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임펄스전류에 의한 매설지선의 과도임피던스특성에 대한 모의해석
조정현(Jeong-Hyeon Joe),이복희(Bok-Hee Lee) 대한전기학회 2009 전기학회논문지 Vol.58 No.10
A ground electrode subjected to lightning surge current shows the transient impedance behaviors. The ground electrode for protection against lightning should be evaluated in view of the transient grounding impedance and conventional grounding impedance, not ground resistance. The transient impedance characteristics of ground electrodes are influenced by the shape of ground electrode and the soil characteristics, as well as the waveform of lightning surge current. In order to propose a simulation method of analyzing the transient impedance characteristics of the grounding system in practical use, this paper suggests a theoretical analysis method of distributed parameter circuit model to simulate the transient impedance characteristics of counterpoise subjected to lightning surge current. EMTP and Matlab programs were employed to compute the transient grounding impedances of three counterpoises with different lengths. As a consequence, the simulated results using the proposed distributed parameter circuit model are in good agreement with the measured results.
조정현(Jeong-Hyeon Joe),김종호(Jong-Ho Kim),백영환(Young-Hwan Beak),김동성(Dong-Seong Kim),이강수(Gang-Su Lee),김기복(Ki-Bok Kim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.5월
For lightning currents, a grounding system shows the transient grounding impedance characteristics. A grounding system for protection against lightning should be evaluated by the transient grounding impedance, not it's ground resistance. The transient grounding impedance varies with the shape of ground electrode and earth characteristics as well as the waveform of lightning surge current. For the analysis and practical use of transient grounding impedance, the characteristics of transient grounding impedance should be analyzed theoretically and this papaer suggests the theoretical analysis for the transient grounding impedance of counterpoise by using the distributed parameter circuit model. EMTP and Matlab are used to simulate the distributed parameter circuit model of counterpoise and the adequacy of the distributed parameter model of counterpoise is examined by comparing the simulated results with the measured results.
이복희(Bok-Hee Lee),조정현(Jeong-Hyeon Joe),이봉(Feng Li),김종호(Jong-Ho Kim),이승주(Seung-Ju Lee),김기복(Ki-Bok Kim),김태기(Tae-ki Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
The impedance of a vertical grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of thr vertical grounding electrode which shows the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertical grounding electrodes are calculated by using the distributed parameter circuit model. The adequacy of the simulations has been confirmed by comparing the simulated results with the measured results.
김기복(Ki-Bok Kim),조정현(Jeong-Hyeon Joe),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.4
접지임피던스는 접지전극의 크기를 증가시켜도 낮아지지 않고, 토양의 특성과 주파수 조건에 따라 접지 임피던스가 최소값을 보이는 접지전극의 길이가 존재하며, 이 접지전극의 길이를 각 토양 특성과 주파수에 따른 임계길이라 한다. 본 논문에서는 대지구조의 조건을 고려하는 새로운 분포정수회로모델을 제안하였으며, 새로이 제안된 해석모델을 적용하여 MATLAB프로그램으로 수직접지전극의 임계길이와 접지임피던스를 해석하였다. 그 결과, 수직접지전극의 임계길이와 접지임피던스의 주파수의존성에 대한 대지구조의 영향이 크며, 접지시스템의 최적 설계를 위해서는 대지구조를 고려하는 것이 바람직한 것으로 밝혀졌다. The grounding impedance is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode which shows the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical Length. In this paper, a new distributed parameter circuit model considering the condition of the multi-layered soil structures was proposed, and the grounding impedance and critical length of the vertical grounding electrode were analyzed by using the newly proposed simulation model and the MATLAB program. As a consequence, it was found that the effect of the soil structure on the frequency-dependent grounding impedance and critical length of the vertical grounding electrode is significant. It is desirable to consider the soil structure in optimal design of the grounding system.
이복희(Bok-Hee Lee),조정현(Jeong-Hyeon Joe),신희경(Hee-Kyung Shin),이강수(Kang-Soo Lee),황등과(Hoang Dang Khoa),김정철(Jung-Cheol Kim) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.10월
This paper presents a theoretical analysis for the grounding impedance influenced by the ground rod's dimension using the distributed parameter model. In this paper, EMTP and Matlab Program were used to simulate the distributed paramter model and to analyze the frequency-dependent characteristics of the ground rods. We compared two kinds of ground rods having different dimensions and the frequency-dependent characteristics of two ground rods were quite different from each other. It is estimated that these different characteristics are caused by the distributed parmeters which are changed by the length of ground rod.
불평등전극계에서 뇌임펄스전압에 대한 N₂기체의 절연파괴 특성
이복희(Bok-Hee Lee),이봉(Feng Li),조정현(Jeong-Hyeon Joe) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.5월
This paper presents the experimental results on breakdown characteristics in N₂ gas under non-uniform electric fields caused by both the positive and negative lightning impulse voltages. N₂ gas have an advantage of em-friendly and cost reduction, and safety aspects. In order to analyze the impulse pre-breakdown processes in N₂ gas, we carried out measurements and observations of the impulse breakdown voltages, pre-breakdown current and luminous signals. They were measured by a voltage divider, a shunt and a photo-multiplier tube, respectively. Additionally, the characteristics of discharge channels were observed by high speed cameras. The breakdown voltages in the positive polarity was lower than those in the negative polarity.
김기복(Ki-Bok Kim),이복희(Bok-Hee Lee),조정현(Jeong-Hyeon Joe) 한국조명·전기설비학회 2009 조명·전기설비학회논문지 Vol.23 No.9
뇌전류와 같이 고주파성분을 함유한 서지전류나 전자통신기기의 전자기장해를 유발하는 고주파 이상전류에 대하여 접지전극은 주파수에 의존적인 상당히 복합적인 임피던스의 특성을 보인다. 접지전극의 접지임피던스는 접지전극의 크기를 증가시켜도 낮아지지 않고, 대지의 특성과 주파수 조건에 따라 접지임피던스가 최소값을 보이는 접지전극의 길이가 존재하며, 이 접지전극의 길이를 대지의 특성과 주파수 조건에 대한 임계길이라 정의한다. 본 논문에서는 분포정수회로모델을 이용하여 수직접지전극과 수평접지전극의 임계길이를 산정하였으며, 실험결과와의 비교를 통해 타당성을 확인하였다. For the surge currents like lightning currents containing high frequency components and the abnormal currents having high frequencies which cause the EMI(Electromagnetic interference) problems for the electronic devices and communication instruments, the linear grounding electrodes have the significantly composite impedance characteristics which are dependent on the frequency of the applied current. The impedance of a grounding electrode is not lowered by expanding the dimension of the grounding electrode, and the length of grounding electrode having the minimum value of the grounding impedance for each condition of frequency and soil characteristics is existent, and it is defined as Critical length. In this paper, the critical lengths for the vertically and horizontally-buried grounding electrodes are calculated by using the distributed parameter circuit model. The propriety of the simulations has been confirmed by comparing the simulated results with the measured results.