• 대한전기학회논문지:전력기술부문A
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• 제53권1호
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• pp.7-12
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• 2004

The role of protective relay with correct setting value is very important for the reliable operation of power : system. The setting process of a protective relay is difficult and requires hard work of calculations. Therefore, KEPCO as been using PROSET2000, a computer program system, in order to automate the setting process of protective relays in power transmission network since 2000. This system has a database and relay setting modules for each type of realy with coresponding Human and Computer Interaction(HCI). For the setting of a new type of relay, it require a new module, a HCI and a database table corresponding to the new relay. But it's update is not easy in case of new type of relay. This paper discussed the update method introducing a concept of Open Interface. It addressd a method to make a new HCI for new relay in view of object-oriented method using UML(Unified Modeling Language). Using the UML, we updated the PROSET2000. HCI screens for a new relay is generated automatically using the information of the new relay stored in the database. And, the database management module is upgraded to solve problems in manage and maintain the database in view of Open Interface.

• 한국정보통신학회논문지
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• 제20권11호
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• pp.2100-2106
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• 2016

자동화시스템은 PLC를 사용하여 생산제품의 제조 공정상태를 감시하고 센서에서 전달되는 센서정보를 처리한다. 본 연구에서는 자동화시스템에 사용되고 있는 제어용 계전기의 상태를 감시하는 원격감시시스템을 제안한다. 제안한 시스템은 제어 릴레이모듈, 원칩프로세서 모듈, 컴퓨터 모니터링시스템과 제어용 계전기의 내역을 입력하고 관리하는 데이터베이스시스템으로 구성한다. 컴퓨터 모니터링시스템은 제어용 계전기의 작동상태와 수명을 모터링할 수 있도록 구성하였고, 데이터베이스는 제어용 계전기의 투입 일자를 입력하고 수정이 가능하게 구성하였으며, 제어용 계전기의 작동상태의 정보를 자동으로 프린트할 수 있도록 구성하였다. 원격감시시스템에서 제어용 계전기의 고장상태를 실시간으로 파악하고, 고장부품을 신속하게 교체하여 정상가동에 소요되는 시간을 최소화할 수 있도록 하였다.

• 한국인터넷방송통신학회논문지
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• 제10권5호
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• pp.39-44
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• 2010

본 논문에서는 최근에 많은 주목을 받고있는 상황인지 시스템을 협동릴레이 시스템에 적용하였을 때 상황인지 협동 릴레이 시스템의 성능을 유도하였다. 협동 릴레이 시스템은 기회전송 릴레이를 채택하였을 때와 채택하지 않았을 때의 성능을 비교하였다. 특히 목적지에서 시스템 구현의 간편성 때문에 많이 채택하고 있는 선택 결합방식을 고려하였는데, 이 경우 필수적으로 발생되는 채널 상태 정보(CSI)를 주고받으면서 발생되는 지연의 영향을 고려하였다. 분석결과 기회전송 릴레이를 채택할 경우 기회전송 릴레이를 채택하지 않은 경우보다 주어진 조건에서 최대 0.6 dB 열화 되었으며, 시스템의 성능은 상황인지 릴레이의 주파수 획득 확률보다는 채널 상태정보의 지연에 더욱 민감한 영향을 받음을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권10호
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• pp.2587-2600
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• 2012

It has been demonstrated that choosing an appropriate relay node can improve the transmission rate for the system. However, such system improvement brought by the relay selection may be degraded with the presence of the malicious relay nodes, which are selected but refuse to cooperate for transmissions deliberately. In this paper, we formulate the relay selection issue as a restless bandit problem with the objective to maximize the average rate, while considering the credibility of each relay node, which may be different at each time instant. Then the optimization problem is solved by using the priority-index heuristic method effectively. Furthermore, a low complexity algorithm is offered in order to facilitate the practical implementations. Simulation results are conducted to demonstrate the effectiveness of the proposed trust-based relay selection scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권2호
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• pp.545-563
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• 2015

Energy harvesting (EH) and network coding (NC) have emerged as two promising technologies for future wireless networks. In this paper, we combine them together in a single system and then present a time switching-based network coding relaying (TSNCR) protocol for the two-way relay system, where an energy constrained relay harvests energy from the transmitted radio frequency (RF) signals from two sources, and then helps the two-way relay information exchange between the two sources with the consumption of the harvested energy. To evaluate the system performance, we derive an explicit expression of the outage probability for the proposed TSNCR protocol. In order to explore the system performance limit, we formulate an optimization problem to minimize the system outage probability. Since the problem is non-convex and cannot be directly solved, we design a genetic algorithm (GA)-based optimization algorithm for it. Numerical results validate our theoretical analysis and show that in such an EH two-way relay system, if NC is applied, the system outage probability can be greatly decreased. Moreover, it is shown that the relay position greatly affects the system performance of TSNCR, where relatively worse outage performance is achieved when the relay is placed in the middle of the two sources. This is the first time to observe such a phenomena in EH two-way relay systems.

