• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.209-213
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• 2015

With the increasing popularity of renewable generation systems and the advancement of power electronics, DC distribution systems have recently received considerable research attention. DC distribution has numerous advantages, including reliability, power quality, and efficiency. Owing to these advantages, DC distribution has been applied to data centers and power quality-sensitive electronic load conditions. Because grounding electrodes in DC are much more susceptible to corrosion than in AC, the IT system defined in IEC Standard 60364 may be a good candidate for an earthing method for DC distribution systems. In addition, IEC Standard 61557 specifies the requirements for insulation monitoring devices (IMD) for protection of the IT system, which continuously monitors the insulation resistances between the power lines and the earth. This paper discusses the development and evaluation of IMD to promote the reliability of distribution systems and increase safety of humans and facilities.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.35.1-35.1
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• 2010

Unlike the initial mass function, the initial size distribution of globular cluster (GC) systems is not well known. We calculate the evolution of the mass function (MF), radial distribution (RD), and size distribution (SD) of the Galactic GC system. By comparing the results from this calculation and the present-day MF, RD, and SD of the Galactic GC system, we infer the initial SD of the GC system. We find that a Gaussian distribution of the half-mass radius and a Gaussian distribution of the half-mass to Jacobi radius ratio are the best-fit initial SDs of the Galactic GC system.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.383-384
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• 2015

DC system is still unexploited in public distribution systems. As the weight of cost efficiency and reliability requirements of distribution networks are expected to increase in the future, with the utilization of distributed generation, there will be demand for novel distribution techniques. The utilization of the Low Voltage DC (LVDC) distribution system opens new possibilities for network development. This paper presents analysis of steady state and transient state according to the number of pole in LVDC distribution system.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.45-51
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• 2014

Distribution system is a critical link between customer and utility. The control of power loss is the main factor which decides the performance of the distribution system. There are two methods such as (i) distribution system reconfiguration and (ii) inclusion of capacitor banks, used for controlling the real power loss. Considering the improvement in voltage profile with the power loss reduction, later method produces better performance than former method. This paper presents an advanced evolutionary algorithm for capacitor inclusion for loss reduction. The conventional sensitivity analysis is used to find the optimal location for the capacitors. In order to achieve a better approximation for the current candidate solution, Opposition based Differential Evolution (ODE) is introduced. The effectiveness of the proposed technique is validated through 10, 33, 34 and85-bus radial distribution systems.

• Earthquakes and Structures
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• v.11 no.1
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• pp.25-43
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• 2016

The uneven distribution of rolling friction coefficient may lead to great uncertainty in the structural seismic isolation performance. This paper attempts to improve the isolation performance of a spring-damper-rolling isolation system by artificially making the uneven friction distribution to be concave. The rolling friction coefficient gradually increases when the isolator rolls away from the original position during an earthquake. After the spring-damper-rolling isolation system under different ground motions was calculated by a numerical analysis method, the system obtained more regular results than that of random uneven friction distributions. Results shows that the concave friction distribution can not only dissipate the earthquake energy, but also change the structural natural period. These functions improve the seismic isolation efficiency of the spring-damper-rolling isolation system in comparison with the random uneven distribution of rolling friction coefficient, and always lead to a relatively acceptable isolation state even if the actual earthquake significantly differs from the design earthquake.

• Journal of Dairy Science and Biotechnology
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• v.17 no.1
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• pp.32-38
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• 1999

Korean dairy industry is placed on the very critical situation with the progress of free trade marketing system internationally. To keep and improve the dairy food market, better measures are imperative for dairy industry. Especially, the milk distribution system is premodern to some extent, in comparison with both the production and the processing part of dairy industry. Reform measures for the promotion of domestic milk consumption by lowering the distribution cost are as follows. First, out-sourcing of the logistics department can decrease the circulation cost of milk. Secondly, milk should be packed into large-size package(more than 1 liter) to save both package and distribution cost. Thirdly, milk should be distributed from plant to consumers through the hygienic distribution system including perfect cold chain system, Above reform measures can not come true through the efforts taken by one company but through co-worker, concerted research, and joint in-vestment among dairy companies that can reduce the distribution cost and provide consumers with the best service, eventually resulting in the increment of milk consumption.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.4
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• pp.45-52
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• 2009

The objective of this was to improve a transportation cost relation between Central Distribution Centers(CDCs) and Regional Distribution Centers(RDCs), to control inventory cost concerning safety stock for each service level, by reviewing distribution steps connecting CDCs and RDCs under the price discount. It was also to examine and compare operating costs for the following two alternative suggestions for setting the service standard as a counter measure for a stock-out of the distribution network system management. First, provision by dispersing the safety stock to the CDCs and RDCs; and second, exclusive provision of the safety stock only to the RDCs. The cost comparison analysis was made for each category of purchase costs, regular transportation costs, express transportation costs, and inventory holding costs.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.36-38
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• 1993

This study considers the economic aspect of the distribution automation system, which is the decision-making criteria of the electric utilities for the investment. The feeder automation candidate region is divided into two types of the urban and the rural. The total investment cost of the feeder automation for each type is estimated. The annual cost, is also estimated, by finding the fixed charge rate. To compare the annual cost and the economic effect cost, for the investment decision-making, the costs are quantitatively estimated on the following effects : the manpower replacement, the outage cost saving, the main transformer utilization improvement, the feeder utilization improvement, and the line loss reduction.

• Journal of Korea Water Resources Association
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• v.40 no.6 s.179
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• pp.495-502
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• 2007

For a water distribution system, it is necessary to evaluate the superiority between different valve distributions in order to improve the reliability of the water distribution system. In cases of placing more valves to an exiting system or building a new system, we suggest a methodology to select a proper valve distribution after various valve distributions are compared. The suggested methodology is based on simulations of pipe and valve failures to estimate failure impacts of the water distribution system due to pipe and valve failures. It is quantified by the number of customers out of service per pipe failure resulted from pipe and valve failures. To demonstrate its applicability, the methodology is applied to a real water distribution system with two different valve distributions and determines the superiority between those valve distributions. Also, customers out of service along with various valve reliabilities are estimated for those valve distributions to prove the effect of the valve reliability on the reliability of a water distribution system.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2099-2104
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• 2015

The paper presents a monitoring system for the cooling of distribution transformers. The suggested system is controlled by a microcontroller scheme. The system is designed to control the oil temperature. It gives a solution to improve the cooling system by adding a number of fans especially for indoor transformers that are placed in badly-ventilated rooms. Also, the paper includes an alarm system with the possibility of tripping the transformer if it is necessary. The monitoring system consists of acquisition temperature sensor, and on-site unit. The hardware and software of the on-site unit are demonstrated with sufficient illustrations. Small prototype is constructed in the laboratory. Some laboratory experiments are carried out for examining the designed circuit by using Proteus Virtual System Modeling as well as for testing the prototype monitoring system. Concerning this research point, a study is carried out to evaluate the economic feasibility. The results are recorded and associated with many recommendations that may be valuable to electrical distribution (utility) companies.