• Title/Summary/Keyword: Soil breakdown

검색결과 57건 처리시간 0.028초

Experimental Research on Impulse Breakdown Characteristics of Soil

  • Lee, Jaebok;Sughun Chang;Sungho Myung;Yuengue Cho
    • KIEE International Transactions on Electrophysics and Applications
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    • 제4C권2호
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    • pp.60-63
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    • 2004
  • The electrical breakdown characteristics of different types of soil samples have been measured. It is shown that the threshold soil breakdown strength is affected by many factors, such as types of soil, grain size, and soil compaction. The breakdown process in the test soil samples appears to be due to air ionization in the voids between the soil particles. The results have been compared with the relevant experimental results of other researchers.

초음파 조사에 의한 토양내 중금속 추출 기작 연구 (Mechanism on Extraction of Heavy Metals from Soil by Ultrasonication)

  • 신연준;이차돌;유종찬;양중석;김호섭;백기태
    • 한국지하수토양환경학회지:지하수토양환경
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    • 제20권1호
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    • pp.28-35
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    • 2015
  • In this study, the mechanisms on ultrasonication enhanced metals extraction were investigated compared with the conventional washing technique. We hypothesized the mechanisms on enhanced extraction of ultrasonication: ultrasonication increased the temperature of soil slurry and decreased average particle size of soil due to breakdown of soil aggregate. Actually, the ultrasonication increased the temperature of soil slurry to $60^{\circ}C$ in this study, and the increase in the temperature enhanced the metal extraction to 15-20% even in the conventional simple mixing. The conventional washing technique decreased average size of soil particles because of breakdown of soil aggregate, and the ultrasonication decreased the size more than that of washing. The breakdown of soil aggregate improved the contact between metals and washing agent, which enhanced the extraction of metals in the ultrasonication. Therefore, we concluded that the main mechanisms of ultrasonication are increase in the temperature and breakdown of the soil aggregate. Finally, the ultrasonicaiton increased the extractability of metals upto 40% compared to conventional washing technique.

봉형접지전극 주변에서 토중방전현상에 대한 실험적 고찰 (Experimental investigations of Breakdown Phenomena in Soils in the vicinity of Ground rod)

  • 이복희;김병근;이우철
    • 한국조명전기설비학회:학술대회논문집
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    • 한국조명전기설비학회 2005년도 춘계학술대회논문집
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    • pp.279-282
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    • 2005
  • Morden electronic equipments are becoming very important in information oriented society, but they are vulnerable to lightning surges. Soil resistivity in the vicinity of grounding electrodes my be affected by the current flowing from the grounding electrodes into the surrounding soil. Electrical conduction in soils depends on the grain size, compactness, and variability of the grain sizes. When a high current is injected into the soil, and the breakdown phenomenon occur. In the present work, Electrical behaviors related to discharge in soils were investigated. The breakdown voltages in soil were lower than that sparkover voltage in air. The breakdown voltage in the gravel layer is relatively low, and the breakdown was caused by the flashover through the surface of gravels

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뇌임펄스전압에 의한 불평등전계에서 토양방전특성 (Soil Discharge Characteristics in Inhomogeneous Field Caused by Lightning Impulse Voltages)

  • 유양우;김승민;김유하;이복희
    • 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.

습한 토양의 임펄스방전특성 (Characteristics of Impulse Discharges in Wet Soil)

  • 김회구;이복희
    • 전기학회논문지
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    • 제66권2호
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    • pp.363-369
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    • 2017
  • This paper presents the experimental results related to soil ionization and electrical breakdown in a concentric hemispherical electrode system under lightning impulse voltages. Dynamic voltage-current and impedance-time characteristics of soil ionization were measured and analyzed. Also the electrical breakdowns of the soil gap were investigated. The time-lag to the peak current corresponds to the soil ionization propagation. The time of ionization propagation in wet sand is found to decrease with increasing the impulse currents. A drastic decrease in ground resistance was observed during the impulse current spreading in sand. The electrical breakdown appears at the wave tail of impulse voltage and results in a wide scatter in V-t curves. The voltage-current curves have a fan-like shape attributed to ionization processes which result in increasing current and decreasing voltage.

