• Title/Summary/Keyword: Over current relay

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A Modified Current Differential Relaying Algorithm for Transformer Protection Considered by a Remanent Flux (잔류자속을 고려한 변압기 보호용 수정 전류차동 계전방식)

  • Kang, Y.C.;Jin, E.S.;Won, S.H.;Lim, U.J.;Kang, S.H.
    • Proceedings of the KIEE Conference
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    • 2003.11a
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    • pp.262-265
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    • 2003
  • During magnetic inrush or over-excitation saturation of the core in a transformer draws a large exciting current. This can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. In order to cope with the remanent flux at the beginning. the start of saturation of the core is detected and the core flux at the instant is estimated by inserting the differential current into a magnetization curve. Then, this core flux value can be used to calculate the core flux. The proposed relay calculates the 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 current and the magnetizing current from the conventional differential current. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

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Response characteristic of over current relay using optical sensor (광센서를 이용한 과전류 보호계전의 응답특성 연구)

  • 박병석;안성준;조홍근
    • 제어로봇시스템학회:학술대회논문집
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    • 1997.10a
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    • pp.1364-1366
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    • 1997
  • To operate electric power systems economically and stably, and to supply the electric power of good quality, it is necessary that the measured information (current, voltage, and so on) be detected and transmutted with high reliability and high effieincy. For the reason, the optical magnetic field sensor is possible to rapidly detect to over current and recover when electric power line have fault. In addition, the optical sensor have no electro magnetic distortion and no electric insulation. In this study, we designed OCR(Over Current Relay) using optical sensor. The designed OCR using optical sensor was measured characteristic and compared contentional OCR. This system have highest optical advantages and reliability.

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A Current Differential Relay for Transformer Protection with a Blocking Method Using the Difference-Function of a Differential Current (차전류 차분 블로킹 변압기 보호용 전류차동 계전기)

  • 강용철;원성호;김대성;양성채
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.12
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    • pp.691-697
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    • 2003
  • This paper proposes a current differential relay for transformer protection that operates in accordance with a blocking method based on the difference-function of a differential current. For magnetic inrush and over-excitation, discontinuities in the first-difference function of the differential current arise at the points of inflection, which correspond to the start and end of each saturation period of the core. These discontinuities are converted into the pulses in the second- and third-difference functions of the differential current. The magnitudes of the pulses are large enough to detect saturation of the core. A blocking signal is issued if the magnitude of the third-difference function exceeds the threshold and is maintained for three quarters of a cycle. The performance of the relay is assessed under various conditions with magnetic inrush, internal faults and external faults. The proposed blocking method can improve significantly the operating time of a relay and achieve high sensitivity of a relay.

Autonomous Adaptive Digital Over Current Relay (계통변화를 고려한 자율 적응형 과전류 계전기)

  • J.S., Jun-Seok;Lee, S.J.;Choi, M.S.;Kang, S.H.;Kim, S.T.;Lim, S.I.;Oh, S.M.;Kim, J.K.;Park, S.J.
    • 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.

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Implementation of Optoelectric Over Current Relay (광전자식 과전류 보호계전기의 구현에 관한 연구)

  • Park, Byung-Seok;Oh, Myun-Taek;Lee, Hwa-Joon;Cho, Hong-Keun
    • Proceedings of the KIEE Conference
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    • 1998.07e
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    • pp.1846-1849
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    • 1998
  • An optical magnetic filed sensor, YIG (Yittrium Iron Garnet), response rapidly, to the power-line currents to be measured. In response to Faraday effect, it shows wide-and-linear measurable range. This paper reports the development and implementation of an OOCR (Optoelectric OverCurrent Relay) using this sensor. This relay is free from environmental electro-magnetic noises and has excellent insulation characteristics inherently. By using this OOCR, we can reduce insulation cost of protective relaying systems and its maintenance cost, and can achieve high reliability of the system.

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A Study of Analysis on Klippon Relay Malfunction in HVDC System (HVDC 시스템에서 클리폰 릴레이 오동작 분석에 관한 연구)

  • Kim Chan-Ki;Park ong-Kwang;Choo Jin-Boo
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.54 no.9
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    • pp.437-443
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    • 2005
  • This paper deals with an experimental study for Klippon reiay in Cheju-Heanam HVDC system Klippon relay was troubled many times for years, and Klippon relay's fault caused the HVDC system trip. So for several years, these reasons of Klippon relay fault were investigated. The malfunction of Klippon relay in Cheju-Haenam HVDC system has been caused by the incoming of random surge(current source and voltage source). This paper has stu야ed the theoretic리 analysis and experimental study of Klippon relay, and the solutions against the problems were suggested according to their causes. Among the problems, grounding problem was removed by one-point earth connection and by modification of grounding circuit. The effects of inrush current was removed by inserting the blocking diodes by series in Klippon relay circuits. Finally, The over-voltage induced on Klippon relay, by a relay excitation coil, was removed by inserting a free-wheeling diode in Parallel with the excitation coil.

