• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.85-90
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• 2006

This paper presents experimental results relating to the preliminary breakdown characteristics in $SF_6/CO_2$ gas mixtures under a highly non-uniform electric field. The impulse pre-breakdown developments are investigated by the measurements of corona current and light emission images. As a result, the preliminary breakdown development mechanisms for both the positive and negative polarities were fundamentally same. The first streamer corona was initiated at the tip of needle electrode, and the leaders developed with a stepwise propagation and bridged the test gap. The pause time of leader pulses in the positive polarity was significantly shorter than that in the negative polarity. Also, the time interval between the first streamer corona onset and breakdown in the negative polarity was much longer than that in the positive polarity. The discharge channel path in the positive polarity was zigzag, and the leader channel in the negative polarity was thicker and brighter than that in the positive polarity.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.8
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• pp.67-74
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• 2008

In this paper we describe discharge characteristics between needle-to-plane electrodes in water in various conditions such as different impulse voltages, polarities and water resistivities. Streamer corona is initiated at the tip of needle electrode and propagates toward plane electrode, and it experiences the final jump across the test gap. The branched channels of streamer coronas for lower water resistivities are much thicker and brighter than those for higher water resistivities at the same level of applied voltage. The negative streamer coronas not only have more branches but also widely spread out compared to the positive streamer coronas. A number of pulse-like currents ranging from some hundreds mA to a few A after streamer corona onset were produced with discharge developments. The time-lags-to breakdown for the positive polarity were remarkably shorter than those for the negative polarity. The pre-breakdown energy supplied into the test gap was inversely proportional to water resistivity.

• Proceedings of the KIEE Conference
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• 2008.04b
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• pp.197-199
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• 2008

전연전선을 핀애자에 고정하기 위해 피복바인드선을 사용하고 있는데, 오손지역에서 전선피복과 바인드 사이에서 트래킹으로 인하여 단선고장이 간혹 발생하고 있다. 과거 간접 활선시 사용하던 핫스틱(Hot-stick) 공법에 필요한 바인드 고리의 불필요성이 검토되었고 이러한 고리가 바인드선 내 순환전류를 제공하여 주울열에 의해 전선의 피복에 손상이 발생한다는 의견이 제기되었다. 본 논문에서는 절연전선의 바인드 끝단 형태를 변경하여 전선피복에 대한 침식 영향을 평가하였다.

• Electrical & Electronic Materials
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• v.3 no.2
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• pp.99-104
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• 1990

두께 30[.mu.m]의 코로나 대전된 포리비닐후로라이드 박막에 전압 -3~-6[kV]를 인가한 후, 온도범위 -100~200[.deg.C]에서 열자격 전류를 측정하였다. 결과로 .betha., .alpha. 그리고 .delta. 피크가 온도 -40, 40 그리고 90[.deg.C] 부근에서 각각 나타났다. 이들 피크의 기원으로 첫째 .betha. 피크는 카보닐기의 기여로 둘째로 .alpha. 피크는 주쇄와 비정질 영역의 측쇄에 트랩된 캐리어의 탈트랩의 기여로 나타났고 끝으로 .delta. 피크는 비정질 영역 또는 비정질과 결정질 영역 사이의 경계에 트랩된 캐리어의 탈트랩에 기여로 사료된다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.248-248
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• 2011

유전체 모세관을 이용한 해수에서의 펄스고전압 방전 특성을 연구하였다. 내경 1, 2, 3 mm의 구멍이 뚫린 Quartz 블럭에 외경 1, 2, 3 mm의 SUS 핀을 삽입하였고 삽입된 핀의 끝이 해수에 담구어 지도록 하여 고전압 방전을 발생 시켰다. 인가된 펄스 고전압은 5 kHz의 반복 주파수를 가지며, Pulse 폭을 $1{\sim}2.5{\mu}sec$까지 변화 시켜 전압전류 파형과 방전양상을 살펴 보았다. 방전은 펄스폭 변화에 따라 전해전도 전류에 의한 모세관 가열, 모세관내 미세기포형성, 기포내의 코로나 방전 개시 그리고 글로우 또는 아크방전으로 발전하는 것을 확인하였다. 모세관의 길이는 각각의 구경에 대하여 5 mm, 10 mm 두 가지로 변화하여 실험하였고, 모세관 길이 10 mm 조건에서는 방전이 매우 불안정 하였다. 각각의 방전조건별로 1~5분간 방전을 진행하여 해수내의 유리염소의 농도 변화를 살펴본 결과 방전모드가 글로우 또는 아크 방전 모드에서 단위 에너지당 유리염소 발생 수율이 큰 폭으로 증가하는 것을 확인할 수 있었다.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.759-767
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• 1995

This paper examines the electrical properties according to a curing time and a corona degradation in epoxy composites which are used for transformers. To consider these phenomena, the electrets were formed by appling high voltages to five kinds of specimens designed according to a constant mixing rate and then TSC(Thermally Stimulated Current) values at the temperature range of -160-200[>$^{\circ}C$] were measured from a series of experiments. The behaviour of carrier and its possible origins in epoxy composites were studied. Various effects of curing time and electric field on epoxy composites were also investigated.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.40-46
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• 2007

A laboratory scale experiment on phenol conversion properties by pulsed corona discharge process was carried out. Effects of operating parameters such as applied voltage, input oxygen, and electrode geometry on phenol conversion and solution properties were investigated. Electrical discharges generated in liquid phase increased the liquid temperature by heat transfer from current flow, decreased the pH value by producing various organic acids from phenol degradation, and increased conductivity by generating charge carriers and organic acids. The oxygen supply enhanced the phenol conversion through the ozone generation dissolution and the production of OH radicals. Series type electrode configuration induced more ozone production than reference type configuration because it produced gas phase discharges as well as liquid phase discharges. Therefore, the higher phenol conversion and TOC(total organic carbon) removal efficiency were obtained in series type configuration.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.94-100
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• 2015

Coronal mass ejection (CME) released due to solar flare explosion cause geomagnetic disturbance. The induced current by massive geomagnetic disturbance can cause damage to the transformer. The calculated geoelectric field is a major parameter of the geomagnetically induced current (GIC). The method applying a Fourier transform has a high accuracy but it needs all data measured for 24 hours. And the other method applying a integral equation can calculate in real time but it requires to check an accuracy. To reduce the gap between the calculated results of two methods, it adjusts the integration section. As a result, the correlation between two calculated geoelectric fields is high, and the event time and direction of the calculated current is the same as that of the measured current, and it's accuracy rate is above 92 percent.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.887-893
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• 1999

The characteristics of ozone generator targeted for air or water sterilizing in the vessel utilizing the surface corona discharge between the electrodes on the ceramic substrate was investigated by using the frequency control method. The frequency control was achieved by controlling the degree of resonance between the secondary winding inductance of transformer and the electrode capacitance of ceramic discharge plate, and the range of control was found to be 5 times of discharge current. This frequency control method showed the efficiency of 28 mP ozone generation and the stability within 3.4 % when the input voltage was varied within 40% range. The frequency control method is regarded to be more efficient way of corona discharge control compared to the conventional on/off control or voltage control methods.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1105-1107
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• 1995

In order to examine closely the corona degradation of epoxy composites, the corona electrets which are formed by appling high voltages, 300[kV/cm], to epoxy composites are experimented to measure TSC(thermally stimulated currents) at the temperature range of $-160{\sim}200[^{\circ}C]$ and to investigate the various aspects due to corona degradation in this study.