• Title/Summary/Keyword: Transformer

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Operation characteristics of SFCLs combined with a transformer in three-phase power system

  • Jung, B.I.;Choi, H.S.
    • Progress in Superconductivity and Cryogenics
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    • v.15 no.4
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    • pp.30-33
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    • 2013
  • The studies of superconducting fault current limiter (SFCL) for reduction of the fault current are actively underway in the worldwide. In this paper, we analyzed the characteristics of a new type SFCL using the conventional transformer and superconducting elements combined mutually. The secondary and third windings of this SFCL were connected the load and the superconducting element, respectively. The electric power was provided to load connected to secondary windings of the transformer in normal state of power system. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the ripple phenomenon of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the CT(current transformer) and then turn-on and turn-off switching behavior of the SFCL was performed by the SCR(silicon-controlled rectifier). As a result, the proposed SFCL limited the fault current within a half-cycle efficiently. We confirmed that the fault current limitation rate was changed according to the winding ratio of a transformer.

Temperature Characteristic of Transformer in High-Speed Train (고속철도용 변압기의 온도특성 변화)

  • Han, Young-Jae;Kim, Ki-Hwan;Kim, Seog-Won;Mok, Jin-Yong;Lee, Su-Gil;Kim, Jong-Young
    • Proceedings of the KIEE Conference
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    • 2004.04a
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    • pp.226-228
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    • 2004
  • In this study, temperature sensors were adhered to transformer that is used in KHST(Korean High-Speed Train) to verify variation of temperature characteristics about transformer synthetically and efficiently. In the case that temperature of transformer exceeds reference temperature for running of KHST, overheating of transformer may cause a fatal accident of vehicle. Therefore, after on-line measuring system was constructed in vehicle, oil temperature and tank temperature were measured on real-time. Characteristics and main specifications of transformer in KHST were described in this paper Also, measuring system for temperature measurement of transformer was explained in brief. Temperature data of transformer was acquired using measuring system, KRRI(Korea Railroad Research Institute) analyzed characteristic in contrast with comparing with temperature of transformer about month, running speed and running time.

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Analysis of Transient Characteristics of SFCL using the Three-Phase Transformer and Power Switch (삼상 변압기와 전력용 스위치를 이용한 초전도 한류기의 과도특성 해석)

  • Jung, Byung-Ik;Choi, Hyo-Sang;Park, Jung-Il;Cho, Geum-Bae
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.11
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    • pp.1743-1747
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    • 2012
  • The research of superconducting fault current limiter (SFCL) for reduction of the fault current is actively underway in the worldwide. In this paper, we analyzed the characteristics of a SFCL using the transformer and superconducting elements combined mutually in accordance with the fault types. The structure of this SFCL was composed of the secondary and third windings of a transformer connected to the load and the superconducting element, respectively. The provided electric power flew into the load connected to the secondary winding of the transformer in normal state. On the other hand, when the fault occurred in power system, the fault current was limited by closing the line of third winding of the transformer. At this time, the effect of the fault was minimized by opening the fault line in secondary winding of a transformer in power system. The sensing of the fault state was performed by the current transformer(CT) and then turn-on and turn-off switching behavior of the secondary line in the transformer was performed by the silicon-controlled rectifier(SCR). As a result, the proposed SFCL limited the fault current within one-cycle efficiently. Also, the degradation of the superconducting element in the normal state was avoided.

Characteristics of Transformer-Type SFCL according to the Connecting Methods of Secondary Coils (2차 권선의 연결방법에 따른 변압기형 초전도 한류기의 특성)

  • Cho, Yong-Sun;Park, Hyoung-Min;Chung, Soo-Bok;Choi, Hyo-Sang
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.12
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    • pp.2078-2083
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    • 2007
  • We have analyzed operating characteristics of transformer-type superconducting fault current limiter (SFCL) according to the serial or parallel connections of secondary coils with $YBa_2Cu_3O_7$ (YBCO) thin films. The turn ratio between the primary and secondary coils was 63:21. Transformer-type SFCL using a transformer with secondary winding of serial or parallel coils could reduce the unbalanced quench caused by differences of the critical current density between YBCO thin films. We found that transformer-type SFCL having serial or parallel connections induced simultaneous quench between the superconducting units. The limiting current in the transformer-type SFCL with a parallel connection was lowered to 30 % compared to the SFCL with a serial connection. In the meantime, when the currents generated in the superconducting units were similar, the voltage value in the parallel connection was 60 % as low as that in the serial connection. However, the voltage generated in the primary winding was some higher. In conclusion, we found that transformer-type SFCL with parallel connection of secondary coils was more effective in fault current limiting characteristics and in the reduction of the consumption power for superconducting units compared to those of the transformer-type SFCL with serial connection of secondary coils.

The Study of the Harmonic Currents Effects on the Transformer Vibration (고조파 전류가 변압기 진동에 미치는 영향에 관한 연구)

  • Kim, Su-Yeol;Kim, Yeon-Whan;Kim, Jang-Mok;Lim, Ik-Hun;Lee, Hyun
    • Journal of the Korean Society of Safety
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    • v.15 no.1
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    • pp.106-111
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    • 2000
  • EP(Electrostatic Precipitator) has been used to keep the natural environment from fly-ash in the industrial fields and operated in intermittent PEC(Pulse Energized Control) mode to improve dust-collecting efficiency. Intermittent PEC mode induces low-frequency harmonic currents into power system, therefore EP transformer vibrates. This continuous transformer vibration developes transformer abnormal audio-noise and if it is too much or operates in the region of natural frequency, transformer will be damaged in the end. EP interruption caused by transformer damage results in power generation stopped, power quality down and economic loss. Therefore, this paper explains harmonic currents and transformer vibration-core vibration, winding vibration, and proposes the measures of suppressing the vibration with EP operated in intermittent PEC mode. And this results is proposed to be used for future EP transformer design or EP control method to operate EP-concerned equipment safely keeping from system faults caused by transformer vibration.