An Overcurrent Analysis in Neutral Line and Algorithm to Prevent Malfunction of Relay in Distributed Generations (분산전원 연계선로에서 지락고장시 중성선의 과전류 해석 및 보호계전기의 새로운 알고리즘)

  • Shin, Dong-Yeol;Kim, Dong-Myung;Cha, Han-Ju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.10
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    • pp.1916-1922
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    • 2009
  • Introducing distributed generators(DGs) to utility distribution system can cause malfunction of relay on the grid when ground faults or severe load unbalances are occurred on the system. Because DGs interconnected to the grid can contribute fault currents and make bidirectional power flows on the system, fault currents from DGs can cause an interference of relay operation. A directional over current relay(DOCR) can determine the direction of power flow whether a fault occurs at the source side or load side through detecting the phases of voltage and current simultaneously. However, it is identified in this paper that the contributed fault current(Ifdg) from the ground source when was occurred to contribute single-line-to-ground(SLG) fault current, has various phases according to the distances from the ground source. It means that the directionality of Ifdg may not be determined by simply detecting the phases of voltage and current in some fault conditions. The magnitude of Ifdg can be estimated approximately as high as 3 times of a phase current and its maximum is up to 2,000 A depending on the capacity of generation facilities. In order to prevent malfunction of relay and damage of DG facilities from the contribution of ground fault currents, Ifdg should be limited within a proper range. Installation of neutral ground reactor (NGR) at a primary neutral of interconnection transformer was suggested in the paper. Capacity of the proposed NGR can be adjusted easily by controlling taps of the NGR. An algorithm for unidirectional relay was also proposed to prevent the malfunction of relay due to the fault current, Ifdg. By the algorithm, it is possible to determine the directionality of fault from measuring only the magnitude of fault current. It also implies that the directionality of fault can be detected by unidirectional relay without replacement of relay with the bidirectional relay.

Study on the High Sensitive Three Phase Power Factor Meter and Relay (고감도 삼상력률계전기에 관한 연구)

  • 박정후
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.16 no.1
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    • pp.43-47
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    • 1980
  • The author designed and tested the high sensitive three-phase power factor meter and relay circuit, and dealt with the circuit to detect the phase of the current and the voltage. An operational amplifier comparator circuit and two single-phase transformers are used to control and detect the phase angle between the current and the voltage. The results obtained are as follows: 1. Converting the sine wave input current into the constant amplitude rectangular wave form by using a transistor chopper circuit, the power factor can be measured precisely over the load current of 0.08 A. 2. Using the moving coil type current meter, the power factor meter can be read in uniform . scale all over the range. 3. Using the three-phase power factor meter, the power factor relay which works at any power factor can be made.

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Development of the Automative Correction System for the Digital Over-current Relay With Distribution System (배전계통에서의 디지털 과전류 계전기 자동 정정 시스템 개발)

  • Baek, Young-Sik;Lee, Ho-Jun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.4
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    • pp.677-682
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    • 2007
  • In the distribution system, Change of system happens frequently. However, most of the relays are operated manually by a person or not changed when system changed. So, when fault happened, a case that relaydoes not act rapidly happens. Also, in current power system, digital relays are used because of digitization of relay. Digital relay has very many advantages than existing analog relay. One of these advantages is that communication is available and easily can make characteristic curve. If specific values are sent to a relay by communication, A relay can make suitable characteristic curve according to the value. In this paper, by using voltages and currents measured by relay, state of CB(Circuit Breaker) and these relays, SCADA(Supervisory Control And Data Acquisition) system that control and correct characteristic curve of overcurrent relay at system change by using HMI(Human Machine Interface) is proposed.

A Novel Digital Over Current Relay with Variable Time-Current Characteristics for Protective Coordination

  • Park, M. S.;P. S. Cho;Lee, S. J.;S. H. Hyun;Kim, K. H.
    • KIEE International Transactions on Power Engineering
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    • v.2A no.3
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    • pp.83-88
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    • 2002
  • An over current relay(OCR), one of the most frequently used protective devices, has time-current characteristics (TCC) to control its trip time according to the current level. It is because an appropriate operating time interval is necessary for coordination with other protective devices. A set of TCC curves of an OCR is, in general, given by the supplier from which a curve is selected by the operator. Therefore, in many cases, it is impossible to consider the operation condition of the given power system exactly. A novel concept of an OCR is suggested in this paper. The proposed OCR has an internal correction module so that it may produce the most adequate TCC curve according to the given protective information for coordination with other devices. With the generated TCC curve, a variety of operation and coordination conditions can be taken into consideration in an effective manner. The suggested OCR is applied to a simple test power system to show very promising results from a coordination point of view.