• 조명전기설비학회논문지
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• 제22권9호
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• pp.32-39
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• 2008

본 논문은 뇌임펄스전압에 의한 토양의 이온화 현상과 모델접지시스템의 과도적 특성에 관련된 파라미터에 관한 것으로 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

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.436-439
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• 2008

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.

• Mass Spectrometry Letters
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• 제5권1호
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• pp.12-15
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• 2014

Thermal ionization mass spectrometry (TIMS) was used to determine the concentration and isotope ratio of uranium contained in samples of soil and groundwater collected from Korea. Quantification of uranium in ground water samples was performed by isotope dilution mass spectrometry. A series of chemical treatment processes, including chemical separation using extraction chromatography, was applied to the soil samples to extract the uranium. No treatments other than filtration were applied to the groundwater samples. Isotopic analyses by TIMS showed that the isotope ratios of uranium in both the soil and water samples were indistinguishable from those of naturally abundant uranium. The concentration of uranium in the groundwater samples was within the U.S. acceptable standards for drinking water. These results demonstrate the utility of TIMS for monitoring uranium in environmental samples with high analytical reliability.

• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2050-2058
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• 2018

Impulse characteristic of transmission tower grounding grid is needed for lightning protection of transmission line. This paper describes an outdoor experimental test facility established for large-scale grounding grid of transmission tower, made up of four impulse current generators and a circle current return electrode. The amplitude of impulse current is up to 100 kA. The results of the CDEGS simulation and GPR measurement reveal the uniform current distribution in the test arrangement. An impulse test for a square electrode with extended conductors is carried out in condition of three current waveforms with different amplitude. Based on the electrical network model and iterative algorithm method, a calculation model is proposed to simulate the impulse characteristic of large-scale grounding grid considering soil ionization. The curve of impulse resistance against the current amplitude shows the soil ionization both from the simulation and test. Deviation between the simulation and test result is less than 15%.

• 조명전기설비학회논문지
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• 제23권1호
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• pp.92-99
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• 2009

심매설 접지봉의 경우 장마철에 빗물이나 지하수와 접촉하는 경우가 발생한다. 수중에 잠겨있는 접지극에 서지 전압이 인가되면 접지극 주변에서 이온화 현상이 발생하게 된다. 지중이나 수중에서의 이온화 현상은 접지 시스템의 에너지적인 특성에 의해 영향을 받는다. 이 논문의 목적은 축소된 전해 수조를 이용하여 임펄스 전압에 의한 접지시스템의 과도특성을 파악하는데 있다. 매틀랩 프로그램을 활용하여 이온화에 의한 전위저감과 방출된 에너지를 측정하여 정량적인 분석을 수행하였다. 접지극 끝단의 최대 전압은 물의 저항률과 Marx형 전압발생장치의 충전전압에 따라 다양하게 나타났다. 접지극 끝단의 전위는 절연파괴전압에 이르기 전 인가전압에서 대략 절반까지 감소하였다. 또한 절연파괴가 발생하기 전 인가된 에너지의 절반 이상의 에너지가 이온화에 의해 접지극을 통하여 방출되었다.

• 조명전기설비학회논문지
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• 제29권4호
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• pp.95-101
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• 2015

This paper presents experimental results about characteristics of soil discharge as a function of moisture content when the $1.2/50{\mu}s$ lightning impulse voltage is applied. The laboratory experiments, for this study, were carried out based on factors affecting the transient behavior in soils. The electrical breakdown in soils was measured over a 0-6% range of moisture content for sands and a 0-4% range of moisture content for gravels. Needle-plane electrode systems was used As a result, the conduction current prior to ionization growth in dry soil is a little, but it in wet soil is increased with the applied voltage because the wet soil particles act as conductors. The soil impedance curves show an abrupt reduction just after breakdown. The general tendency measured in different soils is that the higher the water content, the lower the breakdown voltage and the shorter the time-lag to breakdown.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.324-327
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• 2009

This paper presents the transient impedance in a discharge region when high voltage lightning impulse is applied to small-sized ground electrodes in frozen soil. For a realistic analysis of ionization characteristics near the ground electrode in the soil, ground rod installed outdoors and high voltage impulse voltage generator were used. From the analysis of response voltage and current flowing ground electrode to earth, it was verified that the ionization near the ground electrode contributes to reduction of ground impedance and limits the ground potential rise effectively under high impulse voltage.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.446-454
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• 2016

In this paper, we present experimental results of the soil discharge characteristics as a function of moisture content when a 1.2/50-㎲ lightning impulse voltage is applied. For this study, laboratory experiments were carried out based on factors affecting the transient behavior in soils. The electrical breakdown voltages in soils were measured for a 0-6% range of moisture content for sand and a 0 - 4% range of moisture content for gravel. A test cell with semi-spherical electrodes buried face-to-face in the middle of a cylindrical container was used. The distance separating the electrodes is 100 mm. As a result, the time-lag to breakdown in soils decreases as the amplitude of applied voltage increases. The time-lag to initiation of ionization streamer is decreased, with an increase in the moisture content. However, the formative time-lag is rarely changed. The behavior of soil discharges depend not only on the type of soil and its moisture content but also on the amplitude of the impulse voltage. When the test voltage is applied repeatedly, electrical breakdown occurs along different discrete paths, leading radially away from the injected electrode. i.e., the fact that the ionization streamers propagate in different paths from shot to shot was observed.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.337-340
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• 2008

When high surge voltage invaded into the ground rod contacted with ground water, the ionization phenomena are happened in the water. Although some researchers have surveyed the ionization phenomena in soil, they have just analyzed the variation of the ground resistance. The most important role of the ground rod is to elect human beings from potential rise and to dissipate energy to the earth safely. In this wort we presented the method evaluating the potential reduction and energy dispersion. Also we analyzed theses factors as a function of charging voltages at the water resistivity of $50\;{\Omega}{\cdot}m$ using the Matlab Program. As a result the ground rod potential was reduced to 38 kV by ionization just below breakdown voltage. The energy more than half of the total injected energy was dispersed through the grounding electrode caused due to ionization.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.63-66
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• 2009

Lighting currents are one of major influences on the dynamic performance of ground electrodes. High lighting current intensity changes in the dynamic grounding performance due to ionization of the soil and very fast fronted pulses. The previous analysis has often been based on quasi-static approximation that is not applicable to very fast fronted pulses. To extend the analysis to fast fronted pulses in this paper, the full-wave analysis method based in the rigorous electromagnetic-field theory approach is used and the effects of the ionization of the soil me disregarded. Based on the simulation results, the empirical formulas applicable for slow and very fast fronted lightning current pulses me reviewed; therefore the validity of the theoretical approach is verified through comparison between the calculated and measured results.