• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.4
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• pp.436-444
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• 2018

Currently, the new substation automation uses the international standard IEC 61850 communication protocol. KEPCO is also constructing a new substation based on IEC 61850 from 2013 through the pilot application and research and development starting from 2007. However, there are few cases where existing substations(Transformer, T/L GIS, D/L GIS, etc.) have been used, and RTU based substations operating systems have been changed to SA substations based on IEC 61850. Therefore, the introduction of IEC 61850 in existing substation facilities has the advantage of enhancing the substantiality of the substation by reusing existing facilities, improving the interoperability with the latest substations introduced, and converting existing substations into systems suitable for unmanned operation. In this paper, we introduce a case of changing the existing RTU based substation operation system to digital substation using IEC 61850 field information processor, Ethernet switch and SA operation system. Also, IEC 61850 client authentication program and Wireshark, which is a packet analysis tool, verify IEC 61850 conformance and its feasibility.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.358-369
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• 2000

Shielded metal arc welding machines with AC transformer have been widely used for thin-plate welding applications. Because of being bulky, heavy and of tap-changing property, so the SMAW's are changing to new power electronic circuits such as inverter circuit in order to reduce the system size and also to improve the welding performances at input output sides. The PWM inverter arc welding machine with diode rectifier has better output welding performances but it is has the plentiful harmonics and the lower input power factor. To solve these problems, input current-controlled scheme is considered for PWM inverter arc welding system, and then total input power factor is maintained to be more than 99%. Also a new combined control is proposed which can control both instantaeous welding output voltage and current under constant power condition, and as a result the variations of instantaneous current and voltage can be reduced to very narrow range in the V-I curve relationship, and hence the variance of welding current and voltage become so reduced. In addition the spatter generated during welding process is greatly reduced up to 70%. And the overall effiency can be improved up to 10%, which becomes higher when the load is lower.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.47-56
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• 2011

Korea Ministry of Knowledge Economy has estimated that wind power (WP) will be occupied 37% in 2020 and 42% in 2030 of the new energy sources, and also green energies such as photovoltaic (PV) and WP are expected to be interconnected with the distribution system because of Renewable Portfolio Standard (RPS) starting from 2012. However, when a large scale wind power plant (over 3[MW]) is connected to the traditional distribution system, protective devices (mainly OCR and OCGR of re-closer) will be occurred mal-function problems due to changed fault currents it be caused by Wye-grounded/Delta winding of interconnection transformer and %impedance of WP's turbine. Therefore, when Double-Fed Induction Generator (DFIG) of typical WP's Generator is connected into distribution system, this paper deals with analysis three-phase short, line to line short and a single line ground faults current by using the symmetrical components of fault analysis and PSCAD/EMTDC modeling.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.166-166
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• 1998

