• Title, Summary, Keyword: Transformer

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Heat Transfer Analysis of Coupled Electromagnetic-Thermal Field for Power Transformer (전자계-열계 결합해석에 의한 전력용 변압기의 열전달 해석)

  • Ahn, Hyun-Mo;Oh, Yeon-Ho;Hahn, Sung-Chin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.58 no.11
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    • pp.2155-2161
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    • 2009
  • In this paper, we dealt with the electro-thermal coupling analysis for temperature prediction of power transformer. Heat transfer coefficient are calculated using Nusselt number in accordance with heat source generated from transformer windings and core materials. The calculated temperatures in power transformer were compared to those of measured ones and showed good agreement. This coupling method using heat transfer coefficient can be used at the design stage of power transformer efficiently.

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

  • Jo, Hyunsik;Cho, Sungwoo;Shin, Changhoon;Cha, Hanju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.6
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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.

Vibration Analysis of Transformer DC bias Caused by HVDC based on EMD Reconstruction

  • Liu, Xingmou;Yang, Yongming;Huang, Yichen
    • Journal of Electrical Engineering and Technology
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    • v.13 no.2
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    • pp.781-789
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    • 2018
  • This paper proposes a new approach utilizing empirical mode decomposition (EMD) reconstruction to process vibration signals of a transformer under DC bias caused by high voltage direction transmission (HVDC), which is the potential cause of additional vibration and noise from transformer. Firstly, the Calculation Method is presented and a 3D model of transformer is simulated to analyze transformer deformation characteristic and the result indicate the main vibration is produced along axial direction of three core limbs. Vibration test system has been built and test points on the core and shell of transformer have been measured. Then, the signal reconstruction method for transformer vibration based on EMD is proposed. Through the EMD decomposition, the corrupted noise can be selectively reconstructed by the certain frequency IMFs and better vibration signals of transformer have been obtained. After EMD reconstruction, the vibrations are compared between transformer in normal work and with DC bias. When DC bias occurs, odd harmonics, vibration of core and shell, behave as a nonlinear increase and the even harmonics keep unchanged with DC current. Experiment results are provided to collaborate our theoretical analysis and to illustrate the effectiveness of the proposed EMD method.

A Study on the Characteristics of Circular Piezoelectric Transformer which has Crescent-shaped Input Type (Crescent-shaped Input Type 원형압전변압기의 특성 연구)

  • Jeong, Seong-Su;Park, Tae-Gone
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.7
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    • pp.644-649
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    • 2006
  • This paper presents a new disk-type piezoelectric transformer. The input side of the transformer has a crescent-shaped electrode and the output side has a focused poling direction. The piezoelectric transformers operated in each transformer's resonance vibration mode. The electrodes and poling directions on commercially available piezoelectric ceramic disks were designed so that the planar or shear mode coupling factor $(k_p\;k_{15})$ becomes effective rather than the transverse mode coupling factor $(k_{31})$. ANSYS finite element code was used to analyze transformer behavior and to optimize electrode and poling configurations. The voltage step-up ratio of the proposed transformer has been markedly improved in comparison with that of the equivalent rectangular(Rosen) type. A single layer prototype transformer, $20\sim30mm$ in diameter and $1.0\sim3.5mm$ thick, was fabricated, such as step-up ratio, power transformation efficiency, and temperature were measured. While the transformer was driving a Cold Cathode Fluorescent Lamp(CCFL), the temperature field of the transformer was also observed.

Design of an HTS Transformer with OLTC (OLTC를 고려한 고온 초전도 변압기의 설계)

  • Choi, J.H.;Lee, S.W.;Park, M.J.;Joo, H.G.;Han, J.H.;Hahn, S.Y.;Choi, K.D.
    • Progress in Superconductivity and Cryogenics
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    • v.9 no.1
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    • pp.67-71
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    • 2007
  • HTS transformers which have been developed until now had only fundamental structures. Among the auxiliary functions of conventional transformers, voltage regulating is the most important one. For the voltage regulation, conventional transformers are equipped with on load tap changers (OLTCS). In this paper, we describe the possibility of the HTS transformer with OLTC. For the case study, we designed a single phase 33 MVA HTS transformer with OLTC. It is one of three individual HTS transformers which composes a 3 phase, 100 MVA transformer. It is expected to substitute for a 3 phase, 60 MVA conventional transformer in Korea. The parameters of an HTS transformer are varied due to the gap length between primary and secondary windings. The length was decided for the transformer to have the impedance of 12 %. Its size was limited to the one of the conventional transformer. The characteristics of the HTS transformer were analyzed in both case of having OLTC and not.

