• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1835-1841
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• 2009

We analyze the problem of recloser-fuse coordination when a superconducting fault current limiter (SFCL) is installed to a power distribution system. Generally, The recloser is installed to upstream of fuse to protect against both permanent fault and temporary one appropriately. However, in a power distribution system with SFCL, the fault current is decreased by the effect of the impedance value of the SFCL and when a permanent fault occurs, the fuse may not melt during the last delay operation of the recloser because of the insufficient heat from the decreased current. Therefore, when SFCLs are applied into a power distribution system, the rating of the fuse has to be reselected to coordinate recloser to fuse effectively. To solve these problems, this paper analysed the operation of recloser-fuse coordination and presented the improved recloser-fuse coordination method in a power distribution system with SFCL using PSCAD/EMTDC.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.5
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• pp.615-621
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• 2014

With development of electrical power system, the DC distribution system has been considered as a promising technology to be used in the future smart distribution system. Among the various components comprising the DC distribution system, the bi-directional DC/DC converter is one of the most important equipment to interconnect between main power system and various renewable resources such as photovoltaic power generation, wind power generation, and electrical vehicles. In this paper, a bi-directional DC/DC converter based on three-phases interleaved method which is effective to reduce ripple of input current and output voltage is modeled using ElectroMagnetic Transient Program(EMTP), and the verification of modeled bi-directional DC/DC converter is conducted.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.29-36
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• 2013

This paper deals with the analysis of the customer voltage characteristic in distribution system interconnected with large scale PV system. There would be many power quality issues which are caused by reverse power flow of PV system interconnected with distribution system. In order to analyze the effect of PV system on the customer voltage, detailed modeling method of distribution system and modified modelling method of PV system are proposed using PSCAD/EMTDC in this paper. So far, less than dozens KW of PV system can be simulated with the existing modelling method. Therefore, a new modeling method which can simulate the large scale PV system is proposed by considering the relationship equation on the phase and voltage in the current control algorithm. From the simulation result of proposed modelling method, it is confirmed that an optimal operation method in distribution system is suggested by analyzing the effect of PV system on customer voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.1
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• pp.103-111
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• 2003

With the proliferation of nonlinear loads such as personal computer in an educational building, high neutral harmonic currents have been observed. High neutral currents in three-phase four ire distribution power systems can cause tots of harmonic problems such as overloaded neutral conductors and malfunction of protective equipment. On-site measurements of harmonic currents and voltages were made and the corresponding equivalent circuits was developed. The circuit model under study was simulated numerically and graphically through the use of the software MATLAB. Simulation results verifying the effect of a single-tuned passive filter for the neutral harmonic current reduction are presented.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.4
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• pp.177-184
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• 2005

This paper proposes a improved investment priority decision method of the facilities considering the reliability of distribution networks. The proposed method decides a investment order of the facilities combining, by fuzzy rules, the investment priority decision of KEPCO and the priority decision considering reliability evaluation indices. Where reliability evaluation indices are SAIFI(System Average Interruption Frequency Index) and SAIDI(System Average Interruption Duration Index), as referred to evaluation index for sustained interruption. The reliability analysis method of distribution networks applied in this paper utilizes analytic method, where the used reliability data is historical data of KEPCO. Particularly, we assumed that the failure rate increased as the equipment ages. To verify the performance of the proposed method, we applied it with the planned projects to reinforce the weak facility electrical facilities in KEPCO in 2004. The evaluation result showed that, under a limited budget, the reliability of the KEPCO in the Busan region using the proposed method can be enhanced than using the conventional KEPCO's method. Therefore, the results verify the proposed method can be efficiently used in the actual priorities method for investing the electrical facilities.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.1
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• pp.15-22
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• 2002

