• Journal of Korean Society on Water Environment
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• v.36 no.6
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• pp.535-545
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• 2020

This study aims to conserve and monitor energy use in public sewage treatment plants by utilizing data from the SCADA system and by controlling the aeration rate required for maintaining effluent water quality. Power consumption in the sewage treatment process was predicted using the equipment's uptime, efficiency, and inherent power consumption. The predicted energy consumption was calibrated by measured data. Additionally, energy efficiency indicators were proposed based on statistical data for energy use, capacity, and effluent quality. In one case study, a sewage treatment plant operated via the SBR process used ~30% of energy consumed in maintaining the bioreactors and treated water tanks (included decanting pump and cleaning systems). Energy consumption analysis with the K-ECO Tool-kit was conducted for unit processing. The results showed that about 58.7% of total energy consumed was used in the preliminary and biological treatment rotating equipment such as the blower and pump. In addition, the energy consumption rate was higher to the order of 19.2% in the phosphorus removal process, 16.0% during sludge treatment, and 6.1% during disinfection and discharge. In terms of equipment energy usage, feeding and decanting pumps accounted for 40% of total energy consumed following 27% for blowers. By controlling the aeration rate based on the proposed feedback control system, the DO concentration was reduced by 56% compared pre-controls and the aeration amount decreased by 28%. The overall power consumption of the plant was reduced by 6% via aeration control.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.398-402
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• 2008

Recently, the development of superconducting fault current limiters (SFCLs) has been required as power demands increase in the power system. A distribution-level prototype resistive SFCL using coated conductor (CC) has been developed by Hyundai Heavy Industries Co., Ltd. and Yonsei University for the first time in the world. The ratings of the SFCL are 13.2kV/630A at normal operating condition. A novel non-inductive winding method is used in fabricating coils so there is almost zero impedance during normal operation. The distribution SFCL is cooled by sub-cooled liquid nitrogen $(LN_2)$ of 65K and 3 bar to enhance cryo-dielectric performance, critical current density, and thermal conductivity. In order to make reliable operation of an SFCL in real power systems, we monitored and controled its operation conditions by using supervisory control and data acquisition (SCADA) method. Thus, a monitoring system for the SFCL employing information technology (IT) is proposed and developed to be on the lookout for the operation conditions such as inside temperature, inside pressure, $LN_2$ level, voltage and current. Since operation temperature should be kept constant, bang-bang control for temperature feedback with a heater attached to the cold head of cryo-cooler is applied to the system. Short-circuit tests with prospective fault current of 10kA and AC dielectric withstand voltage tests up to 143kV for 1 minute were successfully performed at Korea Electrotechnology Research Institute. This paper deals with the development of a distribution level SFCL and its monitoring system for reliable operation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.25-32
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• 2010

The Supervisory Control and Data Acquisition Systems (SCADA) system provides monitoring, data gathering, analysis, and control of the equipment used to manage most infrastructure. The SCADA Network is implemented in a various manner for larger utilities, and multiple types of protocol and communication interfaces are used to network the control center to remote sites. The existing SCADA equipment and protocols were designed and implemented with availability and efficiency, and as a result security was not a consideration. So, performance, reliability, flexibility and safety of SCADA systems are robust, while the security of these systems is often weak. This makes some SCADA networks potentially vulnerable to disruption of service, process redirection, or manipulation of operational data that could result in public safety concerns and/or serious disruptions to the infrastructure. To reduce the risks, therefore, there is a need to have a security device such as cipher devices or cryptographic modules for security solutions. In this paper we develop an embedded cipher device for the SCADA equipment. This paper presents a cipher device designed to improve the security of its networks, especially in the serial communication.

• Journal of Hydrogen and New Energy
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• v.28 no.3
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• pp.252-272
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• 2017

Fuel cell systems have to satisfy acceptable operating reliability, sufficient lifetime and price to enter the market in competition with existing products. Fuel cells are made up of complex element technologies and various problems related to the failure of the components can affect the reliability and safety of the system. This problem can be overcome by introducing a monitoring and supervisory control system in addition to automatic control to detect the failure of the fuel cell quickly and properly diagnose the performance degradation. For the fault detection and diagnosis of polymer electrolyte fuel cells, the model based method using the theoretical superposition value and the non-model based method of checking the signal tendency or the converted signal characteristic can be applied. The methods analyzed in this paper can contribute to the development of integrated monitoring and control technology for the whole system as well as the stack.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2373-2376
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• 1998

This paper describes the development of the SCADA(Supervisory Control and Data Acquisition) system which can be controlled via the Internet. In this paper, the SCADA system is composed of a number of microprocessor-based RTU(Remote Terminal Unit)s, a MMI(Man Machine Interface) host, a SCADA server, and SCADA clients. There are two protocols used in the system. Each RTU and the MMI host are connected by a RS-485 line and CSMA/CD(Carrier Sense Multiple Access / Collision Detection) protocol is used to communicate with each other. TCP/IP(Transmission Control Protocol/Internet Protocol) is used among the MMI host, the SCADA server, and SCADA clients. The equipments installed in the field are controlled by a number of RTUs. The function of the MMI host is to acquire real-time data from RTUs and control them. The SCADA server supports data transfer between the networked MMI host and the SCADA client on the web-server through TCP/lP. Data transfer is possible regardless of the type of network only if there are TCP/lP Winsock-compatible stack driver. The SCADA client is implemented as the shape of web-page by means of JAVA language. Therefore, it runs on a web-browser such as Netscape and Explorer, and allows a number of users to access this SCADA system.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.1
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• pp.35-41
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• 2017

