• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.405-420
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• 2008

Resistivity survey is one of the widely used methods for the investigation of stability of the ground or bedrock around tunnel and is also used as an essential base data for stability and reduction of construction cost through first-hand approximation of rock quality at design step. Generally, the analysis of resistivity survey data is performed by single measurement. When distribution variation of groundwater around a tunnel over time is necessary for maintenance of a tunnel, resistivity monitoring is very useful survey method to grasp distribution variation of groundwater. So we performed the grid line resistivity survey to monitoring resistivity variation for six times. And we also tried to evaluate application possibility of the resistivity monitoring for construction safety through providing detailed information on fault zones.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.379-387
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• 2015

A custom power device provides an integrated solution to the present problems that are faced by the utilities and power distribution. In this paper, a new controller is designed which is connected to a multiconverter unified power quality conditioner (MC-UPQC) for improving the power quality issues adopted modified synchronous reference frame (MSRF) theory with Fuzzy logic control (FLC) technique. This newly designed controller is connected to a source in order to compensate voltage and current in two feeders. The expanded concept of UPQC is multi converter-UPQC; this system has a two-series voltage source inverter and one shunt voltage source inverter connected back to back. This configuration will helps mitigate any type of voltage / current fluctuations and power factor correction in power distribution network to improve power quality issues. In the proposed system the power can be conveyed from one feeder to another in order to mitigate the voltage sag, swell, interruption and transient response of the system. The control strategies of multi converter- UPQC are designed based on the modified synchronous reference frame theory with fuzzy logic controller. The fast dynamics response of dc link capacitor is achieved with the help of Fuzzy logic controller. Different types of fault conditions are taken and simulated for the analysis and the results are compared with the conventional method. The relevant simulation and compensation performance analysis of the proposed multi converter-UPQC with fuzzy logic controller is performed.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.689-700
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• 2017

This paper presents an effective approach for wind turbine (WT) condition assessment based on the data collected from wind farm supervisory control and data acquisition (SCADA) system. Three types of assessment indices are determined based on the monitoring parameters obtained from the SCADA system. Neural Networks (NNs) are used to establish prediction models for the assessment indices that are dependent on environmental conditions such as ambient temperature and wind speed. An abnormal level index (ALI) is defined to quantify the abnormal level of the proposed indices. Prediction errors of the prediction models follow a normal distribution. Thus, the ALIs can be calculated based on the probability density function of normal distribution. For other assessment indices, the ALIs are calculated by the nonparametric estimation based cumulative probability density function. A Back-Propagation NN (BPNN) algorithm is used for the overall WT condition assessment. The inputs to the BPNN are the ALIs of the proposed indices. The network structure and the number of nodes in the hidden layer are carefully chosen when the BPNN model is being trained. The condition assessment method has been used for real 1.5 MW WTs with doubly fed induction generators. Results show that the proposed assessment method could effectively predict the change of operating conditions prior to fault occurrences and provide early alarming of the developing faults of WTs.

• Journal of the Korean Geographical Society
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• v.39 no.1
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• pp.56-69
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• 2004

We investigated the distribution and geomorphic development of alluvial fan in Gyeongju City including Cheonbuk area. According to a relative height to a river bed, alluvial fans of this area are divided into Higher surface, Middle surface, and Lower surface. As alluvial fans of Bulguk temple∼Ulsan bay area, the confluent fans in Cheonbuk and Gyeongju areas were formed by the Quaternary climatic change alternating glacial and interglacial stages, and the development of N-S and NW-SE fault lines. The Gyeongju alluvial fan, the largest in Korea, has been provided as the significant space for human activity since the prehistoric age. Bukcheon river formed the Gyeongju alluvial fan had not flowed over during the prehistoric and the ancient times. In contrast with general geomorphic characteristics, many springs in the Gyeongju alluvial fan are located in the middle part of the fan because ground water reaches to the surface. It is supposed that sedimental materials were not sufficiently piled up at lower reach of Bukcheon river due to the large deposits at upper and middle reach of the basin.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.76-84
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• 2002

Voltage sags caused by line faults in transmission and distribution lines have become one of the most important power quality problems facing industrial customers and utilities. Voltage sags are normally described by characteristics of both magnitude and duration, but phase angle shifts should be taken account in identifying sag phenomena and finding their solutions. In this paper, voltage sags due to line faults such as three phase-to-ground, single line-to-ground, and line-to-line faults are characterized by using symmetrical component analysis, for fault impedance variations. Voltage sags and their effect on the magnitude and phase angle are examined. Balanced sags of three phase-to-ground faults show that voltages and currents are changed with equivalent levels to all phases and the zero sequence components become zero. However, for unbalanced faults such as single line-to-ground and line-to-line faults, voltage sags give different magnitude variations and phase angle shifts for each phase. In order to verify the analyzed results, some simulations based on power circuit models are also discussed.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.521_523
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• 2009

