• 전기학회논문지
• /
• 제60권6호
• /
• pp.1274-1279
• /
• 2011

The purpose of this paper is to present the manufacturing defect and damage pattern of a 3 phase 22.9/3.3kV oil immersed transformer, as well as to present an objective basis for the prevention of a similar accident and to secure data for the settlement of PL related disputes. It was found that in order to prevent the occurrence of accidents to transformers, insulating oil analysis, thermal image measurement, and corona discharge diagnosis, etc., were performed by establishing relevant regulation. The result of analysis performed on the external appearance of a transformer to which an accident occurred, the internal insulation resistance and protection system, etc., showed that most of the analysis items were judged to be acceptable. However, it was found that the insulation characteristics between the primary winding and the enclosure, those between the ground and the secondary winding, and those between the primary and secondary windings were inappropriate due to an insulating oil leak caused by damage to the pressure relief valve. From the analysis of the acidity values measured over the past 5 years, it is thought that an increase in carbon dioxide (CO2) caused an increase in the temperature inside the transformer and the increase in the ethylene gas increased the possibility of ignition. Even though 17 years have passed since the transformer was installed, it was found that the system's design, manufacture, maintenance and management have been performed well and the insulating paper was in good condition, and that there was no trace of public access or vandalism. However, in the case of transformers to which accidents have occurred, a melted area between the upper and the intermediate bobbins of the W-phase secondary winding as well as between its intermediate and lower bobbins. It can be seen that a V-pattern was formed at the carbonized area of the transformer and that the depth of the carbonization is deeper at the upper side than the lower side. In addition, it was found that physical bending and deformation occurred inside the secondary winding due to non-uniform pressure while performing transformer winding work. Therefore, since it is obvious that the accident occurred due to a manufacturing defect (winding work defect), it is thought that the manufacturer of the transformer is responsible for the accident and that it is lawful for the manufacture to investigate and prove the concrete cause of the accident according to the Product Liability Law (PLL).

• 한국재료학회지
• /
• 제22권6호
• /
• pp.309-315
• /
• 2012

Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were $750^{\circ}C$, $400-500^{\circ}C$, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

• 한국산학기술학회논문지
• /
• 제15권4호
• /
• pp.1819-1824
• /
• 2014

건축물 에너지 효율등급제도, 건축물 에너지 소비증명제 등 건축물 에너지 관련 법 제도가 지속적으로 강화되면서, 이에 대응하기 위한 고성능 단열재, 기능성 유리를 적용한 창호의 개발이 활발히 진행되고 있다. 에너지 절약을 위한 기능성 유리의 중요성이 크게 부각되고 있음에 따라 진공유리에 대한 관심이 높아지고 있다. 진공유리의 핵심공정 중 모서리 접합공정은 진공유리의 기밀성, 강도, 형상에 있어 매우 중요한 공정이다. 본 논문에서는 수소혼합가스를 이용하여 전기로 내부에서 두 장의 유리를 접합하였다. 공정변수에 따른 접합유리의 강도와 형상을 측정 및 분석 하였으며, 다구치 실험계획법을 이용하여 접합유리의 강도를 예측하였다. 추가실험을 통해 예측 값과의 오차율을 확인함으로서 실험의 타당성을 검증하였다.

• Asian Journal of Atmospheric Environment
• /
• 제5권4호
• /
• pp.228-236
• /
• 2011

Since most Green House Gases (GHGs) and air pollutants are generated from the same sources, it will be cost-effective to develop a GHGs reduction plan in combination with simultaneous removal of air pollutants. However, effects on air pollutants reduction according to implementing any GHG abatement plans have been rarely studied. Reflecting simultaneous removal of air pollutants along with the GHGs emission reduction, this study investigated relative cost effectiveness among GHGs reduction action plans in Busan Metropolitan City. We employed the Data Envelopment Analysis (DEA), a methodology that evaluates relative efficiency of decision-making units (DMUs) producing multiple outputs with multiple inputs, for the investigation. Assigning each GHGs reduction action plan to a DMU, implementation cost of each GHGs reduction action plan to an input, and reduction potential of GHGs and air pollutants by each GHGs reduction action plan to an output, we calculated efficiency scores for each GHGs reduction action plan. When the simultaneous removal of air pollutants with the GHGs reduction were considered, green house supply-insulation improvement and intelligent transportation system (ITS) projects had high efficiency scores for cost-positive action plans. For cost-negative action plans, green start network formation and running, and daily car use control program had high efficiency scores. When only the GHGs reduction was considered, project priority orders based on efficiency scores were somewhat different from those when both the removal of air pollutants and GHGs reduction were considered at the same time. The expected action plan priority difference is attributed to great difference of air pollutants reduction potential according to types of energy sources to be reduced.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권9호
• /
• pp.414-420
• /
• 2005

