• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5123-5127
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• 2011

Research and development for the technology, that is about maintenance and accidents prevention of underground power distribution line, are demanding. The precise detection of leakage point of underground power line is very important, because it is difficult to detect the exact location of a fault in underground power line and to repair faults. When earth electric potential is measured to detect underground electric leakage point after transmitting AC electric pulse wave to underground power line, it must be measured in a specific half period of AC pulse wave because the distribution of the electric earth potential varies with the polarity of the transmitted wave. In this paper we proposed the measurement of half period modulated earth potential as a method to detect a underground leakage point. And We compared the proposed method with other methods. Through experiments we verified that the proposed method can be implemented and operated properly.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.141-144
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• 2008

Geological storage of carbon dioxide has been studying in advanced countries to reduce greenhouse gases and a pilot site for geological storage is also in operation in the deep saline aquifer. Seismic wave and electrical resistivity tomography methods are applicable to monitoring techniques and they are used to evaluate the distribution range and behavior of the carbon dioxide injected in the porous sandstone formations. This paper describes the construction of an experimental apparatus which consists of a high pressure vessel and a measurement system for geological storage of carbon dioxide. The experiment apparatus will be used to measure seismic velocities and resistivities during the injection of carbon dioxide at the supercritical phase in the porous sandstones.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.3
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• pp.279-287
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• 2018

This study investigated applicability of the fast running model for damage assessment of underground structures by ground shock. For this reason, the fast running model that consists of two main models such as the ground shock generation and propagation model and the underground structural damage assessment model was developed. The ground shock generation and propagation model was programed using theoretical formula and empirical formula introduced in TM5-855-1(US army manual). The single degree of freedom model of structural components was utilized to predict structural dynamic displacements which are used as index to assess damage level of components. In order to confirm the feasibility of the developed fast running model, underground structural dynamic displacements estimated from the fast running model were compared to displacements obtained from the finite element analysis.

• Geophysics and Geophysical Exploration
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• v.24 no.3
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• pp.78-88
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• 2021

Owing to the abnormal weather conditions due to global warming, carbon capture and storage (CCS) technology has attracted global attention as a countermeasure to reduce CO₂ emissions. In the Pohang CCS demonstration project in South Korea, 100 tons of CO₂ were successfully injected into the subsurface CO₂ storage in early 2017. However, after the 2017 Pohang earthquake, the Pohang CCS demonstration project was suspended due to an increase in social concerns about the safety of the CCS project. In this study, to reconfirm the structural suitability of the CO₂ storage site in the Pohang Basin, we employed seismic imaging based on reverse-time migration (RTM) to analyze small-scale ocean-bottom seismic data, which have not been utilized in previous studies. Compared with seismic images using marine streamer data, the continuity of subsurface layers in the RTM image using the ocean-bottom seismic data is improved. Based on the obtained subsurface image, we discuss the structural suitability of the Pohang CO₂ storage site.

• Economic and Environmental Geology
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• v.46 no.6
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• pp.485-494
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• 2013

$CO_2$ Monitoring, Mitigation and Verification (MMV) is the essential part in the Carbon Capture and Storage (CCS) project in order to assure the storage permanence economically and environmentally. In large-scale CCS projects in the world, the seismic time-lapse survey is a key technology for monitoring the behavior of injected $CO_2$. In this study, we developed a basic process procedure for 3-D seismic baseline data from the Aquistore project, Estevan, Canada. Major target formations of Aquistore CCS project are the Winnipeg and the Deadwood sandstone formations located between 1,800 and 1,900 ms in traveltime. The analysis of trace energy and similarity attributes of seismic data followed by spectral decomposition are carried out for the characterization of $CO_2$ injection zone. High trace energies are concentrated in the northern part of the survey area at 1,800 ms and in the southern part at 1,850 ms in traveltime. The sandstone dominant regions are well recognized with high reflectivity by the trace energy analysis. Similarity attributes show two structural discontinuities trending the NW-SE direction at the target depth. Spectral decomposition of 5, 20 and 40 Hz frequency contents discriminated the successive E-W depositional events at the center of the research area. Additional noise rejection and stratigraphic interpretation on the baseline data followed by applying appropriate imaging technique will be helpful to investigate the differences between baseline data and multi-vintage monitor data.

