• 한국전기전자재료학회논문지
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• 제20권3호
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• pp.273-280
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• 2007

In this paper, the ZnO surge arrester performance of power distribution class has been studied under different manufacturing conditions such as housing materials(polymeric, porcelain), interface sealants and one-body molding type. In the recent years, the polymeric ZnO surge arresters have been developed and put into operations based on their excellent characteristics. For polymeric surge arresters, the inner gas volume is extremely small, especially in solid insulation polymeric arresters there are not any gas volume inside arresters in the structure due to polymeric materials are filled into the internal gas volume. The sealing integrity is related to safe operation of surge arrester, the prime failure reason of porcelain housed arresters is moisture ingress. In this paper, the sealing integrity of polymeric surge arresters is investigated with moisture multi-aging test and ingress test. The evaluation techniques are used to inspect the sealing integrity of polymeric arresters, including leakage current, surface temperature, reference voltage and dissipation factor.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.308-311
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• 2008

As a severe accident mitigation strategy in a nuclear power plant, ERVC(External Reactor Vessel Cooling) has been proposed. Under ERVC conditions, where a molten corium is relocated in a reactor vessel lower head, a natural circulation two-phase flow is driven in the annular gap between the reactor vessel wall and its insulation. This flow should be sufficient to remove the decay heat of the molten corium and maintain the integrity of the reactor vessel. Preliminary experimental study was performed to estimate the natural circulation two-phase flow. The experimental facility which is one dimensional, the half height, and the 1/238 channel area of APR1400, was prepared and the experiments were carried out to estimate the natural circulation two-phase flow with varying the parameters of the coolant inlet area, the heat rate, and the coolant inlet subcooling. In results, the periodic circulation flow was observed and the characteristics were varied from the experimental parameters. The frequency of the natural circulation flow rate increased as the wall heat flux increased.

• 한국공작기계학회논문집
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• 제15권6호
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• pp.15-21
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• 2006

This work deals with the electrical conductivity of dielectric on output parameters such as metal removal rate and surface roughness value of a carbon steel(SM25C) and sintered carbides cut by wire electrical discharge machining (WEDM). Dielectric has several functions like insulation, ionization, cooling, the removal of waste metal particles. The presence of minute metal particles(debris) in spark gap contaminates and lowers the breakdown strength of dielectric. And it is considered that too much debris in spark gap is generally believed to be the cause of arcing. Experimental results show that increases of cobalt amount in carbides affects the metal removal rate and worsens the surface quality as a greater quantity of solidified metal deposits on the eroded surface. Lower electrical conductivity of the dielectric results in a lower metal removal rate because the gap between wire electrode and workpiece reduced. Especially, the surface characteristics of rough-cut workpiece and wire electrode were analyzed too. Debris were analyzed also through scanning electron microscopy(SEM) and surface roughness tester. Micro cracks and some of electrode material are found on the workpiece surface by energy dispersive spectrometer(EDS).

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.148-148
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• 2017

Surface modification is a type of mechanical manipulation skills to achieve extensive aims including corrosion control, exterior appearance, abrasion resistance, electrical insulation and electrical conductivity of substrate materials by generating a protective surface using electrical, physical and chemical treatment on the surface of parts made from metallic materials. Such surface modification includes plating, anodizing, chemical conversion treatment, painting, lining, coating and surface hardening; this study conducted cavitation experiment to assess improvement of durability using anodizing. In order to observe surface characteristics with applied current density, the electrolyte temperature, concentration was maintained at constant condition. To prevent hindrance of stable growth of oxide layer due to local temperature increase during the experiment, stirring was maintained at constant speed. In addition, using galvanostatic method, it was maintained at processing time of 40minutes for 10 to $30mA/cm^2$. The cavitation experiment was carried out with an ultra sonic vibratory apparatus using piezo-electric effect with modified ASTM-G32. The peak-to-peak amplitude was $30{\mu}m$ and the distance between the horn tip and specimen was 1mm. The specimen after the experiment was cleaned in an ultrasonic bath, dried in a vacuum oven for more than 24 hours, and weighed with an electric balance. The surface damage morphology was observed with 3D analysis microscope. As a result of the study, differences were observed surface hardness and anti-cavitation characteristics depending on the development of oxide film with the anodizing process time.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.648-655
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• 1999

