• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.128-132
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• 2003

This paper discusses several electrical properties of tape-type insulation impregnated with liquid nitrogen ($LN_2$) in superconducting cable. Synthetic polypropylene laminated paper has been tested for its short-term breakdown strength and partial discharge(PD) characteristics under AC voltage. furthermore, the effect of winding parameter on breakdown strength, PD incepti on and extinction electrical stress with different test samples are discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1989.06a
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• pp.11-14
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• 1989

Some experimental studies on the dielectric strength characteristics of organic material under compressive stress associated with high magnetic fields and of liquid coolant in the presence of thermally induced bubble, which might be generated at unexpected quench of immersed-cooling superconducting devices, was performed to obtain the basic data on the electrical insulation design for superconducting apparatus. PET and liquid nitrogen were used as test mediums.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.30-33
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• 2001

This thesis deal with ferroelectric and ferrimagnetic materials, PZT/Ferrite ceramics. We conducted test of magnetical and electrical measurement. From this measurement, We obtained tunability and we can control characteristic impedance($Z_0$) from permeability($\mu$) and dielectric constant($\varepsilon$) for impedance matching in transmission line.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.05a
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• pp.235-238
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• 1996

In this paper, We intended to evaluate the characteristics of XLPE/EPDM interface which exists in the cable joint. The fault was mainly occurred in this interface. Thus we looked into the electrical characteristics through the conduction current and the breakdown test. Through from the experiment, we obtained the result that the conduction current in this interface flowed less than other dielectric materials, that the breakdown strength was higher and that the pressure dependance ㅐf the breakdown strength was higher.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.30-33
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• 2001

This thesis deal with ferroelectric and ferrimagnetic materials, PZT/Ferrite ceramics. We conducted test of magnetical and electrical measurement. From this measurement, We obtained tunability and we can control characteristic impedance(Z$_{0}$) from permeability($\mu$) and dielectric constant($\varepsilon$) for impedance matching in transmission line.e.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.5
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• pp.625-632
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• 2004

Perfluorocompounds ($PFC_s$), such as tetrafluoromethane ($CF_4$) and hexafluoroethane ($C_2F_6$), have been widely used as plasma etching and chemical vapor deposition (CVD) gases for semiconductor manufacturing processes. Since these $PFC_s$ are known to cause a greenhouse effect intensively, there has been a growing interest in reducing $PFC_s$ emissions. Among various $CF_4$ decomposing techniques, a dielectric barrier discharge (DBD) is considered as one of a promising candidate because it has been successfully used for generating ozone ($O_3$) and decomposing nitrogen oxide (NO). Firstly, optimal concentration of oxygen for $CF_4$ decomposition was found to figure out how many primary and secondary reactions are associated with DBD process. Secondary, to find effective discharge method for $CF_4$ decomposition, a streamer and a glow mode in DBD are experimentally compared, which includes (i) coaxialcylinder DBD, (ii) DBD reactor packed with glass beads. and (iii) a glow mode operation with a helium gas. The test results showed that optimal concentration of oxygen was ranged 500 ppm~1% for treating 500 ppm of $CF_4$ and helium glow discharge was the most efficient one to decompose $CF_4$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.6
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• pp.1163-1168
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• 2011

Most transformers use insulating and cooling fluids derived from petroleum crude oil, but mineral oil has some possibility of environmental pollution and fire with explosion. vegetable oil fluids extracted from seed has superior biodegradation and fire-resistant properties including an exceptionally high fire point enhancing fire safety. In this study, it is aimed at the practicality of substituting natural ester dielectric fluid for mineral oil in liquid insulation system of transformers. As a rise in coil winding temperature has a direct influence on transformer life time, it is important to evaluate the temperature rise of coil winding in vegetable oil in comparison with mineral oil. Four transformers for the test are designed with 10KVA, 13.2KV, one phase unit. The temperature are directly measured in insulating oil of these transformers with the two sorts of natural ester and mineral oil dielectric fluid respectively. Experiment for aging carry out two means. First means remained $120^{\circ}C$ that transformer of mineral oil were operated at 185% load. Second means is that insulating oils of two natural ester and mineral oil were aged by thermal cycles repeating from $30^{\circ}C$ to $120^{\circ}C$. For the heating, Transformers were operated at 185% load. For the cooling, cooling system was operated in the chamber. Samples were analyzed at 42, 63, 93, 143, 190, 240 300cycles. Analysis contents are dielectric strength, total acid value. Mineral oils compared results of first means with results of second means. And compared two sort natural esters respectively with mineral oil in second means.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.53-58
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• 2002

Electrical insulation and mechanical properties of the plasma sprayed oxide ceramic coatings were studied before and after the sealing treatment of the ceramic coatings. Plasma sprayed A1$_2$O$_3$-TiO$_2$ coating as the reference coating was sealed using three commercial sealants based on polymer. Penetration depth of the sealants to the ceramic coating was evaluated directly from the optical microscope using a fluorescent dye. It is estimated that the penetration depth of the sealants to the ceramic coating is from 0.2 to 0.5 mm depending on the sealants used. The preliminary test results with a DC puncture tester imply that the dielectric breakdown voltage mechanism of plasma sprayed ceramic coatings has been determined to be a corona mechanism. Dielectric breakdown voltage of the as-sprayed and as-ground samples have shown a linear trend with regard to the thickness showing an average dielectric strength of 20 kV/mm for the thickness scale studied. It is also shown that grinding the coating before sealing and adding fluorescent dye do not agent the penetration depth of sealants. All of the microhardness, two-body abrasive wear resistance, bond strength, and surface roughness of the ceramic coating after the sealing treatment are improved. The extent of improvement is different from the sealants used. However, three-point bending stress of the ceramic coating after the sealing treatment is decreased. This is attributed to the reduced micro-crack toughening effect since the cracks propagate easily through the lamellar of the coating without crack deflection and/or branching after the sealing treatment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1222-1228
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• 2005

Analysis on the field uniformity inside of a reverberation chamber was done at 2.45 GHz which is an operating frequency of MWO(Microwave Oven). The Schroeder's Quadratic Residue Diffuser was designed for the chamber, and 3 different types of diffusers have been investigated using the finite-difference time-domain(FDTD) method for the field characteristics of each type. Type 2 and 3 diffusers were filled with dielectric material, and the size of these could be designed smaller than Type 1, without degradation of field characteristic. Type 3 diffuser shows better results among the three types of diffusers in view of increased test region and better field uniformity.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.25-30
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• 2006

When wet soil overlies dry soil, which can be found in the infiltration test, the radar wave is not attenuated and guided within wet soil layer. This phenomenon is known to be the dispersive guided wave and happens when the thickness of upper wet layer is less than or comparable to the wavelength of radar wave. In this study, we have conducted the FDTD modeling and obtained the velocity dispersion curve to identify the dispersive guided wave through F-K analysis. This guided wave can be explained by modal propagation theory and a simple inversion code was developed to obtain the two layer's dielectric constants as well as layer thickness. By inverting the dispersion curve from synthetic modeling data, we could obtain the accurate dielectric constants and layer thickness. Moreover, we could enhance the accuracy by including the higher mode data. We expect this method will be very useful to get the quantitative property of subsurface when the condition is similar.