• 반도체디스플레이기술학회지
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• 제15권3호
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• pp.30-34
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• 2016

We investigated magnetic field, discharged voltage, and as-deposited film uniformity at facing targets sputtering (FTS) system with magnetic field type: i) concentrated and ii) distributed magnetic field type. And Al doped ZnO (AZO) films were prepared at two magnetic field type such as concentrated magnetic field type and distributed magnetic field type, respectively. Discharge voltage at the distribution type is lower than concentration type due to low magnetic flux (middle magnetic flux: Concentration 1200 G and Distribution 600 G). The films deposited at the distributed magnetic field were more uniform than concentration type. All of prepared AZO films had a resistivity of under $10^{-4}[{\Omega}{\cdot}cm]$ and a transmittance of more than 85 % in the visible range.

• 대한수학회논문집
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• 제16권3호
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• pp.459-485
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• 2001

The aim of EIT (electrical impedance tomography) system is to image cross-section conductivity distribution of a human body by means of both generating and sensing electrodes attached on to the surface of the body, where currents are injected and voltages are measured. EIT has been suffered from the severe ill-posedness which is caused by the inherent low sensitivity of boundary measurements to any changes of internal tissue conductivity values. With a limited set of current-to-voltage data, figuring out full structure of the conductivity distribution could be extremely difficult at present time, so it could be worthwhile to extract some necessary partial information of the internal conductivity. We try to extract some key patterns of current-to-voltage data that furnish some core information on the conductivity distribution such s location and size. This overview provides our recent observation on the location search and the size estimation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.35-38
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• 2006

As a display becomes large recently, Acquisition of high luminance and Luminance uniformity is becoming difficult in the existing CCFL or EEFL backlight system. So, study for a performance enhancement has enforced. but lamp development of flat type is asked for high luminance and a luminance uniformity security in of LCD and area anger trend ultimately. In this paper, we changed a tip shape of an electrode for production by the most suitable LCD backlight surface light source, and confirmed discharge characteristic along discharge gas pressure and voltage, and confirmed electric field distribution and discharge energy characteristic through a Maxwell 2D simulation. Therefore the discharge firing voltage characteristic showed a low characteristic than a rectangular type and round type in case of electrode which used tip of a triangle type, and displayed a discharge electric current as a same voltage was low.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 추계학술대회
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• pp.9-11
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• 2018

This paper studies on the development of an electric fire prevention system with the detection and alarm in case of parallel arc fault occurrence in low voltage distribution lines. The proposed detector has the characteristics of high speed operation responsibility and superior system reliability from composition using a large number of semiconductor devices. The line voltage is always feedback, and when an arc or a spark occurs, these are detected by the microcomputer. In addition, we design and develop algorithms using high speed and high precision microcomputer. A new conceptual control technique is adopted that RCD cuts-off by forming a forced short circuit between the phase voltage and ground in the event of an electrical accident. Some experimental tests of the proposed system also confirm practicality and the validity of the analytical results.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.90-100
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• 2015

Green technologies such as renewable energy resources, Electric Vehicles and Plug-in Hybrid Electric Vehicles (EVs/PHEVs), electric locomotives, etc. are continually increasing at the existing power network especially distribution levels, which are Medium Voltage (MV) and Low Voltage (LV). It can be noted that the increasing level of green technologies is driven by the reduction emission policies of carbon dioxide ($CO_2$). The green technologies can affect the quality of power, and hence its impacts of are analysed. In practical, the environment such as wind, solar irradiation, temperature etc. are uncontrollable, and therefore the output power of renewable energy in that area can be varied. Moreover, the technology of the EVs/PHEVs is still developed in order to improve the performance of supply and driving systems. This means that these developed can cause harmonic distortion as the control system is mostly used power electronics. Therefore, this paper aims to analyse the voltage variation and harmonic distortion in distribution power network in urban area in Europe due to the combination between wind turbine, hydro turbine, photovoltaic (PV) system and EVs/PHEVs. More realistic penetration levels of SSDGs and EVs/PHEVs as forecasted for 2020 is used to analyse. The dynamic load demands are also taken into account. In order to ensure the accurate of simulation results, the practical parameters of distribution system are used and the international standards such as Institute of Electrical and Electronics Engineers (IEEE) standards are also complied. The suggestion solutions are also presented. The MATLAB/Simulink software is chosen as it can support complicate modelling and analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1559-1561
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• 2003

