• Title, Summary, Keyword: Differential protection

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Improved Ground differential relaying algorithm for the protection of a line-to-line fault of transformer (변압기의 선간 단락사고 보호를 위한 지락비율차동 계전 알고리즘의 성능향상 방법)

  • Kang, Hae-Gweon;Kim, Jin-Ho;Kim, Se-Chang;Park, Jong-Soo;Park, Jong-Eun
    • Proceedings of the KIEE Conference
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    • pp.760-761
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    • 2011
  • Ground differential relay is used to provide fast, sensitive, and selective protection for the wye connected and grounded electrical power equipment such as generators, power transformers, and grounding transformers. The ground differential protection only protects the ground faults within the protection zone, so that it can't protect the line-to-line fault. This paper proposes the algorithm to provide the protection for the line-to-line fault through the ground differential protection. The proposed algorithm detects the line-to-line fault of transformer using the comparison between the positive and the negative current, when the ground differential relay dose not operate. The performance of the algorithm is verified using a PSCAD/EMTDC simulator under various case studies.

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Numerical Algorithm for Power Transformer Protection

  • Park, Chul-Won;Suh, Hee-Seok;Shin, Myong-Chul
    • KIEE International Transactions on Power Engineering
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    • v.4A no.3
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    • pp.146-151
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    • 2004
  • The most widely used primary protection for the internal fault detection of the power transformer is current ratio differential relaying (CRDR) with harmonic restraint. However, the second harmonic component could be decreased by magnetizing inrush when there have been changes to the material of the iron core or its design methodology. The higher the capacitance of the high voltage status and underground distribution, the more the differential current includes the second harmonic during the occurrence of an internal fault. Therefore, the conventional second harmonic restraint CRDR must be modified. This paper proposes a numerical algorithm for enhanced power transformer protection. This algorithm enables a clear distinction regarding internal faults as well as magnetizing inrush and steady state. It does this by analyzing the RMS fluctuation of terminal voltage, instantaneous value of the differential current, RMS changes, harmonic component analysis of differential current, and analysis of flux-differential slope characteristics. Based on the results of testing with WatATP99 simulation data, the proposed algorithm demonstrated more rapid and reliable performance.

Transformer Differential Relay by Using Neural-Fuzzy System

  • Kim, Byung Whan;Masatoshi, Nakamura
    • 제어로봇시스템학회:학술대회논문집
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    • pp.157.2-157
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    • 2001
  • This paper describes the synergism of Artificial Neural Network and Fuzzy Logic based approach to improve the reliability of transformer differential protection, the conventional transformer differential protection commonly used a harmonic restraint principle to prevent a tripping from inrush current during initial transformer´s energization but such a principle can not performs the best optimization on tripping time. Furthermore, in some cases there may be false operation such as during CT saturation, high DC offset or harmonic containing in the line. Therefore an artificial neural network and fuzzy logic has been proposed to improve reliability of the transformer protection relay. By using EMTP-ATP the power transformer is modeled, all currents flowing ...

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Graphical Modeling for Operational Scheme of Current Differential Relay for Transmission Line Protection (송전선 보호용 차동전류 계전기의 동작원리에 대한 그래픽 표현)

  • Lee, Jong-Beom
    • Proceedings of the KIEE Conference
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    • pp.1407-1409
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    • 1999
  • Distance relay is being used for transmission line protection. Recently, current differential relay is used with high reliability in power system. This kind of relay is reported that it has a reliable detection ability, even so high impedance faults take place in transmission line. Therefore it is expected to use and expand widely in many utilities. Tripping of the relay is decided according to the difference between differential and restraint current. However the tripping criterion can be changed by the manufacturers. This paper presents an operational scheme of current differential relay for transmission line protection with graphical model. It is developed for educational purpose for students interesting in power system and protection engineer in utility. MATLAB is used to establish the models.

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A Percentage Differential Current Relaying Algorithm for Bus Protection Using Current Transformer Saturation Detecting Algorithm (변류기 포화검출 알고리즘을 적용한 모선보호용 비율전류차동 계전방식)

  • Kang, Yong-Cheol;Yun, Jae-Sung;Ok, Seung-Hun
    • Proceedings of the KIEE Conference
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    • pp.115-117
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    • 2001
  • A percentage current differential relaying algorithm is widely used for bus protection. However, it may maloperate external faults with CT saturation. This paper proposes a percentage current differential relaying algorithm for bus protection using CT saturation detecting algorithm. The CT saturation detecting algorithm uses difference of secondary current of CT and detects CT saturation. The proposed method distinguishes percentage differential relay operation caused by faults from percentage differential relay operation caused by CT saturations.