Comparison of Reciprocal and Concentric Winding Arrangement of HTS Transformer (고온초전도 변압기의 교호 배치 권선과 동심형 배치 권선의 비교)

  • Kim, Sung-Hoon;Kim, Woo-Seok;Lee, Sang-Jin;Park, Kyeong-Dal;Joo, Hyeong-Gil;Hong, Gye-Won;Han, Jin-Ho;Hahn, Song-yop;Park, Chan-Bae
    • Progress in Superconductivity
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    • v.5 no.1
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    • pp.61-64
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    • 2003
  • In HTS transformer with double pancake windings, the perpendicular component of leakage magnetic flux density ($B_{r}$ ) applied to HTS tapes of double pancake windings of HTS transformer acts as a cause to decrease the critical current in HTS tape. So, in this paper, HTS transformer with reciprocal arrangement winding is designed. And in order to investigate the$ B_{r}$ applied to HTS windings, the 2-D non-linear electromagnetic analysis of HTS transformer is performed by using the OPERA 2D. The maximum $B_{r}$ applied to winding of HTS transformer is 0.112 T and the characteristics of HTS transformer were also obtained. But in this type of winding arrangement, reciprocal arrangement, the generated ac-loss to the HTS windings is very high because of the applied $B_{r}$ to HTS windings. Therefore, in order to reduce the generated ac-loss to the HTS windings, the new design of HTS transformer with concentric winding arrangement is presented in this paper and the 2-D non-linear electromagnetic analysis and the ac-loss for HTS transformer with the concentric winding arrangement is also carried out.

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Design of 1 MVA Single Phase HTS Transformer with Pancake Windings Cooled by Natural Convection of Sub-cooled Liquid Nitrogen

  • Kim, Woo-Seok;Kim, Sung-Hoon;Hahn, Song-yop;Park, Kyeong-Dal;Joo, Hyeong-Gil;Hong, Gye-Won;Han, Jin-Ho;Lee, Don-Kun;Park, Yeon-Suk
    • Progress in Superconductivity and Cryogenics
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    • v.5 no.3
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    • pp.34-37
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    • 2003
  • A 1 MVA single-phase high temperature superconducting (HTS) transformer with BSCCO-2223 wire was designed in this paper. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings arranged reciprocally will be used for the transformer windings, because of the advantages of insulation and distribution of surge voltage in case of a large power and high voltage transformer. Single HTS wire was used for the primary windings and four parallel wires were used for the secondary windings of the transformer with transposition. A core of the transformer was designed as a shell type core separated with the windings by a cryostat made of GFRP with a room temperature bore. The operating temperature of the HTS windings will be about 65K with sub-cooled liquid nitrogen. A cryogenic cooling system using a GM-cryocooler for this HTS transformer by natural convection of liquid nitrogen was designed. This type of cooling system can be a good option for compactness, efficiency, and reliability of the HTS transformer.

Scott Transformer Modeling using Simulink on the AC Substation (Simulink를 이용한 교류 급전변전소의 스코트변압기 모델링)

  • Kim, Tae-Geun;Park, Young;Lee, Jong-Woo
    • Proceedings of the KSR Conference
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    • pp.2317-2322
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    • 2011
  • In three-phase power, when the power is supplied to the single phase load, there is the unbalance of load in the three-phase power. So the scott transformer is used in the power system to supply a single phase load in three-phase power without the unbalance of loads. Especially, the scott transformer is used in the AC substation of electric railroad. Two single phase transformers are combined by T-wiring in the scott transformer. So, two single phase voltage is provided by differing $90^{\circ}$ phase in three-phase power. The selection of related equipment and correction of protective relay are not easy from characteristic of the scott transformer when shunt and ground faults occur. In this paper, electric model of the scott transformer is suggested and the current of the scott transformer in shunt and ground faults is analyzed. Also, the scott transformer model is demonstrated by using Sinulink.

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Problem Analysis by Iron Core Structure of the Transformer on Asymmetric three Phase lines and Prevention Measures (비대칭 3상 선로에서 변압기의 철심구조별 문제점 분석 및 방지대책)

  • Shin, Dong-Yeol;Yun, Dong-Hyun;Cha, Han-Ju
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.10
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    • pp.1536-1541
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    • 2012
  • The study analyzed problems by iron core structure of the three phased transformer on asymmetric three phase lines, which included line disconnections, ground faults, COS OFF, and unbalanced loads on the power distribution system. In particular, by analyzing PT combustion cases within the MOF, the study was able to analyze the combustion cause of the core-type transformer and its effect on the system, conduct simulations and practice demonstrations on the characteristics for each iron core structure of the three phase transformer using PSCAD/EMTDC, and suggest measures to prevent the combustion of the core-type transformer.

Transformer Protective Relaying Algorithm Using Neuro-Fuzzy based on Wavelet Transform (웨이브렛 변환기반 뉴로-퍼지를 이용한 변압기 보호계전 알고리즘)

  • Lee Myoung Rhun;Lee Jong Beom;Hong Dong suk
    • Proceedings of the KIEE Conference
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    • pp.607-609
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    • 2004
  • A breakdown occurred in power transformer causes interruption of power transmission. Protective relay should be installed in transformer to detect such a fault. Protective relaying algorithm for transformer must be included a function to discriminate between winding fault and inrushing state. Recently, current differential relay is widely used to protect power transformer. However if inrush occurs in transformer, relay can be tripped by judging as internal fault. New algorithms are required in order to such problem. This study proposes a new protective relaying algorithm using Neuro-Fuzzy inference and wavelet. A variety of transformer transient states are simulated by BCTRAN and HYSDT in EMTP. D1 coefficients of differential current are obtained by wavelet transform. D1 coefficients and RMS of 3-phase primary voltage are used to make a target data and are trained by Nwo-Fuzzy algorithm which distinguishes correctly whether internal fault occurs or not within 1/2 after fault detection. It is evaluated that the results obtained by simulations can effectively protect a transformer by contact discriminating between winding fault and inrushing state.

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