristics of vacuum with air are studied in non-uniform field. The gap of needle to plane was 0.5mm, 0.8mm. The pressure of vacuum the range of 10^-4-10^-5torr. The diameter of a plane made of the stainless steel is150mm. As a result of the experiment, the breakdown voltage is increased about electrode gap distance increased. The electrode material influenced breakdown voltage in vacuum.

• 전기의세계
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• 제27권6호
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• pp.76-83
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• 1978

This paper reveals the results of fundamental experiments with the breakdown strength- and treeing phenomena, by A.C voltage and impulse voltage, of cross-linked polyethylene insulator, respectively compared in each case of the various specimens; nonvoid, air void, water void, oil void and oil impregnated one, all articially made. In this research, the V-t and V-n characteristics are investigated by means of the Weibull distribution and are analysed the characteristics of fatigue breakdown caused by the A.C and impulse voltage. Based on numerous tests, treeing effect and treeing breakdown mechanism is investigated through microscopic photographs taken to clarify the shapes of each tree and treeing breakdown phenomena.

• 한국초전도ㆍ저온공학회논문지
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• 제8권2호
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• pp.37-42
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• 2006

A research on several characteristics such as volume breakdown and surface discharge of insulators for a termination of power transmission class HTS cable was performed. We investigated the surface discharge of glass fiber reinforced plastic (GFRP) under air, cryogenic nitrogen gas and nitrogen gas media. The breakdown characteristics of these media were studied. Experimental results revealed that flashover voltage greatly depends on pressure, temperature, the kinds of insulating media and voltages, but it is slightly affected by shape and material of electrode. The breakdown voltage of liquid nitrogen, cryogenic nitrogen gas and nitrogen gas deeply depends on the shape and dimension of electrode, kinds of voltages and pressure. Moreover, the breakdown voltage of cryogenic nitrogen gas and flashover voltage of GFRP in the cryogenic nitrogen gas is also influenced by temperature and vapour-mist density of the gas.

• Journal of Electrical Engineering and information Science
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• 제2권3호
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• pp.71-76
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• 1997

A lot of experiments and analyses have been done to determine the aging mechanism of mica-epoxy composite material used for large generator stator windings in order to estimate remaining life of the generator for last decades. After degrading artificially the mica-epoxy composite material, the surface analysis is performed to analyze breakdown mechanism of insulation in air and hydrogen atmosphere; i) In the case of air atmosphere, it is observed that an aging propagation from conductor to core by partial discharge effect and the formation of cracks between layers is widely carbonized surface. ii) In case of hydrogen atmosphere, the partial discharge effect is reduced by the hydrogen pressure (4kg/$\textrm{cm}^2$). Potassium ions forming a sheet of mica is replaced by hydrogen ions, which can lead to microcracks. It is confirmed that the sizes of crack by SEM analysis are 10∼20[$\mu\textrm{m}$] in length under air, and 1∼5[$\mu\textrm{m}$] in diameter, 10∼50[$\mu\textrm{m}$] in length under hydrogen atmosphere respectively. The breakdown mechanism of sttor winding insulation materials which are composed of mica-epoxy is analyzed by the component of materials with EDS, SEM techniques. We concluded that the postassium ions of mica components are replaced by H\ulcorner, H$_3$O\ulcorner at boundary area of mica-epoxy and/or mica-mica. It is proposed that through these phenomena, the conductive layers of potassium enable creation of voids and cracks due to thermal, mechanical, electrical and environmental stresses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.113-114
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• 2008

The purpose of this paper is to analyze AC Breakdown of solid/air composite insulation depending on the thickness and the pressure of dry air for eco-friendly insulation. SF6 gas has been widely used in electric equipment as gas insulation because of high dielectric strength and arc extinguishing performance. However, because SF6 gas is one of the green house effect gases, alternative insulation such as SF6 mixture, extremely low temperature gas, vacuum, liquid and solid insulating are being investigated.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.253-255
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• 2008

This paper gives a basic data of the surface discharge characteristics for epoxy resin in Dry-Air. Used electrodes are needle to plane, sphere to plane and KS M3015 electrodes. With the changing electrodes in same condition, we can obtain different creeping lengthes, breakdown voltages and dielectric strengths, respectively. Dielectric strengths of Needle to plane electrodes are more higher than the others. Breakdown voltage and dielectric strength increase as the thickness of epoxy resin and creeping strength increase.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.194-195
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• 2007

$SF_6$ gas used widely as insulating component in electric power industry has excellent in insulation and arc extinguishing performance in gas-insulated switchgear. However, the concern about eco-friendly alternative gas is currently rising because $SF_6$ gas is one of the main greenhouse gases. In this paper, dry-air and composite-insulation (dry-air+epoxy) as the alternative technology for $SF_6$ gas insulation is studied. Under the gas pressure ranged from 0.1 to 0.6MPa, the breakdown voltage of dry-air were measured in AC electric field. The data of composite-insulation were acquired by changing the thickness of epoxy used in each composite-insulation under the same condition.

• 한국재료학회지
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• 제4권3호
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• pp.312-318
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• 1994

이 논문은 절연유를 정제하여 $SF_6$ 가스를 용해시켰을 때 절연유의 수십 MHz대의 고주파 절연파괴 전압과 유전특성에 관해서 연구한 것이다. 1)절연유에서의 고주파 전류는 전압의 1/2승에 거의 비례하여 증가한다. 2)전원주파수가 증가함에 따라 고주파 절연파괴는 주파수의 제곱에 역비례하여 감소하는 현상을 나타내고 AC절연파괴의 전압때보다 약 35%정도가 감소한다. 3) 용해된 기체의 압력을 증가시킴에 따라 고주파 절연파괴 전압은 원만하게 증하한다. 4)전원주파수의 증가에 따른 유전정접(tan $\delta$)은 거의 지수 함수적으로 증가하고 유전률($\varepsilon$)은 [0.6% MHZ]의 기울기로 삼소하는 경향을 나타낸다. 5) $SF_6$ 가스를 용해시켰을때 절연파괴 특성은 Air 또는 Ar을 용해시켰을 때 보다 약 25% 정도 향상되는 특성을 나타낸다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.605-608
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• 1993

Breakdown characteristics of a small rod-to-rod microairgap has been studied for obtain an optimum breakdown voltage and an airgap spacing to be used as an emission control means by the electrical arc-burning unburnt carbon particulates exhausted from a power station burner. It is found that the breakdown voltage at the rod-to-rod airgap spacing in the rang of $1{\sim}100{\mu}m$ decreased with decrease in the rod-to-rod airgap spacing. And there were no minimum breakdown voltage on a $V_b$-Pd characteristics which is known as the minimum voltage in Paschen's law in air atmosphere. Breakdown voltages of the airgap at the constant airgap spacing were $V_{b-dc}>V_{b-ac}>V_{b-pulse}$, and it was lowest for the pulse voltage applied. As a result, it is found that a pulse power was one of effective power compared with dc or ac to be used as such an unburnt carbon particulate emission control means and the airgap spacing became to several tens ${\mu}m$, then the breakdown voltages were down to several handreds voltages.