• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.94-99
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• 2005

This paper presents the integrity evaluation method of the windings in cast resin transformers using vertical thermal distribution analysis. The method is the result from comparing the temperature distribution in a sound condition specimen with that in the failure condition specimen layer-shorted by accelerated testing. The temperature distribution was acquisited by a infrared thermography system, and the Arrhenius equation was adopted to the accelerated testing. The proposed method may be available to detect the failures in cast resin transformers.

• 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.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.3
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• pp.199-203
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• 2016

The cost needed to managing equipment is constantly increasing because of increase of power equipment. The regulations such as PAS 55 and ISO 55000 were enacted to manage equipment assets. The advanced management methods such as real-time monitoring, condition evaluation, and health indices are avalable in generation system, transmission system, and substation transformers. However, These methods can not be applied to distribution equipment because of a lot of equipment. Therefore reliability assessment is very important in case of distribution equipment. In this paper, failure rates are extracted considering characteristics of regions, and which are the essential factors to reliability evaluation.

• Journal of Distribution Research
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• v.13 no.1
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• pp.61-77
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• 2008

This study proposes new fashion brand evaluation criteria. In developing the criteria, we emphasize the following considerations: first, the object of the evaluation should be the brand rather than the products or store second, the "new" brand should be the "new" brand from the consumer's perspective finally, only fashion brands available in department store are included to examine the relationship between evaluation criteria and consumers' relationship quality perception with a department store. Our data analysis of an online survey panel sample of 537 female consumers produced six new fashion brand evaluation criteria: merchandise power, in-store communication, brand/company image, salesperson, VMD, and assortment variety. New fashion brand evaluation criteria factors include both brand attributes and store attributes. Brand-related evaluation criteria are merchandise power, assortment variety, and brand/company images, whereas store-related criteria are VMD, salesperson, and in-store communication. The associations among brand evaluation criteria, brand attitudes, and the consumers' relationship quality with department store were tested by regression analysis.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1084-1092
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• 2002

The frequency dependency of Rayleigh surface wave is investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in two kinds of degraded specimens by scuffing or corrosion. Then, the frequency dependency is compared with the residual stress distribution or the corrosion-fatigue characteristics for the scuffed or corroded specimens, respectively. The width of the backward radiation profile increases with the increase of the variation in residual stress distribution for the scuffed specimens. In the corroded specimens, the profile width decreases with the increase of the effective aging layer thickness and is inversely proportional to the exponent, m, in the Paris' law that can predict the crack size increase due to fatigue. The result observed in this study demonstrates high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradient of material degradation generated by scuffing or corrosion.

• KIEE International Transactions on Power Engineering
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• v.3A no.1
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• pp.7-16
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• 2003

A new method to evaluate the protection capability of distribution systems is reported in this paper. This work describes the fuzzy evaluation attributes and aggregation method of evaluation results based on a hierarchical model and the modified combination rule. An evaluation grade index called "protectability" is proposed and is expected to be a very uscful tool in defining an optimal protection and realizing the adaptive protection.rotection.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.133-135
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• 2002

It is raised for methodology to evaluate power system reliability using interruption cost which is converted customer loss due to interruption into cost according to power industry is rushed into competition appearance. This paper presents algorithms to evaluate reliability of distribution power system taking into consideration customer interruption cost. Customer interruption cost is considered as one of the valuable index to estimate reliability of the distribution power system from customer situation. Also. this paper estimate evaluation results regarding the reliability of distribution power system using a sample model system. Finally, evaluation results of unserved energy and system interruption cost based on customer interruption cost are shown in detail.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.8
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• pp.457-462
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• 2003

This paper presents an optimal operating strategy of distributed generation (DG) with reliability worth evaluation of distribution systems. Using DG for peak-shaving unit could reduce the overall system operating cost, and using DG for standby power unit could reduce the customer interruption cost. If DG operating cost is less than utility power cost in peak time, DG should be running to reduce the overall system operating cost. When customer interruption cost enlarges, however, standby power strategy may be the better operating strategy than peak-shaving strategy. Selection of whether DG should be operated for peak-shaving or for standby power, needs the accurate reliability worth evaluation and the accurate power cost evaluation. Instead of using annual average reliability worth, the concept of hourly reliability worth is introduced in this paper to determine the optimal operating decision of DG. Applying suggested hourly reliability worth, the distribution companies that possess DG could set up the optimal operating strategy of DG.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.887-889
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• 1996

This paper presents Variance Reduction Techniques of the Monte Carlo Simulation considering Non-Exponential Distribution for Power System Reliability Evaluation. Generally, the components consisting of power system are assumed to be exponentially distributed in their state residence time. Sometimes, however, this assumption may cause a lot of errors in the reliability index evaluation. Non-exponential distribution can be approximated by a sum of several Erlangian distributions, whose inverse transform is easily calculated by using composition method. This paper proposes a new approach to deal with the non-exponential distribution and to reduce the simulation time by virtue of Variance Reduction Techniques such as Control Variate and Antithetic Variate.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.686-691
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• 1994

For evaluating the response fluctuation of the actual environmental acoustic system excited by arbitrary random inputs, it is important to predict a whole probability distribution form closely connected with evaluation indexes Lx, Leq and so on. In this paper, a new type evaluation method is proposed by introducing three functional models matched to the prediction of the response probability distribution from a problem-oriented viewpoint. Because of the positive variable of the sound intensity, the response probability density function can be reasonably expressed theoretically by a statistical Laguerre expansion series form. The relationship between input and output is described by the regression relationship between the distribution parameters(containing expansion coefficients of this expression) and the stochastic input. These regression functions are expressed in terms of the orthogonal series expansion and their parameters are determined based on the least-squares error criterion and the measure of statistical independency.