최근 고유가에 따른 발전비용 증가와 교토의정서 발휘로 인한 $CO_2$ 저감의무 등 환경보전이라는 사회적 요구와 맞물려 새로운 신재생에너지 분야에 관심이 고조되고 있는 실정이다. 이러한 신재생에너지로 대표되는 풍력, 태양광, 연료전지 등을 이용하는 발전방식은 저용량의 발전으로 대규모 집중형 전원이 아니 전력 수요지 근방에서 설치되는 비교적 작은 규모의 분산형전원(DG;Distribution Generator)으로 배전선로에 직접 연계됨에 따라 배전계통에도 큰 변화가 일고 있다. 분산전원(DG)이 배전계통에 연계됨에 따라 전압변동에 따른 전압조정, 고조파 계통유입에 따른 전기품질, 계통고장시의 분산전원의 단독운전 방지, 고장전류의 분산에 따른 선로의 보호협조 등 다양한 새로운 문제점이 대두되고 있고 이를 해결하기 위해 연구개발 및 신기자재개발 등이 활발히 진행되고 있다. 현재 배전자동화시스템에 적용되고 있는 고장검출 알고리즘은 단방향으로 전기를 공급하던 전통적인 배전방식에서 단순 과전류요소에 의해 고장검출하는 알고리즘을 적용하고 있기 때문에 분산전원이 연계된 양방향 전기공급 배전계통에서는 정확하게 고장구간을 검출하기 어렵다. 이로 인해 고장판단 문제점과 보호기기의 오동작 등으로 정확하게 고장구간을 판단하지 못하여 광역정전이 발생되고 고장복구가 장시간 소요되고 있는 실정이다. 본 논문에서는 이를 해소하기 위해 양방향 전기공급 배전계통에서 고장이 발생시 고장점으로 유입되는 고장전류의 파형형태를 분석하여 고장 구간을 판단하는 알고리즘을 소개하고자 한다. 또한 다기능 mFRTU(mFRTUmulti-function Feeder Remote Terminal Unit) 의 고장 구간 판단 알고리즘의 신뢰성을 검증하기 위해 실선로에서 실증시험을 시행하였으며, 그 결과를 분석하여 타당성을 제시하고자 한다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.5
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• pp.339-344
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• 2015

NHPP software reliability models for failure analysis can have, in the literature, exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, infinite failures NHPP models that repairing software failure point in time reflects the situation, was presented for comparing property. Commonly used in the field of software reliability based on Weibull extension distribution software reliability of infinite failures was presented for comparison problem. The result is that a relatively large shape parameter was effectively. The parameters estimation using maximum likelihood estimation was conducted and Model selection was performed using the mean square error and the coefficient of determination. In this research, software developers to identify software failure property follows shape parameter, some extent be able to help is considered.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.35-45
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• 2011

Recently, with the increasement of the interest about global warming, pollutions, and so on, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with distribution systems. However, installing of DGs makes power flow changes such as directions, one-direction to bi-direction, and increasing/decreasing of fault current. Therefore, it may cause the critical problems. This paper proposes an evaluation algorithm for bi-directional protection coordination and presents an evaluation system for protection coordination based on this algorithm. Additionally, the result shows that the existing method may cause critical problems, and also the effectiveness of proposed method is verified.

• Spatial Information Research
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• v.14 no.1 s.36
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• pp.57-65
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• 2006

In general, the investigation for reservoir dredging are conducting a observation on the horizontal position and the depth of water by assembling GPS/Echo Sounder and Total Station/Echo Sounder, and it is computed at a section computation of riverbed, reservoir volume and dredging plan etc. at that times, the detail plane is determinated about soil volume, height for dredging. Planning has a fault that the method of sound detection using the Echo Sounder doesn't check up distribution of reservoir deposit. In this study, the author emphasizes that implementation of dredging with combined Global Positioning System(GPS) and Ground Penetration Radar(GPR) is well-done more than existed GPS/Echo Sounder. the combined equipment can be adapted to computation and dredging reffering to distribution of deposition. First of all, it is executed water tank modelling test through sampling for apply to test area and is estimated the possibility after passed far accuracy verification of equipment.

• Journal of KIISE:Software and Applications
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• v.28 no.12
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• pp.896-909
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• 2001

Recently, above 50 percentages of software are being developed based on distributed application platforms. And recent technologies such as EJB(Enterprise Java Beans)[1]COM(Component Object Model)[2] CORBA(Common Object Request Broker Architecture)[3] have been advanced for distributed component-based software development . Therefore a systematic development process is necessary to develop component based applications using distributed application platforms. However, most of component-base software development processes do not define concrete flows between tasks and relationships among artifacts of each task Also, distribution issues are not considered explicitly in most of component-based software development In this paper, we present an approach to analyze and design software based on distributed components. In this approach, we propose systematic guidelines for developing a software based on Unified process and the relationships among artifacts which are produced, Also we explicitly consider the distribution issues such as performance, fault tolerance, security, distributed transaction of CORBA environments.