• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 전기설비
• /
• pp.79-81
• /
• 2005

Chemical methods for moisture contents detection of insulation system in transformer must dismount equipment for sampling, and there is shortcoming such as acquiring partial data for measuring. Also the samples can't immediately analyze in field. The Recovery Voltage Method (RVM) will be able to measure a moisture contents at low voltage without dismounting equipment. Therefore, in advanced countries RVM would be used to measure the moisture contents which permeates to the insulation system without weighting additive degradation or mechanical damage. In this paper we have investigated for overcoming these shortcomings using the RVM, and we have measured the moisture contents of transformer insulation with temperature.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 추계학술대회 논문집
• /
• pp.428-431
• /
• 1997

In order to compare with domestic underground distribution cables, the foreign cable which was manufactured in USA, 1982 and has been serviced in field for 13 years was characterized with several tests. Water trees, voids, and convolutions are not found in insulation. In hot oil test, insulation is very clean and there was no separation of insulation and conductor shield. The results of degree of crosslinking, FTIR, and DSC are also usual. Specially, the distribution of OIT is very good, which is different from that of domestic cables. The content of impurities is relatively small. This cables was manufactured with good state and no extraordinary degradation is found.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2002년도 추계학술대회 논문집
• /
• pp.163-166
• /
• 2002

Recently, the insulation breakdown accident has been experienced at 6.6kV inverter driving motor. That brought about the reliability degradation of motor driving system.. We need to find the solution with system engineering level. The objectives of this study are developing the appropriate filter for the drive to protect the motor and the Insulation system of motor which Is driven by inverter. We clarify the cause of the deterioration of the inverter driving motor through the analysis of Insulation breakdown accidents.

• International Journal of Safety
• /
• 제7권1호
• /
• pp.10-14
• /
• 2008

For evaluating the radiation degradation of cross-linked polyethylene (XLPE) cable insulation due to the irradiated oxidation, XLPE was irradiated with ${\gamma}$-ray. For each irradiated samples, TGA, DSC, FT-IR, and tensile tests were carried out. Regarding radiation degradation, oxidative process was predominant. TGA, DSC and FT-IR can be useful tools for evaluating the radiation degradation due to the irradiated oxidation because these analyses need only small amount of samples. The results of TGA, DSC and FTIR analyses showed the similar tendency for irradiated degradation. They can be useful tools for evaluating the oxidation of insulating material by non-destructive testing.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2007년도 제38회 하계학술대회
• /
• pp.975-976
• /
• 2007

Thermal and mechanical stresses, caused by repetitive start and stop and load fluctuation during long time operation, on winding stator bars are one of the main causes for electrical degradation of insulating materials. To understand the degradation process, we manufactured bar specimens with the same processes that make generator winding stator bars and the specimens were subjected to various degrees of thermal cycling. Measurements of the insulation properties, such as dissipation factor, tip-up and partial discharge, for un-aged specimens and for specimens aged by thermal cycling at 50, 100, 250, 500 and 1000 thermal cycles were performed. Finally all specimens were tested to obtain electrical breakdown voltages. In this paper we present the data and electrical degradation analysis results obtained during this program.

• 한국전기전자재료학회논문지
• /
• 제24권3호
• /
• pp.208-214
• /
• 2011

In this thesis, the partial discharge according to applied voltage and variations of cross-sectional area and length of the conductor related to general condition for using cable was measured in order to study degradation diagnosis for 2-Core cable of the PVC insulator used in industrial fields for other safety installations. Also the thermal degradation conditions under various installation circumstances of cables were studied by assuming degradation conditions with each different degradation rate (50%, 67%, 100%) such as variation in degradated temperature, thermal exposure time, normal state, partially degradated state and overall degradated state for thermal degradation diagnosis. The quantity of electric discharge (V-Q) according to applied voltage was measured for measurement of inception voltage and extinction voltage. The quantity of electric discharge and the number of electric discharge (Q-N) were measured with applied voltage kept constantly. In addition, pictures were taken using SEM (scanning electron microscope) to compare the surface of external insulator to degradated state of internal insulator according to thermal degradation temperature and also compare the surface of external insulator to degradated surface state of internal insulator according exposure time of cables to thermal stress.

• Journal of Electrical Engineering and Technology
• /
• 제13권3호
• /
• pp.1166-1172
• /
• 2018

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.231-235
• /
• 2001

Insulation aging diagnosis system provides early warning regarding electrical equipment defect. Early warning is very important in that it can avoid great losses resulting from unexpected shutdown of the production line. Since relations of insulation aging and partial discharge dynamics are non-linear, it is very difficult to provide early warning in an electrical equipment. In this paper, we propose the design method of insulation aging diagnosis system that use a magnetic wave and acoustic signal to diagnoses an electrical equipment. Proposed system measures the partial discharge on-line from DAS(Data Acquisition System) and acquires 2D Patterns from analyzing it. For fettering the noise contained in sensor signals we used ICA algorithms. Using this data design of the neuro-fuzzy model that diagnoses an electrical equipment is investigated. Validity of the new method is asserted by numerical simulation.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.263-264
• /
• 2006

For practical electrical insulation design of high temperature superconducting (HTS) power apparatuses, knowledge of the dielectric behavior of insulators in cryogenic liquid such as liquid nitrogen ($LN_2$) is essential. So in this paper, we discussed experimental investigations of breakdown and V-t characteristics of several insulators such as Kapton and glass fiber reinforced plastic (GFRP) that are candidates of insulator for HTS apparatus in cryogenic liquid. And we investigated the degradation of these insulation samples after breakdown with the microscope and SEM photograph. Moreover, survival and hazard analysis were performed.

• 한국화재소방학회논문지
• /
• 제23권3호
• /
• pp.17-22
• /
• 2009

에폭시 분체도료는 부스닥트, 및 전기기기에 절연재료로 광범위하게 사용되어 진다. 특히 Coating 절연 방식의 경우 전류에 의한 줄 열로 인해 전기화재 및 폭발의 점화 원인이 된다. 본 연구는 에폭시분체도료의 열화특성에 대해 절연파괴, 아크방전, 수명특성(V-t)을 중심으로 비교검토하고 이에 대한 기초데이터 확보 및 전기화재 원인인 절연특성에 대해 연구 하였다. 온도변화에 따른 절연특성은 시편 KS가 유리전이온도(Tg) 이전까지 $8{\sim}10%$ 정도의 감소로 안정적이었다. V-t 및 아크방전특성의 경우, 열화시편에서도 안정적 특성을 유지하였다. 열화에 의한 전기적특성의 경우 시편KS가 우수한 성능을 가지고 있다.