• Progress in Superconductivity
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• 제11권1호
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• pp.1-7
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• 2009

고온초전도 CC를 다른 산소 분압에서 Ag과 YBCO의 녹는점 보다 낮은 온도에서 열처리시 CC의 특성에 미치는 영향을 실험하였다. 전류의 수송능력과 미세구조는 보호층인 Ag의 존재여부에 다양하게 영향을 미친다. Ag를 제거한 CC를 $850^{\circ}C$의 산소 분위기에서 2시간 동안 열처리 한 시편의 경우 CC의 임계전류의 특성에 영향을 미치지 않았다. 그러나 Ag를 제거하지 않은 CC를 $800^{\circ}C$의 산소 분위기에서 2시간 동안 열처리한 시편의 경우 임계전류가 140 A에서 8 A로 떨어지는 결과를 보였다. 또한, Ag을 제거하지 않은 CC를 1000 ppm 산소 분위기의 $800^{\circ}C$에서 2시간 동안 열처리한 시편의 경우 임계전류 값이 원래 $I_c$ 값의 $70{\sim}80%$의 임계전류 값이 나타났다. SEM 이미지와 XRD 회절 분석 결과 Ni과 Cr 원자들이 표면으로 확산되어 CC의 전류수송 특성에 영향을 미친다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.75-82
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• 2015

This paper presents a new technique for enhancing power quality by reducing harmonics in the neutral conductor. Three-Phase Four-Wire (3P4W) system is commonly used where single and three phase loads are connected to Point of Common Coupling (PCC). Due to unbalance loads, the 3P4W distribution system becomes unbalance and current flows in the neutral conductor. If loads are non-linear, then the harmonic content of current will flow in neutral conductor. The neutral current that may flow towards transformer neutral point is compensated by using a series active filter. In order to reduce the harmonic content, the series active filter is connected in series with the neutral conductor by which neutral and phase current harmonics are reduced significantly. In this paper, solar PV based inverter circuit is proposed for compensating neutral current harmonics. The simulation is carried out in MATLAB/SIMULINK and also an experimental setup is developed to verify the effectiveness of the proposed method.

• 전기전자학회논문지
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• 제16권1호
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• pp.1-6
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• 2012

적절한 송전용량으로 전력공급을 안정하게 유지하기 위하여 노후 가공송전선의 열용량이나 수명 평가가 더욱 중요한 관심사가 되었다. 부하정격과 이도/이격거리 모두는 송전용량을 결정하는 중요한 요소들이다. 국내의 2회선 송전선로에 대한 열용량 및 도체수명을 평가하기 위하여, 전기설비기술기준은 물론 이도 및 지상고에 대한 설계기준들이 검토된다. 상정사고를 가정하여 도체온도와 이도를 계산하고 부하용량을 증대시키기 위한 방안이 모색되었다. 본 논문에서는 노후 도체에 대한 열용량과 한계이도를 적절히 평가함으로써, 기존 전력계통의 신뢰성을 보장하기 위한 개선 방안이 제시되었다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.576-585
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• 2017

Dynamic thermal rating (DTR) of overhead transmission lines can provide a significant increase in transmission capacity compared to the static thermal rating. However, the DTR are usually estimated by the traditional thermal model of overhead conductor that is highly dependent on the solar, wind speed and wind direction data. Consequently, the estimated DTR would be unreliable and the safety of transmission lines would be reduced when the solar and wind sensors are out of function. To address this issue, this study proposed a novel thermal model of overhead conductor based on the thermal-electric analogy theory and Markov chain. Using this thermal model, the random variation of conductor temperature can be simulated with any specific current level and ambient temperature, even if the solar and wind sensors are out of function or uninstalled. On this basis, an estimation method was proposed to determine the DTR in the form of probability. The laboratory experiments prove that the proposed method can estimate the DTR reliably without measured solar and wind data.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.344-345
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• 2009

The flux-coupling type superconducting fault current limiter(SFCL) is composed of a series transformer and superconducting unit of the YBCO coated conductor. The primary and secondary coils in the transformer were wound in series each other through an iron core and the YBCO coated conductor was connected with secondary coil in parallel. In a normal condition, the flux generated from a primary coil is cancelled out by its structure and the zero resistance of the YBCO thin films. When a fault occurs, the resistance of the YBCO coated conductor was generated and the fault current was limited by the SFCL. In this paper, we investigated the fault current limiting characteristics according to turn ratio in the flux-coupling type SFCL. The experiment results that the fault current limiting characteristics was improved according to turn ratio.

