• Advances in Energy Research
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• v.6 no.1
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• pp.55-73
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• 2019

The cost incurred by voltage sag effect in power networks has always been of important concern for discussions. Due to the environmental constraints, fossil fuel shortage crisis and low efficiency of conventional power plants, decentralized generation and renewable based DG have become trends in recent decades; because DGs can reduce the voltage sag effect in distribution networks noticeably; therefore, optimum allocation of DGs in order to maximize their effectiveness is highly important in order to maximize their effectiveness. In this paper, a new method is proposed for calculating the cost incurred by voltage sag effect in power networks. Thus, a new objective function is provided that comprehends technical standards as minimization of the cost incurred by voltage sag effect, active power losses and economic criterion as the installation and maintenance costs of DGs. Considering operational constraints of the system, the optimum allocation of DGs is a constrained optimization problem in which Lightning Attachment procedure optimization (LAPO) is used to resolve it and is the optimum number, size and location of DGs are determined in IEEE 33 bus test system and IEEE 34 bus test system. The results show that optimum allocation of DGs not only reduces the cost incurred by voltage sag effect, but also improves the other characteristics of the system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.143-148
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• 2010

Recently, the KEPCO is constructing the PQMS(Power Quality Monitoring System) each of the distribution line and will establish the voltage sag standard based on the long time measurement data of PQMS. The voltage sag prospect is difficult for the power system manager, however, the voltage sag forecasted is very important because the damage effect of the voltage sag is very broad. This paper describes the prospect formula of the voltage sag magnitude in the PCC(Point Common Coupling) by the starting current when the high capacity equipment is connected with the distribution line. To achieve this, this paper has proposed the sag prospect formula revision of KEPCO for the reliability improvement and the proposed formula has been applied the voltage sag real case to inspect the calculation procedure and reliability.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.288-296
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• 2016

A 400km/h simple catenary system was constructed as a test line in Korea. In the design stage of this system, the pre-sag was one of the engineering issues most focused on. It is known that the pre-sag improves the current collection performance in a certain band of high speed. However, the effect of pre-sag at 400km/h has not yet been established. To grasp a better pre-sag in the 400km/h catenary, we transacted the dynamic performance prediction simulation between catenary and pantograph under conditions of 0 and 1/3000 pre-sag. The level of 0 pre-sag was adapted for the 400km/h catenary design after reviewing predictions. We constituted the 1/3000 pre-sag sample section (about 1km) while constructing the 400km/h catenary test-bed (28km) of 0 pre-sag. With a HEMU-430X train, the contact forces were measured in the test-bed including the pre-sag sample section. In this paper, the predicted and measured dynamic performance values (contact forces) for 0 and 1/3000 pre-sag are described and compared. It is conclusively confirmed by analytical and experimental examination that the non pre-sag showed better dynamic (current collection) performance than that of the 1/3000 pre-sag for the 400km/h catenary system.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.156-158
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• 2002

In this paper, we analyze about voltage sag effect at load side during fault according to change of power system condition. through the case studies, we find that there is no close connection between substation bus transfer and voltage sag during fault. however, we find that other feeder connecting with the faulted transmission is directly affected by fault type and magnitude, therefore, the main subject can be divided into the utility and customer side countermeasures, utilities concentrate their effort to prevent the faults and to modify the fault clearing practice in power system. however, the faults in power system can never be completely eliminated. therefore, customer side solutions usually involve the power conditioning equipment for sensitive loads aiso, we investigate that the several methods to reduce the number and severity of voltage sag and to dull the sensitivity of equipment for voltage sag have developed. moreover, about SEMI, the industry association for the semiconductor two voltage sag immunity standards.(SEMI F47, SEMI F42) The simulation is accomplished by PSS/E 26.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.22-27
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• 2010

This paper analyzed bus voltage sag caused by recloser-fuse coordination in a power distribution system with SFCL. Generally, the recloser is installed to upstream of fuse to clear against both permanent and temporary faults appropriately, when the fault happened and to block expansion of the fault area. Furthermore, when the fault occurred, bus voltage sag is caused by increased fault currents. However, in a power distribution system with SFCL, the fault current could be decreased by the effect of the impedance value of the SFCL and place to install one as long as it could improve bus voltage sag. Therefore, to analyze the effect of the improvement of bus voltage sag caused by recloser-fuse coordination in a power distribution system with SFCL, we used PSCAD/EMTDC about a permanent fault at the place behind the fuse.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1085-1087
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• 1999

In this paper, we propose the method for assessing the effect of voltage sag in power distribution system using fuzzy risk assessment model. The proposed method is based on SCBEMA curve that expresses the representative susceptibility curve by voltage sag for each customer type. These corves are made using the CBEMA curves obtained from the experiment for the customers'sensitive equipment. In order to transform SCBEMA curves to the probability damage by voltage sag, the fuzzy risk assessment model is used in this paper. Case studies were performed to analyze the effect of voltage sag by varying parameters. The Monte Carlo simulation method and the historical reliability data in KEPCO are used for case studies.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.11
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• pp.558-565
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• 2000

In this paper, we propose a method for mitigating for mitigating the effect of voltage of voltage sag in radial power distribution systems using load transfer switching (LTS). The term of LTS is defined that the weakness load points for voltage sag transfer to the alternative source during the fault clearing practices. The sequenced of proposed LTS method is divided into the search of weakness points for voltage sag using the risk assessment model and transfer behavior of weakness points. The search of weakness point is carried out using the risk assessment model of voltage sag and Monte Carlo simulation method and the historical reliability data in Korea Electric Power Corporation (KEPCO) are also used. Through the case studies, we verify the effectiveness of proposed LTS method and present the searching method of effective application points of LTS method using the risk assessment model.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.208-210
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• 2000

In this paper, we present a method for mitigating the effect of voltage sag in radial power distribution systems using load transfer switching (LTS). The term of LTS is defined that the weakness load points for voltage sag transfer to the alternative source during the fault clearing practices. The sequences of proposed LTS method is divided into the search of weakness points for voltage sag using the risk assessment model and transfer behavior of weakness points. Through the case studies, we verify the effectiveness of proposed LTS method and present the searching method of effective application points of LTS method using the risk assessment model.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.954-955
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• 2008

In this paper, the voltage harmonics are investigated in terms of the voltage sag versus the time constants of electric machinery under the source voltage variation condition. The electric machinery and compensation equipment are established on the proposed design scheme based on voltage quality effect assessment technology. It have been analyzed how the variation of harmonic order, the output current, the DC-Link voltage and the induction motor speed is carried out under the voltage sag and switching frequency variation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.4
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• pp.177-184
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• 2000

In this paper, we proposes a method for assessing the effect of voltage sag in power distribution systems using fuzzy model. The proposed method is based on the reliability data of distribution system and specified computer business equipment manufacturer association(SCBEMA) curve that express the representative power acceptability curve by voltage sag for each customer type. The SCBEMA curves are made by using the CBEMA curves obtained from the experiment for the customers sensitive equipment. In order to transform SCBEMA curves to the differential damage by voltage sag, a fuzzy model is used. The proposed fuzzy model is composed to reflect two parameters of customers damage by voltage sag. One is the duration and magnitude of voltage sag and the other is the different risk due to the customer types. The Monte Carlo simulation method and the historical reliability data in KEPCO ae used for case studies.