• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.1
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.11
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• pp.2100-2106
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• 2016

The automation system uses PLC to monitor the manufacturing process status of the production product and processes the sensor information transmitted from the sensor. In this paper, we propose a remote surveillance system to monitor the status of control relay used in automation system. The proposed system consists of a control relay module, a one-chip processor module, a computer monitoring system, and a database system that inputs and manages the details of the control relay. The computer monitoring system is configured to monitor the operating condition and life time of the control relay. The database is configured so that the input date of the control relay can be input and corrected, and the operating state information of the control relay can be automatically printed. In the remote monitoring system, the failure status of the control relay is recognized in real time, and the time required for normal operation can be minimized by quickly replacing faulty parts.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.39-44
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• 2010

In this paper, we analyze the performance of the cooperative cognitive radio relay system which is adapted the recently highly focused cognitive radio system. The performance comparison is made between the system with and that without the opportunistic transmission relay. Especially the selection combining is considered at the destination for simple implementation. In this case, the effect of the channel state information (CSI) delay, which is caused essentially by the process during the CSI delivery, to the system performance is considered. It is noticed that the performance of the system with the opportunistic relay degrades up to 0.6 dB at a given condition compared to the system without the opportunistic relay. And it is shown that the system performance is more sensitive to the CSI delay compared to the frequency acquisition probability of the cognitive radio relay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.10
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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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• v.9 no.2
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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.

• Journal of Internet Computing and Services
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• v.19 no.2
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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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• v.8 no.10
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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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• v.18 no.3
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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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• v.5 no.4
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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.

• Proceedings of the KIEE Conference
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• 2002.07a
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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.