• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1587-1589
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• 2000

In this paper the weight loss, surface potential decay, surface resistivity and dielectric constant are measured to investigate the surface properties, insulation characteristic changes of PET film according to the discharge treatment. As a result of the test, up to the 10[min] the surface potential decay and surface resistivity have increased. Also, from the result of dielectric constant has decreased. On the other hand, the insulation characteristic of PET film have decreased after 10[min] in the discharge treatment.

• 기술사
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• 제44권4호
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• pp.44-49
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• 2011

For the pleasant dwelling place, the most of apartments are designed with the increased green area ratio in ground space and the underground parking lot. However, the condensation in underground space has occasionally occurred due to the insufficient ventilation and insulation treatment. Despite reinforcement of the insulation treatment and mechanical ventilation for the preventing method of condensation. It seems difficult to expect preventing effects for the condensation without consideration of the thermal characteristic of structures. Furthermore, no fundamental measure has been established because maintenance work for these defects incurs a lot of costs and these defects could be occurred again. This study suggests a new method for preventing floor surface condensation through analyzing the reasons of condensation which occurred in the underground floor.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1468-1473
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• 2013

This paper dealt with the propagation characteristics of acoustic signals produced by partial discharges and the positioning of PD origin in insulation oil to develop insulation diagnostic techniques of oil-immerged transformers. Electrode systems such as needle to plane, plane to plane, and particle electrodes were fabricated to simulate some defects of power transformers. In addition, the frequency spectrum and propagation characteristics of acoustic signals with partial discharge (PD) in insulation oil were analyzed. Although there were differences based on the type of defect, the frequency spectra of the acoustic signals measured by wide and narrow band acoustic emission (AE) sensors were distributed in the range of 50 kHz-400 kHz. Therefore, a narrowband AE sensor is suitable for the diagnosis of oil-immersed power transformers. We could find the position of the PD source with an error margin of 10% in the experiments by calculating the position of the PD occurrence using the time difference of arrival measured by five AE sensors.

• Journal of Electrical Engineering and Technology
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• 제9권2호
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• pp.635-642
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• 2014

The space charge behaviors of oil-paper insulation affect the stability and security of oil-filled converter transformers of traditional and new energies. This paper presents the results of the electrical aging of oil-impregnated paper under AC-DC combined voltages by the pulsed electro-acoustic technique. Data mining and feature extractions were performed on the influence of electrical aging on charge dynamics based on the experiment results in the first stage. Characteristic parameters such as total charge injection and apparent charge mobility were calculated. The influences of electrical aging on the trap energy distribution of an oil-paper insulation system were analyzed and discussed. Longer electrical aging time would increase the depth and energy density of charge trap, which decelerates the apparent charge mobility and increases the probability of hot electron formation. This mechanism would accelerate damage to the cellulose and the formation of discharge channels, enhance the acceleration of the electric field distortion, and shorten insulation lifetime under AC-DC combined voltages.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1512-1519
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• 2013

Oil-impregnated paper is a major type of insulation used in oil-filled converter transformers for both traditional and new energy systems. This paper presents and analyzes the results of the experiment conducted on the electrical aging of oil-impregnated paper under AC-DC combined voltages using the pulsed electro-acoustic (PEA) technique. The formation and dynamics of space charge affected the performance of insulation material. The electrical aged oil-paper insulation was obtained through electrical aged experiments under the voltages. Based on the PEA technique, measurements were carried out when the oil-paper insulation system was subjected to different stressing and aging times. The space charge dynamics in the bulk of the oil-paper insulation system with different aging times were measured and analyzed. Characteristic parameters such as the total charge injection amount, the total charges of fast moving and slow moving, and the distortion factor of electric field were calculated and discussed. Results show that the longer electrical aging time, the more charges trapped in the bulk of aging sample. It leads to larger distortion factor of electric field in the bulk of aging samples and accelerate degradation of oil-paper insulation under AC-DC combined voltages.

