• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
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• pp.449-452
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• 2004

The life of power transformer is basically dependent on the aging deterioration of insulating paper. Analysis of insulating paper for its DP value or tensile strength requires removal of a few strips of paper but direct measurement of this properties is not practical for in-service transformers. For this reason furfural analysis by HPLC has gained increasing favor as a means of estimating degradation of insulating papers in power transformers and this paper reports on the analysis of data on the concentration of furfural in oil samples from about 50 power transformers and the case study. The data showed that furfural content can estimate more accurately aging characteristics compared to concentration of CO, $CO_2$. We expect that these results can be useful to predict the aging characteristics and life diagnosis of power transformers and further the study must be continued.

• 한국초전도ㆍ저온공학회논문지
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• 제16권1호
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• pp.14-18
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• 2014

The mechanical, electrical and thermal characteristics of insulating materials may significantly affect the performance and reliability of electrical devices using superconductors. General method to provide insulating layer between coated conductors is wrapping coated conductor with Kapton tape. But uniform and compact wrapping without failure or delamination in whole coverage for long length conductor is not a simple task and need careful control. Coating of insulating layer directly on coated conductor is desirable for providing compact insulating layer rather than wrapping insulating layers around conductor. Ceramic added polymer has been widely used as an insulating material for electric machine because of its good electrical insulating properties as well as excellent heat resistance and fairy good mechanical properties. The insulating layer of coated conductor should have high breakdown voltage and possesses suitable mechanical strength and maintain adhesiveness at the cryogenic temperature where it is used and withstand stress from thermal cycling. The insulating and mechanical properties of polymer can be improved by adding functional filler. In this study, insulating layer has been made by adding ceramic particles such as $SiO_2$ to a polymer resin. The size, amount and morphology of added ceramic powder was controlled and their effect on dielectric property of the final composite was measured and discussed for optimum composite fabrication.

• 한국생활과학회지
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• 제8권1호
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• pp.125-134
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• 1999

The purpose of this study was to investigate the effects of heat transfer characteristics of fibers on the Qmax of insulating nonwovens. The effects of fiber type, moisture content, washing cycles on the Qmax were observed. The correlations between Qmax measured by KES-F7 system and subjective warm/cool touch perception test was analyzed. The results obtained were as followed: 1. Heat transfer characteristics of fibers effected on the Qmax of insulating nonwovens. 2. Moisture transport properties of fibers effected considerably on the Qmax of nonwovens and the increasing rate of Qmax by increasing moisture content was much higher at wool than polyester. 3. As a result of subjective perception test, subjective warm/cool touch and wettness of wool nonwoven was increased obviously by increasing moisture content. 4. At the same moisture content, wool nonwoven showed higher subjective cool touch and wetness than polyester. 5. In the physical properties of nonwovens, thickness was the most effective factor on the Qmax of insulating nonwovens.

• 대한방사선기술학회지:방사선기술과학
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• 제9권1호
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• pp.73-81
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• 1986

This paper carried out an experiment on the characteristics of time, temperature, electric field and the dependense of electrode materials and gap length by the conduction current of the insulating oil used for x-ray tube housing. The obtained results can be summarized as following: 1. In the x-ray tube housing insulating oil with vacuum condition, conduction current is declined more than the x-ray tube housing insultaing oil with the air, and is held stable states. 2. At the low electric field the higher temperature of the x-ray tube housing insulating oil is increased, the more conduction current. 3. The dependence of electrode material is appeared at the low electric field and the short gap length than the high and the long with Fe> Cu >Al. 4. At the I-E characteristics, the low electric field than 1000 [V/cm] is appeared Ohm's law region, and the high become saturation region. 5. At the same electric field, the longer gap length become, the more conduction current is increased, and the same applied voltage, the longer, the less conduction current is decreased, the less low than high temperature x-ray tube housing insulating oil.

• Tribology and Lubricants
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• 제29권1호
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• pp.51-55
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• 2013

In this work, a new fluorescence emission measurement technology was introduced and experimentally compared with other measurement methods, such as the titration method and IR spectroscopy, to validate it for the oil oxidation measurement of electrical insulating oil. The oxidation characteristics of insulating oil were found to be fairly represented by the titration method and IR spectroscopy, and the results are comparable to a change in the fluorescence emission ratio that is defined as the shift in fluorescence intensity in the measured wavelength range. The result also shows that by the measurement of fluorescence emission ratio, it is possible to detect the oxidation of oil relatively earlier than by other methods. This study suggests that the developed technology can provide sufficient information for evaluating the insulating oil quality, and that the developed FER sensor can be used as an effective condition monitoring device of electrical insulating oil oxidation.

