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Kim S.-N.,Hyundai Heavy Industries | Lee M.-S.,Hanyang University | Lee J.-G.,Daeduk College | Rhee S.-B.,ATT Co. | Kim K.-H.,Korea University
Journal of Electrical Engineering and Technology | Year: 2011

This paper presents a method for the development of the impedance locus to test the dynamic characteristics of protective relays. Specifically, using the proposed method, the impedance locus can comprise three impedance points, and the speed of impedance trajectory can be adjusted by frequency deviation. This paper is divided into two main sections. The first section deals with the configuration of impedance locus with voltage magnitude, total impedance magnitude, and impedance angle. The second section discusses the control of the locus speed with the means of the deviation between two frequencies. The proposed method is applied to two machine equivalent systems with offline simulation (i.e., PSCAD) and real-time simulation (i.e., real-time simulation environment) to demonstrate its effectiveness. Source


Rhee S.B.,ATT Co. | Lee J.K.,Woosuk University | Lee B.W.,Hanyang University
IEEE Transactions on Applied Superconductivity | Year: 2011

Superconducting fault current limiter (SFCL) is a promising novel electric equipment to reduce excessive fault current in electric power systems effectively. However, in practical application of this novel device into electric networks, SFCL could cause some unfavorable impacts on the electric power system. Especially, coordination between the SFCL and the recloser which has a conventional protection scheme is a major concern because it could cause severe reliability and stability problems in power systems. Several important characteristics of SFCL, which affects on a recloser operation scheme, are quenching phenomena, recovery from the quenching state, limiting impedance and its triggering time. Therefore, careful assessment of coordination issues with a recloser should be investigated to evaluate reliabilities of electric power system by installing SFCL into conventional power networks. This paper presents the impacts of SFCL on the recloser operation by considering various aspects of newly developed hybrid resistive SFCL into distribution systems in Korea. Consequently, it was deduced that conventional recloser scheme might be altered in order to meet the performance and requirements of hybrid SFCL into distribution electric power systems. © 2010 IEEE. Source


Trademark
At&T, AT & T Corporation and American Telephone Company | Date: 1989-05-23

LUGGAGE TAGS MADE OF LEATHER, UMBRELLAS, ALL-PURPOSE SPORTS BAGS, TOTE BAGS, LEATHER BUSINESS PORTFOLIO-TYPE BRIEF CASES, AND VINYL BUSINESS CARD CASES.


Trademark
At&T, AT & T Corporation and American Telephone Company | Date: 1989-05-23

LUGGAGE TAGS MADE OF LEATHER, UMBRELLAS, ALL-PURPOSE SPORTS BAGS, TOTE BAGS, LEATHER BUSINESS PORTFOLIO-TYPE BRIEF CASES, AND VINYL BUSINESS CARD CASES.


Kim K.-H.,Hankyong National University | Rhee S.-B.,ATT Co. | Song K.-B.,Soongsil University | Hwang K.-J.,University of Ulsan | Lee K.Y.,Baylor University
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2012

This paper presents an optimal power flow method based on the generation rescheduling priority to enhance transient stability in power systems. In order to determine the generation rescheduling priority the energy margin sensitivity indices are calculated. The candidate generators for generation rescheduling are determined by the energy margin sensitivity indices and then optimal power flow (OPF) is calculated. The OPF formulates the Lagrangian function with the power flow equations and the fuel cost function and searches the optimal solution of the Lagrangian function by using the Newton's approach. The method proposed is applied to a 6-bus 7-lines system to demonstrate its effectiveness. Source

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