• Economic and Environmental Geology
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• v.47 no.6
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• pp.625-633
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• 2014

The Aquistore project is the world's first commercial capture, transportation, utilization and storage project of post-combustion $CO_2$ from a coal-fired thermo electric power plant, and the proposed storage is a saline aquifer at a depth of about 3,500 m. Deep saline aquifer, compared to hydrocarbon reservoir, provides the great volumetric potential for storage of $CO_2$ anywhere in the world, therefore the research results from the project may be exported globally to other sites. Geological $CO_2$ storage characterization for saline aquifer instead of hydrocarbon reservoir needs to estimate the geophysical properties of subsurface geology. This study calculated the geophysical property of water-saturated formation by applying amplitude variation analysis developed from oil and gas exploration. We correlated horizon tops at the well logs to seismic traveltime of 1,815 and 1,857 ms as Winnipeg and Deadwood formations. Gradient analysis from seismic traces showed correlation coefficient of 45 - 81 % on amplitude variation with respect to incident angle. Crossplot of intercept and gradient shows the inverse proportional trend which represents typical water saturated sediments. Product attribute of intercept and gradient described the base of wet sediment. Poisson's ratio change attribute increased at the top of target area satisfying with wet sediment and decreased at the top of basement in a dry rock bed.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.367-368
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• 2015

최근에 인도와 유럽을 중심으로 기존의 AC 송전계통 중 일부를 DC 송전계통으로 대체하는 하이브리드형 송전방식에 대한 연구가 진행중이다. 따라서 본 연구는 기존에 연구되고 있는 하이브리드형 가공송전계통을 기반으로 지중송전계통을 포함한 하이브리드형 혼합송전계통이 향후 머지않아 국내에서 계획 및 건설될 것을 대비한 초기 연구로서 진행하였다. 본 논문의 관점은 하이브리드 혼합송전계통 중 지중송전계통구간에서 DC 선로가 AC선로로부터 얼마나 고조파 전압 및 전류 측면에서 영향을 받는가를 평가하고, 이를 근거로 DC 케이블의 배열을 선정하고자 한다. 또한 DC 케이블 배열 선정을 위해 가능성이 있는 여러 개의 CASE별로 구분하고, 가장 타당한다고 평가되는 배열을 제안하고자한다. 본 연구에서 계통 모델링 및 해석은 EMTP를 이용하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1C
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• pp.11-20
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• 2009

A new alternative method based on HWAW method to detect underground anomaly was introduced. The location of underground anomaly can be estimated by using 2-dimensional image of phase velocity image with position and wavelength based on distortion phenomena of surface wave due to underground anomaly. Overall procedure of proposed method such as field testing, signal processing and interpretation of the result was introduced. Numerical verification study was performed by using various ground models containing underground anomaly. According to the condition of anomaly, the propagation and reflection characteristics of surface wave were different and this could be more easily shown in the image of phase velocity. Some rules of distortion phenomena were found and these become clues for estimating underground anomaly in interpreting real field data. Field verification tests were performed with conventional geophysical methods such as DC resistivity method and GPR. Though field condition is not homogeneous like numerical models, similar distortion phenomena were found in the testing results and estimated location of underground anomaly was agreed well with the results of another geophysical methods.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.2093-2094
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• 2011

가교폴리에틸렌(XLPE) 절연체를 적용한 MV급 지중케이블은 1972년부터 KEPCO에서 본격적으로 사용되기 시작하였다. 이후 도심지 지중화사업에 힘입어 매년 6.5%정도의 케이블 설비가 증가하였으며 오늘날 29,000C-km이상의 MV급 케이블이 설치되어 있다. 과거 비약적인 경제성장과 더불어 전력망 확충을 위한 투자가 KEPCO의 주된 역할이었다면 오늘날에 있어서는 확충된 설비를 최적의 상태로 유지 관리하는 것으로 패러다임이 변하고 있다. 특히 지중설비의 동맥(動脈)으로 볼 수 있는 케이블에 대한 관리방법이 화두가 되고 있으며 최적관리의 전제조건인 열화진단 분야가 KEPCO가 이끌고 나가야 할 새로운 개척분야로써 많은 역량이 집중되고 있다. 2010년에는 VLF TD/PD를 새로운 진단기법으로 적용하였으며 케이블 설치공사 준공 검수시험으로 0.1Hz 저주파 교류내전압시험 도입 및 활선 PD진단장치를 자체 개발하여 현장 적용성 검토를 추진하는 등 MV급 지중설비의 관리기법에 있어 큰 전환점을 만들고 있다. 본 고에서는 KEPCO의 MV급 케이블 변천사와 추진하고 있는 진단기법 및 관리 지향점을 논하고자 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.107-115
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• 2003

Nondestructive testing was carried out in order to evaluate the structural integrity and construction quality of the slurry wall of the underground LNG storage tank. 9 test points were selected, and the wall thickness, rebar spacing, and compressive strength of the slurry wall were evaluated by stress wave impact-resonance method, GPR, sonic velocity, and rebound testing, respectively. As results, the wall thickness, rebar sparing and estimated compressive strength satisfy the design criteria.