This paper presents the development of a monitoring and control system for a vehicle cluster using a model-based design technique. For MBD(model-based design), MATLAB GUI(Graphic User Interface), M programs, simulink, state flow, and tool boxes are used to monitor a number of data such as warning, interrupts, and etc. connected to a real vehicle cluster. As a monitoring tool, a PC(Personal Computer) station interworks with the real vehicle cluster through the interface commands of tool boxes. Thus, unlike existing text-based designs, the MBD based vehicle cluster system provides very easy algorithm updates and addition, since it offers a number of blocks and state flow programs for each functional actions. Furthermore, the proposed MBD technique reduces the required time and cost for the development and modification of a vehicle cluster, because of verification and validation of the cluster algorithm on the monitor through a PC.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.19 no.6
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• pp.145-152
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• 2009

SCADA(Supervisory Control And Data Acquisition) systems are widely used for control and monitoring of critical infrastructures including electricity, gas and transportation. Any compromise in the security of SCADA systems could result in massive chaos and disaster at a national level if a malicious attacker takes the control of the system. Therefore, sound countermeasures must be provided when the SCADA systems are being developed as well as when they are being operated. Unlike general information processing system, SCADA systems have different service responses, communication protocols and network architectures and therefore a different approach should be applied to each SCADA systems that takes into consideration of each system's security characteristics and architectures. In addition, legal basis should be established to ensure the nationwide management of the systems security. This paper examines the vulnerabilites of SCADA systems and proposes action plans to protect the systems against cyber attacks.

• Industrial Engineering and Management Systems
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• v.4 no.2
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• pp.176-183
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• 2005

The theory of signal detection has been applied to a wide range of practical situation for a long time, including sonar detection, air traffic control and so on. In general, in this theory, sensitivity parametric index d' and bias parametric index $\beta$ are used to evaluated the performance of vigilance. These indices use observer's response "hit" and "false alarm" to explain and evaluate vigilance, but not considering reaction time. However, the reaction time of detecting should be considered in measuring vigilance in some supervisory tasks such as unlimited monitoring tasks (e.g., supervisors in nuclear plant). There are some researchers have used the segments of reaction time to generate a pair of probabilities of hit and false alarm probabilities and plot the receiver operating characteristic curve. The purpose of this study was to develop a quantitative vigilance-measuring model by fuzzy sets, which combined the concepts of hit, false alarm and reaction time. The model extends two-values logic to multi-values logic by membership functions of fuzzy sets. A simulated experiment of monitoring task in nuclear plant was carried out. Results indicated that the new vigilance-measuring model is more efficient than traditional indices; the characteristics of vigilance would be realized more clearly in unlimited monitoring task.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.6
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• pp.115-122
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• 2010

The main purpose of centralized monitoring system is to manage factory electrical installation efficiently by on-line data acquisition and supervisory control. The existing centralized system is only able to be managed by operator whenever electrical installation's faults are detected. Therefore, it may be possible for propagating the installation's faults when operator make the unexpected mistakes. To overcome the unexpected mistakes, in this paper, the author presents a centralized monitoring system for factory electrical installation using active database. by using active database production rule, stated system can minimize unexpected mistake and can operate centralized monitoring system efficiently. Test results on the five factory electrical installations show that performance is efficient and robust.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.261-263
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• 2006

전력 계통은 발전설비, 송전설비, 변전설비, 배전설비 등으로 크게 나눌 수 있다. 전력계통을 구성하는 이런 설비들을 원격 감시하고 제어하는 시스템을 전력자동화 시스템이라고 한다. 이런 전력자동화 시스템은 국내 전체 에너지의 수요, 공급, 수송을 제어하는 에너지 관리시스템(EMS : Energy Management System), 송전 및 변전설비의 감시제어를 담당하는 송변전소 감시제어 시스템(SCADA : Supervisory Control And Data Acquisition), 배전계통의 실비관리 및 운영을 담당하는 배전자동화시스템(DAS : Distribution Automation System), 수용가의 계량기를 원격으로 읽어오는 원격검침시스템 (AMR : Automatic Meter Reading) 통으로 구성되어 있다. 국내에서 운용중인 배전자동화 시스템은 배전선로에 설치되어 있는 개폐기만을 원격 감시 및 제어 하는 보편적인 시스템이다. 한편, 2005년도 전력IT 국가 전략과제로 수행하고 있는 배전지능화 시스템 개발 과제에서는 변전소부터 배전계통과 수용가까지의 모든 전력 설비에 대한 원격감시제어가 가능한 시스템을 배전지능화 시스템이라고 정의하고 이의 개발을 추진하고 있다. 본 논문에서는 ABB, SIEMENS, GE와 같은 국외의 배전 자동화 시스템들을 소개하고, 배전지능화 시스템에서 목표로 하고 있는 GIS 기반 위에서 고 저압 배전설비를 관리하고, SCADA, DAS, GIS(Geographic Information System), AMR, TCS(Trouble Call System) 등 배전지능화 시스템의 중앙제어장치가 갖추어야 하는 주요 기능들에 대해 기술하고자 한다.