반도체 공정에서 기존보다 큰 30cm 웨이퍼훌 이용하기 위해서 기존의 ECR, Helicon, ICP, 등 공정용 고 밀도 플라즈마 원들의 대면적화에 대한 연구가 세계적으로 진행되고 있다 현 상황에서는 평판형 안테 나룰 이용한 TCP가 대면적용 폴라즈마 원의 가장 유력한 후보로 여겨지고 있다 TCP롤 대면적화 하는 데 있어서 중요한 문제점으로는 대면적에서의 큰 안테나 인되턴스로 인한 임피던스 정합과 대면적에서 의 유전울질의 기계적 강도이다. 앓은 유전물질올 사용힐 수 있도록 대면적 TCP 플라즈마 원올 실계 저l작하였고 이차원 가열이론올 이용한 TCPRP code 률 이용하여 안테나의 반경옳 결정하였디 안테나의 인덕턴스 값올 줄이기 위해서는 주m수는 13.56MHz 보다 낮은 4-5MHz 부근에서 작동하는 RF 파워룰 선택하였다 이 파워 서플라이는 보통 사용되는 50n 흩력 입묘$\mid$던스훌 갖는 형태가 Of니라 LC 공진현상 올 이용하여 부하에 파워률 전달하는 형태이다 .. TCP 장치에 사용할 수 있도록 파워 서플라이 흩력 단에 안테나와 직혈로 가변 콘덴서를 달아서 임11I던스 정합올 힐 수 있게 하였다 안테나에 직훌로 달Of줌으 로써 안테니의 인덕턴스훌 훌여주는 효과훌 얻올 수 있다 안테나에 흐르는 전류룰 측정하기 위해서 사 각형 루프로 전류 픽업 코일을 만들었고 진공상태에서 RF 파워률 인가하고 안테나의 전류와 전압을 측정하여 픽업 코일걸과훌 조정하였다. 발생기체로는 헬륨올 사용하였고 1-100mTorr 의 압력범위에서 실험을 하였다 플라즈마롤 빌샘시키고 파워를 증가 시킴에 따라 E-H mode transition 현상이 관찰되었고 그 때의 임계 전류 값을 측정하였다. 압력이 낮올수록 모드 변화가 일어나는 전류의 값이 작았다 임계 전류는 압력에 대해서 선형적인 특성을 보였다 이는 압력이 낮을수록 유도걸힘이 더 잘 된다는 것을 의미한다 1 1 mTorr에서는 H-mode에서 안테나의 전류가 파워훌 증가시킴에 따라 계속 증가하였으니, 압력이 올라 갈수록 조금씩 증가하는 정도가 줄어들고. 100mTorr에서는 포화된 값을 나타냈다 H-mode로 넘어간 후 에는 파워가 증가황에 따라 안테나의 임피던스 값이 모든 압력영역에서 줄어드는 경황을 보였고, 이는 플라즈마의 인덕턴스에 의해서 안테나의 인덕턴스 기 감소되기 때문이다, 파워가 증가할수록 안테U오} 플라즈마 루프사이의 상호걸합이 증가하는 걸로 해석힐 수 있다 안테나의 인되턴스 변화보다는 저항.성 분의 변화가 컸다 하지만 전체 임피던스로 볼 때 저항성분이 상대적으로 작기 때문에 인덕턴스의 감소 가 더 큰 영향을 미치는 걸로 볼 수 있다. 하지만 플라즈마로의 파워 전달에는 저항성분만이 영향올 미 치므로 저항성분의 큰 변화는 파워가 많이 전달될올 의미한다 피워전달 효율을 계산해 본 결과 수 r mTorr 부근이 80-90% 정도의 높은 효율올 보였고 5mTorr 일 때가 가장 좋았다.

• Journal of The Korean Association For Science Education
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• v.33 no.7
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• pp.1486-1509
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• 2013

This study aims to identify the image types of secondary school students' perception about the talented person in convergence and to find the differences in drawing images of the talented person in convergence among the students who have taken STEAM class and the ones who haven't. One hundred and eighty seven students in middle and high schools located in the southern part of South Korea participated in this study and they were asked to draw a picture of the talented person in convergence with a brief explanation. Based on students' pictures, researchers categorized their perception about convergence and talented person in convergence by using an inductive method. The result indicated that secondary school students' perceptions were categorized into convergence as individual cognitive processing and collective cognitive processing and convergence as outcomes. The image of the convergence in a talented person leaning toward individual cognitive processing was divided into the following seven types: idea banker type, various talented celebrity type, multi-tasking master type, multi-talented career type, active problem-solver type, creative developer type, and unrealistic ideal man type. Another image of collective cognitive processing was split into expert group type and interactive-mates group type. The other image was transformer type which is the subcategory of convergence as outcomes. From this study, it can be suggested that secondary school students express the various images of the talented person in convergence depending on experiencing STEAM or not.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.106
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• pp.249-258
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• 2006

In this letter, we propose a novel printed helix antenna for RFID reader in UHF band. The printed strip line of the antenna is first wound up outside a polygonal shaped layer and then the winding continues on an inner layer to control the overall gain and the radiation pattern. In addition, the winding pitch angles on each layer have either negative or positive values resulting in the broad CP bandwidth. The detail structure of the antenna was optimized using Pareto genetic algorithm(GA), so as to obtain excellent performances for RFID reader antennas. The optimized two-layered polygonal helix was fabricated on the cardboard of a flexible substrate and the performances were measured and compared with the simulations. The fabricated antenna was made up of copper tape which can adhere to a flexible cardboard and had 21.4 % matching bandwidth, 31.9 % CP bandwidth, readable range of $5.5m^2$ with kr=3.2. Also based on the current distribution of the strip line of the antenna and sensitivity of the antenna bents points, we confirmed that the antenna has the quarter-wave transformer near the feed for the broad matching bandwidth and radiates the traveling wave for the broad CP bandwidth using the bent strip line.

