• 제목/요약/키워드: current transformer

검색결과 1,365건 처리시간 0.035초

전류변성기 비교기와 정밀션트저항을 이용한 전류변성기용 부담의 평가기술 (Evaluation Technique of Burden for Current Transformer using Current Transformer Comparator and Precise Shunt Resistor)

  • 이상화;강전홍;김명수;정재갑
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제55권5호
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    • pp.250-256
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    • 2006
  • Both ratio error and phase angle error in current transformer(CT) depend critically on values of CT burden. Thus, precise measurement of CT burden is very important for the evaluation of CT. A method for the measurement of CT burden has been developed by employing the portable shunt precise resistor with negligible AC-DC resistance difference less than $10^{-5}$. The burden value(value and power factor) can be calculated from resistance and reactance obtained by measuring the change of ratio error and phase angle error caused by the change of shunt resistor. The uncertainty for the method is evaluated and found to be abut 2 %.

웨이블렛 변환을 이용한 변압기 보호계전 알고리즘 (Protective Relaying Algorithm for Transformer Using Wavelet Transform)

  • 홍동석;이종범
    • 대한전기학회논문지:전력기술부문A
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    • 제52권2호
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    • pp.134-141
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    • 2003
  • The power transformer is one of the very important electric facilities in power systems. Recently, current differential relay is widely used to protect such power transformer But if inrush occurs in transformer, relay can be tripped by judging like internal fault. Therefore the correct discrimination between internal winding fault, inrush and overexcitation should be performed. This paper presents a new protective relaying algorithm which discriminates inrush, internal faults and overexcitation of transformer modelled using BCTRAN and HYSDAT of EMTP. Discrimination between internal winding fault and inrush is revealed in simulation within 1/2 cycle after fault. Accordingly, it is evaluated that the proposed algorithm has better discrimination characteristics in various cases thin the current relaying for protection of transformer.

다중권선 변압기를 이용한 능동형 셀 밸런싱 회로에서 밸런싱 전류 전달 효율을 높이기 위한 변압기 설계 방안 (Transformer Design Methodology to Improve Transfer Efficiency of Balancing Current in Active Cell Balancing Circuit using Multi-Winding Transformer)

  • 이상중;김명호;백주원;정지훈
    • 전력전자학회논문지
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    • 제23권4호
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    • pp.247-255
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    • 2018
  • This paper proposes a transformer design of a direct cell-to-cell active cell balancing circuit with a multi-winding transformer for battery management system (BMS) applications. The coupling coefficient of the multi-winding transformer and the output capacitance of MOSFETs significantly affect the balancing current transfer efficiency of the cell balancing operation. During the operation, the multi-winding transformer stores the energy charged in a specific source cell and subsequently transfers this energy to the target cell. However, the leakage inductance of the multi-winding transformer and the output capacitance of the MOSFET induce an abnormal energy transfer to the non-target cells, thereby degrading the transfer efficiency of the balancing current in each cell balancing operation. The impacts of the balancing current transfer efficiency deterioration are analyzed and a transformer design methodology that considers the coupling coefficient is proposed to enhance the transfer efficiency of the balancing current. The efficiency improvements resulting from the selection of an appropriate coupling coefficient are verified by conducting a simulation and experiment with a 1 W prototype cell balancing circuit.

절연유(絶緣油) 열화(劣化)센서 특성(特性) 연구(硏究) (A Study on the characteristics of degradation sensor for insulation oil)

  • 전영갑;선종호;강동식;주병수;윤진열;정상진
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1995년도 하계학술대회 논문집 C
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    • pp.1371-1374
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    • 1995
  • It is well known that the degradation of transformer oil conseqently lead to the failure of transformer. This paper discussed the characteristics of the degradation sensor checking transformer oil condition in live line. The degadation sensor is composed of base ring, electrodes and porous ceramic, passed through the transformer oil and checks the transformer oil condition through sensor's leakage current. So it is important to minimize the leakage current of base ring and connection parts. To investigate the leakage current of base ring and connection parts the characteristics of V-T-I and DC 2 KV and other examinations were performed. It is verified that ionized transformer oil caused by the expansion of temperature increases in the leakage current of porous ceramic sensor. It is certification that the leakage current of other parts of porous ceramic is very small(about 2%) compared with the porous ceramic body and it is confirmed that the leakage current in porous ceramic is changed sensitively according to the new oil(NO) and and the degradation oil(DO).

