• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.406-409
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• 2002

The primary insulation system used in an oil-filled transformer is Kraft paper, wood, porcelain and, of course, oil. Modern transformers use paper that is chemically treated to improve its tensile strength properties and resistance to aging caused by immersion in oil. These insulation papers are mainly aged to thermal stress. Over the course of the insulation paper and oil's life it is exposed to high temperatures, oxygen and water. Its interaction with the steel of the tank and core plus the copper and aluminium of the windings will eventually cause the chemical properties of the oil to decay. High temperature have an effect on mechanical strength of cellulous paper using the layer insulation. We made two aging cell in which thermal aging tests of insulation papers and mineral oil are conducted. It is measured dielectric strength, number of acid, moisture, etc. of insulation paper and oil aged in the aging cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.12
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• pp.1289-1295
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• 2004

In this paper, degradation in field-aged PV modules including degradation of interconnect, discoloration of encapsulant and hot spot have been observed and analyzed. From the results, photovoltaic module installed for 6 years shows around 16 % drop of electrical properties due to the interconnect degradation and PV module passed 18 years has been found to drop of around 20 % mainly by the encapsulant discoloration. Furthermore the difference between low and high temperature of PV array at hot spot goes up to 3$0^{\circ}C$ and it leads to interconnect degradation. On the other hands, the temperature difference was observed to be around 15$^{\circ}C$ at the encapsulant discoloration spot of PV array.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.461-461
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• 2008

According to previous report, aged sleeves for old transmission lines have various defect such as biased installation or corrosion of steel sleeve. These defects occupied almost 50 percent of investigated aged sleeves. The defects have been limited power capacity of transmission line. And it can cause serious problems such as rapid increasing of sag or falling out of overhead conductor from sleeve. This paper study on thermal behavior of sleeve with various defect model. The detailed results were presented in the text.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.255-257
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• 2001

In this paper, the silicon rubber insulator for transmission line was experimented for 1,000 hours aging test in salt-fog condition. To evaluate and examine the aging properties of silicon rubber insulator for test, the leakage current of surface was measured. Also hydrophobicity and scanning electron microscopy were compared with initial and aged sample respectively. Above results, we can confirm that the surface properties of silicon rubber insulator easily aged by salt-fog condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.203-207
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• 2002

In order to evaluate the aging of mineral oil immersed distribution transformers, it gathered some insulation oil in over loaded and long time(exceed their service life, 13yrs.) aged transformers in the field, we measured moisture content, acid number, dielectric strength of the oil as defined in KS C 2101 standard. And also, it had been measured dielectric constant, specific resistant, $tan{\delta}$ on aged transformer oil at from $10^{\circ}C$ to $130^{\circ}C$. These results are compared with a new mineral oil. From this study, it can be considered that the analysis of mineral oil may be suitable for evaluation of life expectancy in distribution transformers

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.3
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• pp.287-291
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• 2006

This paper describes mechanical and electric properties of ACSR $410\;mm^2$ conductor from many of older overhead conductor. Samples of conductors itemized two division according to operation sector, green area, salt and pollution area. Samples of conductors operated various environment conditions have undergone laboratory metallurigical investigation and tensile strength torsional ductility and electrical performance. The steel core were found to have retained their original properties to a large degree in both tensile strength and the number of turns to failure. On the other hand the aluminum conductor showed reductions in tensile strength. To determine the remaining useful life of aged conductor, an unacceptable deterioration level has to established for each diagnostic procedure.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.104-105
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• 2008

According to previous report, aged sleeves of old transmission line showed several defaulted installation patterns, which is biased or corrosive-fractured of steel sleeve installed cases. The latter case occupied almost 25 percent of investigated aged sleeves. These defects can cause serious accidents such as rapid increasing of sag or falling out of overhead conductor from sleeves. This paper studies thermal properties and tension for ACSR conductor in case of fractured steel sleeve model. The detailed results were presented in the text.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.396-403
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• 2004

The dielectric properties of Y-ray irradiated and thermally aged polyetheretherketone (PEEK) have been investigated. Results of the temperature dependency of dielectric properties indicated that the glass transition temperature of aged PEEK increased as radiative and thermal ageing. The frequency dependency of dielectric properties implied that the magnitude of radiation and thermal induced dipoles, ions increased as radiative and thermal ageing. The values of relaxation intensity calculated using Cole-Cole's circular arc can be useful for evaluation of degradation level of PEEK.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.596-598
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• 2000

This paper presents a new accelerating aging test facility for distribution lightning arresters. Aging parameters of lightning arrester are moisture ingress, electrical stress and surge absorption and so on. In this system, we applied 13.2kV to 6 samples and controled temperature and humidity of chamber and measured leakage currents of the all samples. Also we developed accelerating aging cycle which consists of -35$^{\circ}C$∼90$^{\circ}C$ temperature and 40%∼90% humidity. Through the aging test we found out the leakage current of aged sample increases rapidly according to the temperature rising. Hereafter we can determine the replacement guide of leakage current for field operating arresters and condition assessment of aged samples through this aging test.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.11-17
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• 1999

Aging characteristics of the crosslinked polyethylene have been measured after applying electrical, thermal and combined stresses. ICP and FT-IR measurements confirmed diffusion of low molecular weight components such as antioxidant and presence of carbonyl group. Carbonyl group of aged crosslinked polyethylene under combined stress was detected by FT-IR. As deterioration of the crosslinked polyethylene progresses, crystallinity degree and density decrease. Also, dielectric properties have been measured by tan $\delta$ and $\varepsilon$$_{r}$ measurements. The three-parameter Weibull distribution was found to be the best suited among other probabilistic distribution representing the dielectric breakdown strength of aged crosslinked polyethylene. The scale parameter and location parameter decreases as the applied stress increases. The shape parameter increases as the stress increases.s.