• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.164-167
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• 1997

A series of interpenetrating polymer networks(IPN) based on Epoxy, MA and PU were synthesized in order to improve withstand voltage properties of Epoxy resin. Dielectric breakdown characteristics are investigated for six types of specimens. As a result, it was found that impulse voltage dielectric breakdown characteristic of SIN specimen was the most excellent. It was also found that SIN specimens were stronger than anything else in scanning electron microscopy. On the other hand, as a result of consideration of dielectric breakdown strength change according to adding fi1ter, it was confirmed that the decrease of dielectric breakdown strength are controlled slightly by IPN method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.43-46
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• 2001

The DC dielectric breakdown of epoxy composites used for transformer was experimented and then its data were simulated by Weibull distribution equation in this study. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it was believed that the adding filler formed interface, charges were accumulated in it, the molecular mobility was raised, the electric field was concentrated, electrons were accelerated and then electron avalanche was early accomplished. From the analysis of Wei bull distribution equation, it was confirmed that as the allowed breakdown probability was· given by 0.1[%], the value of 'applied field was needed to be under 17.20[kV/mm].

• Progress in Superconductivity and Cryogenics
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• v.13 no.3
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• pp.5-9
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• 2011

DC high-temperature superconducting(HTS) cable system has attracted a great deal of interest from the view point of low loss, dense structure and large capacity. A HTS cable system is made of cable and termination. The insulating materials and insulation technology must be solved for the long life, reliability and compact of cable system. In this paper, we will report on the dielectric breakdown characteristics of insulating materials for HTS cable and termination. The AC, DC and lightning impulse breakdown strength of laminated polypropylene paper(PPLP) and glass fiber reinforced plastic(GFRP) have been measured under nitrogen pressures in the range of 0.l-0.4MPa. PPLP and GFRP are found to have a significantly higher DC breakdown strength. Also, DC surface flashover voltage of negative polarity is slightly higher than that of positive polarity in GFRP.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05b
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• pp.159-163
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• 2003

In this study, the DC dielectric breakdown of epoxy composites used for PCB material was experimented and then its data were simulated by Weibull distribution equation. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised, the electric field is concentrated, and the acceleration of electron and the growth of electron avalanche are early accomplished. From the analysis of Weibull distribution, it was confirmed that as the allowed breakdown probability was given by 0.1[%], the applied field value needed to be under 21.5[kV/mm].

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.8
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• pp.1398-1406
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• 2008

This paper describes the electrical breakdown characteristics of broken toughened glass stem insulators by comparing with those of sound ones. The broken toughened glass stem insulators were taken from the electric railway field. According to the international standards, the sound and broken toughened glass stem insulators were tested in electrical strength. In the test, the power frequency voltage and the impulse voltage with a standard waveform were applied to the insulators. The power frequency voltage tests were carried out under both dry and wet condition and the impulse voltage tests under only dry condition. The acquired results were compared one another and discussed in electrical breakdown characteristic by analyzing the flashover progress pictures. As a result, the electrical strength of the broken toughened glass insulators was acquired and the processes of the surface breakdown on the toughened glass insulators were confirmed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.724-728
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• 2001

In this study, the dielectric breakdown of epoxy composites used for transformers was experimented and then its data were simulated by Weibull distribution probability. The dielectric breakdown characteristics origin in epoxy composites were examined and various effects of dielectric breakdown on epoxy composites were also discussed. As a result, first of all, speaking of dielectric breakdown properties, the more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical. And the breakdown strength of specimens with filler was lower than it of non-filler specimens because it is believed that the adding filler forms interface and charge is accumulated in it, therefore the molecular motility is raised, the electric field is concentrated, and the acceleration of electron and the growth of electron avalanche are early accomplished. In the case of filled specimens with treating silane, the breakdown strength become much higher since this suggests that silane coupling agent improves interfacial combination and relaxs electric field concentration. Finally, from the analysis of weibull distribution, it was confirmed that as the allowed breakdown probability was given by 0.1%, the applied field value needed to be under 21.5㎹/cm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.9
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• pp.1511-1517
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• 2016

The aim of this study is to improve of properties for electrical AC insulation breakdown strength using epoxy/micro-nano alumina composites with adding glycerol diglycidyl ether (GDE:1,3,5g). This paper deals with the effects of GDE addition for epoxy/micro alumina contents (40,50,60wt%)+surface modified nano alumina(1_phr) composites. 14 kinds specimen were prepared with containing epoxy resins, epoxy micro composites and epoxy nano-micro alumina mixture composites. Average particle size of nano and micro alumina used were 30nm and $1{\sim}2{\mu}m$, respectively. The micro alumina used were alpha phase with Heterogeneous and nano alumina were gamma phase particles of spherical shape. The electrical AC insulation breakdown strength was evaluated by sphere to sphere electrode system and raising velocity 1kV/s. The AC breakdown strength decreased insulation properties of multi-composites according to increasing micro alumina and GDE addition contents.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.477-481
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• 2011

Composites of insulating polyethylene and carbon black are widely used in switching elements, conductive paint, and other applications due to the large gap of resistance value. This research addresses the critical exponent of dielectric breakdown strength of polymer matrix composites (PMC) made with carbon black and polyethylene below the percolation threshold (Pt) for the first time. Here, Pt means the volume fraction of carbon black of which the resistance of the PMC is transferred from its sharp decrease to gradual decrease in accordance with the increase of carbon-black-filled content. First, the Pt is determined based on the critical exponents of resistivity and relative permittivity. Although huge cohesive bodies of carbon black are formed in case of being less than the Pt, a percolation path connecting the conducting phases is not formed. The dielectric breakdown strength (Dbs) of the PMC below Pt is measured by using an impulse voltage in the range from 10 kV to 40 kV to avoid the effect of joule heating. Although the observed Dbs data seems to be well fitted to a straight line with a slope of 0.9 on a double logarithm of (Pt-$V_{CB}$) and Dbs, the least squares method gives a slope of 0.97 for the PMC. It has been found that finite carbon-black clusters play an important role in dielectric breakdown.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.364-371
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• 1996

In this study, in order to investigate the applicability of IPN structure to epoxy resin which has been widely used as electrical and electronic insulating materials, DC dielectric breakdown properties and morphology were compared and analyzed according to variation of network structure, using the single network structure specimen formed of epoxy resin alone, interpenetrating polymer network specimen formed of epoxy resin/methacrylic acid resin, and interpenetrating polymer network specimen formed of epoxy resin/methacrylic acid resin/polyurethane resin. As results of the measunnent of DC dielectric breakdown strength at 50[.deg. C] and 130[>$^{\circ}C$], IPN specimen formed of epoxn, resin 100[phr] and methacrylic acid resin 35[phr] was the most excellent, and which corresponded to the SEM phenomena. The effect of IPN was more remarkable at high temperature region than at low temperature region. It is supposed that the defect of epoxy resin, dielectric breakdown strength is lowered remarkably at high temperature region, be complemented according to introducing IPN method.