• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.1
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• pp.28-37
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• 2001

This paper presents an efficient algorithm for the loss minimization of distribution system by automatic sectionalizing switch operation in large scale distribution systems. Simulated annealing is particularly well suited for large combinational optimization problem, but the use of this algorithm is also responsible for an excessive computation time requirement. Tabu search attempts to determine a better solution in the manner of a greatest-descent algorithm, but it can not give any guarantee for the convergence property. The hybrid algorithm of two methods with two tabu lists and the proposed perturbation mechanism is applied to improve the computation time and convergence property Numerical examples demonstrate the validity and effectiveness of the proposed methodology using a KEPCO's distribution system.

• Transactions on Electrical and Electronic Materials
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• v.4 no.6
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• pp.5-8
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• 2003

In this paper, we investigated the fracture distribution in indium-tin-oxide (ITO) coating with compressive bending stress on polymer. Under compressive strain, the ITO island delaminates, buckles and cracks. As the mechanical compressive stress increases, the buckling width of ITO seems to be increased. These created cracks are related to well-defined distribution of mechanical stress in ITO island-arrays. We related. mechanical bending stress to crack distribution and derived theoretical equation of position-dependent bending stress. And, we verified the bending stress's magnitude to crack distribution observed from optical photographs.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.8
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• pp.1077-1082
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• 2012

This paper analyzes the lightning-induced overvoltage and current in buried underground distribution cable. Based on analytical expressions, the lightning-induced overvoltage and current in buried underground distribution cable is calculated by EMTP/MODELS. The modeling is verified by comparing with the results in reference. Also, the type and buried arrangement of cables used in domestic distribution line are modeled by EMTP/ATPDraw. The various simulations according to the type and buried arrangement of cable are performed and the simulation results are analyzed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1667-1673
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• 2009

This paper presents a application of new algorithm for feeder reconfiguration problem in distribution systems. Harmony Search (HS) algorithm, which is motivated from the musical performance, is used to reconfigure distribution systems so that active power losses are globally minimized with turning on/off the sectionalizing and the tie-line switches. In optimization processing, the HS algorithm has searching ability for the global optimal solution, simple coding of the iteration procedure, and fast convergence to get the solution. The HS algorithm is tested on 15 buses and 69 buses distribution systems, and the results prove its effectiveness to determine appropriate switching options without the occurrence of any misdetermination in switching and get the minimum power loss.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1681-1688
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• 2009

This paper proposes a new fault restoration method which adopts the recloser as top agent to release the problems of the data concentration and fault processing delay of the existing DAS(distribution Automation System) under the ubiquitous distribution system. In proposed method, top agent collects the data based on the multi-casting communication with the tie switches of the interconnection point, and then selects a closed switch(tie switch) to transfer the sound outage load to other feeders based on the heuristic search strategy step by step until the load transfer work is finished. Here, a new heuristic rule is developed which can guarantee the relational load balancing and line loss from the collected voltage data. Finally, the several faults are simulated for typical multi-section and multi-interconnection distribution system to prove the effectiveness of the proposed strategy, in particular, for each simulation cases, the load balancing index and line loss index of the obtained solution from the proposed method is compared with those of all of feasible solutions.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.7
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• pp.11-17
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• 1982

In this paper, a reliable and convenient evaluation method for the adequacy of any radial distribution line's voltage drop is proposed for improvement of the voltage regulation of the distribution line under operation. Using the voltage measurement of the first load branch point and the last point on the given distribution line its average line voltage drop and the line voltage drop variance by pure load variation are computed. And by these values and allowable or required line drop from proper voltage regulation view point, present adequency index and operation improvement index of the line drop are newly introduced for the evaluation of the given distribution line's voltage regulation. As a result of application to the 4 cases of study, the proposed method is proved to be reliable and convenient.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.2B no.4
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• pp.168-173
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• 2002

A new identification algorithm for the Preisach model is presented. The algorithm treats the identification procedure of the Preisach model as an inverse problem where the independent variables are parameters of the distribution function and the objective function is constructed using only the initial magnetization curve or only tile major loop of the hysteresis curve as well as the whole reversal curves. To parameterize the distribution function, the Bezier spline and Gaussian function are used for the coercive and interaction fields axes, respectively. The presented algorithm is applied to the ferrite permanent magnets, and the distribution functions are correctly found from the major loop of the hysteresis curve or the initial magnetization curve.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.86-90
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• 2003

This paper describes the electrical characteristics of Nomex paper employed as an insulating material for distribution transformers. The relative permittivities (dielectric constants) and tan$\delta$ (dielectric dissipation factors) were measured as dielectric characteristics and the partial discharge inception voltages (PDIVs) and breakdown voltages were also measured as electrical strength characteristics of Nomex paper. As a result, the permittivity and tan $\delta$ of Nomex paper demonstrated both temperature and frequency dependency. Of particular note, the permittivity of 0.18 mm Nomex paper was 2.4 according to the ASTM condition, The PDIVs and breakdown voltages were almost linearly increased with the thickness of Nomex paper. Furthermore, its electrical strength was superior to conventional Kraft paper.

• KIEE International Transactions on Power Engineering
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• v.3A no.2
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• pp.79-84
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• 2003

Unbalanced systems, such as distribution systems, have difficulties in fault locations due to single-phase laterals and loads. This paper proposes new fault locations developed by the direct three-phase circuit analysis algorithms using matrix inverse lemma for the line-to-ground fault case and the line-to-line fault case in unbalanced systems. The fault location for balanced systems has been studied using the current distribution factor, by a conventional symmetrical transformation, but that for unbalanced systems has not been investigated due to their high complexity. The proposed algorithms overcome the limit of the conventional algorithm using the conventional symmetrical transformation, which requires the balanced system and are applicable to any power system but are particularly useful for unbalanced distribution systems. Their effectiveness has been proven through many EMTP simulations.

• The Transactions of the Korea Information Processing Society
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• v.6 no.5
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• pp.1362-1372
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• 1999

Ray-tracing algorithm can synthesize photo-realistic image, but its computational cost is high. Fast image synthesis based on ray-tracing is one of the most important topics in computer graphics. There are two methods for high speed ray-tracing. First this paper discusses various load distribution and scheduling of multiprocessor for high sped ray-tracing. Then this paper proposes load distribution strategies based on them, implements and evaluates it on multiprocessor. The experiment results show that the proposed method can solve the unbalanced load problem of dynamic load distribution, and scan line method and dot method among a kind of static load distribution strategies disperse the load efficiently.