• 정보학연구
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• 제6권1호
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• pp.65-70
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• 2003

본 논문에서 우리는 변압기의 부분방전형태를 진단하기위하여 새로운 방법을 제시하였다. 웨이블렛 변화을 위하여, 다우비치 필터가 사용되어졌다. 우리는 3개의 전극 종류(침대평판자극, IEC전극, 보이드 전극)마다 고주파 전류신호에 관한 통계적인 특징 파라메터(최대값, 평균값, 분산, 왜도, 첨쇄도)를 추출하기위하여 사용하였다. 역시 이들 계수들은 변압기내 내부부분방전의 신호의 정체를 알기위하여 사용되어졌다. 그 결과로서 고주파전류신호의 진폭과 평균값의 비교로부터 우리는 IEC electrode> Void electrode> Needle-Plane electrode의 결과를 얻었다. 반면에 왜도와 첨쇄도의 경우, 우리는 Void electrode> IEC electrode> Needle-Plane electrode을 얻었다.

• 전기학회논문지
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• 제61권7호
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• pp.1056-1060
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• 2012

Online monitoring system is becoming an essential element of railway traction system for utilized to condition based malignance management and various techniques currently employed in railway traction system. Among the various techniques, it is efficient to detect partial discharge signals by electromagnetic wave detection in order to detect insulation fault of rectifier. Although VHF (Very High Frequency), UHF (Ultra High Frequency) sensors were adopted to detect partial discharge of power facilities, due to characteristics of urban railway, excessive noise occurs from 500 MHz to 1.5 GHz on UHF bandwidth. In this paper a new measurement system able to monitoring the conditions of power facilities on DC substation in metro was studied and set up. The system uses UHF sensors to measure the partial discharge of the rectifier due to electric faulting and dielectric breakdown. Comparison and estimation for performance of SHF sensor which had devised to detect partial discharge signal of urban railway rectifier has conducted. In order to estimate performance of SHF sensor, we have compared the sensor with existing UHF sensor on sensitivity upon frequency bandwidth generated by pulse generator, and also we have verified performance of the SHF sensor by detection results of partial discharge signal from urban railway rectifier.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1998-1999
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• 2007

Before applying the HTS(High Temperature Superconductor) power devices to a real utility network, system analysis should be carried out by some simulation tools. PSCAD/EMTDC simulation tool is one of the most popularized useful analysis tools for electrical power system. Unfortunately the model component for HTS coil is not provided in PSCAD/EMTDC simulation tool. In this paper, EMTDC model component for HTS coil has been developed considering real characteristics of HTS coil like critical current, temperature and magnetic field. The developed model component of HTS coil could be used for power system application. Using the developed model component for HTS coil, we can easily do the simulation of HTS power devices application test in utility with the various inductance, quench current, inner magnetic field, and temperature values, for instances; SMES(Superconducting Magnetic Energy Storage) system, superconducting motor, transformer, and FCL(Fault Current Limiter)

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1108-1110
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• 2007

The resonant converters cause the high voltage stress according to the input voltage, which increases the conduction loss in converter power switches. The topology of LLC half bridge resonant converter provides ZVS characteristic and also the stress of voltage and current is smaller than that of the general resonant converters. So we can expect the higher efficiency. In this paper, the LLC resonant converter is designed for slim adapter. In the adapter design, we should consider the weight, the size and overheat of the adapter. Thus the optimal design of transformer is the most important facts. Some parameters should be considered in order to get the highest efficiency. The LLC resonant converter input is 390VDC Link voltage of PFC and the output has 16VDC/90W ratings. The efficiency measured is about up to 93%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.211-212
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• 2007

There have three kinds of partial discharge diagnosis testing: online, offline and dismantled testing on high voltage rotating machine. Our lab testing is dismantled testing, taking off pieces into individual parts of stator coil of high voltage rotating machine in laboratory. We investigate internal discharge, slot discharge, corona discharge and normal state on pre-made stator winding by using spiral patch antenna sensor. In this lab test we compare the experimental results of our spiral patch antenna sensor and reference commercial HFCT sensor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.585-591
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• 2000

