• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
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• pp.108-111
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• 2003

The main objective of this paper is to module design and pressure relief test a new type of polymer gapless surge arrester for power distribution line. Metal oxide surge arrester for most electric power system applications, power distribution line and electric train are now being used extensively to protect overvoltage due to lightning. Surge arresters with porcelain housing must not have explosive breakage of the housing to minimize damage to other equipment when subjected to internal high short circuit current. When breakdown of gapless elements in a surge arrester occurs due to flashover, fault short current flows through the arrester and internal pressure of the arrester rises. The pressure rise can usually be limited by fitting a pressure relief diaphragm and transferring the arc from the inside to the outside of the housing. However, there is possibility of porcelain fragmentation caused by the thermal shock, pressure rise, etc. Non-fragmenting of the housing is the most desired way to prevent damage to other equipment. The pressure change which is occurred by flashover become discharge energy. This discharge energy raises to damage arrester housing and arrester housing is dispersed as small fragment. Therefore, the pressure relief design is requested to obstruct housing dispersion.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마연구회
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• pp.35-39
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• 2003

An ageing characteristics of RTV coating materials by corona discharge have been studied. The recovery of a hydrophobicity of RTV coating materials with the thickness of $300{\mu}m$ was in identical with a bulk silicone materials. The hydrophobicity of RTV coating materials has been almost lost when its were discharged during 40 seconds by corona with 10kV, and recovered after about 45 hours. But the resistivity of RTV coating materials has not been recovered after 45 hours, even though after 80 hours the 95% of initiation resistivity value has been recovered. There was no critical compounds(such as Si and Al) changes on RTV surfaces by the corona discharge treatment until 100 seconds. In the test of arc erosion, it was seen that the coating sample with silicone rubber as a base material have more longer bum-out time than other samples with FRP or glass base.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권10호
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• pp.479-488
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• 2001

The effects of accelerated Ultraviolet (UV) radiation on High temperature vulcanized (HTV), Room temperature vulcanized (RTV) silicone rubber and two types of ethylene propylene diene terpolymer (EPDM) used for composite insulator were inverstigated by hydrophobicity class (HC), surface voltage decay after corona charging, SEM-EDS, FTIR and XPS. The contact angle in two kinds of silicone rubber was scarcely change, but EPDM occurred to the loss of hydrophobicity followed by surface cracking and chalking. The surface voltage decay on UV-treated silicone rubber and EPDM showed a different decay trend with UV treatment. EDS and XPS analysis indicated that the oxygen content increased with UV treatment time in all samples. For silicone rubber, the oxidized groups of inorganic silica-like structure increased with UV treatment time. The oxidized carbon of C=0, O=C-O in EPDM increased. These oxidized surface for each material had different electrostatic characteristics, so deposited charges were expected to have different impacts on their surface hydrophobicity. The degradation mechanism based on our results was discussed.

• 한국전기전자재료학회논문지
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• 제21권6호
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• pp.530-537
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• 2008

This paper describes the results of a study on the tracking performance of outdoor insulating materials based on the rotating wheel dip test(RWDT). And, the influence of surface degradation was evaluated through such as measurement of the flashover voltage after and before tracking test, also aspects of surface degradation using scanning electron microscopy. The time to tracking breakdown of treated filled specimen is longer than untreated filled specimen. And, after the RWDT, the surface of specimen by adding untreated filler appeared heavy erosion. It was found that the addition to surface treated filler, the better tracking resistance. In the RWDT, the breakdown specimen is not affected by the dry flashover voltage, despite the fact that the surface degradation of tracking test has different state on each specimen. This suggests that wet flashover voltage play an important role in evaluating of tracking and erosion on the surface degradation in tracking test. And, the flashover voltage of specimen under wet conditions are greatly affected by the salt concentration and degree of degradation by the RWDT Because of hydrophobicity and degree of degradation by the RWDT, the flashover voltage of treated filled specimen is higher than that of untreated filled specimen. Different types of specimen may have different hydrophobicity and their surface state under contaminated conditions may not be the same.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.398-403
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• 2006

This paper describes the evaluation of the long duration current impulse withstand characteristics of ZnO blocks for high voltage surge arresters. Four ZnO varistors were manufactured with the general ceramic production method and the long duration current impulse withstand test, electrical uniformity evaluation test and microstructure observation were performed. All varistors exhibited high density, which was in the range of $5.42{\sim}5.46g/cm^3$. In the electrical properties, the reference voltage of samples was in the range of $5.11{\sim}5.25\;kV$ and the residual voltage was in the range of $8.314{\sim}8.523\;kV$. In the long duration current impulse withstand test, sample No.2 and No.3 failed at the 2nd and 4th shot of series impulse currents, respectively, but the rest survived 18 shots during the test. Before and after this test, the variation ratio of the residual voltage of samples survived was below 0.5 %, which was in the acceptance range of 5 %. According to the results of the test, it is thought that if the soldering method is improved, ZnO varistors would be possible to apply to the high voltage arresters like the station class and transmission line arresters in the near future.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.1057-1060
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• 2001

