• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1501-1510
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• 2014

Low voltage direct current (LVDC) distribution system is a suitable techno-economic candidate which can create an innovative solution for distribution network development with respect to rural electrification. This research focuses on the use of LVDC distribution system to replace some of KEPCO's existing traditional medium voltage alternating current (MVAC) distribution network for rural electrification in South Korea. Considering the technical and economic risks and benefits involved in such project, a comparative techno-economic analysis on the LVDC and the MVAC distribution networks is conducted using economic assessment method such as the net present value (NPV) on a discounted cash flow (DCF) basis as well as the sensitivity analysis technique. Each would play a role in an economic performance indicator and a measure of uncertainty and risk involved in the project. In this work, a simulation model and a computational tool are concurrently developed and employed to aid the techno-economic analysis, evaluation, and estimation of the various systems efficiency and/or performance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.46-51
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• 2005

Grounding insures a reference potential point for electric devices and also provides a low resistance path for fault currents in the earth. The ground impedance as a function of frequency is necessary for determining its performance since fault currents could contain a wide range of frequencies. A cower rod electrode is the most commonly used grounding electrode in electric distribution systems. In this paper, the ground impedance of cower rods has been measured in frequency ranging from 60[Hz] up to 100[kHz] and an equivalent circuit model, transfer function model of the ground impedance are identified from the measured values.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1674-1683
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• 2011

More than 80% of electric loads need DC electricity rather than AC at the moment. If DC power could be supplied directly to the terminal loads, power conversion stages including rectifiers, converters, and power adapters can be reduced or simplified. Therefore, DC microgrids may be able to improve energy efficiency of power distribution systems. In addition, DC microgrids can increase the penetration level of renewable energy resources because many renewable energy resources such as solar photovoltaic(PV) generators, fuel cells, and batteries generate electric power in the form of DC power. The integration of the DC generators to AC electric power systems requires the power conversion circuits that may cause additional energy loss. This paper discusses the capability and feasibility of DC microgrids with regard to energy efficiency analysis through detailed dynamic simulation of DC and AC microgrids. The dynamic simulation models of DC and AC microgrids based on the Microgrid Test System in KEPCO Research Institute are described in detail. Through simulation studies on various conditions, this paper compares the energy efficiency and advantages of DC and AC microgrids.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.103-104
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• 2008

this paper describes the electric field distribution analysis along a shield gap inner vacuum interrupter(VI). The equipotential line and electric field and field vector in a VI are analysed by a finite element method and experiment at shield gap. in result, The equipotential line and electric field distribution was affected to VI shield gap. The reason is as it gets distortion of equipotential line done. finally, this paper recognized whether or not affected, and proposed gap with the most suitable shield length and an external insulation.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.242-244
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• 1997

This paper presents an advanced automat ic reclosing scheme in power distribution system to minimize the impact of electric facilities and the customers' damage. This scheme can determines the number of reclosing attempts to reduce the influence of electric equipment and injury of customers' load using a magnitude of fault current and types. To verify the effectiveness of the proposed scheme, numerical simulation is carried out with field data. Results demonstrate that the proposed scheme can minimizes the impact of electric facility and customers' damage than exist ing scheme.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.838-846
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• 2015

This paper deals with the modified modeling of PV system based on the PSCAD/EMTDC and optimal control method of customer voltages in real distribution system interconnected with the photovoltaic (PV) systems. In order to analyze voltage variation characteristics, the specific modeling of PV system which contains the theory of d-q transformation, current-control algorithm and sinusoidal PWM method is being required. However, the conventional modeling of PV system can only perform the modeling of small-scale active power of less than 60 [kW]. Therefore, this paper presents a modified modeling that can perform the large-scale active power of more than 1 [MW]. And also, this paper proposes the optimal operation method of step voltage regulator (SVR) in order to solve the voltage variation problem when the PV systems are interconnected with the distribution feeders. From the simulation results, it is confirmed that this paper is effective tool for voltage analysis in distribution system with PV systems.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.4
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• pp.313-319
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• 2000

As the interest of flexible manufacturing systems and computer integrated manufacturing systems increase, the distribution of centralized control systems using industrial control networks is getting more attention. In this paper, we investigate the rate-based traffic control of industrial control networks to improve the performance regarding the throughput, fairness, and error rates. Especially, we consider the protocol of Lon-$Works^{(TM)}$ which consists of all OSI 7-layers and supports various communication media at a low cost. Basically, the proposed rate-based traffic control system is closed loop by utilizing the feedback channel errors, which shows improved performance when compared with other industrial control networks commonly operated in open loop. To this end, an additional network node called monitoring node is introduced to check the channel status without increasing the channel load. The Proposed control loop is in effect whenever the feedback channel error becomes greater than an admittable value. We demonstrate the improved performance of the controlled network system in view of throughput and fairness measures by implementing the lab-scale network system based on LonWorks and through the experimentation upon it.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.102-103
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• 2007

In order to apply resistive superconducting fault current limiters into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. Thus, in order to make practical SFCL, we designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for practical applications are in the process.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.1
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• pp.1-5
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• 2000

This paper presents a new algorithm to restore the de-energized loads in electric power distribution systems for restoration by utilizing object-based structure and heuristic rules without branch and feeder overloading. In order to cope with a complex network configuration and frequent breaker switching operations in distribution systems, the component of power system is described as objects and the information of system configuration is constructed by connecting objects each other. Such a strategy is developed mainly based on the object search algorithm to increase computation efficiency. As a result, the proposed system has been implemented to efficiently deal with large distribution systems by reducing computational burden remarkably compared with the conventional methods.

• Current Optics and Photonics
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• v.3 no.6
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• pp.566-570
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• 2019

To investigate dependence of the sensitivity of THz metamaterials on the position of target dielectric materials, we functionalized the metamaterial gap with an adhesive polymer. A shift in resonance frequency occurs when polystyrene microbeads are deposited in the gap of the metamaterial's metal resonator pattern, while little change is observed when they are deposited on other areas of the metasurface. A two-dimensional mapping of the sensitivity, with a grid size of 1 ㎛, is obtained from a finite-difference time-domain simulation: The frequency shift is displayed as a function of the position of a target dielectric cube. The resulting sensitivity distribution clearly reveals the crucial role of the gap in sensing with metamaterials, which is consistent with the electric field distribution near the gap.