• 조명전기설비학회논문지
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• 제27권2호
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• pp.54-61
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• 2013

This paper presents transient response behavior and frequency-dependent ground impedance of a single carbon ground electrode. The ground impedance of the carbon ground electrode was measured as a function of frequency of injected currents and simulated by using the distributed parameter circuit model with due regard to the frequency-dependent soil parameters, and the transient response behavior of the carbon ground electrode against impulse currents were investigated. As a consequence, the frequency-dependent ground impedance of the carbon ground electrode showed the capacitive behavior, that is, the ground impedance decreases with increasing the frequency of injected currents and lowers at the fast front time of impulse current. It was found that the carbon ground electrode is effective in grounding system for lightning protection. The ground impedance simulated with due regard to the frequency-dependent soil parameters was in good agreement with the measured data. The adequacy of the simulation technique and the distributed parameter circuit model for the carbon ground electrode was verified. It is expected that the simulation methodology, which analyzes the frequency-dependent ground impedance of the carbon ground electrode proposed in this work, can be used in the design of a grounding system for protection against lightning.

• 전자공학회논문지
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• 제53권4호
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• pp.117-128
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• 2016

대지의 접지 시스템 설치는 안전성과 전기 기기의 올바른 작동을 위해 필수적이며, 대지 파라미터, 특히 토양의 저항률은 대지 접지 시스템 설계에서 결정되어야 한다. 토양의 저항률을 측정하기 위한 가장 흔한 방법은 Wenner의 4전극 방법이 있으며, 이 방법은 1차원의 저항률을 얻기 위하여 가변 전극 간격을 갖는 큰 측정 세트가 요구되어 번거롭고, 시간소모가 많으며 비용이 많이 든다. 전기 저항 단층촬영법은 저비용이며 빠른 측정이 가능하다는 장점 때문에 토양의 저항률 분포를 추정하기 위해 적용될 수 있다. 전기 저항 단층은 관심지역에 놓인 전극에서 얻은 측정데이터를 사용하여 토양 저항률 분포를 특성화한다. 이때 전기 단층 촬영법의 역문제는 비선형성이 강하여 저항률 분포를 추정하기 위하여 Tikhonov 조정 방법을 갖는 반복적 Gauss-Newton 방법을 사용한다. 다양한 시뮬레이션을 수행하여 3차원 토양의 저항률 분포를 추정하는데 전기 저항 단층 촬영법은 유용한 성능을 제공하고 있음을 확인하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2007년도 춘계학술대회 논문집
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• pp.437-439
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• 2007

This paper was analyzed the resistivity change characteristic of mortar model block and concrete that was made earth electrode that's used concrete or basic concrete of building for 1 year. The early resistivity measurement value of concrete model block is higher than mortar model block. But after 1 year the resistivity measurement value of mortar model block is significantly higher than concrete model block. Because depends on time elapsed complete dryness factor of mortar model block that has not gravel is higher than concrete model block. And absorptance and function of mortar mode block was by far outstanding than concrete model block in the data for verification of the amount of contained water and the amount of dryness of mortar model block and concrete model block.

• 전력전자학회논문지
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• 제20권3호
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• pp.209-213
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• 2015

With the increasing popularity of renewable generation systems and the advancement of power electronics, DC distribution systems have recently received considerable research attention. DC distribution has numerous advantages, including reliability, power quality, and efficiency. Owing to these advantages, DC distribution has been applied to data centers and power quality-sensitive electronic load conditions. Because grounding electrodes in DC are much more susceptible to corrosion than in AC, the IT system defined in IEC Standard 60364 may be a good candidate for an earthing method for DC distribution systems. In addition, IEC Standard 61557 specifies the requirements for insulation monitoring devices (IMD) for protection of the IT system, which continuously monitors the insulation resistances between the power lines and the earth. This paper discusses the development and evaluation of IMD to promote the reliability of distribution systems and increase safety of humans and facilities.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 춘계학술대회 논문집
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• pp.259-262
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• 2008

This paper describes the ground surface potential profiles near the object to be grounded. The hemisphere water tank was used to simulate the. scale model. As a result, the ground surface potential near the ground electrode was considerably raised. In particular the ground surface potential at the just upper part of ground rod was higher than other part. The ground surface potential was lowered with increasing the buried depth of ground rod.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.71-74
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• 2003

Fall-of-potential method is used usually to measure the ground impedance of large scale grounding system exactly. Because the interlinked magnetic flux between closed loops to inject test current and to measure potential rise is existed in E-P-C straight line arrangement, mutual(or inductive) coupling influences greatly on the measurement correctness. Measurement errors produced from inductive coupling could be reduced by the arrangement methods of auxiliary electrodes. Right angle or P-E-C order arrangement methods were effective to reduce the inductive coupling and the decrease degree of measurement error was analysed as quantitative through an experiment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1849-1851
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• 2003

To obtain a low ground resistance in high resistivity soil, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flow into the grounding system, the ground impedance is significantly increased because of the inductive behavior. This paper presents how the impulse current works on the long vertical ground electrodes. The different shape of current was impressed between ground rods and auxiliary electrode by using impulse generator and the ground impedance was calculated from the ground potential rise.

• 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.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.472-477
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• 2013

This paper carried out the comparative analysis on ground impedance of a carbon block and a copper rod. Two types of grounding electrode were compared ; a carbon block (L : 1 m, ${\Phi}$ : 245 mm) buried at a depth of 0.8 m and a three-linked copper rod (L : 1 m, ${\Phi}$ : 10 mm) of equilateral triangles with 1 m spacing. Ground impedance depending on applied current source was evaluated by the application of a sine wave current with 60 Hz ~ 3.5 MHz, a fast-rise pulse with rising time of 200 ns, a standard lightning impulse of $8/20{\mu}s$ and a 600 Hz square wave. Ground impedance for both electrodes were almost the same value below 100 kHz, and increased rapidly afterwards. The maximum ground impedance appeared $400{\Omega}$ at around 1.5 MHz. Ground impedance of the carbon block was lower at the square wave and was higher at fast-rise pulse than that of the copper rod. Also, ground impedance as ages showed no difference for the last 8 months. From the results, it is likely that ground performance for both electrodes shows no difference against commercial frequency and lightning impulse current, while the copper rod shows better performance against a fast-rise pulse with rise-time of a few hundred ns.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.84-94
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• 2007

In order to collect information on local distribution of conductivity and permittivity underneath a scan probe, we developed a multi-frequency trans-admittance scanner (TAS). Applying a sinusoidal voltage with variable frequency on a chosen distal part of a human body, we measure exit currents from 320 grounded electrodes placed on a chosen surface of the subject. The electrodes are packaged inside a small and light scan probe. The system includes one voltage source and 17 digital ammeters. Front-end of each ammeter is a current-to-voltage converter with virtual grounding of a chosen electrode. The rest of the ammeter is a voltmeter performing digital phase-sensitive demodulation. Using resistor loads, we calibrate the system including the scan probe to compensate frequency-dependent variability of current measurements and also inter-channel variability among multiple. We found that SNR of each ammeter is about 85dB and the minimal measurable current is 5nA. Using saline phantoms with objects made from TX-151, we verified the performance of the lesion estimation algorithm. The error rate of the depth estimation was about 19.7%. For the size estimate, the error rate was about 15.3%. The results suggest improvement in lesion estimation algorithm based on multi-frequency trans-admittance data.