• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.146-150
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• 2015

Insulation breakdown voltage and insulation lifetime were investigated in straight lines or twisted pairs with polyesterimide-polyamideimide enameled round wires (EI/AIW ). The enamel thickness was 50 μm and the conducting copper radius was 0.50, 0.75, 1.09, and 1.50 mm, respectively. There were many air gaps in a twisted pair therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge according to Paschen's law. Insulation breakdown voltage and insulation lifetime were highest in the sample of 0.75 mm conductor radius, which was higher than those values for 0.50 mm or 1.09 and 1.55 mm.

• 한국안전학회지
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• 제34권1호
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• pp.8-13
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• 2019

Weight and elongation changes of IV and HIV insulations were measured simultaneously at several given temperature of $80^{\circ}C$, $90^{\circ}C$ and $100^{\circ}C$. And the lifetime was predicted using the Arrhenius model. Based on the initial weight values, a 50% elongation reduction was seen at 6.96% for the IV insulation and 10.29% for the HIV insulation. The activation energy from the slope of the lifetime regression equation was calculated as 92.895 kJ/mol(0.9632 eV) for the IV insulation and 95.213 kJ/mol(0.9873 eV) for the HIV insulation. Also, the expected lifetime at the operating temperature of $30^{\circ}C$ to $90^{\circ}C$ is 2.02 to 94.32 years, and longer lifetime was predicted on HIV insulated wires than on IV insulated wires. As a result, it was found that the thermal characteristics of the HIV insulated wires were about 12.44% better than those of IV insulated wires under the same conditions of use.

• Transactions on Electrical and Electronic Materials
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• 제17권5호
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• pp.297-301
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• 2016

The effects of ambient temperature and diameter on the insulation lifetime of winding coils prepared with polyamideimide (PAI), flexural PAI (nanosilica 5 wt%) and anti-corona PAI (nanosilica 15 wt%) wires were investigated. The winding coils were made of enameled wire with enamel thickness of 30~50 μm. The thickness and width of the rectangular copper wires were 0.77~0.83 mm and 1.17~1.23 mm, respectively. The insulation breakdown lifetime decreased with increasing ambient temperature regardless of wire type and winding coil diameter under an inverter surge of 1.5 kV/20 kHz. The insulation breakdown lifetimes of φ5 mm winding coils at 150, 200, and 250℃ were 11.38, 5.19, and 4.22 min respectively, and those of φ10 mm winding coils at 150, 200, and 250℃ were 11.32, 5.79, and 4.57min respectively. The winding coil diameter had little effect on the insulation lifetime.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.840-845
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• 2017

In this paper, in order to investigate the lifetime of oil-paper insulation, specimens were artificially aged with thermal and electrical multiple stresses. Accelerated ageing factors and equivalent operating years for each aging temperatures were derived from results of tensile strengths for the aged paper specimens. Also, the evaluation for the multi-stress aged specimens were carried out through the measurement of impulse breakdown voltage at high temperature of $85^{\circ}C$. The lifetimes of the oil-paper insulations were calculated with the value of 66.7 for 1.0 mm thickness specimens and 69.7 for 1.25 mm thickness specimens throughout the analysis of impulse BD voltages using equivalent operating years, which means that dielectric strengths would not be severely decreased until the mechanical lifetime limit. Therefore, for the lifetime evaluation of the oil-paper insulation, thermal aging would be considered as a dominant factor whereas electrical degradation would be less effective.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.296-297
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• 2011

본 연구에서는 PTFE 전기절연재의 수명예측을 위해 일련의 열중량 분석시험을 수행하였다. PTFE 시료는 온도상승률을 달리하며 상온에서 $700^{\circ}C$까지 온도를 가하였다. PTFE의 활성화에너지는 일정한 중량감소가 발생할 때의 로그 형태 온도상승률에 대한 변환온도 역수 선도에서 계산하였다. 또한 Toop에 의해 제안된 활성화 에너지와 추정 수명과의 관계식을 이용하면 주어진 운용온도 하에서의 PTFE 수명시간도 예측할 수 있다.

