• Title, Summary, Keyword: Magnetizing inrush current

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A Discriminating Algorithm between Magnetizing Inrush and Internal Faults of Transformers Using Difference of a differential current (차동전류의 변화율을 이용한 변압기의 여자돌입과 내부사고 구분 알고리즘)

  • Kang, Y.C.;Lee, B.E.;Yun, J.S.
    • Proceedings of the KIEE Conference
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    • pp.171-173
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    • 2000
  • This paper presents a discriminating algorithm between magnetizing inrush and internal faults of transformers using difference of a differential current. Incase of inrush, change of magnetizing inductance repeats. Thus, second difference of differential current periodically shows pulse while periodic pulse is not represented in case of internal winding fault. The proposed algorithm is suitable irrespective of the amount of remanent flux.

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Modified-Current-Differential Relay for Transformer Protection

  • Kang Yong-Cheol;Jin En-Shu;Won Sung-Ho
    • KIEE International Transactions on Power Engineering
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    • v.5A no.1
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    • pp.1-8
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    • 2005
  • During magnetic inrush or over-excitation, saturation of the core in a transformer draws a significant exciting current, which can cause malfunction of a current-differential relay. This paper proposes a modified-current-differential relay for transformer protection. The relay calculates the core-loss current from the induced voltage and the core-loss resistance as well as 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. A comparative study of the conventional differential relay with harmonic blocking is presented. The proposed relay not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the relay speed.

A Modified Current Differential Relay for Transformer Protection (변압기 보호용 수정 전류차동 계전방식)

  • 강용철;김은수;원성호
    • 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.

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.

Identification of Inrush and Internal Fault in Indirect Symmetrical Phase Shift Transformer Using Wavelet Transform

  • Bhasker, Shailendra Kumar;Tripathy, Manoj;Kumar, Vishal
    • Journal of Electrical Engineering and Technology
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    • v.12 no.5
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    • pp.1697-1708
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    • 2017
  • This paper proposes an algorithm for the differential protection of an Indirect Symmetrical Phase Shift Transformer (ISPST) by considering the different behaviors of the compensated differential current under internal fault and magnetizing inrush conditions. In this algorithm, a criterion function is defined which is based on the difference of amplitude of the wavelet transformation over a specific frequency band. The function has been used for the discrimination between three phase magnetizing inrush and internal fault condition and requires less than a quarter cycle after disturbance. This method is independent of any coefficient or threshold values of wavelet transformation. The merit of this algorithm is demonstrated by the simulation of different faults in series and excitation unit and magnetizing inrush with varying switching conditions on ISPST using PSCAD/EMTDC. Due to unavailability of in-field large interconnected transformers for such a large number of destructive tests, the results are further verified by Real Time Digital Simulator (RSCAD/RTDS). The proposed algorithm has been compared with the conventional harmonic restraint based method that justifies the application of wavelet transform for differential protection of ISPST. The proposed algorithm has also been verified for different rating of ISPSTs and satisfactory results were obtained.

Digital Relaying Algorithm for Power Transformer Protection using Fuzzy Logic Approach

  • Park, Chul-Won;Shin, Myong-Chul
    • KIEE International Transactions on Power Engineering
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    • v.2A no.4
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    • pp.153-159
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    • 2002
  • Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from EMTP simulation package and showed a fast and accurate trip operation.

Modified Current Differential Relay for Transformer Protection Unaffected by Remanent flux (잔류자속에 무관한 변압기 보호용 수정전류차동 계전기)

  • 강용철;김은숙
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.9
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    • pp.500-506
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    • 2004
  • This paper proposes a modified current differential relay for transformer protection unaffected by the remanent flux. The 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. To cope with the remanent flux, before saturation, the relay calculates the core-loss current and uses it to modify the measured differential current. When the core then enters saturation, the initial value of the flux is obtained by inserting the modified differential current at the start of saturation into the magnetization cure. Thereafter, the actual core flux is then derived and used in conjunction with the magnetization curve to calculate the magnetizing current. A modified differential current is then derived that compensates for the core-loss and magnetizing currents. The performance of the proposed differential relay was compared against a conventional differential relay. Results indicate that the modified relay remained stable during severe magnetic inrush and over-excitation because the exciting current was successfully compensated. This paper concludes by implementing the relay on a hardware platform based on a digital signal processor. The relay discriminates magnetic inrush and over-excitation from an internal fault and is not affected by the level of remanent flux.