임펄스전류에 의한 토양의 절연파괴특성 (Breakdown Characteristics of Soils Caused by Impulse Currents)

  • 이복희;이강수;김회구
    • 조명전기설비학회논문지
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    • 제24권4호
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    • pp.103-109
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    • 2010
  • 이 논문은 동축원통형 전극계에서 임펄스전류에 의한 토양의 절연파괴특성에 관한 것으로 4종의 토양에 대한 절연파괴전압과 전류를 측정하고, 절연파괴를 일으키는 전계의 세기, 절연파괴까지의 지연시간과 전압-전류곡선을 분석하고 검토하였다. 그 결과, 절연파괴전압과 전류 파형은 토양입자의 크기에 의존하며, 자갈과 모래의 절연파괴 전압과 전류 파형은 마사토와 황토의 파형과는 다르게 나타났다. 절연파괴를 일으키는 전계의 세기는 자갈, 모래, 황토, 마사토의 순으로 높았으며, 모든 시료의 전압-전류곡선은 ${\infty}$모양의 교차폐곡선을 나타내었다. 또한 자갈과 모래의 절연파괴까지의 시간지연은 마사토나 황토보다 길게 나타났다. 본 연구 결과는 토양의 이온화를 고려하여 낙뢰전류가 입사되는 접지전극시스템의 과도적 성능의 향상을 위한 설계에 유용한 정보가 될 것이다.

Discharge Characteristics in Soils Subjected to Lightning Impulse Voltages

  • Kim, Seung Min;Yoo, Yang-Woo;Lee, Bok-Hee
    • 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.

낙뢰 리더의 대지부착과정에 대한 기초적 연구 (A Basic Study on the Attachment Process of Lightning Leader to Ground)

  • 유양우;김승민;김유하;이복희
    • 조명전기설비학회논문지
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    • 제28권10호
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    • pp.82-88
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    • 2014
  • This paper presents the results of model tests for the attachment process of lightning leader to ground which is one of poorly understood processes of cloud-to-ground lightning discharges. In order to simulate the attachment process of lightning leader to ground, we investigated the discharge characteristics of air gap between the tip of needle-shaped electrode and the soil surface as a parameter of moisture content in soils when the positive and negative $1.2/50{\mu}s$ lightning impulse voltages are applied. The breakdown voltage and the discharge light were observed. As a result, the attachment processes of lightning leader to ground are strongly dependent on the grain size and the moisture content of soils. The time to breakdown was shortened with increasing the magnitude of incident impulse voltages. The delay time from application of the highest voltage to breakdown in sand is shortened with increasing the moisture content. The delay time from application of the voltage to breakdown in gravel varied from about $0.5{\mu}s$ to several ${\mu}s$. As the moisture content in soil increases, the breakdown voltages are decreased and the breakdown voltage versus time to breakdown curves are shifted toward the lower side. The results obtained in this work are similar to those for non-uniform air gap stressed by lightning impulse voltages.

토중방전을 수반하는 접지봉의 임펄스응답에 대한 기초적 연구 (A Fundamental Study on the Impulse Responses of Ground Rod Attendant upon Soil Discharges)

  • 유양우;조성철;이복희
    • 조명전기설비학회논문지
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    • 제28권4호
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    • pp.62-69
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    • 2014
  • This paper deals with the fundamental characteristics of transient and conventional ground impedances associated with soil discharges when the lightning impulse voltage was applied to a small-sized ground rod. The potential rise responses of the test ground rod to impulse currents were observed. The current-voltage (I-V)curves, transient and conventional ground impedance curves were examined.. To analyze the transient behaviors of ground rod attendant upon soil discharges, the impulse responses of ground rod were compared with those of non-inductive resistor. As a consequence, the potential rise and impedance of ground rod were reduced and the currents dispersed into the earth were increased due to soil discharges near the ground rod. Soil discharges are classified into two regimes; ionization and breakdown phenomena. The potential rise and impulse impedance of ground rod are significantly decreased by breakdown processes in soil.

Fixture를 이용한 토양 절연파괴 실험 (Soil Breakdown Test using Fixture)

  • 이현구;하태현;정동학;하윤철;김대경;배정효
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2007년도 제38회 하계학술대회
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    • pp.384-385
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    • 2007
  • The fault current through the earth originated from a power line ground fault might cause arcing through the soil to an adjacent pipeline, which might bring about not only a catastrophic accident such as gas explosion and oil leakage but also a hazard to the safety of workers responsible for the maintenance and repair of the pipeline. In this paper we experimented on the soil breakdown test using the fixture and outlined the standards for the separation distance of a buried pipeline adjacent to the power line tower.

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