In northeast Asia, there will be several important HVDC transmission lines to be established in Korea and China for perspective electric network market. 5500V 4-inches High voltage thyristor can be used in the DC transmission and distribution of electric power system. In this application, many thyristors are connected in series for each thyristor valves. Therefore, the required low reverse-recovery charge QRR and low on-state voltage drop $V_{TM}$ for such thyristor is necessary to this application. In our work, the on-state and off-state voltage performance was simulated by commercial simulation software.

• 전력전자학회논문지
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• 제23권5호
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• 한국산학기술학회논문지
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• 제22권2호
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• pp.487-495
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• 2021

선박에서 주로 사용하는 전압은 450[V], 6.6[kV], 11[kV]이며, 운항 중 전력계통의 안정성 확보를 위해 접지 시스템이 적용된다. 일반적으로 450[V]를 사용하는 저전압 선박은 비접지 시스템을 6.6[kV], 11[kV]를 사용하는 고전압 선박은 고저항 접지 시스템을 적용한다. 선박의 전력계통에서 지락 고장이 발생하면 건전상의 대지 전압이 선간전압 또는 그 이상으로 증가하고, 케이블의 절연에 과도한 충격을 주게 되므로 이를 분석하는 것은 매우 중요한 부분이다. 따라서 본 논문에서는 선박에서 주로 채택하고 있는 고저항 접지 및 비접지 시스템에 대해 지락 고장에 따른 선박 전력계통의 대지 전압의 변동 특성과 고장 상의 판단 방법을 대칭 좌표법을 이용하여 분석하고자 한다. 이를 위해 대칭 좌표법을 이용하여 대지 전압의 수학적 모델을 유도하고, 시뮬레이션을 위한 선박 전압은 6.6[kV]와 450[V]로 선정하였다. MATLAB을 이용한 시뮬레이션 결과 두 접지 시스템 모두 지락상 보다 위상이 120° 앞선 상의 대지 전압이 가장 높게 상승하였고, 이를 이용하여 고장 상을 정확하게 판단할 수 있음을 확인하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 추계학술대회 논문집
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• pp.195-197
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• 2007

This paper presents experimental results on the safety of persons due to a ground fault in 22.9 kV-Y distribution system In order to evaluate the touch voltages due to internal ground faults in a step down transformer based on the newly prescribed KS C IEC 60364 standard series, the verification tests in a 22.9 kV multi-grounded neutral system were carried out From the experimental results, it was found that there will be significant potential rise jeopardizing LV equipment insulation in case of separate grounding between HV and LV system and the effective measures against hazardous touch voltages due to a IN side ground fault in the common grounding system between HV and LV system are proposed. As a consequence, it was found that the equipotential bonding is an important prerequisite for the effectiveness of the protective measures for the safety of persons in the common ground system between 22.9 kV-Y and low-voltage grounding system.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2006년도 춘계학술대회 논문집
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• pp.69-73
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• 2006

The calculation of depth and duration of a sag is in both methods based on two simple assumptions. One is that due to the short circuit, the voltage drops to a low value immediately magnitude. Another is that when the fault is cleared. the voltage recovers immediately. These assumptions, however, do not hold in the case of a substantial part of the load consisting of electrical motors like in many industrial power systems. During the short circuit, the motors will slow down. Their reacceleration after the fault will increase the load current and thus prolong the voltage sag. This paper will discuss some of the aspects of the influence of induction motors on voltage sags.