A method for partial discharge diagnosis based on UHF narrow band type for GIS has been developed and calibrated. In generally, PD cannot be directly measured under on-line condition, but we can indirectly measure the electromagnetic wave made by PD using the high-frequency antenna. Compared with VHF band, electromagnetic waves of UHF band have a low influence for external noise in high-voltage substation. Therefore, we can detect the real abnormality with several pC in GIS using UHF narrow-band type method. For the case of no internal VHF sensor for GIS of the domestic substation, it has applied to use the external UHF sensor attached in spacer in GIS of existing substation. In this paper, we firstly described the technique of partial discharge measurement using frequency analysis and phase analysis in UHF band. Secondly, we presented the results of sensitivity test, the relationship of dBm-pC and diagnosis result of the cause of PD source by phase analysis. And then, we report the diagnosis result of partial discharge on the real GIS in domestic substation. These results make above method applicable for measurement of quantity and cause of PD for real operation GIS in high-voltage substation.

• 한국건축시공학회지
• /
• 제8권6호
• /
• pp.131-137
• /
• 2008

In recent years, the light-weight aggregate has widely been used to reduce the weight of construction structures, and to achieve the thermal insulation of building structures. The purpose of this study is to evaluate the heat resistance of polymer concrete composites with light-weight aggregate made by binders as resin and cement with polymer dispersion. The light-weight polymer concrete composites are prepared with various conditions such as binder content, filler content, void-filling ratio, light-weight aggregate content and polymer-cement ratio, and tested for heat resistant test, and measured the weight reducing ratio, strengths and exhaustion content of gas such as CO, NO and $SO_2$. From the test results, the weight reducing ratio of light weight polymer concrete using UP binder after heat resistance test increase with an increase in the UP content irrespective of the filler content. The weight reducing ratio of polymer cement concrete is considerably smaller than that of UP concrete. In general, the strengths after heat resistance of polymer concrete composites are reduced about 40 to 65% compared with those before test. The exhausted quantity of CO, NO and $SO_2$ gases in polymer concrete composites is less than EPS(Expanded poly styrene). From the this study, it is confirmed that the many types gases discharge according to binder type of polymer concrete composites, its amount is controlled by selection of the binder type and mix proportions.

• 한국산학기술학회논문지
• /
• 제14권2호
• /
• pp.511-516
• /
• 2013

유리 모서리 접합은 디스플레이 및 건축, 가전 등 산업계의 다양한 분야에 활용되고 있으며, 패널 접합부의 두께 및 형상은 단열성능 및 강도 등 패널의 주요 성능에 큰 영향을 미치는 요인으로 작용한다. 이런 모서리 접합부의 단면은 수소혼합가스토치를 이용하여 모서리를 용융 접합 할 경우 공정변수에 의해 형상이 결정된다. 따라서 본 논문에서는 가스토치를 이용하여 모서리 접합 시 접합부에 영향을 미치는 공정변수를 설정하고, 접합단면의 형상변수를 설정하여 두 변수간의 상관관계를 분석하기 위한 회귀식을 도출하고자 하였다. 회귀식 도출을 위해 공정변수가 형상변수에 미치는 주효과 및 교호작용을 분석하였으며, 변수간의 교호작용을 고려한 다항회귀식을 도출하였다. 도출된 다항회귀식을 통해 각 공정변수 변화에 따라 모서리 접합 두께 예측 및 처짐량 예측이 가능하다.