• 한국재난정보학회 논문집
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• 제12권3호
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• pp.292-299
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• 2016

건축물에서 단열재는 매우 중요하다. 건축물에 사용하는 단열재는 재료에 따라 유기단열재와 무기단열재로 크게 나누는데 스티로폼이나 우레탄으로 만들어진 유기단열재는 화재에 매우 취약하다. 반면 펄라이트 무기단열재는 불연재이나 습기에 매우 취약하여 사용범위가 제한적이다. 본 연구에서는 단열성능이 보드의 두께가 50mm 이내의 샘플에서 열전도율과 흡수율은 각각 0.05W/mk, 3.0% 이하, 휨강도와 발수율은 각각 $25N/cm^2$, 98% 이상인 무기단열재를 개발하고 열전도 특성을 평가하였다.

• 한국전기전자재료학회논문지
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• 제37권3호
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• pp.286-291
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• 2024

Research on aged insulation of cables by stress is constantly being considered for reliable and stable power transmission of offshore wind farms. This study aimed to evaluate the insulation characteristic of aged XLPE (cross-linked polyethylene) insulation for application of offshore wind farms. In this study, The XLPE insulation of cable was set as various mechanical strains. The XLPE insulation is exposed to the mechanical stress below yield strain of 5%, 10%, and 20%. Aged samples were tested by using the method of AC BDV (alternative current breakdown voltage), tensile strength, elongation, and SEM (scanning electron microscope) to obtain insulation characteristics. The experimental results show that the dielectric breakdown of the sample with a strain 20% was 50% lower than the unaged sample; thereby, demonstrating that the mechanical strain that occurred in the submarine cables can weaken the insulation characteristics. Therefore, mechanical strain should be monitored when laying and operating submarine cables for offshore wind farms.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.78-83
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• 2010

본 논문은 배전선으로 널리 사용되고 있는 비닐캡타이어 타원형코드(Polyvinyl chloride insulated cabtyre oval cord, VCTFK)의 끝단에서 발생되는 트래킹의 진전특성에 대하여 언급하고 있다. 트래킹은 VCTFK의 끝단에 전해액을 적하함으로써 발생시켰다. VCTFK 끝단에서 발생되는 트래킹 진전과정 및 그 특징은 다음과 같다. 방전으로 인해 VCTFK 끝단에서 탄화가 시작되었고 침식도 일어났다. 도체에서 가까운 절연층이 먼저 침식되었으며, 피복층은 그 이후에 침식되었다. 침식이 진행된 이후, VCTFK 끝단의 표면에서 탄화물의 적층이 시작되었다. 적층 단계에서 아크를 동반했으며, 트래킹 파괴로 이어졌다.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.31-35
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• 2019

The lumped-parameter circuit model for a no- insulation (NI) high temperature superconductor (HTS) magnet has been well understood after many experimental and analytic studies over a decade. It successfully explains the non-linear charging behaviors of NI magnets. Yet, recently, multiple groups reported that the post-quench electromechanical behaviors of an NI HTS magnet may not be well explained by the lumped circuit model. The characteristic resistance of an NI magnet is one of the key parameters to characterize the so-called "NI behaviors" of an NI magnet and recently a few groups reported a potential that the characteristic resistance of an NI magnet may substantially vary during a quench. This paper deals with this issue, the increment of contact resistance of the no-insulation (NI) REBCO magnet during a quench and its impact on the post-quench behaviors. A 7 T 78 mm NI REBCO magnet that was previously built by the MIT Francis Bitter Magnet Laboratory was chosen for our simulation to investigate the increment of contact resistance to better duplicate the post-quench coil voltages in the simulation. The simulation results showed that using the contact resistance value measured in the liquid nitrogen test, the magnitude of the current through the coil must be much greater than the critical current. This indicates that the value of the contact resistance should increase sharply after the quench occurs, depending on the lumped circuit model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1783-1785
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• 1999

In this paper, we apply V-Q Lissajoucs' figure for observation of a V-Q (Voltage-Charge) hysteresis loop at interface between phosphor and insulation layer in P-ELDz which are a simple structure and the back lighting of LCDs (Liquid Crystal Display). In V-Q Lissajous' figure, we measured a change of hysteresis loop according to the thickness of Insulation and phosphor layer. From experiment result, we will be obtained a optimum thickness of insulation with comparing the correlation of a V-L (Voltage-Luminance) and V-Q hysteresis loop.