• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.1
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• pp.17-28
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• 2003

Digital technology has advanced very significantly over the years both in terms of software tools and hardware available. It is now applied extensively in many area of electrical engineering including protective relaying in power systems. Digital relays based on digital technology have many advantages over the traditional analog relays. The digital relay is able to do what is difficult or impossible in the analog relays. However, the complex algorithms associated with the digital relays are difficult to test and verify in real time on real power systems. Although non real-time simulators like PSCAD/EMTDC are employed to test the algorithms, such simulations have the disadvantage that they cannot test the relay dynamically. Hence, real-time simulators like RTDS are used, but the latter needs large space and it is very expensive. This paper uses EMTP MODELS to simulate the power system and the distance relay. The distance relay algorithm is constructed and the distance relay is interfaced with a test power system. The distance relays performance is then assessed interactively under various fault types, fault distances and fault inception angles. The test results show that we can simulate the distance relay effectively and we can examine the operation of the distance relay very closely including debugging by using EMTP MODELS.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.255-263
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• 2010

The compensated-current-differential relay uses the same restraining current as a conventional relay, but the differential current is modified to compensate for the effects of the exciting current. Delta winding current is necessary to obtain the modified differential current for a $Y-\Delta$ transformer. This paper describes an estimation algorithm of the delta winding current and its application to a compensated-current-differential relay for a $Y-\Delta$ transformer. Prior to saturation, the core-loss current is calculated and used to modify the differential current. When the core first enters saturation, the initial value of the core flux is obtained by inserting the modified differential current into the magnetization curve. This flux value is used to derive the magnetizing current and consequently the modified differential current. The operating performance of the proposed relay was compared against a conventional current differential relay with harmonic blocking. Test results indicate that the proposed relay remained stable during severe magnetic inrush and over-excitation, and its operating time is significantly faster than a conventional relay. The relay is unaffected by the level of remanent flux and does not require an additional restraining or blocking signal to maintain stability. This paper concludes by implementing the proposed algorithm into a prototype relay based on a digital signal processor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.481-484
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• 2009

In this paper, we suggest a precoding algorithm for full-duplex relay with multiple antennas. Because full-duplex relay performs transmission and reception at the same time in the same frequency band another existing half-duplex relay differently, self interference arise between transmit and receive antennas of relay. The proposed precoding algorithm eliminates self interference by block diagonalization algorithm and makes the relay perform full-duplex operation. Also we verify that full-duplex relay have improved channel capacity than existing half-duplex relay by computer simulation.

• ETRI Journal
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• v.35 no.5
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• pp.919-922
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• 2013

A MIMO multi-way relay channel with full data exchange in which K users exchange messages with each other via the help of a single relay is considered. For the case in which each link is quasi-static Rayleigh fading and the relay is full-duplex, the fundamental diversity-multiplexing tradeoff (DMT) is investigated, and we show that a compress-and-forward relay protocol can achieve the optimal DMT.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.124.4-124
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• 2001

It needs a skillful experience to design and implement sequential circuits with a relay circuit or LD (Ladder Diagram). One makes out the operation of relay contacts sequentially in case of analyzing a relay circuit or LD. Still more, the design and analyzing of a complex relay circuit or LD are difficult. In this paper, we propose the EMFG (Extended Mark Graph) representation on relay circuits and LD.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.60.5-60
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• 2001

It is very difficult to design and analyze the relay circuit because one have to consider and analyze in order the behavior in which the relay contacts. In this paper, we propose the relay circuit to EMPG (Extended Mark Flow Graph) convension with a box´s characteristic equation. It will give you a lot of benefits in case of analysis and check of the relay circuit to convert the relay circuit into EMPG.

• Journal of information and communication convergence engineering
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• v.9 no.6
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• pp.647-651
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• 2011

In this letter, non-regenerative Amplify-and-Forward (AF) relay systems based on half and full duplex schemes are investigated and their performance is analyzed and compared in terms of outage probability. Although the AF relay systems have been widely investigated in many previous literatures, most of them adopted a half duplex scheme due to hardware limitation and mathematical tractability. To the best of our knowledge, this letter is the first study to investigate the performance of the full duplex AF relay system considering practical hardware limitations. In full duplex AF relay systems, it is important to secure the isolation between transmit and receive antennas. Our numerical and simulation results show that there exists a threshold point of the isolation gain that the full duplex relay system outperforms the half duplex relay system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.646-649
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• 2008

This study deals with mechanism of relay operation and modeling of transfer function between impact force and sound pressure due to the impact force in order to reduce relay noise. A collision between a moving-contact and fix-contact produces impact noise. Therefore impact noise of relay is determined by not only excitation force but also transfer function from impact force to noise. In this study, we find mechanism of relay operation, make impact force model and measure characteristic of relay noise. And also we find transfer function of relay noise.

• Proceedings of the KIEE Conference
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• 2008.10b
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• pp.225-226
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• 2008

본 논문은 스케줄링 기반 Ad-hoc Network에서의 Relay Network Protocol에 관한 것으로, Koinonia V2.0의 MAC Layer Protocol을 기반으로 Relay Network Protocol을 설계하였다. Ad-hoc Network 기반의 Relay Network Protocol은 단일 주파수 채널을 이용한 Relay Network Protocol과 듀얼 주파수 채널을 이용한 Relay Network Protocol이 있다. 전자는 하나의 모뎀 칩을 사용하여 시스템이 단순하고 전력소모가 적은 반면, 데이터 전송 속도가 낮아지고, 후자는 데이터 전송 속도에서 손해를 보지 않는 반면, 시스템이 복잡하고 전력소모가 많은 단점이 있다. 본 연구를 통해 Ad-hoc Network 기반의 Relay Network Protocol 구현에 대한 방법론을 제시할 수 있었다.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.2
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• pp.80-86
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• 2004

During magnetic inrush or over-excitation, saturation of the core in a transformer draws a large exciting current, which can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. The relay calculates core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss and the magnetizing currents from the conventional differential current. Comparison study with the conventional differential relay with harmonic blocking is also shown. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.