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박건훈(Geon-Hun Park),김회구(Hoe-Gu Kim),최종혁(Jong-Hyuk Choi),양순만(Soon-Man Yang),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.5월
This paper presents characteristics of soil ionization when high currents such as lightning and switching surge currents are injected into a grounding rod. Soil ionization phenomena are investigated by using both voltage and current signals recorded by oscilloscope. As a result, a critical electric field intensity(E<SUB>c</SUB>) for ionization is decreased with reduction of grain size. The pre-ionization resistance(R₁) and post-ionization resistance(R₂) at the sand with fine grain size are getting lower with increasing current magnitude. Finally, the time to ionization(t₁) and ionization current peak(t₂) of fine grain size are significantly shorter than those of medium grain size.
반구형 전극계에서 뇌임펄스전압에 의한 토양의 종류별 이온화 특성
李圭善(Kyu-Sun Lee),朴建勳(Geon-Hun Park),金會九(Hoe-Gu Kim),李福熙(Bok-Hee Lee) 대한전기학회 2009 전기학회논문지 Vol.58 No.1
This paper deals with the characteristics of soil ionization affecting the dynamic performance of grounding systems under lightning impulse voltage. A concentric hemispherical electrode system was employed in order to facilitate the field calculation and analysis of the experimental results. The parameters such as the ionization threshold and breakdown field intensity, the pre-ionization and the post-ionization resistances, the time-lag to ionization, the transient impedance, the equivalent ionized radius for various soil media were measured and analyzed. The dynamic characteristics of ionization processes under lightning impulse voltage are strongly dependent on the types of soil and water content. As a result, a soil ionization reduces the ground resistance and there is a little effect of applied impulse polarity on the soil ionization threshold field intensity. Although the ionization threshold field intensity of wet clay with 30 % water content is the highest, its ionized zone was found to be the smallest amongst the test samples.
임펄스전압에 의한 동심원통형 전극계에서 토양 이온화특성 분석
김회구(Hoe-Gu Kim),박건훈(Geon-Hun Park),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.9
본 논문은 뇌임펄스전압에 의한 토양의 이온화 현상과 모델접지시스템의 과도적 특성에 관련된 파라미터에 관한것으로 건조 모래와 습한 모래에 대한 이온화 특성을 치수가 다른 동심원통형 전극계의 실험 용기를 이용하여 연구하였다. 결과로써, 높은 임펄스전압이 인가된 모래의 비선형 전기적 특성은 이온화 과정에 의해 발생하였다. 모래의 과도임피던스는 수분의 함유량과 인가임펄스전압의 크기에 의존하며, 수분의 함유량과 인가전압의 크기의 증가에 따라 접지임피던스는 감소하였다. 본 연구결과는 뇌서지에 대하여 우수한 성능을 가지는 접지시스템의 설계에 유용한 정보가 될 것이다. This paper presents the soil ionization phenomena and the parameters with the transient characteristics of model grounding system under lightning impulse voltages. Ionization properties of dry and wet sands were investigated by using two test cells of concentric cylindrical electrode system with different dimensions. As a result, non-linear electrical behavior of sand under high impulse voltage is caused by ionization process. The transient impedance of sand depends not only on the water content but also on the magnitude of applied impulse voltages. The grounding impedance is decreased with increasing the water content and the magnitude of applied voltages. The results presented in this paper will provide useful information on the design of high performance grounding systems against lightning surge.
