• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.224-227
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• 2003

According to the increasing power demands for the power transmission of major cities, HTS power cables which have large current capacity and low power loss will be needed. In this paper we have studied breakdown voltage properties of paper/liquid composite insulating system for HTS cable insulation. And we measured the dielectric loss(tan$\delta$) of mini-model cable. From results, the insulation paper-ice composite insulation system is thought to be one of good candidate for the electrical insulating system at cryogenic temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1299-1304
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• 2003

Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.08a
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• pp.58-63
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• 2002

For the experiment the four types of spacer were distinguished by arrangement. The flashover characteristic on each types of spacer was investigated and the flashover phenomena were observed to understand breakdown mechanism in liquid nitrogen($LN_{2}$). The spacer should be placed interior coil as an insulator, a cooling channel and s supporter of structures. The simulated electrode used in the experiment was made from five turns of HTS tape. Experimental results revealed that multi-layer and barrier effects did work well in Air but did not in $LN_{2}$. These result suggested that the flashover in LN2 caused by the bubbles due to partial discharge at micro gap, g. The flashover characteristics decreased to 70% when g is 0.2 mm. The degradation was improved by even treatment on surface of coil electrode.

• Korean Journal of Clinical Pharmacy
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• v.22 no.2
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• pp.176-180
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• 2012

The stability of triamcinolone in three kinds of oral liquid syrups at 4 and $25^{\circ}C$ was studied for 21 days. Twenty tablets of 4 mg triamcinolone were mixed with 100 mL of each oral liquid syrup, which is Levotuss$^{(R)}$Syrup (levodropropizine 6 mg/mL), Ucerax$^{(R)}$Syrup (hydroxyzine 2 mg/mL), and Xyzal$^{(R)}$Liquid (levocetirizine 0.5 mg/mL). The chromatographic analysis after deliberate degradation showed no evidence of any breakdown product likely to interfere with the chromatographic peak of the parent substance. The relationship between triamcinolone concentrations and peak areas was linear from 50 to 1000 ${\mu}g/mL$ ($r^2$ = 0.9998). The analysis method was precise, with coefficients of variation no greater than 5.4%. Triamcinolone was stable for up to 14 and 21 days in Levotuss$^{(R)}$Syrup at 25 and $4^{\circ}C$, respectively; in Ucerax$^{(R)}$Syrup and Xyzal$^{(R)}$Syrup, it was stable for at least 21 days at both temperatures. The percentages of initial triamcinolone concentration remaining after 21 days were $72.3{\pm}3.2$ and $94.9{\pm}6.0%$ and $93.2{\pm}4.9$ and $92.4{\pm}5.7%$, and $92.6{\pm}1.2$ and $92.7{\pm}2.2%$ in Levotuss$^{(R)}$Syrup, Ucerax$^{(R)}$Syrup, and Xyzal$^{(R)}$Syrup at 25 and $4^{\circ}C$, respectively. The pH variations of all test solutions were within 0.8. Based on the results, it was concluded that triamcinolone in three oral liquid syrups which are Levotuss$^{(R)}$syrup, Ucerax$^{(R)}$syrup and Xyzal$^{(R)}$syrup was chemically and physically stable in both states of refrigeration and room temperature for at least 14 days.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.15-18
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• 2003

Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.8
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• pp.144-149
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• 2005

In this paper, insulations characteristics by temperature changes($+30{\sim}-40[^{\circ}C]$) of $SF_6$ gas in the experimental chamber were studied. From this result, The breakdown characteristics classify the vapor stage of $SF_6$ according the Paschen's law, the gas & liquid coexisted stage of voltage value increases & much deviation and the VB low stage as the interior of chamber gets filled with mixture of $SF_6$ that are not liquefacted and remaining air which couldn't be ventilated. In addition the ability of insulation of liquid $SF_6$ was higher than that of the highly pressurized $SF_6$ gas. In this research, we want to provide the base data on designing insulation of high-temperature superconductor and the cryogenic equipments by investigating the insulation characteristics of $SF_6$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.7
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• pp.2298-2314
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• 1996

Electric field effect on boiling of refrigerants R11, R113, and FC72 has been investigated experimentally. One purpose of the experimental investigation is to determine the effects of the electrode arrangements on electrohydrodynamic boiling of the above mentioned liquids. The test equipment employed in the experiment consists of a shell and tube heat exchanger with six or six and twelve rows of electrode wires around the tube. It has been found that the applied voltage promotes the boiling heat transfer coefficient except FC72. Boiling heat transfer enhancement obtained is about 230% for R11, 280% for R113. It has also been observed that bubbles detached from the tube aggregate at the place where the electrical gradient force balances with the buoyancy one. These aggregated bubbles force to decrease the boiling heat transfer coefficient as well as to reduce the voltage needed to the dielectric breakdown.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1548-1549
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• 2011

High voltage cryogenic insulation issues need to be addressed in order to promote the commercialization of high temperature superconducting (HTS) equipment. As a fundamental step in the development of the optimum bushings for HTS devices, the breakdown characteristics of liquid nitrogen mixed with liquefied insulating gases such as $N_2$, $SF_6$, and $CF_4$ have been investigated. In order to investigate the possibility of substituting $CF_4$ gas for $SF_6$ gas for the bushings of HTS electrical equipment, AC withstanding voltage tests have been performed. In this paper, finding the maximum electric field $E_{max}$ using utilization factor ${\eta}$. This result is applicable to developing the real scale HTS equipment of the design parameters.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.10
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• pp.1471-1476
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• 2012

A study on the dielectric characteristics of the Glass Fiber Reinforced Plastic (GFRP) is important for designing a reliable high voltage superconducting machines such as transmission superconducting fault current limiters, superconducting cables, and superconducting transformers. In this paper, dielectric experiments of the GFRP under lightning impulse voltage are conducted in liquid nitrogen($LN_2$) according to various experimental conditions such as the thicknesses of the GFRP, the diameters of electrode systems and the pressures. The dielectric characteristics of the GFRP are analyzed by using a Finite Elements Method(FEM) according to various field utilization factors. It has been reported that the electrical insulation design of the GFRP would be conducted by considering the mean electric field intensity($E_{mean}$) distributed inside the GFRP. In this study, it is found that the dielectric performance of the GFRP could be explained by not only $E_{mean}$ but also the maximum electric field intensity ($E_{max}$). Finally, the empirical formulae of the GFRP to estimate an electrical breakdown voltage at sparkover under the lightning impulse condition are deduced. It is expected that the presented experimental results in this paper are helpful to design electrically reliable high voltage superconducting machines using the GFRP as an insulation material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.494-498
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• 2002

HTS transformer experimentally. High temperature superconductors can only be applied against an engineering specification that has to be determined for each particular application form the design requirements for economic viability and for operation margins in service. High temperature superconducting(HTS) power apparatus are very promising candidates for application. Especially, these advantages make superconducting transformers very promising candidates for application in electrical power engineering and locomotives. In order to realize the HTS transformer, it is necessary to establish the high voltage insulation technique in cryogenic temperature. So far, insulation research of Pancake type HTS transformer is lacking nothing but insulation research of . solenoid type transformer consisted. Therefore, the composite insulation of double pancake coil type transformer are described and ac breakdown voltage characteristics of liquid nitrogen(LN$_2$) under HTS pancake coil electrode made by Bi-2223/Ag are studied. Breakdown in LN$_2$ is dominated electrode shape and distance. The relation between surface flashover voltage is considered for FRP. This research presented basis information of electrical insulation design for double pancake coil type HTS transformer.