• 인터넷정보학회논문지
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• 제19권2호
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• pp.9-15
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• 2018

This paper proposes an energy efficient adaptive relay station ON/OFF scheme with different frequency reuse factors (FRFs) to enhance the system throughput and reduce the transmission energy consumption for the transparent mode of 2-hop cellular relay networks (CRNs) based on orthogonal frequency division multiple access and time division duplex. In the proposed scheme, the base station turns on or off the relay stations (RSs) when they are overutilized and undertuilized based on the traffic density of the cell coverage, respectively. Through the simulation results, we show that the proposed scheme outperforms the conventional CRN in terms of the energy consumption with the same system throughput. Further, in order to increase the system throughput with low energy consumption, the best way is FRF 1 when the number of operating RSs is up to 4 and FRF 2 otherwise.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권10호
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• pp.3321-3341
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• 2014

This paper investigates the outage performance and optimization for the four-phase two-way transmission network with an energy harvesting (EH) relay. To enable the simultaneous information processing and energy harvesting at the relay, we firstly propose a power splitting-based two-way relaying protocol (PSTWR). Then, we discuss its outage performance theoretically and derive an explicit expression for the system outage probability. In order to find the optimal system configuration parameters such as the optimal power splitting ratio and the optimal transmit power redistribution factor, we formulate an outage-minimized optimization problem. As the problem is difficult to solve, we design a genetic algorithm (GA) based algorithm for it. Besides, we also investigate the effects of the power splitting ratio, the power redistribution factor at the relay, and the source to relay distance on the system outage performance. Finally, extensive simulation results are provided to demonstrate the accuracy of the analytical results and the effectiveness of the GA-based algorithm. Moreover, it is also shown that, the relay position greatly affects the system performance, where relatively worse outage performance is achieved when the EH relay is placed in the middle of the two sources.

• Journal of Communications and Networks
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• 제18권3호
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• pp.299-310
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• 2016

In practical wireless relay communication systems, non-destination nodes are assumed to be idle not receiving signals while the relay sends messages to a particular destination node, which results in reduced bandwidth efficiency. To improve the bandwidth efficiency, we relax the idle assumption of non-destination nodes and assume that non-destination nodes may receive signals from sources. We note that the message relayed to a particular node in such a system gives rise to interference to other nodes. To study such a more general relay system, we consider, in this paper, a relay system in which the relay first listens to the source, then routes the source message to the destination, and finally produces interference to the destination in sending messages for other systems. We obtain capacity upper and lower bounds and study the optimal method to deal with the interference as well as the optimal routing schemes. From analytic results obtained, we find the conditions on which the direct transmission provides higher transmission rate. Next, we find the conditions, by numerical evaluation of the theoretical results, on which it is better for the destination to cancel and decode the interference. Also we find the optimal source power allocation scheme that achieves the lower bound depending on various channel conditions. We believe that the results provided in this paper will provide useful insights to system designers in strategically choosing the optimal routing algorithms depending on the channel conditions.

• Journal of Electrical Engineering and Technology
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• 제5권4호
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• pp.522-529
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• 2010

Distance relay plays an important role in the protection of transmission lines. The application of flexible AC transmission systems (FACTS) devices, such as the static synchronous compensator (STATCOM), could affect the performance of the distance relay because of compensation effect. This paper analyzes the application of distance relay on the protection of a transmission line containing STATCOM. New setting principles for different protection zones are proposed based on this analysis. A typical 500 kV transmission system employing STATCOM is modeled using Matlab/Simulink. The impact of STATCOM on distance protection scheme is studied for different fault types, fault locations, and system configurations. Based on simulation results, the performance of distance relay is evaluated. The setting principle can be verified for the transmission line with STATCOM.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.6-8
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• 2002

In this paper present Autonomous Adaptive Digital Over Current Relay which acts autonomous setting using voltage and current measured by relay in the change of power systems. Automation of relay setting is required for distribution automation although manual relay setting is used at present. This paper presents Autonomous Relay Setting which knows change of the power system and acquires setting element using the Recursive Least Squares. Relay setting is very difficult work. But proposed relay is expected to decrease burden of relay setting using acquired information of power system change and autonomous setting. Also fast protective ability is expected according to change of power system.