최종혁(Jong-Hyuk Choi),박건훈(Geon-Hun Park),이복희(Bok-Hee Lee) 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.8
이 논문은 수중의 침 대 평판 전극에서 임펄스전압의 크기와 극성, 물의 저항률 등과 같은 다양한 조건에 따른 방전특성을 나타낸다. 스트리머코로나가 침전극 끝단에서 발생하며 평판전극을 향하여 진전하여 최종적으로 전극 사이가 섬락에 이르게 된다. 동일한 전압에서 물의 저항률이 작을 때 스트리머코로나의 분기로는 물의 저항률이 클 때 보다 더욱 굵고 밝게 나타났다. 정극성에 비해서 부극성 스트리머코로나가 더욱 많은 분기로를 형성하며 더욱 넓게 퍼지는 것으로 나타났다. 스트리머코로나의 개시 후 방전의 진전과 더불어 수 백 [㎃]에서 수 [A]에 이르는 많은 수의 전류펄스가 발생하였다. 정극성의 절연파괴까지의 지연시간은 부극성에 비하여 매우 짧았으며, 전극에 공급되는 전구방전에너지는 물의 저항률에 반비례하였다. In this pap we describe discharge characteristics between needle-to-plane electrodes in water in various conditions such as different impulse voltages, polarities and water resistivities. Streamer corona is initiated at the tip of needle electrode and propagates toward plane electrode, and it experiences the final jump across the test gap. The branched channels of streamer coronas for lower water resistivities are much thicker and brighter than those for higher water resistivities at the same level of applied voltage. The negative streamer coronas not only have more branches but also widely spread out compared to the positive streamer coronas. A number of pulse-like currents ranging from some hundreds ㎃ to a few A after streamer corona onset were produced with discharge developments. The time-lags-to breakdown for the positive polarity were remarkably shorter than those for the negative polarity. The pre-breakdown energy supplied into the test gap was inversely proportional to water resistivity.
이복희(Bok-Hee Lee),김회구(Hoe-Gu Kim),박건훈(Geon-Hun Park),백영환(Young-Hwan Baek) 한국조명·전기설비학회 2008 조명·전기설비학회논문지 Vol.22 No.12
이 논문은 뇌 임펀스전류에 의한 접지시스템의 과도적 득성에 관련된 토양의 이온화 현상과 파라미터를 기술하였다. 몇 가지 토양에서 빌생하는 이온화 특성을 실험적으로 조사하였다. 절연파괴 임계전계강도와 이온화 반경을 용이하게 분석하기 위하여 원주형 실험용기를 사용하였다. 전압과 전류 파형을 기초로 모양의 절연파괴 임계전계강도, 임피던스의 임펄스 전류 크기에 대한 의존성, V-I곡선과 과도임피던스를 검토하였다. 이온화 과정과 비선형 특성은 토양 종류에 매우 의존적이며, 포장용수량의 토양에서 2개의 전류피크는 나타나지 않았다. 본 연구 결과는 토양의 이온화를 고려하여 임펄스전류의 영향을 받는 접지시스템의 과도적 성능의 향상에 유용한 정보가 될 것이다. This paper presents the soil ionization phenomena and parameters associated to characterize the transient performances of grounding system under lightning impulse currents. Ionization properties in occuring some soil media were experimentally investigated. The cylinchical test cell was employed in order to facilitate the analysis of soil breakdown field intensity and ionized radius. The soil breakdown field intensity, dependence of impedance on the amplitude of impulse current, V-I curves and transient impedances were discussed based on the voltage and current oscillograms. It was found that the ionization process and dynamic behaviors were strongly dependent on the types of soil and two current peaks were not observed in highly water-saturated soils. The results presented in this paper will provide useful information on the improvement of transient performance of a grounding system subjected to lightning impulse current considering the soil ionization.
이복희(Bok-Hee Lee),김회구(Hoe-Gu Kim),박건훈(Geon-Hun Park),이규선(Kyu-Sun Lee),안창환(chang-Hwan Ahn) 한국조명·전기설비학회 2008 한국조명·전기설비학회 학술대회논문집 Vol.2008 No.5월
It has been known that the value of soil resistance drops when a high impulse curennt is injected into a grounding electrode. In this paper, impulse generator is used to investigate the dry soil and wet soil characteristics in cylinderical test cell. The impulse resistances and breakdown characteristics were discussed based on its voltage and current traces. As a result, sand resistances are decreased with increasing the applied currents. It was thought that a decrease in resistance of dry sand with increasing current is due to both thermal and ionization processes. On the other hand, in case there is no water presence in the soil, the reduction in resistance as the currents are of dry sand increased is mainly due to the ionization process.