• 한국안전학회지
• /
• 제30권6호
• /
• pp.40-47
• /
• 2015

In this study, temperature characteristics and fire damage form were analyzed to investigate flame spreading form and fire probability from ignition sources subject to drivit component materials which is finishing material in architecture. Ignition sources were limited to a gas torch and exterior panel board fire, and the size of the sample was manufacture in 30 cm length ${\times}$ 50 cm height ${\times}$ 5cm thickness size. Marble (inner wall) + 3 mm drivit (outer wall), marble (inner wall) + 4 mm plaster stone (outer wall), sandwich panel + 3 mm driver bit (outer wall), sandwich panel + 3 mm driver bit + insulation (outer wall), and gypsum board (inner wall) + 3 mm drivit (outer wall) were prepared for the sample. As result of the research for temperature characteristics, large temperature difference by each material was shown in $218^{\circ}C{\sim}995^{\circ}C$ at 30 seconds and $501^{\circ}C{\sim}1078^{\circ}C$ at 300 seconds. Especially when the inner wall was a plaster board, lowest temperature of $501^{\circ}C$ was shown at 300 seconds and marble inner wall showed the following lowest temperature of $900^{\circ}C$. Temperature rising over $1000^{\circ}C$ was shown in other materials. Regarding fire damage form, drivit or gypsum board outer wall parts exposed to fire showed combustion and carbonization to show calcination(breaking phenomenon) and influence of heat exposure was higher as calcination became more severe.

• 한국음향학회지
• /
• 제14권6호
• /
• pp.13-20
• /
• 1995

본 논문에서는 열음향 냉장시스템을 실제로 설계, 제작하고 그 동작을 확인하였다. 제작된 시스템은 4인치의 중음부 스피커로 구동되며 스피커 하우징, 챔버, 스택하우징, 스택, 열교환기, 가는관, 그리고 공명구로 구성되었으며 내부에 10기압의 He을 채워 실험하였다. 실행 중 온도하강측정을 위하여 T 타입의 열전쌍을 열교환기에 부착하였고, 내부음압측정용 콘덴서 마이크로폰을 장착하였다. 스피커의 열손상을 막고 고온 열교환기를 냉각시키기 위하여 냉각수를 공급하였다. 실제 실험을 위하여 제작된 열음향기관의 전기적인 임피던스를 측정하여 공진특성을 파악하였는데, 실험 결과 설계치와는 약간 다르게 340Hz로 구동하는 것이 효율적이었다. 이러한 해석을 기초로 실제 냉장실험을 수행한 결과 $30^\circ{C}$의 조건하에서 340Hz, 50W로 구동하였을 때 $16^\circ{C}$의 냉장효과를 관찰하였다. 관찰된 냉각효과와 설계치의 차이를 규명하기 위하여 제작된 열음향기관의 미비점을 고찰하였는 바, 냉각부의 단열이 제일 중요한 문제임을 파악하였으며 그외의 보완이 필요한 사항은 이후의 진행될 연구의 과제로서 제시하였다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제35권2호
• /
• pp.232-237
• /
• 2011

최근 초저온 밸브 관련 산업의 급속한 발전과 함께 초저온 밸브에 대한 지속적인 연구가 이루어지고 있고 특히, 기계, 조선, 반도체 및 디스플레이 산업, 항공 우주산업분야의 비약적인 발전과 사용자의 요구 등으로 인하여 초저온용 밸브의 고성능화가 되고 있는 추세이나, 진공 단열에 관한 초저온 응용 장비들에 대한 기술개발 및 연구는 미흡한 실정이다. 본 연구에서는 초저온용 진공자켓밸브의 스템 외부에 자켓 배관을 설치 한 후 낮은 압력을 유지함으로써 외부로부터 자켓 내부로의 유입 열전달량을 감소시키는 것에 주안점을 두었고, 효과적인 전열 제어를 위하여 외부로부터 자켓 내부로의 유입 열전달량을 감소시킬수 있는 자켓 내부의 압력과 자켓부의 두께 변화에 관한 열전달 특성을 3차원 수치해석적인 방법으로 연구하여 고찰하였다.