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유재덕(Jae-Duk Yoo),조용승(Yong-Seung Cho),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.12
This paper deal with an analysis of the ground surface potential profiles using a hemispherical scaled-model. Because it is very difficult to draw valid conclusions concerning a general grounding problem from actual field data, scale model tests can be used to determine the ground surface potential profile around the grounding electrodes according to the configuration of grounding electrodes. In this work, a hemispherical vessel with a diameter of 1,100 [㎜] was employed to simulate uniform soil and CDEGS program was employed to compare the measured and simulated results. As a result, the ground surface potential around the grounding electrode was significantly raised and the ground surface potential at the just upper point of ground electrode particularly was higher than other points. The ground surface potential of counterpoise was higher than other grounding electrodes such as mesh and grounding rods and the ground surface potential strongly depends on the frequency responses of grounding electrodes. Also the results measured with the small-sized model were in reasonably agreement with the data obtained from simulation.
조용승(Yong-Seung Cho),이봉(Feng Li),유재덕(Jae-Duk Yoo),김동성(Dong-Sung Kim),김기복(Ki-Bok Kim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.9월
This paper presents the ground surface potential rises caused by a counterpoise buried in two-layered soils. To propose fundamental data relevant to the risk reduction of electric shock of human beings, the ground surface potential rises near the counterpoise were computed by CDEGS program. Touch and step voltages are calculated on the basis of the distribution of the ground surface potential rises. As a result, touch and step voltages, ground surface potential rises depend on the soil resistivity of installation point of counterpoise in the two-layered soil structure.
이복희(bok-hee Lee),이봉(Feng Li),유재덕(Jae-Duk Yoo),유양우(Yang-Woo Yoo),김동성(Dong-Seng Kim) 한국조명·전기설비학회 2010 한국조명·전기설비학회 학술대회논문집 Vol.2010 No.5월
In this paper, in order to substitute dry-air for SF? gas in distribution power system equipment, breakdown characteristics of dry-air and SF? gases are investigated in a quasi-uniform electric field. The dielectric behaviors of dry-air and SF? gases are measured under the positive and negative 1.2/50㎲ impulse voltages. As a result, The 50% breakdown voltages in SF? gas at gas pressure of higher than 0.15[㎫] and dry-air at the gas pressure of higher than 0.4[㎫] are greater than 150[㎸<SUB>p</SUB>] in the negative polarity, respectively.
임펄스전류의 인가위치에 따른 매설지선의 과도접지임피던스 특성
이봉(Feng Li),정동철(Dong-Chul Jung),김종호(Jong-Ho Kim),유재덕(Jae-Duk Yoo),김동규(Dong-Kyu Kim),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2010 조명·전기설비학회논문지 Vol.24 No.5
본 논문은 매설지선의 과도접지임피던스의 임펄스전류의 인가위치와 대지구조에 대한 의존성에 관한것으로 다른 저항률을 가지는 토양에 매설된 길이 25, 50[m]인 매설지선의 과도접지임피던스와 규약접지 임피던스를 임펄스전류의 상승시간에 따라 측정하고 분석하였다. 그 결과, 매설지선의 과도접지임피던스는 유도성을 나타냈으며, 규약접지임피던스는 과도접지임피던스와 비슷한 경향성을 보였다. 매설지선의 접지저항은 임펄스전류의 인가위치에 관계없지만 특히 과도접지임피던스와 규약접지임피던스는 짧은 시간영역에서 임펄스전류의 인가위치와 대지저항률에 의존적이었다. This paper presents the dependances of transient grounding impedances of counterpoises on the soil structures and the injected point of impulse currents. The transient and conventional grounding impedances of the 25 and 50[m] counterpoises buried in the soil with different resistivity were measured and analyzed as a function of the rise time of impulse currents. As a result, the transient grounding impedances give an inductive behavior, and the trend of the conventional grounding impedances is similar to that of the transient grounding impedances. The ground resistance of counterpoises is irrespective to the injected of impulse current, but the transient and conventional grounding impedances in a short time range especially depend on the soil resistivity and position of the injected point of impulse currents.
이복희(Bok-Hee Lee),최종혁(Jong-Hyuk Choi),최영철(Young-Chul Choi),유재덕(Jae-Duk Yoo),백영환(Young-Hwan Beak),김동성(Dong-Seong Kim),신희경(Hee-Kyung Shin),유양우(Yang-Woo Yoo) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
In these days, the common grounding systems are adapted in most large structures. In order to evaluate the performance of grounding system, it is needed to measure ground impedance. Measuring methods of ground impedance for a large scale grounding systems have not been yet presented in detail. In this paper, we analyze earth mutual resistance and mutual coupling of 15×15m grounding grid in different arrangements of auxiliary electrode. As a results, the auxiliary electrodes are installed where the error rate due to earth mutual resistance is less than 5%. Also, the potential lead is installed at obtuse angle from the current lead and the overlapped length between potential lead and grounding grid are minimized.
이복희(Bok-Hee Lee),이봉(Feng Li),이승주(Song-Zhu Lee),유재덕(Jae-duk Yoo),조성철(Sung-Chul Cho) 한국조명·전기설비학회 2009 한국조명·전기설비학회 학술대회논문집 Vol.2009 No.5월
This paper presents the behaviors of transient and conventional grounding impedances of a 30m counterpoise according to the injection point of lightning impulse currents. As a result, the trend of the conventional grounding impedances measured as a function of risetime of impulse current is similar to the transient grounding impedance of counterpoise. The injection point of impulse current greatly influences on the transient grounding impedance characteristics of counterpoise. The transient grounding impedances strongly depend on the injection point and the rising time of impulse current and the soil characteristics.
이복희(Bok-Hee Lee),김정철(Jung-cheol Kim),김종호(Jong-Ho Kim),유재덕(Jae-Duk Yoo),김동규(Dong-Kyu Kim) 대한전기학회 2009 대한전기학회 학술대회 논문집 Vol.2009 No.7
Lightning currents are one of major influences on the dynamic performance of counterpoise. High lightning current causes the dynamic grounding performance of counterpoise due to very fast fronted pulses. The previous analysis has often been based on quasi-static approximation that can not be applicable to very fast fronted pulses. To extend the analysis for fast fronted pulses in this paper, the full-wave analysis method based on the rigorous electromagnetic-field theory approach is used and the effects of the ionization of the soil are disregarded. Based on the simulation results, the empirical formulas applicable for slow and fast fronted lightning current pulses are reviewed; therefore, the validity of the theoretical approach is verified through comparison between the calculated and measured results.