This paper proposes a new power flow method for distribution system analysis by modifying the conventional back/forward sweep method using symmetrical components. Since the proposed method backward and forward sweeps with the variables expressed by symmetrical components, this method reduces computation time for matrix calculations; therefore, it is able to reduce the computational burden for real-time distribution network analysis. The proposed method was also developed to effectively analyze the unbalanced distribution system installing AVR(Auto Voltage Regulator), shunt capacitors. The proposed algorithm was compared with the conventional Back/forward Sweep method by applying both methods to three phase unbalanced distribution system of IEEE 123-bus model, and the test results showed that the proposed method would outperformed the conventional method in real-time distribution system analysis.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.3
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• pp.112-119
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• 2001

This paper proposes an adaptive reclosing scheme which is based on the classification of fault patterns. In case that the first reclosing is unsuccessful in distribution system employing with two-shot reclosing scheme, the proposed method can determine whether the second reclosing will be attempted of not. If the first reclosing is unsuccessful two fault currents can be measured before the second reclosing is attempted, where these two fault currents are utilized for an adaptive reclosing scheme. Total harmonic distortion and RMS are used for extracting the characteristics of two fault currents. And the pattern of two fault currents is respectively classified using a mountain clustering method a minimum-distance classifier. Mountain clustering method searches the cluster centers using the acquired past data. And minimum-distance classifier is used for classifying the measured two currents into one of the searched centers respectively. If two currents have the different pattern it is interpreted as temporary fault. But in case of the same pattern, the occurred fault is interpreted as permanent. The proposed method was tested for the fault data which had been measured in KEPCO's distribution system, and the test results can demonstrate the effectiveness of the adaptive reclosing scheme.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.862-864
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• 1996

This paper presents a new approach to evaluate reliability indices of electric distribution systems using genetic algorithm(GA). The use of reliability evaluation is an important aspect of distribution system planning and operation to adjust the reliability level of each area. In this paper, the reliability model is based on the optimal load transferring problem to minimize over load generated load point outage in each sub-section. This kind of the approach is one of the most difficult procedure which becomes a combination problems. A new approach using GA Was developed for this problem. We proposed a tree search algorithm which satisfied the tree constraint. GA is general purpose optimization techniques based on principles inspired from the biological evolution such as natural selection, genetic recombination and survival of the fittest Test results for the model system with 24 nodes and 29 branches are reported in the paper.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.174-177
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• 2003

Kinds of most frequent faults happened on overhead distribution system are the single line-to-ground fault, the line-to-line fault and the two line-to-ground fault. Occasionally, the three line-to-ground fault and the disconnection of a wire are happened in severe conditions. In this study, the single line-to-ground fault, the line-to-line fault, two line-to-ground fault on three-phase four-wire overhead distribution system were experimentally simulated and characteristics of total leakage current of distribution arrester caused by these faults were investigated. Also, the changing aspect of total leakage current of distribution arrester caused by voltage variation was investigated. In a consequence, abnormal voltages caused by voltage variation, the line-to-line fault, the two line-to-ground fault have a little effect on total leakage current of ZnO arrester. But abnormal voltages caused by the single line-to-ground fault have an important effect on total leakage current of ZnO arrester.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.4
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• pp.210-215
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• 2013

This paper analyze the bus voltage sags in the power distribution system with a small scale cogeneration system when the superconducting fault current limiter was introduced. Among the solutions to decrease the short-circuit current considering the locations of the small scale cogeneration system, the superconducting fault current limiter (SFCL) has been announced as one of the promising methods to reduce the fault current because the installation of the small scale cogeneration system which increases the short-circuit current. According to the application locations of the small scale cogeneration system in a power distribution system, it has caused the variations of voltage sag and duration which depends on the change of the short-circuit current, which can make the operation of the protective device deviate from its original set value when the fault occurs. To investigate the voltage sag when a SFCL was applied into a power distribution system where the small scale cogeneration system was introduced into various locations, the SFCL, small scale cogeneration system, and power system are modeled using PSCAD/EMTDC. In this paper, the effects on voltage sags are assessed when the SFCL is installed in power distribution system with various locations of the small scale cogeneration system.