• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.119-123
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• 2002

In this study, we discussed the characteristics of breakdown and surface flashover of FRP in L$N_2$ for applying it to spacer of a superconducting power equipment. Fiberglass reinforced plastic(FRP) has high breakdown puncture strength and has high mechanical strength. So the research of its dielectric properties have been conducted in liquid nitrogen($LN_2$). We measured breakdown voltage of FRP and distinguished four types of surface flashover along solid insulator with arrangement of electrodes and measured the surface flashover voltages of each types of electrode arrangement. The type of a electrode set at the back of the insulator showed the worst dielectric property. The property of surface flashover depending on pressure was tested.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.1-4
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• 2002

Electrical properties of liquid nitrogen ($LN_2$) and gaseous nitrogen($GN_2$) have become of great interest again since the discovery of high temperature superconductors . It is very important from a point of superconducting apparatus protection to elucidate breakdown characteristics in $LN_2$ and $GN_2$ at atmospheric and pressurized conditions Therefore. this paper studies the effect of pressure on the breakdown characteristics in $LN_2$ and $GN_2$. Af high voltage is applied to electrode system with uniform and non-unform field in various gap length. And Breakdown voltages of $LN_2$ and $GN_2$ are investigated under AC voltage for Pressure ranging from 0 and 0.5 MPa. This research presented basis information of electrical insulation design for liquid nitrogen immersed HTS power apparatus.

• Geomechanics and Engineering
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• v.1 no.2
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• pp.155-168
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• 2009

Breakdown pressures obtained from the classic, linear elastic breakdown model are compared with the corresponding pressures obtained using a nonlinear material model. Compression test results obtained on sandstone and siltstone are used for that purpose together with previously formulated nonlinear model which introduces elasticity functions to address nonlinear stress-strain behaviour of rocks exhibiting stress-dependent mechanical properties. Linear and nonlinear collapse pressures are also compared and it is shown that material nonlinearities have significant effect on both breakdown and collapse pressures and on tangential stresses which control breakdown pressure around a borehole. This means that the estimates of ${\sigma}_H$ made using linear models give stress values which are different than the real values in the earth. Thus the importance of a more accurate analysis, such as provided by the nonlinear models, is emphasised. It is shown, however, that the linear elastic model does not necessarily over-predict borehole stresses and the opposite case can be true, depending on rock type and test interpretation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.104-104
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• 2010

With the advent of nano-particle fillers in insulating materials, the insulating materials of superior quality have come to fore. In the recent past, nanocomposite LDPE/XLPE (Low Density Polyethylene/Cross Linked Polyethylene) power cable dielectrics have been synthesized. A preliminary evaluation of these new class of materials seem to show that, addition of small amounts of sub-micron inorganic fillers improved the dielectric properties of the composite, in particular, the volume resistivity, and the DC breakdown strength. The thermal behaviour, for example, the stability of composites against decomposition and ensuing electrical failure, do not seem to have been addressed. In a conventional XLPE insulated cable, the average thermal breakdown strength and maximum temperature at the onset of breakdown were seen to be markedly lower than the corresponding intrinsic breakdown strength and decomposition temperature. In this page, analysis of DC Breakdown of nano-composite insulating material for HVDC Cable is introduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.48-48
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• 2010

In this paper, we have investigated temperature dependence of dielectric breakdown voltage at epoxy with added nano-filler(MgO), which is used as a filler of epoxy additives for HVDC(high voltage direct current) submarine cable insulating material with high thermal conductivity and restraining tree to improve electrical properties of epoxy resin in high temperature region. In order to find dispersion of the specimen, the cross sectional area of nano-composite material is observed by using the SEM(Scanning Electron Microscope) and it is conformed that each specimen is evenly distributed without the cohesion. As a result, it is confirmed that the strength of breakdown of all specimen at 50 [$^{\circ}C$] decreased more than that of the dielectric breakdown strength at room temperature. When temperature increases from 50 [$^{\circ}C$] to 100 [$^{\circ}C$], we have confirmed that breakdown strength of virgin specimen decreases, but specimens with added MgO show constant dielectric breakdown strength.

• Journal of the Korea Safety Management & Science
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• v.6 no.1
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• pp.301-309
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• 2004

An inorganic filling agent, ATH (alumina trihydrate) was used to induce inorganic-organic coupling by mixing with stearic acid, acryl silane, vinyl silane as surface treatment agents in order to apply as a high voltage insulating material. Volumetric resistivity was shown to vary with surface treatment agents, and the highest value was obtained in case of the mixture with vinyl silane. The dielectric breakdown intensity was shown to decrease gradually and saturate to a stable value, possibly due to the increase of cross link density in the vinyl radicals introduced to silica surface, resulting in stable dielectric breakdown intensity in the final stages. Tracking and flame retardant properties were also shown to be the best among the samples investigated in this study.

• International Journal of Safety
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• v.8 no.1
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• pp.14-17
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• 2009

The $Co^{60}$ $\gamma$-ray irradiation effects on the electrical and thermal characteristics of low density polyethylene crosslinked by Dicumyl peroxide (DCP) were investigated. We experimented on electrical properties as following; electrical tree inception and growing type for applying AC step voltage, AC breakdown strength, volume resistivity with increasing dosage. Also, chemical analyses were performed TGA, gel fraction. These electrical properties changed depending upon its crosslinking degree and byproducts from crosslinking reactions. Crosslinking reactions were considered causing by $\gamma$-ray irradiation and DCP had contained in low density polyethylene.

• Progress in Superconductivity and Cryogenics
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• v.6 no.1
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• pp.22-27
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• 2004

It is important to mechanical properties of dielectric paper and cable to optimum electrical insulation design of HTS cable, because the cable has experience of mechanical stress, such as tensile stress, bending stress. Also, it is operated at cryogenic temperature. From the results, it was observed that the tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen is decreased. Because PPLP was deteriorated by microcrack and tensile strain. According as bending radius multiple is decrease, the ac and impulse breakdown stress of mini-model cable is sharply decreased.

• Transactions on Electrical and Electronic Materials
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• v.14 no.1
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• pp.39-42
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• 2013

The effects of particle size on the mechanical and electrical properties of epoxy/spherical silica composites were studied. The silica particle sizes were varied from 5 to 30 ${\mu}m$ and the filler content was fixed to 60 wt%. Tensile and flexural tests were carried out and the interfacial morphology was observed by scanning electron microscopy (SEM). The electrical insulation breakdown strength was estimated using sphere-sphere electrodes with different insulation thicknesses of 1, 2 and 3 mm. The tensile strength and flexural strength increased with decreasing particle size, while electrical insulation breakdown strength increased with increasing particle size.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.343-346
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• 1998

Ultra-thin gate oxide in MOS devices are subjected to high-field stress during device operation, which degrades the oxide and exentually causes dielectric breakdown. In this paper, we investigate the electrical properties of ultra-thin nitrided oxide (NO) and reoxidized nitrided oxide(ONO) films that are considered to be promising candidates for replacing conventional silicon dioxide film in ULSI level integration. We study vriations of I-V characteristics due to F-N tunneling, and time-dependent dielectric breakdown (TDDB) of thin layer NO and ONO depending on nitridation and reoxidation condition, and compare with thermal $SiO_{2}$. From the measurement results, we find that these NO and ONO thin films are strongly depending on its condition and that optimized reoxided nitrided oxides (ONO) films show superior dielectric characteristics, and breakdown-to-change ( $Q_{bd}$ ) performance over the NO films, while maintaining a similar electric field dependence compared to NO layer.