In this study, a relationship between DC discharge and the radiated electromagnetic waves is investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum ofthe radiated electromagnetic waves was measured at the atmospheric pressure in Liquid Nitrogen $(LN_2)$ during partial discharges in nonuniform and uniform electric field depend on positive DC power. From this experiment results, it was confirmed that when partial discharge was produced in Liquid Nitrogen and Air, the signal of partial discharge was detected by this experiment and the analysis method. It is considered thatthese results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on the equipments ultra-high voltage, superconducting and cryogenic applications.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.1-5
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• 2001

This paper describes the electrical characteristics of Nomex paper employed as an insulating material of distribution transformers. The relative permittivities(dielectric constants) and $tan{\delta}$(dielectric dissipation factors) were measured as a dielectric characteristic and the partial discharge inception voltages(PDIVs) and breakdown voltages were also measured as an electrical strength characteristic of Nomex paper. As a result, the permittivity and $tan{\delta}$ of Nomex paper showed temperature and frequency dependency. Especially, the permittivity of 0.18mm Nomex paper was 2.4 according to the ASTM condition. And the PDIVs and breakdown voltages were, almost linearly increased with the thickness of Nomex paper and its electrical strength was better than conventional kraft paper.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.43-46
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• 2001

Polymers are widely used as insulating materials at various part of power industry. However, electrical properties of these polymers are easily degraded with their working environments, especially radiation areas. In this research, radiation degradation of low density polyethylene (LDPE) used as cable insulation was evaluated with thermoluminescence characteristics. LDPE was irradiated with gamma ray up to 1000 kGy at a dose rate of 5 kGy/hr in the presence of air at room temperature. Each of the irradiated samples were carried out thermoluminescence analysis as a function of temperature. Interrelationships between thermoluminescence and dielectric characteristics and volume resistivity are investigated as well. The results of thermoluminescence analysis showed that those would be significant factors for evaluation of radiation degradation.

• Design & Manufacturing
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• 제14권3호
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• pp.57-62
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• 2020

In the drug delivery system industry, the technology with even split injection becomes important for maximizing efficiency and minimizing the side effects. In conventional drug delivery system, infection can occur due to pain and splashing. Also, various applications are impossible due to disposable use, and it is the reason to avoid to use this system because of the complexity of the driving method. Therefore, in this study, a painless drug delivery device is developed for non-pain with electrical insulation breakdown method. Finite elements analysis was used to evaluate the ejection characteristics of drugs according to the shape of the micro ejection nozzle. The effect of the number of holes in the micro nozzle, the length of the nozzle and the inner shape of the nozzle on the drug discharge characteristics were analyzed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.231-234
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• 1998

In this experiment, A1$_2$O$_3$thick films were prepared by electrophoretic method using A1$_2$O$_3$ fine powder of which compositions were FA-5-500 and FA-5-900. As a result of measurement for A1$_2$O$_3$ thick film characteristics due to applied voltage, deposition time and additives condition, the result of deposited films exhibited superior than others when the applied voltage and deposition time were 65 volts and 2 seconds in case of using modified suspension medium added additives. When taken a heat treatment and sintered A1$_2$O$_3$ deposition film made by electrophoresis with A1$_2$O$_3$ suspension medium at 1$700^{\circ}C$ for 5 minutes in hydrogen environment, it could be fabricated in good uniformity and electric characteristics as the A1$_2$O$_3$ insulating thick films.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1975-1977
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• 2000

In this study, a relationship between AC discharge progress and the radiated electromagnetic waves were investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum of the radiated electromagnetic waves was measured at the atmospheric pressure in liquid nitrogen($LN_2$) during partial discharges progress in nonuniform electric field depend on AC power supply. From this results, it was confirmed that when partial discharge was produced in liquid nitrogen, the signal of partial discharge was detected by frequency spectrum of the radiated electromagnetic waves. It is considered that these results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on superconducting and cryogenic power equipments.