• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.56-59
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• 2003

As electric power systems grow to supply the increasing electric power demand short-circuit current tends to increase and impose a severe burden on circuit breakers and power system apparatuses. Thus, all electric equipment in a power system has to he designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Among current limiting devices, Fault Current Limiter (FCL) is expected to reduce the short-circuit current. Especially, Superconducting Fault Current Limiters (SFCL) offer ideal performance: in normal operation the SFCL is in its superconducting state and has negligible impedance, in the event of a fault, the transition into the normal conducting state passively limits the current. The SFCL using high-temperature superconductors offers a positive resolution to controlling fault-current levels on utility distribution and transmission networks. This study contributes to the EMTDC based modeling and simulation method of DC Reactor type SFCL. Single and three phase faults in the utility system with DC reactor type SFCLs have been simulated using EMTDC in order to coordinate with other equipments, and the results are discussed in detail.

• 전기학회논문지P
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• 제61권1호
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• pp.29-34
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• 2012

Due to the increasing of nonlinear loads such as converters and inverters connected to the electric power distribution system, and extensive application of harmonic generation sources with power electronic devices, disturbance of the electric power system and its influences on industries have been continuously increasing. Thus, it is difficult to construct accurate load model for active and reactive power in environments with harmonics. In this research, we develop a load modeling method based on Extreme Learning Machine(ELM) with fast learning procedure for residential loads. Using data sets acquired from various residential loads, the proposed method has been intensively tested. As the experimental results, we confirm that the proposed method makes it possible to effective estimate active and reactive powers than conventional methods.

• 전기학회논문지
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• 제57권9호
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• pp.1522-1530
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• 2008

This paper presents a discrete wavelet analysis based algorithm to address the fault impedance calculation under transient state in radial power distribution networks. The fault impedances have been derived under different fault conditions. Furthermore, a recursive fault distance estimation method is proposed utilizing the measured fault impedance and power line parameters. The proposed scheme can resolve the errors caused by the non-homogeneous power lines, the presence of lateral loads since, the fault impedance will always be updated with the recursive form. For the verification of the proposed scheme, a filed test has been peformed with varying fault resistances in the 22.9(kV) radial system. Power meters and fault locators were installed at the substation. It was figured out that the performance of the discrete wavelet and the recursive scheme are very good even for high fault resistance condition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.122-124
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• 1995

Electrical transmission and distribution networks must withstand an occasionally abnormal condition such as a fault, with prejudicial consequences for the line, transformers or generators. And the improvement of reliability and quality of the delivered power from an electric utility motivates the development of new technologies in power applications. As a part of these studies, the usefulness and utility of a superconduction fault current limiter(SFCL) are shown. The SFCL is applied to 22.9KV three-phase power system and performed short circuit studies. The verified quench characteristic of SFCL is adopted for fault simulation and the results are compared with those of system which have not SFCL.

• 한국전자파학회논문지
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• 제21권2호
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• pp.110-120
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• 2010

본 논문에서는 대 면적 기판 집적 도파관 전력 분배 네트워크(Substrate Integrated Waveguide Power Distribution Network: SIW PDN)의 출력 단자 간 위상차를 제거하기 위해 유전체 나사를 적용한 가변 기판 집적 도파관(SIW: Substrate Integrated Waveguide)을 제안한다. 본 제안 구조는 가변 기판 집적 도파관에 비 도금된 비아 홀에 부분적으로 유전체 나사를 삽입하여 S-parameter의 크기에 거의 영향을 주지 않고 위상 천이를 이룬다. 이로써, 유전체 나사가 삽입되지 않은 가변 기판 집적 도파관이 적용된 대 면적 SIW PDN($370\;mm{\times}195\;mm$)의 측정된 ${\pm}33.9^{\circ}$의 위상 차이가 본 제안 구조를 통하여 ${\pm}4.65^{\circ}$까지 크게 감소되었다. 본 논문에서 제안된 유전체 나사를 이용한 가변 SIW는 향후 초경량, 고성능 기판 집적 위상 배열 시스템 및 대 면적 SIW 회로 응용에 중요한 역할을 할 것으로 기대된다.