• Transactions on Electrical and Electronic Materials
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• 제17권3호
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• pp.163-167
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• 2016

Inverter surge resistant enameled wire was prepared with an organic/inorganic hybrid nanocomposite, and the effect of ambient temperature on the insulation lifetime of the enameled wire in the form of twisted pair was studied by a withstanding voltage tester. The organic polymer was Polyesterimide-polyamideimide (EI/AI) and the inorganic material was a Nano-sized silica (average particle size : 15 nm). The enamel thickness was 50 μm and the ambient temperature was 100, 150, 200, and 250, respectively. Transmission electron microscopy (TEM) observation showed that Nano-sized Silica were evenly dispersed in EI/AI. There were many air gaps in a twisted pair, therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge accordi, ng to Paschen’s law. As ambient temperature increased, insulation lifetime decreased according to Arrhenius relationship, which was explained by the increasing mobility of polymer chains in EI or AI. And insulation breakdown voltage value at 10 kHz was 1,864.5 sec (31.1 min), which is 1.9 times higher than at 20 kHz, 981.6 sec (16.4 min).

• 한국전기전자재료학회논문지
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• 제29권10호
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• pp.641-646
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• 2016

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at $20^{\circ}C$, $70^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

• 한국인터넷방송통신학회논문지
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• 제14권5호
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• pp.237-242
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• 2014

이 논문은 발전소에서 설치 운전 중인 6.6kV 고전압 케이블이 시간에 따라 성능이 악화되는 현상의 추세를 결정하는 수명지수를 파악하기 위한 논문이다. 우리가 연구한 케이블 시스템은 설치 후 13 년 동안 운전하고 있다. 삼상전력에 연결되는 변류기, 온도센서 LPF 등을 이용한 측정장치를 개발하여 케이블의 절연저항 변화 특성을 해석하였다. 고전압 22kV 케이블과 비교하면 절연체의 두께가 더 두껍기 때문에 특성을 다르게 나타낸다. 동작시간이 경과함에 따라, 절연저항이 계속 감소하지 않음을 확인 하였다. 일정한 값으로 감소하다가 더 이상 감소하지 않고 상하진동하는 특성을 나타내었다. 지난 13 년 동안의 열화과정을 파악할 수 없었지만, 시스템이 안정 상태에서 동작을 하였다는 사실은 열화가 아직 발생하지 않았다는 의미이다. 이런 경우에는, 수명지수를 예측할 수 없기 때문에 케이블의 수명을 정량적으로 예측할 수 없음을 확인하였다.

• Transactions on Electrical and Electronic Materials
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• 제16권4호
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• pp.190-193
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• 2015

Insulation breakdown characteristics of an inverter surge resistant enameled wire were investigated in a twisted pair prepared with organic/inorganic hybrid nanocomposite. Organic polymer was polyesterimide-polyamideimide (EI/AI) and inorganic material was a nano-sized silica. The enamel thickness was 50 μm and the diameters of enameled copper wires were 0.75, 1.024, and 1.09 mm, respectively. There were many air gaps in a twisted pair. Therefore, when the voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge according to Paschen’s law. The insulation lifetime of the hybrid wire (HW) was 41,750 sec, which was 515.4 times more than the 81 sec of EI/AIW. In addition, the shape parameter of HW was 2.58, which was 3.4 times higher than 0.75 of EI/AIW.

• 한국전기전자재료학회논문지
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• 제29권1호
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• pp.17-22
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• 2016

The activation energy of a material is an important factor that significantly affects the lifetime and can be used to develop a degradation model. In this study, a thermal analysis was carried out to evaluate and collect quantitative data on the degradation of insulation materials like EPR and CSP used for nuclear power plant cables. The activation energy was determined from the relationship between log ${\beta}$ and 1/T based on the Flynn.Wall.Ozawa method, by a TGA test. The activation energy was also derived from the relationship between ln(t) and 1/T based on isothermal analysis, by an OIT test. The activation energy of EPR derived from thermal analysis was used to calculate the accelerated aging time corresponding to the number of years of use, employing the Arrhenius equation, and determine the elongation corresponding to the accelerated aging time.