• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.886-889
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• 2001

Silicone rubber is being used for the housing material of outdoor high voltage insulators such as composite insulator, bushing, surge arrestor and cable terminator because of good tracking and erosion resistance, good hydrophobicity and recovery of hydrophobicity and chemical stability. But, the leakge current occurs on surface of the composite polymeric insulation materials when the insulator is used for a long time with severe contaminative condition and it can lead the contamination flashover. So the leakage current is important to estimate the condition of the silicone rubber surface. In this paper, aging characteristics of silicone rubber used for outdoor insulation have been hydrophobicity of silicone rubber in salt fog chamber with average leakage current monitoring for observing the transformation of surface degradation properties of silicone rubber with different ATH(alumina trihydrate, A1$_2$O$_3$$.$3H$_2$O) filler contents. The experimental results show that a higher peak leakage current and to raise a long time for tracking with increasing amount of ATH by the salt fog and heat recycle ageing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.19-23
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• 1998

Water tree degradations have been considered as one of the most important causes of failure in underground distribution cables with polymeric insulation. Water tree growth is a preliminary step in the sequence of electrical tree initiation and electrical breakdown of the insulation. In this paper, needle electrode is made use of the etching methods and the pellet type specimen is made to observe the water tree in succession. In previous methods are able to observe the tree degradations without cutting and dyeing. The water tree image is recorded on VTR with CCD camera. The tree length of X, Y axis direction and aging area(treeing area) are calculated with image measurement. As a result of this study, water tree is observed by non-destructive method. Electrical tree is initiated from needle electrode tip only but water tree is initiated from total area of water electrode. Electrical tree owing to water treeing is initiated at low electric field and grown with discontinuously. Namely, water tree is shown up a different characteristics of tree growth.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.409-412
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• 1997

The phenomenon of water tree degradation of underground distribution power cables is taking place in polymeric insulation materials under the existence of water and application of electric stress, but water tree is not easy to observe, o water tree features in power cables are shown after cutting and dying with methyleneblue. In previous method, it is impossible to acquire continuous treeing data, and when the insulation material has been cut, the micro crack(water tree) has been damaged. In this paper, to overcome these deflects, the etching method is made use of making needle electrode about 170[${\mu}{\textrm}{m}$] diameter, and AgNO$_3$(silver nitrate) solution is used as liquid electrode to accelerate the growth of water trees. As a result of this study, water tree is observed in real-time with microscope. Electrical tree owing to water treeing is initiated at low electric field and grown with discontinuous. Namely, water tree is shown up a different characteristics of tree growth.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.56-57
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• 2008

폴리머 애자는 자기제 애자에 비해서 경량이면서 오손특성이 내환경성이 우수하여 전세계적으로 배전 및 송전선로에 사용되고 있으며, 우리나라에서는 1973년 철도청에서 전철화 구간에 처음으로 사용하기 시작하여, 배전선로에는 90년대 중반에 본격적으로 사용되기 시작하였다. 현재 배전선로에 최초로 설치된 애자가 10여년이 지난 현재 각 지역의 환경적인 요소에 따라 폴리머애자 성능에 상이한 차이를 보이고 있다. 특히, 최근에 들어 배전선로현장에서 오염에 의한 폴리머애자 사고가 빈번하게 보고되고 있는바, 본 논문에서는 폴리머애자의 소손 분석 방법과 애자 표면의 오손이 절연성능에 미치는 영향을 연구 하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.05a
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• pp.49-51
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• 1993

Recently, use of High Voltage cables with extruded insualtion is increasing. Generally this polymeric insuation contains residual stresses. The effect of internal residual stresses is the so-called shrink-back of the insulation. If not controlled, these stresses may lead to problems during installation and service of the cables. Therefore in this paper, the definition and cause of shrinkage are described and furthermore the influence due to shrink-back at cable joint-box.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1919-1920
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• 2008

대부분의 인터넷 사용자들은 본인도 모르는 사이에 쿠키의 사용을 허용하고 있으며 이에 따른 각종 해킹과 트랙킹의 위험도 아울러 묵과하고 있는 실정이다. 하지만 역시 대부분의 사용자들은 쿠키의 위험성에도 불구하고 쿠키의 사용을 멈추지 않을 것이다. 쿠키로 인해 향상되는 인터넷 속도의 이점을 포기하지 못하기 때문이다. 쿠키를 비롯 해 해킹과 트랙킹의 위험을 내포하고 있는 또 하나의 인터넷 컨텐츠는 HTML 문서이다. 현재 HTML 문서는 소스보기를 통해 원본의 모든 출처를 노출하고 있다. 따라서 쿠키만큼 해킹과 트랙킹의 기회를 제공하고 있는 셈이다. 본 논문은 이렇게 불가피하게 사용되는 쿠키 필연적인 성격을 이용하여 웹 페이지의 암호화를 제안한다. 특히, 웹 서버와 클라이 언트 환경으로 한정하여 웹 서버가 클라이언트에게 웹 페이지를 전송할 시 쿠키를 키로 한 알고리즘을 사용하여 암호화를 한 후 전송함으로써 해킹이나 트랙킹의 위험을 최대한 낮추고자 한다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2019-2020
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• 2008

옥외에서 폴리머 애자의 사용량이 급격하게 증가하는 이유는 자기제 애자에 비해 경량이면서 오손특성이 우수하다는 장점 때문이다. 약 10년 전 국내 배전선로에 설치된 EPDM(Ethylene propylene diene monomer) 재질의 폴리머 현수애자의 섬락고장이 있었다. 폴리머 애자는 재질 특성상 사용시간에 따라 표면 열화가 진행되고, 표면의 절연저항이 감소하여 누설전류가 증가하게 된다. 표면 섬락고장을 유발하는 누설전류는 절연물 표면 상태에 많은 영향을 받는다. 본 연구에서는 폴리머애자 표면에 부착된 오손물이 전기적 특성에 미치는 영향을 분석하였다. 표면에 부착된 미세한 오손물은 발수성을 급격히 저하시켰으며, 장시간 수분에 노출될 경우 상용전압에서 표면 방전의 원인이 되었다. 결과적으로 부착된 오손물은 누설전류와 절연내력에 영향을 주어 절연 특성을 저하시키게 된다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.214-217
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• 1999

Polymeric composite insulators have been in use for outdoor insulation. However, our knowledge about their long-term performance in a outdoor environment is still very limited. Especially, these insulator are subjected to the environmental stress such as ultraviolet radiation. Hence, in this paper. the influence of UV radiation on the aging of the shed materials was evaluated. For the aging evaluation, these insulators studied by experiment methods such as contact angle measurement. oxidation induced time. SEM/EDX, FTRI-ATR, tracking test for the different insulator samples. With the increased UV exposure time, samples are shown to exhibit degradation comparable to those of new ones

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1948-1950
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• 2000

Polymeric composite insulators have been in use for outdoor insulation. However, our knowledge about their long-term performance in an outdoor environment is still very limited. Especially, these insulators are subjected to the environmental stress such as ultraviolet radiation, electrical stress, mechanical load, etc.. Hence, in this paper, we simulated the factors having influence on aging of polymer insulators using the combined aging test chamber. In order to evaluate an aging characteristics with time, we measured leakage current on these insulators to make out the degree of aging.