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Numerical analysis for the dis tribution transformer design (400KVA급 배전 변 압기 열 유동해석)

  • Yang, S.W.;Kim, W.S.;Kweon, K.Y.;Lee, S.K.
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.699-702
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    • 2008
  • This paper describes the numerical simulations in the cooling of the radiator in a distribution transformer. The aim of this work is the cooling optimization of the transformer by CFD simulations. A clear understanding of the cooling pattern in a radiator which is a main heat remover in the power transformer is essential for optimizing the radiator design increasing the thermal efficiency. In this paper we study the heat transfer and fluid flow in a 3-phase 400kVA transformer. The plate radiators of this transformer become wrinkled (corrugated radiator) and there are filled with transformer oil. The oil is circulated due to the natural convection driven by buoyancy effects through radiators so that the ultimate cooling medium is the surrounding air. In the design of transformers, it is of interest to minimize the cost and size of radiators. The obtained results show the temperature and flow distributions and the possibility to optimize the transformer with 3-dimensional CFD models using FLUENT.

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A Study on Temperature Characteristics of Main Transformers using Measurement System (계측시스템을 이용한 변압기의 온도 특성 연구)

  • Han Young-Jae;Kim Ki-Hwan;Kim Seog-Won;Mok Jin-Yong;Choi Jung-Sun;Kim Jung-Su
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.3
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    • pp.240-245
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    • 2006
  • Recently, as the road capacity reaches the limit and environmental problems becomes serious, there is gradually increased a need for railroad vehicles that are environment-friendly and have time regularity, reliability, and safety. Accordingly, in addition to conventional railroad vehicles, lots of vehicles are being newly developed. In this study, temperature sensors were adhered to transformer that is used in KHST(Korean High-Speed Train) to verify variation of temperature characteristics about transformer synthetically and efficiently. In the case that temperature of transformer exceeds reference temperature for running of KHST, overheating of transformer may cause a fatal accident of vehicle. Therefore, after on-line measuring system was constructed in vehicle, oil temperature and tank temperature were measured on real-time. Characteristics and main specifications of transformer in KHST were described in this paper. Also, measuring system for temperature measurement of transformer was explained in brief. Temperature data of transformer was acquired using measuring system, KRRI(Korea Railroad Research Institute) analyzed characteristic in contrast with comparing with temperature of transformer about month, running speed and running time.

A Study on the on Line Monitoring Techniques of the Partial Discharge for Transformer (변압기 부분방전 상시 감시기법에 관한 연구)

  • 권동진;박재준
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.14 no.12
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    • pp.1032-1040
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    • 2001
  • In order to apply the partial discharge measuring technique utilizing electrical pulse to the transformer at sites, this paper describes the measuring technique obtaining only the signals due to internal partial discharge in the transformer, but the noises due to external corona which has been a major problem so far. At first, partial discharge and corona noise were simultaneously generated in the model transformer by using needle-plane electrodes and rod-sphere electrodes out of it in a high voltage laboratory, respectively. It was verified that only the partial discharge signals in the transformer could be measured by removing the noise signals from the superposed signals of partial discharges and noises on the grounding wire of the model transformer. By application to a 345kV transformer in service, it was also confirmed that the partial discharge could be on-line monitored by removing the noise signals measured by the inductance sensor on the grounding wire of a 154kV lightning arrester from the superposed signals of internal partial discharge and external corona noise measured by bushing tap coupler of the transformer.

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The Energized Aging Property of Pole Mount Mold transformer by Back-to-back Method (반환부하법에 의한 옥외 주상용 몰드변압기의 과전열화 특정)

  • Hwang, Bo-Guk;Cho, Han-Goo;Lee, Un-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.11a
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    • pp.484-487
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    • 2002
  • The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. In this paper, the proto type mold transformer of 50kVA class is investigated by routine, type, special test. The outdoor energized aging test is investigated by back-to-back method to verify the long time performance of pole mold transformer. The aging process of transformer is analyzed by various diagnosis method such as DC voltage-current test, $tan{\delta}$, Meggar measurement, winding temperature and etc.

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Analysis of the Ultrasonic Signals by the Partial Discharge and Noises from the Transformer (변압기 부분방전과 노이즈에 의한 초음파 신호 분석)

  • Gwon, Dong-Jin;Jeong, Gil-Jo;Jin, Sang-Beom;Gwak, Hui-Ro
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.51 no.8
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    • pp.354-360
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    • 2002
  • The partial discharge detecting method using the ultrasonic technique has been investigated to monitor the insulation ageing of a transformer. However, the result of the studies on the ultrasonic technique for detecting of partial discharge in the operating transformer is not enough yet to utilize. This paper presents the analysis of the ultrasonic signals due to the partial discharge in a model transformer and the corona in air at a shielded high voltage room. In addition, the ultrasonic signals due to the vibration from the core, operation of the cooling pump, the fan and the OLTC at the 345㎸ power transformer, were analyzed and corona noise from overhead transmission line in 345㎸ substation were measured to remove the electrical and mechanical noises from the transformer. Furthermore, ultrasonic signal due to the partial discharge in the 154㎸ power transformer with in $C_2$$H_2$ gas warning condition was measured. The inside of the transformer was examined with care. which confirms the existence of the partial discharge source.