• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.204-207
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• 1995

This paper deals with the dielectric characteristics of $SF_{6}$ gas stressed by non-oscillating and oscillating impulse voltages in inhomogeneous field perturbed by a fixed needle shaped-protrusion. The breakdown voltage-time characteristics were measured for both polarities and over the gas pressure range from 0.1 to 0.5 [MPa], and the temporal developments of the prebreakdown were observed. The dependence of the leader stepping time on the gas pressure were obtained.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.271-273
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• 2007

This paper presents the experimental results of underwater discharges in 25 mm point-plane gap caused by impulse voltage. Discharge phenomena were observed by digital cameras and recorded by oscilloscope. As a result, discharge patterns in positive and negative polarity have different shapes according to applied voltage amplitudes. The positive discharge is like root but the negative discharge is similar to bush. As the voltage is increased, the discharge routs are thick and have more branches. Also the time to breakdown is inversely proportional to voltage.

• Proceedings of the KIEE Conference
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.718-720
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• 2005

This paper analyses the transient phenomena against lightning surge on underground power cable systems. For analysis, several actual underground power cable systems are modeled using ATP. In lightning surge strokes, the various unbalanced conditions including the length of crossbonded lead, the breakdown of CCPU and distance unbalance are considered. This paper is expected to contribute the establishment of proper protection methods against transients on underground power cable systems.

• Journal of the Korean Institute of Telematics and Electronics A
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• 제29A권1호
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• pp.41-47
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• 1992

In SFB Process, after 110$0^{\circ}C$ annealing in wet OS12T(95$^{\circ}C$ HS12TO bubbling) atmosphere, the existence of the interfacial oxide film in micro-gap at Si-Si bonding interface was identified. The angle lapping/staining and SEM morphologies of bonding interface showed that the growing behavior of interfacial oxide made a contribution to eliminate the micro-gaps having a width of 200-300$\AA$. In case of the diodes composed of p-n wafer pairs made by SFB processes, the annealed one in wet OS12T atmosphere exhibited a dielectric breakdown phenomena of interfacial oxide at 37-40 volts d.c.

• Proceedings of the KIEE Conference
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1735-1737
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• 2001

The occurrence of fires under transmission lines is responsible for a great number of power line outages. In this paper, the ac flashover voltages and the corona onset voltages of a needle-plane electrode gap of vertical arrangement in the presence of flame were investigated. We also observed the corona discharge current and variation of shapes in flame with increasing the applied voltages. We found that the corona onset voltages and the flashover voltages were drastically decreased with the position of flames and gap length of electrodes, and observed that the deflection or fluctuation phenomena in the shape of flames.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.100-100
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• 2010

Because of power consumption increase, global wanning, and limitation of installation, not only high reliability and interruption capability but also compact and light power apparatuses are needed. To improve the insulation performance, the high E field concentration phenomena was considered. Breakdown mechanism in vacuum is different from that in other insulation materials. therefore, It is necessary to understand the electric field distribution and insulation characteristics. This paper discusses the simulation and LI(light impulse) test of the shield of outside vacuum interrupter As a result, FEM simulation and LI test show that improve distribution of electrical field and equi-potential line. due to external shield. in this case, outside shield induced electric field of triple junction point.

• Proceedings of the KIEE Conference
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1797-1800
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• 1996

In this study, the insulation selected in degra-dated-power cable has been observed and aging process about the insulation has been investigated. Most Insulation aging process initiates in the interface of semiconducting layer and the type of the process is the fractal form that was observed between the the semiconducting layer and insulation layer. It is possible to estimate degree of the degration of cable with breakdown test and obtained data have been used to get parameters in order to use Weibull distribution. With this method it is considered to be possible to estimate situation of degration and life prediction.

• Proceedings of the KIEE Conference
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1597-1599
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• 1996

In this study, we investigated the electrical characteristics such as tracking resistance, dielectric constant, insulating resistance, and arc resistance, of silicone rubber for outdoor use, and, focused on the tracking resistance. In the Inclined Plane Test, two kind of the contamination solutions were used, and their phenomena were observed. The average leakage current and the tracking breakdown time decreased, and erosion rate increased, using anionic surfactant added contaminant solution. The dielectric constant and dissipation factor were increased with increasing temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제14권12호
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• pp.1041-1047
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• 2001

In this paper, reduction characteristics of the ac flashover voltage in the horizontal air gap of sphere-sphere/needle-needle electrode system were investigated when the combustion flame was present near the high-voltage electrodes. The voltage and current waveforms were measured, when the flashover is occurred, in order to examine the flashover polarity by flame. The reduction characteristics of ac flashover voltage were discussed with the thermal ionization process, the relative air density and the deflection phenomena in the shape of flames that changed by the corona wind and coulomb\`s force. As the results of an experimental investigation, It was found that the reduction of flashover voltages in sphere-sphere system, in comparison with the no-flame case, are 79.9 [%] for k=0, 82.9 [%] for k=0.5, 87.5 [%] for k=1.0, 85.0 [%] for h=0 [cm], 40.8 [%] for h=5 [cm] and 28.2 [%] for h=9 [cm] when ac voltage is applied.

• Proceedings of the KSR Conference
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.321-326
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• 2008

Light weight of vehicles by composite materials makes possible high speed, energy saving, and low repair cost. As Bimodal Tram and Tilting Train eXpress(TTX) use carbon composite material for their bodies, safety for passengers and electrical devices against unexpected failures has been issued more than ever. Lightning strike which generates high voltages and large currents is the worst case for the safety of passengers and devices. With this background, we experimentally investigated the insulation breakdown phenomena on carbon composite materials by the application of lightning surge voltage and current. From the experimental results, we could estimate whether the composite body is safe or not for the inside passengers and devices against lightning strikes.