• Journal of Communications and Networks
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• 제15권2호
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• pp.164-172
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• 2013

We consider the problem of secure and robust clustering for quantized target tracking in wireless sensor networks (WSN) where the observed system is assumed to evolve according to a probabilistic state space model. We propose a new method for jointly activating the best group of candidate sensors that participate in data aggregation, detecting the malicious sensors and estimating the target position. Firstly, we select the appropriate group in order to balance the energy dissipation and to provide the required data of the target in the WSN. This selection is also based on the transmission power between a sensor node and a cluster head. Secondly, we detect the malicious sensor nodes based on the information relevance of their measurements. Then, we estimate the target position using quantized variational filtering (QVF) algorithm. The selection of the candidate sensors group is based on multi-criteria function, which is computed by using the predicted target position provided by the QVF algorithm, while the malicious sensor nodes detection is based on Kullback-Leibler distance between the current target position distribution and the predicted sensor observation. The performance of the proposed method is validated by simulation results in target tracking for WSN.

• 융합보안논문지
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• 제24권3호
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• pp.95-104
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• 2024

미래 전장의 전쟁수행 역량은 AICBMS(AI, Cloud, Bigdata, Mobile, Security)라 일컫는 4차 산업혁명의 차세대 기술을 적용하여 혁신적인 국방력을 확보할 수 있는가에 달려 있다 해도 과언이 아니다. 또한, 미래의 군 작전환경은 네트워크를 기반으로 모든 무기체계가 하나의 통합된 정보통신망 내에서 실시간으로 전장정보를 상호공유하며 작전을 수행하게 되는 네트워크 중심전(NCW)으로 급변하고, 유·무인 복합전투체계 운용범위로 확대되고 있다. 특히, 초고속, 초연결성을 책임지는 통신 네트워크는 여러 전투 요소를 연결하고 정보의 원활한 유통을 위해 높은 생존성과 다계층(국방 모바일, 위성, M/W, 유선) 네트워크 기반의 전력 운용의 효율성을 요구한다. 이러한 관점에서 본 연구는 제원이 고정된 기존의 단일매체, 단일경로 전송과는 달리, 가용한 통신 유무선 인프라 다매체를 동시 사용하여 통신량 폭주시 부하분산과 RNN(Recurrent Neural Networks) 알고리즘을 이용한 인공지능 기반의 전송기술로 다매체다중경로(MMMP-Multi-Media Multi-Path) 적응적 네트워크 기술 개발하는 것이다.

• 대한산업공학회지
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• 제40권1호
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• pp.1-7
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• 2014

We consider a human contact social network that has connections through cellphone addresses. To construct such a social network, we use real call records provided by a large carrier, and connect to each other if there exists a call record between any two cellphone users. Due to its huge amount of data, we down-sample it in a way that the smallest-degree nodes are removed, in turn, from the network. For a moderate size of the networks we show that the degree distribution of the network follows a power-law distribution via linear regression analysis, implying the so-called scale-free property. We finally suggest some alternative measures to analyze a social network.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(II)
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• pp.829-836
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• 2002

The paper presents a multi-objective genetic algorithm approach to the design of a water distribution network. The objectives considered are minimization of network cost and maximization of a reliability measure. In this study, a new reliability measure, called network resilience, is introduced. This measure mimics a designer's desire of providing excess power at nodes and designing reliable loops with practicable pipe diameters. The proposed method produces a set of Pareto-optimal solutions in the search space of cost and network resilience. Genetic algorithms are observed to be poor in handling constraints. To handle constraints in a better way, a constraint handling technique that does not require a penalty coefficient and applicable to water distribution systems is presented. The present model is applied to two example problems, which were widely reported. Pipe failure analysis carried out on some of the solutions obtained revealed that the network resilience based approach gave better results in terms of network reliability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.47-48
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• 2015

As the power system develops rapidly into a smarter and more flexible state, so must the communication technologies that support it. Machine to machine (M2M) communication in Smart Grid environment has been discussed in European Telecommunications Standards Institute (ETSI). The power system is not easily replaceable, due to system replacement cost. The M2M gateway is required in other to improve interoperability in M2M environment. The Distributed Network Protocol 3.0 (DNP3.0) is the most important standard in the SCADA systems for the power. It has been used for device data collection/control in Substation Systems, Distribution Automation System. If the DNP3.0 data model is combined with a set of contemporary web protocols, it can result in a major shift. We selected Constrained Application Protocol (CoAP) based on RESTful as M2M protocol. It is a specialized web transfer protocol for use with constrained nodes and constrained networks. We have used the OPNET Modeler 17.1 in order to verity the SOAP versus CoAP. In this paper, we propose the CoAP-based M2M Gateway to Distribution Automation system using DNP3.0 in Smart Grid Environment.