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Yg-Yg 3상 내철형 변압기의 영상분 임피던스 분석 (Zero Sequence Impedance of Yg-Yg Three Phase Core Type Transformer)

  • 조현식;조성우;신창훈;차한주
    • 전기학회논문지
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    • 제65권6호
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    • pp.940-945
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    • 2016
  • In this paper, zero sequence equivalent circuit of Yg-Yg three phase core-type transformer is analyzed. Many problems by iron core structure of the three phase transformer due to asymmetric three phase lines, which includes line disconnection, ground fault, COS OFF, and unbalanced load are reported in the distribution system. To verify a feasibility of zero sequence impedance of Yg-Yg type three phase transformer, fault current generation in the three phase core and shell-type Yg-Yg transformer is compared by PSCAD/EMTDC when single line ground fault is occurred. As a result, shell-type transformer does not affect the flow of fault current, but core-type transformer generate an adverse effect by the zero sequence impedance. The adverse effect is explained by the zero sequence equivalent circuit of core-type transformer and Yg-Yg type three phase core-type transformer supplies a zero sequence fault current to the distribution system.

변압기 권선을 이용한 자속구속형 초전도 전류제한기의 전류제한 및 전압강하 보상 특성 (Current Limiting and Voltage Sag Compensation Characteristics of Flux-Lock Type SFCL Using a Transformer Winding)

  • 고석철
    • 한국전기전자재료학회논문지
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    • 제25권12호
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    • pp.1000-1003
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    • 2012
  • The superconducting fault current limiter (SFCL) can quickly limit the fault current shortly after the short circuit occurs and recover the superconducting state after the fault removes and plays a role in compensating the voltage sag of the sound feeder adjacent to the fault feeder as well as the fault current limiting operation of the fault feeder. Especially, the flux-lock type SFCL with an isolated transformer, which consists of two parallel connected coils on an iron core and the isolated transformer connected in series with one of two coils, has different voltage sag compensating and current limiting characteristics due to the winding direction and the inductance ratio of two coils. The current limiting and the voltage sag compensating characteristics of a SFCL using a transformer winding were analyzed. Through the analysis on the short-circuit tests results considering the winding direction of two coils, the SFCL designed with the additive polarity winding has shown the higher limited fault current than the SFCL designed with the subtractive polarity winding. It could be confirmed that the higher fault current limitation of the SFCL could be contributed to the higher load voltage sag compensation.

대전력 시험설비용 변류기 특성에 관한 연구 (A Study of Current Transformer for High Power Testing Facility)

  • 정흥수;나대열;김선구;노창일;김원만;이동준
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2002년도 하계학술대회 논문집 B
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    • pp.735-737
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    • 2002
  • A current transformer for measuring current in high power testing laboratory is exactly proportional to the current including D.C component due to electrical transient. But, current transformer isn't designed to consider D.C component, therefore when data acquisition system measure that current. the error is increased because of saturation of core. This paper describe the concept of transient factor and how to design the current transformer.

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EMTP를 이용한 제주계통의 여자돌입전류 모델링 (Modeling of Transformer Inrush Current on Jeju Power System using EMTP)

  • 서훈철;여상민;김철환;유영식;조범섭
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2007년도 추계학술대회 논문집 전력기술부문
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    • pp.95-97
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    • 2007
  • Transformer inrush current can cause the voltage drop by source impedance. The accurate modeling and analysis for inrush current is first step to limit the inrush current and improve the power qualify. This paper presents the modeling of transformer inrush current by EMTP-RV using Jeju power system, Korea. The method to model the hysteresis curve of transformer in EMTP-RV is discussed. Simulations demonstrate the verification of modeling of inrush current by comparing the data recorded in field with simulation values and analyzing the harmonics of inrush current.

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Current limiting characteristics of transformer type SFCL with coupled secondary windings according to its winding direction

  • Han, Tae Hee;Lim, Sung Hun
    • 한국초전도ㆍ저온공학회논문지
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    • 제19권2호
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    • pp.44-47
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    • 2017
  • In this paper, the current limiting characteristics of the transformer type superconducting fault current limiter (SFCL) with the two coupled secondary windings due to its winding direction were analyzed. To analyze the dependence of transient fault current limiting characteristics on the winding direction of the additional secondary winding, the fault current limiting tests of the SFCL with an additional secondary winding, wound as subtractive polarity winding and additive polarity winding, were carried out. The time interval of quench occurrence between two superconducting elements comprising the transformer type SFCL with the additional secondary winding was confirmed to be affected by the winding direction of the additional secondary winding. In case of the subtractive polarity winding of the additional secondary winding, the time interval of the quench occurrence in two superconducting elements was shorter than the case of the additive polarity winding.

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

  • 김수환;강상희
    • 전기학회논문지
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    • 제60권1호
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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.