• 한국안전학회지
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• 제26권6호
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• pp.7-12
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• 2011

In recent years, environmental concerns have been raised on the use of poorly biodegradable fluids in electrical apparatus in regions where spills from leaks and equipment failure could contaminate the surroundings. The newly invented vegetable insulating oil is highly biodegradable and have negligible impact on the environment, human health and the ecosystem. For development of the environmental-friendly pole transformer using vegetable insulating oil, the dielectric constructions of the pole transformer were discussed in this paper. Depending on the dielectric constructions, the AC breakdown characteristics of the Nomex insulating papers and the vegetable insulating oil were studied by simulated electrode systems. Based on the experimental results, the maximum design stress($E_{max}$) for insulation design of the environmental-friendly pole transformer were suggested.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권6호
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• pp.321-326
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• 2002

This paper describes the mechanical and electrical characteristics of insulating paper impregnated with diluted varnish(W-128), according to Korean Standards. The varnish was diluted with a solvent of 6 different wt%. Kraft paper and Nomex paper were impregnated with the diluted varnish in a vacuum condition, and then completely dried. As the mechanical characteristics, the thickness of the completely dried varnish, the drying time and the tensile strength of the specimens were measured, and as the electrical characteristics, the permittivity, the tan $\delta$ and the specific resistance were evaluated as well.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.347-349
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• 1999

We have fabricated insulating thin films using p-hexadecoxyphenol(p-Hp) that was formed phenol-formaldehyde resin of crosslinked structure from reaction with formaldehyde by LB technique. For fabricated MIM device, the possibility for insulating layers of electronic were investigated by electrical properties of their LB films according to crosslinking of LB films current-voltage (I-V) properties and frequency-capacitance (C-F) characteristics. We have provided evidence for the high insulating performance of phenol-formaldehyde thin films by the LB method. Conductivity of their LB films was as follows: pure water > 1 % aq. Formaldehyde > heat treatment, in the current-voltage (I-V) characteristics. It is demonstrated that insulation properties of crosslinked p-HP LB films were improved. In capacitance-frequency properties, the heat-treated p-HP LB films for crosslinking showed a low relative dielectric constant.

• 대한방사선기술학회지:방사선기술과학
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• 제10권1호
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• pp.75-83
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• 1987

The insulating oil used for X-ray tube housing were degraded by X-ray irrdiation, high temperature and high anode voltage for normal operation. This study was measured the conduction current-X-ray dose, heating degradation, time, temperature and electric field characteristics and the dependense of electrode materials and gap length in the X-ray irradiatied insulating oil under of D.C voltage. The obtained results can be summarized as following. 1. The conduction current of X-ray irradiated insulating oil is more about $2.5{\sim}3$ times as large as than that of non x-ray irradiated, and is become saturation phenomena after some degree. 2. The conduction current of many times heating x-ray irradiated insulating oil is more than that of a few times heating. 3. The higher temperature x-ray irradiated insulating oil is increased, the more conduction current, and that is increased about ten times as large as when it's temperatures is increased to $80^{\circ}C\;at\;30^{\circ}C$, twenty five times at $100^{\circ}C$. 4. The dependence of electrode materials is appeared at the low electric field, and the small gap length with Fe > Cu > Al. 5. The low electric field than 3000 v/cm is appeared Ohm's law region, and the high is become saturation region at the I-E characteristics. 6. The larger gap length is become, the more conduction current is increased at the same electric field.

• 전기학회논문지P
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• 제58권4호
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• pp.476-482
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• 2009

This paper describes the development of capacitive sensor for the diagnosis of liquid dielectrics, which is widely used as the electrical insulating oil of transformer, circuit breaker, cable and etc. To survey the dielectric properties of the virgin and aged electrical insulating oils, we utilized the highly precise measuring system, using the principle of cross capacitance. The measured properties were used to determine the design factors of the sensor. Then the factors were optimized with the help of computational analysis. To evaluate diagnosis by the sensor, we performed accelerated thermal aging test about electrical insulating oils. The condition of aged specimens were investigated by measurements of relative permittivity i.e. capacitance change by capacitive sensor. And to evaluate the hysteresis characteristics with the change of temperature, we constructed a testing system, which was composed with vacuum drying oven, oil chamber and measuring instruments, such as LCR meter, MUX and so forth. Through the results of this investigation, we confirmed the superior characteristics of the newly developed sensor.