• 천문학회보
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• 제42권2호
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• pp.67.2-67.2
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• 2017

Korea Astronomy and Space Science Institute (KASI) plans to develop a coronagraph to measure the coronal electron density, temperature, and speed using four different filters around 400 nm, where strong Fraunhofer lines from the photosphere are scattered by coronal electrons. During the total solar eclipse occurring on August 21 across USA, KASI will organize an expedition team to demonstrate the coronagraph measurement scheme and the instrumental technology. The observation site is in Jackson Hole, Wyoming, USA. We plan to build two coronagraphs without occulter to improve signal to noise ratio. In addition, images of white light corona, wide field background, and all sky are planned to be taken with DSLR cameras. We will present the preliminary results of the expedition.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
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• pp.217-219
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• 2005

To detect partial discharge of 154kV joint box, we have made experiment by using the HFCT sensor. Generally the signals which are detected in partial discharge test of underground power transmission cable are accompanied with both noises of high voltage and noises of surrounding power cable. The most noise in near to end part of joint box is corona, beside other noises flowed from surrounding area. Partial discharge test is difficulty due to these noises. First, we test reliability on both injection of calibration signal in NJB and removal of low frequency. After that, we had analyzed frequencies by measuring signals in IJB with 300[m] distance from NJB. Also we had measured S/N ratio by using the indirected injection method of calibration signal in IJB. In this experiment, two measurement methods were difference of detection acquisition, but these had the equal frequency properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.142-144
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• 2005

To detect partial discharge of 154kV joint box, we have made experiment by using the Al-foil electrode sensor. Generally the signals which are detected in partial discharge test of underground power transmission cable are accompanied wi th both noises of high voltage and noises of surrounding power cable. The most noise in near to end part of joint box is corona, beside other noises flowed from surrounding area. Partial discharge test is difficulty due to these noises. First, we had used Al-Foi1 sensor on middle joint box of 154[kV] underground transmission power cable, and then analyzed reliability of calibration signal by using the Al-Foi1 electrode sensor of NJB. From above results, decrement properties measured highly. But incase of injecting calibration signal of 500[pC] after measuring signals in IJB, the S/N ratio had about 25[dB] acquisition.

• Journal of Electrical Engineering and Technology
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• 제7권3호
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• pp.389-395
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• 2012

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기설비전문위원
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• pp.75-78
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• 2007

To detect partial discharge of 154kV joint box, we have made experiment by using the HFCT sensor. Generally the signals which are detected in partial discharge test of underground power transmission cable are accompanied with both noises of high voltage and noises of surrounding power cable. The most noise in near to end part of joint box is corona, beside other noises flowed from surrounding area. Partial discharge test is difficulty due to these noises. First, we test reliability on both injection of calibration signal in NJB and removal of low frequency. After that, we had analyzed frequencies by measuring signals in IJB with 300[m] distance from NJB. Also we had measured S/N ratio by using the indirected injection method of calibration signal in IJB. In this experiment, two measurement methods were difference of detection acquisition, but these had the equal frequency properties.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기설비전문위원
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• pp.79-81
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• 2007

To detect partial discharge of 154kV joint box, we have made experiment by using the Al-foil electrode sensor. Generally the signals which are detected in partial discharge test of underground power transmission cable are accompanied with both noises of high voltage and noises of surrounding power cable. The most noise in near to end part of joint box is corona, beside other noises flowed from surrounding area. Partial discharge test is difficulty due to these noises. First, we had used Al-Foil sensor on middle joint box of 154[kV] underground transmission power cable, and then analyzed reliability of calibration signal by using the Al-Foil electrode sensor of NJB. From above results, decrement properties measured highly. But incase of injecting calibration signal of 500[pC] after measuring signals in IJB, the S/N ratio had about 25[dB] acquisition.

• 전자공학회논문지
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• 제51권6호
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• pp.244-251
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• 2014

본 논문에서, 가스절연개폐장치(GIS)의 정상상태와 비정상상태에 대해 예방진단기술을 이용하여 자세하게 서술하였다. 이 기술은 지능형 GIS 감시시스템에 의해 저장된 GIS의 데이터의 분석과 진단에 근거한다. GIS음의 파형은 방전과 자체내의 코로나 방전음에 의해 발생되는 것으로 잡음과 비슷하다. 그러므로, 본 논문에서, GIS음의 정상 상태와 비정상 상태로 분류하는데, 정상과 비정상 상태를 레벨교차율(LCR)과 스펙트로그램 에너지비율로 이용하여 구분하였다.

• 조명전기설비학회논문지
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• 제16권4호
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• pp.80-91
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• 2002

운전중인 변압기 내부의 부분방전에 의한 초음파 신호를 상시 감시하기 위한 초음파 상시 측정장치를 개발하였다. 초음파 상시 측정장치는 변압기 외부에서 발생하는 전기적 및 기계적인 노이즈를 제거하고 변압기 내부의 부분방전에 의한 초음파 신호만을 측정하기 위하여 50~300[KHz] 주파수 대역만 집중 측정하도록 협대역 필터를 설계하였으며, 초음파 센서는 60[dB] 증폭도의 프리앰프 내장형으로 개발하였다. 부분방전에 의한 초음파 신호와 특성이 유사한 부하시 탭 절환장치의 동작에 의한 초음파 신호를 제거하기 위하여, 초음파 신호의 지속시간으로 판별하는 초음파 신호판별 알고리즘을 개발하였다. 본 연구에서 개발한 초음파 상시 측정장치는 실험실의 모의 변압기와 현장에서 운전중인 변압기에서 부분방전에 의한 초음파 신호를 측정하여 신뢰성을 확인하였다.