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이복희(Bok-Hee Lee),최종혁(Jong-Hyuk Choi),백영환(Young-Hwan Beak),정동철(Dong-Cheol Jeong),안창환(Chang-Hwan Ahn) 한국조명·전기설비학회 2006 한국조명·전기설비학회 학술대회논문집 Vol.2006 No.11월
This paper presents the experimental results of under water discharges caused by impulse voltage in different resistivities. Discharge phenomena were observed by digital cameras. As a result, discharge patterns in the positive and negative polarity showed different route of discharge. The positive discharge comes from the rod toward the bottom of a hemisphere water tank. On the other hand, the route of negative towards the surface along the rod and bridges the side of hemisphere water tank. As the voltage is higher, the discharge routes are more thick and have more branches in positive polarity. Finally, the arc discharge voltages for high resistivities is lower than those for low resistivities. At the low resistivity, the corona discharge is predominant, because the discharge current flows before the arc discharge.
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),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),정현욱(Hyun-Uk Jung),최종혁(Jong-Hyuk Choi),조성철(Sung-Cheol Cho),백영환(Young-Hwan Beak),이규선(Kyu-Sun Lee),안창환(Chang-Hwan Ahn) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
This paper describes touch and step voltage in the reinforced concrete and steel poles. Ground surface potential rises were measured as a function of the separation between pole and ground rod. Touch and step voltage are calculated on the basis of the distribution of ground surface potential rises. As a result, touch and step voltages strongly depend on the position of installation of ground rod.
이복희(Bok-Hee Lee),최종혁(Jong-Hyuk Choi),박건훈(Geon-Hun Park),전병욱(Byung-Wook Jun),김회구(Hoe-Gu Kim),백영환(Young-Hwan Beak),이규선(Kyu-Sun Lee) 한국조명·전기설비학회 2007 한국조명·전기설비학회 학술대회논문집 Vol.2007 No.11월
In this paper we describe streamer propagations characterizing underwater pre-breakdown and breakdown behaviour under impulse voltages. Streamer corona branches in lower resistivities are much thicker and brighter than those in higher resistivities. The negative streamer channels not only have more branches but also widely spread out than the positive streamer channels. The succession of streamer coronas during pre-breakdown produces a stepwise propagation. The pre-breakdown currents consist of the conduction current and streamer corona current pulses.