• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.11
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• pp.66-73
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• 2015

AC-based power systems, having the advantages that voltage transformation and long distance transmission are easy, have been constructed since the last 19th century. However, DC-based power system is paid attention these days because of the development of power electronic devices as well as the increase of digital loads and distributed generation. For instance, the transmission systems using High Voltage DC (HVDC) are commercially operated in the world and the researches on distribution system using Low Voltage DC (LVDC) are gradually increased. This paper analyzes voltage sag, resulted from faults, in LVDC distribution system according to the number of poles. Modeling and simulation with various conditions are conducted by using ElectroMagnetic Transients Program (EMTP). Moreover, some countermeasures to reduce voltage sag in LVDC distribution system are suggested briefly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.75-81
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• 2015

At the end of the 19th century, Edison's DC power system and Tesla's AC power system was debated in power market. Finally, AC system became the primary system of the power market because both step-up and step-down of voltage by using transformer and long-distance power transmission are easily possible. However, nowadays the power market takes some action for introducing DC system. Both domestic and foreign researchers are conducting the study on the DC system as well. Some researchers have conducted the studies on power quality and economic evaluation of the DC distribution system but DC distribution system is still controversial in terms of the effectiveness and reliability. In this paper, we calculate the reliability indices of the Low Voltage Direct Current(LVDC) distribution system considering arrangement of power electronics, layout of the distribution system, and distance between load points.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.5
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• pp.71-79
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• 2015

Recently, new Low Voltage DC (LVDC) power distribution systems have been constantly researched as uses of DC in end-user equipment are increased. As in conventional AC distribution system, High Impedance Fault (HIF) which may cause a failure of protective relay can occur in LVDC distribution system as well. It, however, is hard to be detected since change in magnitude of current due to the fault is too small to detect the fault by the protective relay using overcurrent element. In order to solve the problem, this paper presents an algorithm for detecting HIF using accumulated energy in LVDC distribution system. Wavelet Singular Value Decomposition (WSVD) is used to extract abnormal high frequency components from fault current and accumulated energy of high frequency components is considered as the element to detect the fault. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed algorithm using ElectroMagnetic Transient Program (EMTP) software. Simulation results considering various conditions show that the proposed algorithm can be utilized to effectively detect HIF.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.83-89
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• 2013

Power distribution system has been changed from radial system to closed loop or mesh system due to connection of distributed generation growth. Data from distribution equipments which are installed at distribution line is required to be accurate for the performance of DMS(Distribution Management System). This paper analyzes the voltage measurement data from distribution equipment. However, the results of the analysis are confirmed to have some errors in voltage measurement data from distribution equipment. These errors come from aging of voltage sensor in distribution equipment and inaccurate data transfer to FRTU(feeder remote terminal unit) through the controller. The main problem is that the voltage measurement data of distribution equipment can not be assessed after it's first installation at the distribution line. The voltage measurement accuracy assessment system is to assess the voltage measurement data from distribution equipment on hot-line. This study had a field test to verify the performance of system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.3
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• pp.79-86
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• 2013

In order to analyze the electrical performance of ZnO surge arresters stressed by the combined DC and AC voltages that are generated in DC/AC converter systems, the leakage current properties of ZnO surge arrester blocks deteriorated by impulse currents were investigated. The test specimens were deteriorated by the 8/$20{\mu}s$ impulse current of 2.5kA and the leakage currents flowing into the deteriorated zinc oxide(ZnO) arrester blocks subjected to the combined DC and power frequency AC voltages are measured. As a result, the leakage currents flowing through deteriorated ZnO surge arrester blocks were higher than those flowing through the fine ZnO surge arrester blocks and the larger the injection number of 8/$20{\mu}s$ impulse current of 2.5kA is, the greater the leakage current is. The leakage current-voltage curves(I-V curves) of the fine and deteriorated ZnO surge arrester blocks stressed by the combined DC and AC voltages show significant difference in the low conduction region. Also the cross-over phenomenon is observed at the voltage close to the knee of conduction on plots of I-V curves.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.56-57
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• 2013

