• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1463-1464
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• 2015

This paper describes for the diagnosis insulating oil for transformers integrity assessment. The high-capacity oil transformer has several insulators are entered for the purpose of insulation, such as insulating oil, insulating paper and press board. Irradiated with a gas component dissolved in the insulating oil can analyze the status of the transformer, and can prevent a sudden accident in advance.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.681-682
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• 2005

• 전기학회논문지
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• 제60권3호
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• pp.674-679
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• 2011

In this paper, we experimented and analyzed about electric fire risk assessment methods of LED lightings for outdoor. LED lighting is composed of AC power lines, AC/DC converter, DC power lines and LED lamps. There are some risk factors of electric fire in LED lighting such as short circuit between power lines or power line and ground, dielectric breakdown, leakage current, abnormal voltage inflow, poor contacts(connections), etc. As a result of this study, insulation coverings of wire was ignited due to dielectric breakdown between power lines and molten marks were formed in copper conductor. LED lighting was blown out while short circuit, beside that, electrical disorder did not occur. When abnormal voltage was inflowed, electronic components such as varistor, condenser were damaged. Partial heating was produced and insulation was melted and carbonized by arc and heating while poor contacts were happened. We expect that the results of this study would be helpful for electrical safety of LED lightings for outdoor.

• 조명전기설비학회논문지
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• 제23권6호
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• pp.104-108
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• 2009

본 논문에서는 지중전력케이블을 대상으로 케이블의 절연열화특성 분석시험을 통해 케이블의 절연열화와 절연 진단결과 및 파괴강도와의 상관관계에 대한 실증연구를 수행하였다. 시험대상 선로의 제조결함 여부를 확인하기 위해 가교도분석, 핫오일테스트 등을 실시한 결과 제조결함은 없는 것으로 확인되었다. 진단대상 선로는 3상 모두 장기간 사용에 의해 열화가 많이 진전되었고, 특히 B상이 수트리 길이 및 화학구조결함 농도 면에서 가장 열화된 케이블인 것으로 판단되며, C상, A상의 순으로 열화정도가 다소 감소함을 확인하였다. 상기 결과는 진단시험 및 파괴 강도시험 결과와 일치하며, 따라서 열화시정수법을 이용한 진단장치가 열화상태가 심각한 케이블의 선별에 효과적인 진단법임을 확인하였다.

• 대한조선학회논문집
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• 제48권5호
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• pp.451-456
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• 2011

To ensure structural integrity of membrane type LNG tank, the rational assessment of the sloshing impact responses of tank structures should be preceded. The sloshing impact pressures acting on the insulation system of LNG tank are typical irregular loads and the resulting structural responses show very complex behaviors accompanied with fluid structure interaction. So it is not easy to estimate them accurately and immense time consuming calculation process would be necessary. In this research, a simplified method to analyse the dynamic structural responses of LNG tank insulation system under pressure time histories obtained by sloshing model test or numerical analysis was studied. The proposed technique based on the concept of linear combination of the triangular response functions which are the transient responses of structures under the unit triangular impact pressure acting on structures. The validity of suggested method was verified through the example calculations and applied to the dynamic structural response analysis of a real Mark III membrane type insulation system using the sloshing impact pressure time histories obtained by model test.

• 대한조선학회논문집
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• 제44권3호
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• pp.296-304
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• 2007

The objective of this paper is to investigate the dynamic strength characteristics of LNG carriers cargo containment system under impact loads experimentally. The material properties were experimentally obtained for individual components of MARK III insulation system. A series of impact tests was performed using a custom-built drop experiment facility as varying heights and weights of the drop object. Crack initiation and propagation were measured during the cyclic dry drop experiment. The quantitative relationship between impact load and crack initiation as well as the cycle number and crack propagation were reported.

• KIEAE Journal
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• 제12권6호
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• pp.85-92
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• 2012

The Korean government has introduced building regulations with improved energy conservation measures, including higher insulation levels for building envelope. However, there are many existing buildings that tend to consume more energy for heating and cooling than new buildings, as they were built under the former regulations with relatively higher U-values of walls and glazing. In order to improve energy efficiency in existing buildings, green remodelling of building envelope and building services are required. For existing buildings, building services improvements have been achieved through energy service company(ESCO), but much attention has not been paid to building envelope improvements with various reasons, such as uncertainty of energy saving effect design issues and costs. The aim of this study is to evaluate the impact of building envelope improvements in a typical commercial building on its heating and cooling energy loads. The results show that the improvement of glazing with lower U-values has the highest energy saving effects, followed by wall, roof and floor, under the condition of same level of insulation improvements. However, high insulated glazing increased LCC because of higher initial investment costs.

• Journal of Electrical Engineering and Technology
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• 제4권1호
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• pp.123-130
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• 2009

The partial discharge (PD) measurement is a very effective method to assess the winding insulation condition of high-voltage machines, since most of the insulation failure processes are directly or indirectly caused by PD. On-line PD measurements, which can detect insulation defects of winding in the early stages on rotating machines in operation, have been accepted as the most important technique. The epoxy mica capacitive coupler is currently and extensively used for on-line detection of PD pulses of high-voltage rotating machines. To evaluate the feasibility of developing a capacitive coupler that is easier to manufacture at a lower cost compared to epoxy mica couplers, a 100pF capacitive coupler made of ceramic material is designed, fabricated and tested for on-line PD measurements of 23 kV electrical machines. A series of electrical tests and accelerated aging tests are performed on the ceramic coupler to evaluate the performance requirements, long-term reliability and thermal stability for in field application. The test results show that the newly developed ceramic coupler provides equal and improved performance at a lower cost compared to epoxy mica couplers, and estimated voltage life is anticipated to surpass 100 years.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1660-1669
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• 2014

Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.

• 전기학회논문지
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• 제57권10호
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• pp.1818-1821
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• 2008

Several off-line diagnostic tests which include the insulation resistance(IR), polarization index(PI), low-voltage AC, and recurrent surge oscillograph(RSO) tests were performed to assess the condition of generator rotor windings. The low-voltage AC and the RSO tests were performed on the gas turbine generator rotor winding to detect shorted turns. Before intentionally applying artificial shorted faults, it was confirmed by the low voltage AC and the RSO tests that the winding was in sound condition. For simulated shorted rotor winding turns, the RSO test detected the fault in the winding. The RSO test was capable of identifying the number and pole location of the shorted turns for a number of simulated shorted coils.