• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.137-144
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• 2006

This paper proposes novel protection schemes for grid-connected distributed generation (DG) units using the fault location algorithm. The grid-connected DG would be influenced by abnormal distribution line conditions. Identification of the fault location for the distribution lines at the relaying point of DG helps solve the problems of the protection relays for DG. The proposed scheme first identifies fault locations using currents and voltages measured at DG and source impedance of distribution networks. Then the actual faulted feeder is identified, applying time-current characteristic curves (TCC) of overcurrent relay (OCR). The method considering the fault location and TCC of OCR might improve the performance of the conventional relays for DG. Test results show that the method prevents the superfluous operations of protection devices by discriminating the faulted feeder, whether it is a distribution line where DG is integrated or out of the line emanated from the substation to which the DGs are connected.

• KIEE International Transactions on Power Engineering
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• 제3A권1호
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• pp.7-16
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• 2003

A new method to evaluate the protection capability of distribution systems is reported in this paper. This work describes the fuzzy evaluation attributes and aggregation method of evaluation results based on a hierarchical model and the modified combination rule. An evaluation grade index called "protectability" is proposed and is expected to be a very uscful tool in defining an optimal protection and realizing the adaptive protection.rotection.

• 전기학회논문지P
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• 제63권4호
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• pp.322-326
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• 2014

Recently, the LOE(loss of excitation) incidents are occurred in domestic synchronous generator frequently, the synchronous generator protection system has been much attention for the LOE protection of the incidents that threats synchronous generators and power systems. This paper was showed the characteristics and practices of distance relay that widely used LOE protection relaying in generator. Firstly, the operating characteristics and the impedance locus for LOE of the generator protection were introduced. Even if the conventional simulation program is used for modeling, but it is difficult to implement a LOE modeling and simulation of synchronous generator. So, the LOE relay operation data collected from thermal power plant and nuclear power plant in real fields were analyzed. By reviewing the applications of GE Mho relays, the reliability of LOE for synchronous generator protection in domestic were improved.

• Journal of Electrical Engineering and Technology
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• 제1권4호
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• pp.423-426
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• 2006

Distance relays achieve selective tripping by measurement of all short circuit fault conditions inside set reaches. The direction of the fault, forward or reverse is commonly determined with a dedicated measurement to ensure selectivity under all conditions. For the direction decision (measurement) a number of alternatives are available. This paper describes a loop selective direction measurement and illustrates by means of a typical fault why this is superior to a non loop selective direction measurement such as that based on negative sequence quantities.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(II)
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• pp.995-1000
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• 2002

This paper presents general concept of DC switch gear(DCSWGR). Normally, DCSWGR consist of Digital protection unit(DPU), High Speed Circuit Breaker(HSCB), Disconnect Switch (DS), Programmable Logic Control(PLC), Auxiliary Relays and etc. Most of the components has its special characteristics and their interface between each others are various and complex. In this paper every constituent general design are preceded and interface between each component are examined. And also DCSWGR operation logic with logical diagram including interlock signal are introduced.

• Journal of Electrical Engineering and Technology
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• 제8권5호
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• pp.969-974
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• 2013

Protection issues in distribution systems which are to be operated in open and closed-loop modes in a smart grid are studied and a generalized protection setting method is proposed to meet the new requirements. The developed setting method assumes a conventional over-current protection scheme for the system with reclosers and over-current relays. In a closed-loop mode, it identifies protective devices that have to be sacrificed in order to maximize protection coordination for bidirectional fault current flow. The proposed setting method has been tested on many systems with different complexity and is proved effective.

• KIEE International Transactions on Power Engineering
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• 제4A권1호
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• pp.26-32
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• 2004

Digital technology has advanced significantly over the years both in terms of software tools and hardware availability. It is now applied extensively throughout many area of electrical engineering including protective relaying in power systems. Digital relays have numerous advantages over traditional analog relays, such as the ability to accomplish what is difficult or impossible using analog relays. Although non real-time simulators like PSCAD/EMTDC are employed to test the algorithms, such simulations are disadvantaged in that they cannot test the relay dynamically. Hence, real-time simulators like RTDS are used. However, the latter requires large space and is very expensive. This paper uses EMTP MODELS to simulate the power system and the distance relay. The distance relay algorithm is implemented and the distance relay is interfaced with a test power system. The distance relay's 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 its drawbacks/limitations by using EMTP MODELS. Equally important, this approach facilitates any changes that need to be carried out in order to enhance the Distance Relay under test/examination.

• 조명전기설비학회논문지
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• 제19권2호
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• pp.131-137
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• 2005

보호계전기는 고장에 의해 파생되는 단락$\cdot$지락 사고로부터 전력 시스템을 보호하기 위하여 널리 사용되고 있다. 전통적으로 디지털보호계전기는 디지털신호처리 프로세서 혹은 마이크로프로세서로 구현되는데 본 연구는 이를 고성능$\cdot$고효율$\cdot$다기능의 단일칩으로 구현하기 위한 하드웨어 설계 기술에 관해 다룬다. 제작된 디지털보호계전기는 FPGA(Field Programmable Gate Array)로 구현하였고 16KSPS이상의 처리 성능을 가지며 평균 오차율 $0.03(\%)$미만으로 보호계전알고리즘을 수행할 수 있다.

• 한국전기전자재료학회논문지
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• 제32권4호
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• pp.313-319
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• 2019

Induction motors connected with a three-phase AC system may malfunction due to reverse phase or open phase faults. Conventional overcurrent relays and overheating relays are used to prevent such accidents; however, their drawbacks include a low response speed and false operation. Therefore, in this study, a digital relay for the reverse-open phase was designed and fabricated. This relay can detect the reverse phase and open phase faults and send a trigger signal to the control circuit. The proposed relay was developed based on a microcontroller. The detection times of the reverse phase and open phase were verified as 320ms and 80ms, respectively. Compared with conventional relays that only protect the motor from one type of fault, the proposed relay can detect both, reverse phase and open phase faults. In addition, the fault detection, identification criterion, and trigger signal patterns can be modified by programming according to the requirements of users.

• Journal of Electrical Engineering and Technology
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• 제5권3호
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• pp.407-414
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• 2010

This paper proposes a probability measure for the evaluation of relay performance from two aspects, namely, correct trip and no-unwanted trip. They are developed based on the relationship between relay settings and relay measurements, which follow a Gaussian probability model. The proposed method based on strict mathematical derivation is applied to protection capability evaluation of distance relays under various settings. Considering the specific attributes of each protection zone, the optimal settings are also determined accordingly. The protection capability could demonstrate clearly the relay performance under various settings and the optimal settings could provide good references for engineering applications.