Plug-In MCCB는 전원부의 연결 단자가 없으며, 차단기 후면에 설치된 하우징 형태(housing type)의 플러그 유닛으로 부스바에 원터치(one touch) 설치 및 분리 등이 가능하다. 그러므로 차단기의 교체 시간이 짧고, 전원 복구가 신속하여 설비의 효율적 운용에 기여할 수 있다. 차단기의 후면에 있는 플러그 유닛이 동 부스바에 연결되었을 때 저항 특성을 초저항측정기(Resistance Tester)로 분석하였다. 3상 3선식 플러그인 배선용차단기를 동 부스바에 설치했을 때 R-phase과 플러그 단자 사이의 접촉 저항은 $0.51m{\Omega}$으로 확인되었다. 즉, 개발된 Plug-In MCCB를 이용하여 부스바에 설치할 때 접촉(속)부의 전기적 특성이 우수한 것을 확인할 수 있었다.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.353-354
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• 2016

본 논문은 IEC 60479 표준 "인체감전의 생리학적 현상"에 제시되어 있는 인체감전 현상에 대하여 교류환경과 직류환경에서 인체임피던스의 특성을 실험을 통하여 분석한다. 연구 결과, 적어도 상용주파수 이하에서는 IEC 60479 표준에서 제시하는 인체 임피던스 모델의 수정이 필요함을 발견하였다. 또한 도출된 실험 결과를 활용하여 직류 배전시스템의 TN 접지방식에서 인체 감전 및 설비 누전에 따른 사고에 대하여 구분동작이 가능한 직류전용 누설전류 검출(DC Residual Current Detection) 기법을 제안한다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.79-80
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• 2011

전기자동차 급속 충전기는 AC/DC 컨버터와 DC/DC 컨버터와 같은 전력변환장치, 차량과 충전기를 연결하는 충전인터페이스, 전력 공급설비, 차량과 충전기 상호 커뮤니케이션을 위한 통신망 등으로 구성된다. 따라서 전기자동차 급속 충전기의 전력변환장치로부터 전력계통으로 역류, 전력품질 및 전력기기 등에 악영향을 미치는 고조파가 발생되기 때문에 이에 대한 적절한 대책이 필요하다. 본 논문에서는 전기자동차 연계에 따른 전력 계통에서의 고조파 영향을 분석하기 위해 ATPDraw/MODESLS를 이용하여 급속 충전기의 전력변환장치인 AC/DC 컨버터와 DC/DC 컨버터를 모델링 하였고, 이를 한전 실 배전계통에 연계하여 차수별 고조파 및 THD(Total Harmonic Distortion)를 분석하였다.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.271-272
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• 2008

실선로 전력 케이블의 부분방전 측정은 주위 전력설비의 신호들이 혼합되어 검출된다. 본시험에서는 배전전력 케이블을 대상으로 부분방전 신호의 방향 추정 시험을 하였다. 시험 조건으로 모의 선로와 활선 현장선로에서 시행하였다. 2개 HFCT 센서를 사용하여 방전 펄스를 검출하였고 미소신호를 검출하기 위하여 AMP와 필터를 설계하였다. 신호 분석을 위하여 1GS/S의 스코프를 사용하였으며 자동 방향추정 S/W를 제작하였다. S/W의 특징으로는 2개의 채널에서 동일한 펄스의 시간차를 분석하여 방향을 분석하도록 하였다. 센서의 간격이 20CM일 때 약1nS의 시간차가 발생하여 신호의 방향을 추정할 수 있었다.

• Proceedings of the KIEE Conference
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• 2008.11a
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• pp.147-149
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• 2008

본 논문은 배 전자동화 시스템에서 계통의 설비 특성에 따라, 사고발생 시 FI 정보가 발생되지 말아야 할 곳에 생기는 FI 오류에 대한 개선 알고리즘과 적용방안을 제안하고 있다. 제안한 알고리즘을 검증하기 위하며 FI 오류가 발생하는 상황을 Matlab Simulink를 이용하여 모의하였고, 그 결과를 해석하여 알고리즘의 타당성을 입증하였다. 또한 다양한 사고를 고려하여 각기 다르게 나타나는 특성들을 종합할 수 있는 적용방안도 제안하였다.