• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.280-285
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• 2014

In order to evaluate the insulation deterioration in the stator windings of five gas turbine generators(137 MVA, 13.8 kV) which has been operated for more than 13 years, diagnostic test and AC dielectric breakdown test were performed at phases A, B and C. These tests included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B and C) of No. 1 generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable and bad level to the insulation condition. Overall analysis of the results suggested that the generator stator windings were indicated serious insulation deterioration and patterns of the PD in all three phases were analyzed to be internal, slot and spark discharges. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. The breakdown voltage at phases A, B and C of No. 1 generator stator windings failed at 28.0 kV, 17.9 kV, and 21.3 kV, respectively. The breakdown voltage was lower than that expected for good-quality windings (28.6 kV) in a 13.8kV class generator. In the AC dielectric breakdown and diagnostic tests, there was a strong correlation between the breakdown voltage and the voltage at which charging current increases abruptly ($P_{i1}$, $P_{i2}$).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.35-40
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• 1997

As demand of electric power are growing and transmission line limited owing to enlargement of the downtown area The eonfidence of underground transmission cable which shows gradual growth are high. It is found whether insulating ability is good or not. In this paper, The exper iment result is shown that the fall of insulating ability and take preventive measure through the analysis of tans, water content, dielectric breakdown voltage, total acid number, volume resistivity , and gas in the oil in an accordance with the characteristic change of oil used very much for insulating oil of cable.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집
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• pp.270-273
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• 2001

Electrical tree is studied widely by manufacture state of insulating material fare and blazing fire diagnosis system of use in phenomenon of part discharge that happen for main cause of dielectric breakdown of equipment for electric power. Use process that draw tree pattern here measuring above zero to study special quality of this electricity tree, real-time processing by image processing is proposed because reproduction of tree blazing fire process drops and pattern of tree is difficult correct quantification of tree growth by existent visual observation by involution. This research presents general process that need in image processing of tree blazing fire, and that remove various noises that happen in above zero by measuring electrical tree dividing background and complete view in measured above zero taking advantage of specially proposed complete view object abstraction techniques effectively and quantification of tree becomes easy naturally, can apply to dielectric breakdown estimate because can chase growth process of tree.

• 한국전기전자재료학회논문지
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• 제12권1호
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.199-202
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• 1998

Power capacitors are highly reliable equipment due to their completely enclosed configuration. Aging diagnosis system using partial discharge(PD) and acoustic emission(AE) is being highlighted as a research area for degradation of power capacitors. Their dielectric strength can be however reduced due to some stresses such as over-voltage or thermal degradation of the insulation material during their long period of operation. In this paper, it has been developed to express the AE of the EVENT(average amplitude) and HIT(pulse count) according to the source location. And real time measurement of PD signals for aging diagnosis of power capacitors.

• 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.

• 전력전자학회논문지
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• 제8권3호
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• pp.247-252
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• 2003

전동기 절연열화와 파괴는 전동기에 가해지는 스트레스에 영향을 받는다. 즉 절연물의 수명은 주어지는 스트레스의 심한 정도에 따라서 좌우된다. 전동차용 견인전동기에서도 과도서지에 의한 전기적인 열화를 검토하는 것은 매우 중요한 요소이다. 본 논문에서는 인버터에서 발생되는 과도서지에 의한 고정자 코일의 절연특성을 고찰해 보았다. 전동기의 절연상태, 열화진전도, 열화발생 범위 등을 측정하는 유용한 비파괴시험 방법에는 여러 가지가 이용되고 있다. 누설전류, 유전손실(tan$\delta$), 정전용량, 성극지수(PI), 부분방전 등의 방법들을 통하여 고정자 코일의 절연상태를 분석하였다. 이러한 진단 방법들은 전동차의 견인전동기에 대한 열화상태와 수명예측에 유용한 방법이 될 것으로 여겨진다.

• 전기학회논문지
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• 제59권4호
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• pp.728-732
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• 2010

GIS(Gas insulated switching gear) is power equipment with excellent dielectric strength and is economy merit in high confidence and stability. Recently, because equipment of GIS was occurring problem of confidence used for a long time, partial discharge on-line diagnosis systems have been importantly recognized. Partial discharge (PD) detection is an effective means for monitoring and evaluation of dielectric condition of gas insulated system (GIS). The ultra-high-frequency (UHF) PD detection technique can detect and locate the PD sources inside GIS by detecting electromagnetic wave emitted from PD source. Therefore, real-time diagnostic system using UHF detection method has been developed for this application is being expanded gradually. However, the signal of partial discharge occurring in SF6 gas is very weak and susceptible to external noises which mainly consist of PD in air. Thus, it is important to distinguish the PD in SF6 gas more sensitively from the external noises. Unfortunately, these external noise signals and the partial discharge signals have very similar characteristics. Therefore, to solve this problem, we need the signal processing method for distinguish partial discharge signals with external noise signals for improvement of SNR(signal to noise ratio) and sensitivity. In this paper, we proposed internal signal processing method for removing external noise signals with built-in pre.amplifier and frequency conversion circuit.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.270-273
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• 2001

Electrical tree is studied widely by manufacture state of insulating material fare and blazing fire diagnosis system of use in phenomenon of part discharge that happen for main cause of dielectric breakdown of equipment for electric power. Use process that draw tree pattern here measuring above zero to study special quality of this electricity tree, real-time processing by image processing is proposed because reproduction of tree blazing fire process drops and pattern of tree is difficult correct quantification of tree growth by existent visual observation by involution. This research presents general process that need in image processing of tree blazing fire, and that remove various noises that happen in above zero by measuring electrical tree dividing background and complete view in measured above zero taking advantage of specially proposed complete view object abstraction techniques effectively and quantification of tree becomes easy naturally, can apply to dielectric breakdown estimate because can chase growth process of tree.

• KEPCO Journal on Electric Power and Energy
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• 제2권3호
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• pp.421-424
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• 2016

In order to evaluate the insulation deterioration in the stator windings of air-cooled gas turbine generators(119.2 MVA, 13.8 kV) which has been operating for more than 15 years, diagnostic test and AC dielectric breakdown test were performed on phases A, B and C. Diagnostic test included measurements of AC current, dissipation factor, partial discharge (PD) magnitude and capacitance. ${\Delta}I$ and ${\Delta}tan{\delta}$ in all three phases (A, B, and C) of generator stator windings showed that they were in good condition but PD magnitude indicated marginally serviceable condition. After the diagnostic test, an AC overvoltage test was performed by gradually increasing the voltage applied to the generator stator windings until electrical insulation failure occurred, in order to determine the breakdown voltage. Although phase A of generator stator windings failed at breakdown voltage of 29.0 kV, phases B and C endured the 29.0 kV. The breakdown voltage in all three phases was higher than that expected for good-quality windings (28.6 kV) in a 13.8 kV class generator.