• Journal of the Korean Society for Railway
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• v.19 no.1
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• pp.38-45
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• 2016

The power transformation system of High Speed rolling stocks like KTX-Sancheon has shown excellent control capacities in the areas of riding comfortability, switching efficiency, safety and energy consumption due to technical developments in power-electronics, high speed & large scale integrated semiconductors and microprocessors. However, harmonics from IGBT, a high speed switching device used in the Convertor & Invertor equipment of rolling stocks have given rise to various problems in transformer substations, signaling systems, data transmission systems and facility monitoring systems. Especially, TI21 non-insulated track circuits have malfunctioned due to the influence of returning current harmonics which were generated at around of integer times of the number of power transformation equipment in the frequency domain. This paper, measures and analyzes various schemes to analyze the traveling path of the returning current harmonics generated due to the relationship between the rolling stocks and track circuits on site. Ultimately, theseschemes will be used to design high speed rolling stocks, AF track circuits and a common grounding network.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.203-209
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• 2017

Research on condition monitoring and diagnosis of power facilities has been conducted to improve the safety and reliability of electric power supply. Although insulation diagnostic techniques for unit equipment such as gas-insulated switchgears and transformers have been developed rapidly, studies on monitoring of cables have only included aspects such as whether defects exist and partial discharge (PD) detection; other characteristics and features have not been discussed. Therefore, this paper dealt with PD characteristics against void sizes and positions, and with defect localization in XLPE cable. Four types of defects with different sizes and positions were simulated and PD pulses were detected using a high frequency current transformer (HFCT) with a frequency range of 150kHz~30MHz. The results showed that the apparent charge increased when the defect was adjacent to the conductor; the pulse count in the negative half of the applied voltage was about 20% higher than that in the positive half. In addition, the defect location was calculated by time-domain reflectometry (TDR) method, it was revealed that the defect could be localized with an error of less than1m in a 50m cable.

• Journal of Radiation Protection and Research
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• v.40 no.1
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• pp.46-54
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• 2015

The thermoluminescence (TL) and optically stimulated luminescence (OSL) are commonly used to measure and record the expose of individuals to ionization radiation. Design and performance test results of a newly developed TL and OSL measurement system are presented in this paper. For this purpose, the temperature of the TL material can be controlled precisely in the range of $1{\sim}1.5^{\circ}C$ by using high-frequency (35 kHz) heating system. This high-frequency power supply was made of transformer with ferrite core. For optical stimulation, we have completed an optimal combination of the filters with the arrangement of GG420 filter for filtering the stimulating light source and a UG11 filter at the detecting window (PMT). By using a high luminance blue LED (Luxeon V), sufficient luminous intensity could be obtained for optical stimulation. By using various control boards, the TL/OSL reader device was successfully interfaced with a personal computer. A software based on LabView program (National Instruments, Inc.) was also developed to control the TL/OSL reader system. In this study, a multi-functional TL/OSL dosimeter was developed and the performance testing of the system was carried out to confirm its reliability and reproducibility.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.5
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• pp.216-220
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• 2010

Ni-Fe alloys have various applications such as thin film inductor, thin film transformer, magnetic head's shield case, etc. Magnetic properties of Ni-Fe thin films depend on the process parameters such as thickness, contents, deposition rate, substrates, etc. In this study, NiFe films with a thickness of about 150nm were deposited on Si(100) wafer and $SiO_2$/Si(100) substrate at room temperature by a DC magnetron co-sputtering using Fe and Ni targets. Their phase formation and magnetic properties as a function of annealing temperature were investigated with XRD, FE-SEM and VSM. The assputtered films have BCC structure. With increasing annealing temperature, NiFe thin film for $SiO_2$/Si(100) substrate transformed completely from BCC to FCC phase above $500^{\circ}C$, but some BCC phase remained above $500^{\circ}C$ on Si(100) wafer. For samples annealed at $450^{\circ}C$, squareness ratio of NiFe thin film shows peak value and its saturation magnetization is around 0.0118 emu, which means that the optimum annealing temperature of NiFe thin film seems to be $450^{\circ}C$. The saturation magnetization of films decreased rapidly above the annealing temperature of $500^{\circ}C$ due to phase transformation from BCC to FCC phase.