• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.63-68
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• 2005

This paper describes the characteristics of effective impulse ground impedance of deeply driven ground rods combined with grounding grid or counterpoises with needles. The potential rises of the test ground electrodes were measured as a function of the rise time of applied impulse currents and the effective impulse ground impedances were calculated The impulse ground impedances of deeply driven ground rods strongly depend on the rise time of impulse currents and significantly reduced by the connection of grounding grids in parallel.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.347-354
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• 2002

In this paper, when structures are constructed in the soft ground with poor bearing capacity at Incheon International Airport(railroad area), as for the grouting columns built In soft ground by high pressure jet grouting with Triple tube rod(super injection grouting), the effects on reinforcement and bearing capacity of ground are investigated. A unconfined compressive strength tests has been performed on the specimens sampled from the grouting columns and a mass plate bearing test has been performed on a grouting column. The test results show that super injection grouting has a sufficient effect on composite ground improved of foundation ground and reatraint of settlement of structure.

• Structural Engineering and Mechanics
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• v.40 no.4
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• pp.563-581
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• 2011

Many novel materials, developed in recent years, have obvious properties with different modulus of elasticity in tension and compression. The ratio of their tensile modulus to compressive modulus is as high as five times. Nowadays, it has become a new trend to study the mechanical properties of these bimodular materials. At the present stage, there are extensive studies related to the strength analysis of bimodular structures, but the investigation of the buckling stability problem of bimodular rods seems to cover new ground. In this article, a semi-analytical method is proposed to acquire the buckling critical load of bimodular slender rod. By introducing non-dimensional parameters, the position of neutral axis of the bimodular rod in the critical state can be determined. Then by combining the phased integration method, the deflection differential equation of bimodular pin-ended slender rod is deduced. In addition, the buckling critical load is obtained by solving this equation. An example, which is conducted by comparing the calculation results between the three of the methods including the laboratory tests, numerical simulation method and the method we developed here, shows that the method proposed in the present work is reliable to use. Furthermore, the influence of bimodular characteristics on the stability is discussed and analyzed.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.694-696
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• 2005

Although DC ground resistance is a good index of grounding performance for grounding electrodes, it does not reflect the grounding performance during transient state. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute index due to its dependence on impulse current shape. In this paper, ground impedance characteristics of ground electrodes has been measured in frequency domain ranging from 1 Hz to hundreds of kHz. Equivalent circuit models and transfer function models of the ground rod have been identified from the measured values of ground impedance in frequency domain.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.434-436
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• 2000

It is difficult to accurately measure the ground resistance because it varies widely not only with the type of soil but also with the ground parameters; the moisture, the temperature the buried depth of electrodes, and the ground augmentation material and so on. Therefore, in this paper we analyzed the relation between the parameters and the resistance of ground in order to obtain a method of maintaining ground resistance stable. In experiments, the variation coefficients of ground resistance were calculated by the monthly measured data. The ground resistance decreases as the length of the ground rod increases. The variation between the ground resistance and the moisture rate of soil was low in case of using the ground augmentation material. Without the ground augmentation material, the ground resistance decreases as the moisture rate of soil increases. The ground resistance becomes small when the earth temperature becomes low.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.6
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• pp.289-297
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• 2000

This paper presents a comparison on the resistance and characteristics of transient response of grounding systems under surge currents using frequency domain electromagnetic field analysis software package and field test. Analysis is done by computer model, based on electromagnetic field theory approach, that accurately takes into account frequency dependent characteristics of the system. The transient performance of three grounding systems is analyzed by comparison of frequency dependent impedance and the maximal transient GPR. A double exponential lighting surge current is injected at one corner of the grounding systems. The transient GPRs a rod grounding systems are higher than mesh or electrolytic grounding systems. Af field test, the results of resistance measurement and time-variant of ground resistance slightly reduce electorlytic grounding systems less than rod and mesh grounding systems.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.261-263
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• 2005

This paper presents the potential interferences between various grounding electrodes. The ground potential rise and potential interference coefficient between grounding grid and ground rod were calculated. The potential rise and potential interference coefficient strongly depend on the distance between grounding electrodes.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.95-99
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• 2004

A systematic approach of measurement, modeling and analysis of grounding system impedance in the field of lightning protection systems is presented. The measurement and analysis of ground impedance are based on a computer aided technique. The magnitude and phase of ground impedance were measured and analyzed by the modified fall-of-potential method and the proposed computer program algerian using the waveforms of the test current and potential rise. The theoretical analysis of ground impedance were performed with the equivalent circuit models, and the theoretical results were compared with the measured data.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1489_1490
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• 2009

Ground impedance is changed according to frequency of the current injected into the grounding system. Because the lightning surge gives a broad frequency spectrum from some ten Hz to a few MHz, frequency dependance of ground impedance must be evaluated. In this paper, we have constructed 10m, 30m, 50m counterpoise and evaluated frequency dependance of ground impedance. Also we have evaluated frequency dependance of ground impedance according to current injection point. As a result, long counterpoises have low ground resistance, but ground impedances of those are significantly increased in the range of high frequency. In the case that currents are injected into the center of counterpoise, the ground impedance is most lower than any other injection point. Also, additory ground rod of 1.8m long affect ground impedance decrease.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.37-45
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• 2007

Recently, there has been an increase of the use of ground system for lightning protection called deeply driven grounding electrode. In the case of deeply driven grounding electrode, the rod electrode is equipped perpendicularly and deeply, therefore, it has a benefit to have less restriction of place compared to mesh grid electrode. However, ground impedance is largely changed by the local earth resistivity, so it requires a detailed analysis of the ground structure when planning. The measurement of earth resistivity by existing Wenner's method has been widely used, however, this method can not find out a change in the local ground resistance and it shows the result outwardly to be difficult to estimate exact depth. Therefore, this study analyzed the ground structure as 2-D image using 96 channels measurement facility and tried to analyze change in the local ground resistance and depth of the ground in order to design a deeply driven electrode effectively for lightning protection. It used Wenner alpha method dipole-dipole method and Schlumberger method for 2-D image analysis of the ground resistivity ma based on, it the result was compared with the ground structure analyzed with the result using the CDEGS and Wenner 1-D method.