The Protective Relaying Scheme of Power Transformer Using Wavelet Based Neural Networks (웨이브렛 변환을 바탕으로 한 신경회로망을 이용한 전력용 변압기 보호 계전기법)

  • Gwon, Gi-Baek;Seo, Hui-Seok;Yun, Seok-Mu;Sin, Myeong-Cheol
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.51 no.3
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    • pp.134-142
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    • 2002
  • This paper presents a new method for the protective relaying scheme in power transformer using wavelet based neural networks. This approach is as fellows. After approximation and detail information is extracted by daub wavelet transform from differential current of power transformer, the former is used for obtaining the rate of differential currents and restrain currents, the latter used as the input of artificial neural networks to avoid the Hiss-operation in over-exciting state and magnetizing inrush state of power transformer. The simulation of EMTP with respect to different faults, inrush conditions and over-exciting conditions in power transformer have been conducted, and the results preyed that the proposed method is able to discriminate magnetizing inrush states, over-exciting stales and internal faults.

Performance Improvement of Protective Relaying for Large Transformer by Using Voltage-Current Trend and Flux-Differential Current Slope Characteristic (전압-전류 추이와 자속-차전류 기울기 특성을 이용한 변압기 보호계전기법의 성능 개선)

  • Park, Chul-Won;Park, Jae-Sae;Jung, Yun-Man;Ha, Kyung-Jae;Shin, Myong-Chul
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.53 no.2
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    • pp.43-50
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    • 2004
  • Percentage differential characteristic relaying(PDR) has been recognized as the principal basis for power transformer protection. Second harmonic restraint PDR has been widely used for magnetizing inrush in practice. Nowadays, relaying signals can contain 2nd harmonic component to a large extent even in a normal state, and 2nd harmonic ratio indicates a tendency of relative reduction because of the advancement of material. Further, as the power system voltage becomes higher and more underground cables are used, larger 2nd harmonic component in the differential current under internal fault is observed. And then, conventional 2nd harmonic restraint PDR exposes some doubt in reliability. It is, therefore, necessary to develop a new algorithm for performance improvement of conventional protective relaying. This paper proposes an advanced protective relaying algorithm by using voltage-current trend and flux-differential current slope characteristic. To evaluate the performance of the proposed algorithm, we have made comparative studies of PDR, fuzzy relaying and DWT relaying. The paper is constructed power system model including power transformer, utilizing the WatATP, and data collection is made through simulation of various internal faults and inrush. As the results of test, the new proposed algorithm was proven to be faster and more reliable.

Method to Prevent the Malfunction Caused by the Transformer Magnetizing Inrush Current using IEC 61850-based IEDs and Dynamic Performance Test using RTDS Test-bed

  • Kang, Hae-Gweon;Song, Un-Sig;Kim, Jin-Ho;Kim, Se-Chang;Park, Jong-Soo;Park, Jong-Eun
    • Journal of Electrical Engineering and Technology
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    • v.9 no.3
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    • pp.1104-1111
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    • 2014
  • The digital substations are being built based on the IEC 61850 network. The cooperation and protection of power system are becoming more intelligent and reliable in the environment of digital substation. This paper proposes a novel method to prevent the malfunction caused by the Transformer Magnetizing Inrush Current(TMIC) using the IEC 61850 based data sharing between the IEDs. To protect a main transformer, the current differential protection(87T) and over-current protection(50/51) are used generally. The 87T IED applies to the second harmonic blocking method to prevent the malfunction caused by the TMIC. However, the 50/51 IED may malfunction caused by the TMIC. To solve that problem, the proposed method uses a GOOSE inter-lock signal between two IEDs. The 87T IED transmits a blocking GOOSE signal to the 50/51 IED, when the TMIC is detected. The proposed method can make a cooperation of digital substation protection system more intelligent. To verify the performance of proposed method, this paper performs the real time test using the RTDS (Real Time Digital Simulator) test-bed. Using the RTDS, the power system transients are simulated, and the TMIC is generated. The performance of proposed method is verified in real-time using that actual current signals. The reaction of simulated power system responding to the operation of IEDs can be also confirmed.