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Setting Method of a Percentage Current Differential Relay for Transformer Protection (변압기 보호용 전류비율차동 계전기의 동작영역 설정방법)

  • Kim, Su-Hwan;Kang, Sang-Hee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.1
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    • pp.8-13
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    • 2011
  • A percentage current differential relay is widely used for transformer protection. Because many percentage current differential relays recently use modified methods instead of conventional methods for deciding the operating characteristics of the large current region, in this paper, the operating region of a percentage current differential relay is analyzed in input-output current domain instead of operating-restraint current domain. An effective method to set the operating region when a CT is saturated is proposed with a series of investigations comparing a conventional method with the proposed modified method. The performance of the proposed method is evaluated for internal and external faults of a power transformer having the voltage rating of 345/154kV. EMTP-RV is used for the relaying data collection.

Current Differential Relaying Algorithm for Power Transformer Protection Operating in Conjunction with a CT Compensating Algorithm (보상 알고리즘을 적용한 변압기 보호용 전류차동 계전방식)

  • Kang, Yang-Cheol;Park, Jong-Min;Lee, Mi-Sun;Jang, Sung-Il;Kim, Yong-Gyun;So, Soon-Hong
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.11
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    • pp.1873-1878
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    • 2007
  • Current differential relays may maloperate during magnetic inrush and over-excitation because a significant differential current is produced. To prevent maloperation, the relays adopt some harmonic components included in the differential current. The harmonic restraints may increase the security of a relay but cause the operating time delay of a relay when an internal fault occurs. Moreover, the operating time delay is more increased if a current transformer (CT) is saturated. This paper describes a current differential relaying algorithm for power transformer protection with a compensating algorithm for the secondary current of a CT. The comparative study was conducted with and without the compensating algorithm. The performance of the proposed algorithm was investigated when the measurement CT (C400) and the protection CT (C400) are used. The proposed algorithm can compensate the distorted current of a CT and thus reduce the operating time delay of the relay significantly for an internal fault with CT saturation.

A Study on the Harmonics Effect of Ratio Differential Relay for Transformer Protection (변압기 보호용 비율차동계전기의 고조파 영향에 관한 연구)

  • Kim, Kyung-Chul;Hwang, Young-Rok;Kho, Hun;Jung, Dong-Won;Chung, Hae-Sung;Lee, Dong-Wook;Jeong, Chae-Ho;Lee, Jae-Yoon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.6
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    • pp.99-105
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    • 2014
  • Power transformers are applied throughout the power system to connect systems of different voltage to one another. Since a ratio differential relay offers high sensitivity in detection of internal faults in power transformers, it is widely used in the main protection system. The use of nonlinear devices such as rectifiers and other devices utilizing solid state switching have been increased in industry during recent years. For nonlinear loads, the load current is not proportional to the instantaneous voltage. This situation creates harmonic distortion on the system. The harmonic could differential relay misoperation if not recognized. This paper aims at analyzing and probing into the influences of harmonics on a ratio differential relay for power transformer protection.

A Percentage Current Differential Relaying Algorithm for Bus Protection Blocked by a CT Saturation Detection Algorithm (변류기 포화 곤단 알고리즘으로 억제된 모선보호용 비율 전류차동 계전방식)

  • 강용철;윤재성
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.1
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    • pp.44-49
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    • 2003
  • This paper describes a percentage current differential relaying algorithm for bus protection blocked by a CT saturation detection algorithm. The detection algorithm blocks the output of a current differential relay only if a differential current is caused by CT saturation in the case of an external fault. Moreover, if a current differential relay operates faster than the detection algorithm, the blocking signal is not ignited. On the other hand. if the detection algorithm operates faster than a current differential relay, the output of the relay is blocked. The results of the simulation show that the proposed algorithm can discriminate internal faults from external faults ever when a CT is saturated in both cases. This paper concludes by implementing the algorithm into the TMS320C6701 digital signal processor. The results of hardware implementation are also satisfactory The algorithm can not only increase the sensitivity of the current differential relay but Improve the stability of the relay for an external faults.

Digital Ratio Differential Relaying for Main Protection of Large Generator (대형 발전기 주보호를 위한 디지털 비율차동 계전기법)

  • Park, Chul-Won;Ban, Yu-Hyeon
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.61 no.1
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    • pp.35-40
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    • 2012
  • An AC generator is an important component in producing an electric power and so it requires highly reliable protection relays to minimize the possibility of demage occurring under fault conditions. It is a need for research of digital generator protection system(DGPS) for the next-generation ECMS and an efficient operation of protection control system in power station. However, most of protection and control system used in power plants have been still imported as turn-key and operated in domestic. This may cause the lack of the correct understanding on the protection systems and methods, and thus have difficulties in optimal operation. In this paper, presented ratio differential relaying(RDR) is main protective element in generator protection IED. The fault detection technique, operation zone and setting value of the RDR were studied and, compared with two of the fault detection algorithm. For evaluation performance of the RDR, the data obtained from ATPDraw5.7p4 modeling was used. The proposed methods are shown to be able to rapidly identify internal fault and did not operate a miss-operation for all the external fault.