• 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.

• 전기학회논문지
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• 제60권11호
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• pp.2000-2006
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• 2011

Asynchronous phenomenon occurs on the synchronous generators under power system when a generator's amplitude of electromagnetic force, phase angle, frequency and waveform etc become different from those of other synchronous generators which can follow instantly varying speed of turbine. Because the amplitude of electromagnetic force, phase frequency and waveform differ from those of other generators with which are to be put into parallel operation due to the change of excitation condition for load sharing and the sharing load change, if reactive current in the internal circuit circulates among generators, the efficiency varies and the stator winding of generators are overheated by resistance loss. Where calculation method of protection settings and Logic for Protection of Generator Asynchronization will be recommended, A distance relay scheme is commonly used for backup protection. This scheme, called a step distance protection, is comprised of 3 steps for graded zones having different operating time. As for the conventional step distance protection scheme, Zone 2 can exceed the ordinary coverage excessively in case of a transformer protection relay especially. In this case, there can be overlapped protection area from a backup protection relay and, therefore, malfunctions can occur when any fault occurs in the overlapped protection area. Distance relays and overcurrent relays are used for backup protection generally, and both relays have normally this problem, the maloperation, caused by a fault in the overlapped protection area. Corresponding to an IEEE standard, this problem can be solved with the modification of the operating time. On the other hand, in Korea, zones are modified to cope with this problem in some specific conditions. These two methods may not be obvious to handle this problem correctly because these methods, modifying the common rules, can cause another coordination problem. To overcome asynchronizing protection this paper describes an improved backup protection coordination scheme using a new Logic that will be suggested.

• 정보처리학회논문지C
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• 제17C권4호
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• pp.307-314
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• 2010

최근 근접 인증에 사용되는 비접촉식 스마트카드와 같은 RFID 태그들이 경계 위조(distance fraud) 공격, 마피아 위조(mafia fraud) 공격, 테러리스트 위조(terrorist fraud) 공격과 같은 다양한 위치 기반 공격인 중계 공격(relay attack)들에 매우 취약함이 증명되었다. 더 나아가 이러한 중계 공격들을 방지하기 위해 리더와 태그사이의 메시지 송수신 왕복 시간을 측정하는 경계 결정(distance-bounding) 프로토콜이 한 해결책으로 연구되고 있다. 2005년에 Hancke과 Kuhn은 처음으로 해쉬 함수 기반의 RFID 경계 결정 프로토콜을 제안하였다. 하지만 Hancke-Kuhn 프로토콜은 공격자에게 n번의 왕복에서 (3/4)$^n$의 성공 확률을 제공하여 중계 공격을 완벽히 방어할 수 없다. 본 논문에서는 공격자에게 n번의 왕복에서 (5/8)$^n$의 성공 확률을 제공하는 새로운 경량 RFID 경계 결정 프로토콜을 제안한다. 연구 결론으로 제안한 프로토콜은 안전한 해쉬 함수와 XOR 연산을 기반으로 하여 높은 저장 공간 효율성을 제공할 뿐만 아니라, 공격자의 성공 확률을 (5/8)$^n$으로 최적화하여 중계 공격에 대해서도 더욱 더 안전하다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.484_485
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• 2009

Power output of a wind farm fluctuates throughout a day. This affect a distance relay for wind farm intertie protection because a voltage of a relaying point varies due to fluctuating output of a wind farm. This paper describes the analysis of the response of a distance relay for intertie protection when the power output of a wind farm increases. A series of single phase to ground faults were also simulated and analyzed with PSCAD/EMTDC generated data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.278_279
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• 2009

Nowaday, many people study about Black-Out. In this paper, I introduce how to calculate the Dangerous Index against Black-Out, and prediction of Distance relay error action on Zone 3. we consider the real data by I-PIU which will be set on the system. The dangerous Index is calculated three index about Cascading. The prediction of Distance relay is considered by other facilities of power system. This two algorithm can be used on the center system, when the system is on danger, also on the normal states for security.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.212-214
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• 2000

The distance relay technique used for transmission line protection operates overreach and underreach to the self protection region because the power system becomes complex and fault conditions are different. To solve these problems, this paper describes new technique to set the reliable self protection lesion. The trip region of the quadrilateral distance relay is set by training of multi layer recurrent elman network. The proposed network is able to reach the trip zone for the fault impedance, fault initial angle and source impedance variance correctly.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.502-503
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• 2006

If the fault occurs on the underground Power cable system, the fault current on the sheath has the influence on all sections because it's returned through earth at the directly grounded point and operation point of SVL(Sheath Voltage Limiter) at joint box. Therefore, the earth resistance and the operation of SVL have an effect on the zero-sequence current. Then the impedance between relaying point and fault point is Increased. That causes the overreach of distance relay. For these reasons, the distance relay algorithm for protecting of the underground power cable systems was developed. It effectively advance the errors using ACI(Advanced Computing Intelligence) technique. In this algorithm, the optimization was performed by fuzzy inference system and genetic algorithm.

• 대한전기학회논문지:전력기술부문A
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• 제48권10호
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• pp.1215-1221
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• 1999

A high speed digital distance relaying algorithm based on a Wavelet Transformation is proposed. To obtain stable phasor values very quickly, first, a lowpass filter which has low cutoff frequency is used. Secondly, db2(Daubechies 2) Wavelet which has the data window of 4 samples is used. A FIR filter which removes the DC-offset component in current relaying signals is applied. In accordance with a series of tests, the operation time of the relaying algorithm is less than 3/4 cycles after faults in a 80 [km], 154[kV], 60[Hz] over-head transmission line system.

• 대한전기학회논문지
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• 제41권3호
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• pp.227-236
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• 1992

In this paper, a simulation program of relaying system including the CT and CPD ( capacitive potential device ) is developed to study the effect of its operation under various system conditions. To deal with the dynamic characteristics of relaying system, state space technique is applied, and then the state equations of CT, CPD and mho distance relay are constructed. Also the dynamic response characteristics of overall relaying system is verified by digital simulation. Since the proposed model is capable of taking arbitrary input waveforms from EMTP in analyzing its dynamic responses, the effects of CT-saturation and CPD-subsidence transient characteristics on the operating points of who distance relay can be accurately prodicted. It gives more effective results, compared with the model without considering those characteristics by checking the exprimental data.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.296-298
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• 2001

This paper represents protective management system for transmission line involving the UPFC(Unified Power Flow Controller) device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover, depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. Therefore, established protective system should be taken into account the variable injected voltage of the UPFC and constructed data base system.