By comparison of the experimental results in two systems of ZnO varistors, its appear that Sb$_2$O$_3$is the indispensable element for twinning in ZnO varistors, and the Zn$_{7}$Sb$_2$O$_{12}$ spinel acts as the nucleus to form twins. A1$_2$O$_3$is not the origin of twinning in ZnO varistor, but it was found that A1$_2$O$_3$could strengthen the twinning and form a deformation twinning by ZnA$_{12}$O$_4$-dragging and pinning effect. The inhibition ratios of grain growth and nonuniformity of two systems ZnO varistors increase with the increase of A1$_2$O$_3$content. The twins affect the inhibition of grain growth, the mechanism could be explained follow as : twins increase the mobility viscosity of ZnO grain and grain boundary, and drag ZnO grain and liquid grain boundary during the sintering, then the grain growth is inhibited, and the microstructure becomes more uniform.orm.m.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.348-352
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• 2004

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and ow loss, but it needs some cooling method because heat radiation between each winding is difficult. The life of transformer is significantly dependent on the thermal behavior in windings. Many transformer designers have calculated temperature distribution and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, The thermal analysis of pole mount mold transformer with one body molding by duct condition is investigated and the test result of temperature rise is compared with simulation data.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.353-359
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• 2004

In this study. porcelain insulator samples which have a different alumina composition were manufactured in order to test electrical and mechanical properties and make an analysis of the propagation phenomena of micro cracks on porcelain body. From XRD quantitative analysis the crystalline phases were different with alumina composition, sample C and D which have about l7wt％ Corundum phase without the Cristobalite phase shows better electrical and mechanical properties than sample A and B which have the Cristobalite phase. In dielectrics test on porcelain samples with below l7wt％ alumina composition, it was found that the amount of glass phase(SiO$_2$) have an main effect to decrease the dielectric loss(tan$\delta$), and the dielectric breakdown voltage of aluminous porcelain insulators was largely affected by its relative density. As a micro tracks analysis, HRB were measured, then the intensity of HRB increased with the amount of alumina composition. On the other hand, the propagation behaviors of cracks was fairly influenced by the distribution of pores.

• 한국전기전자재료학회논문지
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• 제19권12호
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• pp.1154-1159
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• 2006

The mold transformers have been widely used in underground substations of large building and have some advantages when compared with oil-transformer. Those advantages are low fire risk, environmental compatibility, compact size and high reliability. The mold transformer is generally known to have cooling duct between low voltage and high voltage coil. To achieve better compact structure and low loss, mold transformers made by one body molding method has been developed. Nevertheless, such kinds of transformer need better cooling method because heat radiation between each winding is still of problem. The life of transformer is significantly dependent on the thermal behavior in windings. Many designers have calculated temperature distribution in transformers and hot spot point by finite element method(FEM) to analyze winding temperature rise. In this paper, the temperature distribution analysis of 100 kVA pole mold transformer for power distribution were investigated by FEM program and the thermal analysis results were compared with temperature rise test.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.120-124
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• 2004

본 연구는 Diluted Ceria 입자를 사용한 $SiO_2$(Oxide) CMP 현상에 대한 내용이다. Ceria Slurry의 경우 Silica Slurry와 비교하였을 때 Oxide Wafer 표면과 축합 화학반응을 일으키며 Chemistry Dominant한 CMP Mechanism을 따르고, Wafer Center Removal Rate(RR) Fast 의 특성을 가진다. Ceria Slurry의 문제점인 연마 불균일도를 해결하기 위해 Tribological System을 이용하였다. CMP Tribology는 Pad-Slurry 유막-Wafer의 System을 가지며 윤활막에 작용하는 마찰계수(COF)가 주요 인자이다. Tribology에 적용되는 Stribeck Curve를 통해 Slurry 윤활막의 두께(h) 정도를 예상할 수 있으며, 이 윤활막의 두께를 조절함으로써 Uniformity 향상이 가능하다. 이 Ceria Slurry CMP의 연마 불균일도를 향상시킬 수 있는 방법으로 pH 조절 및 점도 증가가 있다. Ceria 입자 CMP는 분산액의 pH 변화에 강한 작용을 받게 되며 PH5 근방에서 최적화된 Uniformity가 가능하다. 점도를 증가시키는 경우 유막 h가 증가하게 되어 Ceria Slurry의 유동이 균일 분포 상태에 가까워지며 Wafer Uniformity 향상이 가능하다.