The wavelet transform is the most recent technique for processing signals with time-varying spectra. In this paper, the wavelet transform is utilized to improved the assessment and multi-resolution analysis of acoustic emission signals generating in partial discharge. This paper especially deals with the assessment of process statistical parameter using the features extracted from the wavelet coefficients of measured acoustic emission signals in case of applied voltage 20[kv]. Since the parameter assessment using all wavelet coefficients will often turn out leads to inefficient or inaccurate results, we selected that level-3 stage of multi decomposition in discrete wavelet transform. We applied FIR(Finite Impulse Response)digital filter algorithm in discrete to suppression for random noise. The white noise be included high frequency component denoised as decomposition of discrete wavelet transform level-3. We make use of the feature extraction parameter namely, maximum value of acoustic emission signal, average value, dispersion, skewness, kurtosis, etc. The effectiveness of this new method has been verified on ability a diagnosis transformer go through feature extraction in stage of acting(the early period, the last period) .

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.550-551
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• 2005

고밀도 유도결합 플라즈마 장치의 $O_2$ 방전에 대한 공간 평균 시뮬레이터를 제작하였다. 제작된 시뮬레이터는 $O_2$ 플라즈마 방전에서 발생되는 전자, 양이온, 음이온 및 중성종, 활성종들에 대해 공간 평균된 유체 방정식을 기반으로 하고 있으며, 고밀도 유도결합 플라즈마 장치에서 전자가열 모델은 anomalous skin effect 를 고려한 파워 흡수 모델을 적용하여 전자가 흡수하는 고주파 파워량을 결정하였다. 완성된 시뮬레이터에서 RF- 파워, gas-inlet, pumping-speed등의 조정 변수를 비롯한 여러 가지 장치 변수들의 변화에 대한 하전입자, 중성종, 활성종들의 밀도 변화 및 전자 온도 의존성을 계산하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1515-1517
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• 2005

In this paper, we represent both occurrence reason of Surge-voltage and Leakage-current of AC drive system which is operated by Voltage-type PWM Inverter. It generates a compensating voltage which has the same amplitude as, but the opposite phase to, the common-mode voltage produced by the PWM inverter. The compensating voltage is superimposed on the inverter output by a common-mode transformer. As a result, the common-mode voltage applied to the load is canceled completely. The design method of the active common-mode noise canceler is also presented in detail. Therefore, we try to describe the method controling both of them and all of the proprieties are proved by our experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1610-1612
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• 2005

In this paper, the inductive power collector using electromagnetic induction for vehicle such as the PRT(Personal Rapid Transit) system is suggested and some ideas for power collector design to improve the power transfer performance are presented. The proposed the inductive power collector is used for the PRT system, which has a large air-gap and demands a large electrical power capability. But, low output power is generated due to a loosely coupled characteristic of the large air-gap. Therefore, double layer construction of secondary winding, which was divided in half to increase both output current and output voltage was suggested. Also, a model of power collector and parallel winding structure and a model of concentration/decentralization winding are presented, in addition, the performance of inductive power collector to alignment condition between the primary power line and the inductive power transformer was verified by computer simulation of 2kW model.

• 한국전기전자재료학회논문지
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• 제23권1호
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• pp.53-60
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• 2010

This paper dealt with the acoustic detection of partial discharge (PD) in insulation oil for insulation diagnostics of oil immersed transformers. Electrode systems such as needle to plane, plane to plane, and floating were fabricated to simulate some defects in transformers. A wide band acoustic emission(AE) sensor with the frequency ranges of 100 kHz~1 MHz and a narrow band AE sensor with the resonant frequency of 140 kHz were used in the experiment. Also, a decoupler and an amplifier were designed to detect and amplify the acoustic signal only. The decoupler separates acoustic signal from DC source without any distortion, and the amplifier has the gain of 40 dB in frequency ranges of 11 kHz~4 MHz. In the experiment, frequency components and propagation characteristics of acoustic signal were analyzed, and an algorithm of positioning of PD occurrence by the time difference of arrival was proposed. From the results, the frequency components of the acoustic signal exist from 50 kHz to 200 kHz and the positioning error of PD calculated by three AE sensors was within 1%.