• 한국정밀공학회지
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• 제21권12호
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• pp.67-74
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• 2004

Linear motor has been considered to be the most suitable electric machine for high speed and high precision linear motion control. Thrust of linear motor is one of the important factor to specify motor performance. Maximum thrust can be obtained by increasing the current in conductor and is relative to the sizes of conductor and magnet. But, the current and the size of conductor have an effect on temperature of linear motor. Therefore, it is practically important to find design results that can effectively maximize the thrust of linear motor within limited range of temperature. Finite element analysis was applied to calculate thrust and numerical solutions were compared with experiment. The temperature of the conductor was calculated by the thermal resistance which was measured by experiment. The optimum design process was coded by the ADPL of ANSYS which is a commercial finite element analysis software. Design variables and constraints were chosen based on manufacturing feasibility and existing products. As a result, it is shown that temperature of linear motor plays an important role in determining optimum design.

• 한국전기전자재료학회논문지
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• 제23권9호
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• pp.714-717
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• 2010

The improved flux-lock type superconducting fault current limiter (SFCL) is composed of a series transformer and superconducting unit of the yttrium-barium-copper-oxide (YBCO) coated conductor. In this paper, we investigated current limiting characteristics through winding direction of coil 2 and variable number of coil 1 and coil 2 in improved flux-lock type SFCL. The better fault current characteristics and the burden of YBCO coated conductor can be confirmed from the experimental result in the higher turn ratio of coil 1 and coil 2 in the additive conditions. In case of subtractive condition, we can confirm a similar result in the same case of experimental conditions. but the burden of YBCO coated conductor has been increased from an increase in winding numbers of coil 2.

• 한국전기전자재료학회논문지
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• 제23권9호
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• pp.730-735
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• 2010

Forest fire can cause a serious damage to overhead conductors. Therefore, detailed investigation on the changes of mechanical and electrical properties of damaged conductors should be carried out to understand the effect of forest fires on conductors. This is of critical importance in maintaining transmission line safely. This paper examines the changes of mechanical and electrical properties of flame exposed conductor. Tensile strength (TS) decreased according to increase of forest fire temperature and conductivity changed according to forest fire temperature. Specimens were aluminum conductors of aluminium conductor steel reinforced (ACSR) 410, 240, 480 $mm^2$. In this paper, the electrical and mechanical characteristics of forest fires exposed overhead conductors depending on the diameter of aluminum conductors are presented. It was possible to estimate the degree of deterioration caused by forest fires. The detailed results are given in the paper.

• 조명전기설비학회논문지
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• 제27권4호
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• pp.73-80
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• 2013

Breakdown characteristics of air in the vertical arrangement of line conductor and plane electrode in case of combustion flame on the plane electrode are examined by the application of AC. and DC voltages to the gap. In order to investigate the effect of paraffin flame on the breakdown characteristics of air, flashover voltages are measured according to the variation of the gap length and the horizontal distance between the flame and the line conductor. As the result of the experiment, flashover voltages are substantially lowered down to 29.8% in case of the AC voltage, and 16.1% in case of the negative DC voltage, when in the presence of the flame. from 100% when in the absence of flame. Flashover voltages of air in the range of smaller than 3㎝ at the horizontal distance are increased in the proportion of the gap length and the horizontal distance in case of both AC and negative DC voltages. But before the flashover occurs, the flame is extinguished by such corona wind that is produced from the line conductor when the gap length and the horizontal distance reach to a certain degree. The effect of relative air density and the phenomenon of thermal ionization are analysed as the reduction factors of flashover voltages, due to high temperature of the flame.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권11호
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• pp.520-526
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• 2006

Corona interferences, such as radio noise, audible noise and television noise, need to be taken into account in the design of HVDC transmission line conductor configuration. Therefore the line designer requires data from which to estimate the corona performance of any set of conductors. To get a sufficiently complete set of design data, it is necessary to examine the corona test of a large number of conductor geometries. This paper presents the results of corona cage test among three types of candidate conductors. It is quite clear from test results that the conductor geometries play an important role in establishing the magnitude of corona noise. Corona noise data from corona cage test are expressed as a statistical distribution of results obtained over long periods of time and various weather conditions. Therefore we can determine an environmentally-friendly conductor bundle for HVDC overhead transmission line. Based on this finding results, various simulations about HVDC line configurations, such as pole space and pole height, will be conducted. And then finally an optimal configuration for HVDC transmission line will be decided.