• Journal of Institute of Control, Robotics and Systems
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• v.6 no.3
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• pp.284-290
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• 2000

The measurement of electric current using optical techniques provides a number of important practical advantages including effective isolation from high line potentials and freedom from the saturation effects observed in conventional current transformers. In this work the optical current sensor which uses thin YIG(Yittrium Ion Garnet) film as a Faraday element has been developed. We have characterized this optical current sensor and implemented it to the OOCR(Opto-electronic OverCurrent Realy) Performance of the OOCR shows the possibility of replacing the present overcurrent relays with OOCR.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.50-67
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• 2015

The Cognitive Radio (CR) paradigm in tactical ad hoc networks is an important element of future military communications for network-centric warfare. This paper presents a novel Cognitive Link State Routing protocol for CR-based tactical ad hoc networks. The proposed scheme provides prompt and reliable routes for Primary User (PU) activity through procedures that incorporate two main functions: PU-aware power adaptation and channel switching. For the PU-aware power adaptation, closer multipoint relay nodes are selected to prevent network partition and ensure successful PU communication. The PU-aware channel switching is proactively conducted using control messages to switch to a new available channel based on a common channel list. Our simulation study based on the ns-3 simulator demonstrates that the proposed routing scheme delivers significantly improved performance in terms of average end-to-end delay, jitter, and packet delivery ratio.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.491-496
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• 2012

There are several protective relays used to protect DC traction power supply system for DC railway. These relays, however, are made by different manufactures and they have different ways for their operations. Therefore, there are difficulties for cooperation between the devices or the devices and an upper system. In order to increase interoperability and stability of the system composed of devices made by different manufactures, IEC 61850 international standards are applied to design logical nodes for modeling protective elements used in protective relays.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.1979-1985
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• 2016

A protection algorithm using a voltage-controlled overcurrent element for a looped collection circuit in a wind farm is suggested in this paper. Because the proposed algorithm uses voltage relaying signals as well as current relaying signals, any fault in the looped collection circuit can be cleared by voltage-controlled overcurrent relays located at the two adjacent relaying points, the nearest place in each direction from the fault point. The algorithm can also distinguish the external faults which occur at the outside of a wind farm from the internal faults. It means that the proposed algorithm can provide the proper ability of protection coordination to the relays in the looped collection circuits of a large wind farm. The performance of the proposed algorithm is verified under various fault conditions using PSCAD/EMTDC simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.52-68
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• 2019

Aiming at the optimal placement of communication relay nodes (OPCRN) problem in manned/unmanned aerial vehicle cooperative engagement system, this paper designed a kind of fully connected broadband backbone communication topology. Firstly, problem description of OPCRN was given. Secondly, based on problem analysis, the element attributes and decision variables were defined, and a bi-level programming model including physical layer and logical layer was established. Thirdly, a hierarchical artificial bee colony (HABC) algorithm was adopted to solve the model. Finally, multiple sets of simulation experiments were carried out to prove the effectiveness and superiority of the algorithm.

• Proceedings of the KIEE Conference
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• 2004.11d
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• pp.37-39
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• 2004

To restrain abnormal voltage and effective operation in protect system, some of customer in Korea earth their own transformer in 154kV power system. The above ground system has some problems if ground fault occurs in other related area such as ground relay errors, under count register in two element register system. There for most huge customers opens the ground neutral and it causes errors in insulate and protection coordination and register system. In this paper presents the solution for above system.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.5
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• pp.485-493
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• 1990

The idea of expert control is to incorporate a rule based expert system in a feedback control system. In this paper, we present some heuristic rules based on relay experiment for the choice of controller structure and the setting of the controller parameters. Heuristic rules are used as an element of the feedback loop in an auto-tuning PID controller. The algorithms are coded in a form which is as pure as possible and the heuristic logic is implemented with the rules. This paper reports an implementation of an expert controller on microcomputer-based system, including an industrial programmable controller.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.12
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• pp.542-548
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• 2002

We consider an unknown linear time invariant plan with static load disturbance. A saturation function nonlinear element is sued to find th one point information in the frequency domain. We analyze an asymmetric self-oscillation caused by static load disturbance with relay feedback and saturation function feedback. We propose a new method to tune a PID controller using a saturation nonlinear feedback element in the presence of asymmetric oscillation. The proposed method does not require the knowledge of plant d.c. gain with an asymmetric oscillation in the plat output.

• 전기의세계
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• v.24 no.2
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• pp.84-91
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• 1975

This paper describes the results of a study for the system characteristics, especislly for the abnormal frequency drop of power system, when a large generation unit such as Kori Nuclear 1 (595MW) pulls out from the system. The automatic load shedding method now adopted in our system was re-studied to ameliorate the above problem. From the results of the study, a new under-frequency relay with an element for detecting the slope of frequency change and with time delay element to raise the lowered frequency to a desired value, was found to be effective, and should be purchased and utilized. By this study, an optimal and concrete load shedding method was recommended for reliable operation of power system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.461-464
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• 2009

The conventional electro-mechanical circuit break and relay are widely used in large-sized DC power system. However, recently due to high reliability, remote controllability and small power dissipation of a RSPC (Remote Solid State Power Controller), high-friendly DC power systems have increasingly adopted the RSPC as an essential element. In this paper, we have conducted the modeling of a RSPC circuit and the simulation analysis for $I^2t$ curve, respectively.