• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.12
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• pp.592-596
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• 2005

Recently, substations have been constructed in GIS (Gas Insulated Switchgear) and indoor type because of the increasing difficulties of securing locations. In case of urban substations, it is also common that the substations are exclusively fed by underground cables. Sometimes, the infrastructures in urban area, such as communication facilities, are located near substations to be constructed. In this paper, we examined such a case that a branch office building of KT(Korea Telecom) was located near 154 kV underground GIS substation under construction with about 100 meters of the lateral distance between two facilities. GPR (Ground Potential Rise) at the substation and the transferred earth potential at the KT building through the earth in SLG (Single-Line-to- Ground) fault condition were investigated based on a series of computer simulations. The calculated earth potential at a distance of 100 m from the substation was below 120 V which satisfying the limit value of 650 V.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.645-649
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• 2007

Ground systems flow fault currents into the ground, and suppress Ground Potential Rise (GPR) by the current. In this paper, we designed and fabricated a surge impedance meter to analyze the ground impedance in wide frequency ranges. The meter consists of a surge generator, a high speed sample/hold (S/H) circuit and an associated electronics. The surge generator produces surge voltage up to 5kV in ranges of $50\sim500ns$. Field tests were carried out to evaluate the surge impedance meter at a driven-rod ground system. The results showed that surge impedance of ground systems should be measured by various fast surge waveforms, since the impedance increases as the rise time of applied voltage increases.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.4
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• pp.117-122
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• 2003

The AC power lines and signal lines of info-communication networks are routed on overhead poles and are highly exposed to lightning strikes. Due to the potential difference between grounding points of AC power lines and signal lines, the electronic equipments connected to the signal lines can easily be damaged by lightning surges. In this work, in order to develop reliable methods of protecting information and communication facilities from lightning surges, the reliability and performance of SPDs (surge protective devices) were experimentally investigated in an actual-sized test circuit. The behaviors of SPDs against lightning surges from AC power lines and signal lines and the coordinated effects of SPD installation methods were evaluated. As a consequence, it was confirmed that the bypass arrester methods and common grounding system are both highly effective.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1120-1131
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• 2006

This paper describes the numerical analysis techniques using the Combined Integration/Matrix Method to calculate ground potential rise which can be occurred in the various grounding systems. Combined Integration/Matrix Method is used to reduce the error and computation time with the analytical integration equation and the proper segmentaion of earth embedded conductor. To do it, optimal segmentaion method for the buried conductors is presented through error analysis which is capable of applying the practical scaled various grounding systems. The optimum length of segmented element is much co-related with the buried depth of grounding electrode and the maximum length of buried electrode. As a result, less 3 precent errors was obtained by proposed model. The proposed model is applied to verify an effect of multi-grounding problems which was aroused much controversy with separated or common grounding between the high power grounding system and low power grounding system such as signal and telecommunication grounding.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2025-2027
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• 2004

The grounding system design of the communication base station can be on the unfavorable conditions to induce the safe designing because of the limited area of the communication base station and the week point of surge caused by the given geographical condition such as the top point of mountain. In this paper, it is examined throughly about the way of safe designing that can reduce GPR(Ground Potential Rise) within the normal frequency band. And it is also considered the effective counter plan to cope with a transient phenomena that happen when surge of scores MHz-band inserted.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1188-1191
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• 1998

Detailed estimation of subsurface resistivity distribution and accurate estimation of actual fault current coming into the grounding system are indispensible to optimun grounding system design. Especially, it is essential for efficient grounding design to estimate subsurface resistivity distribution quantitatively and logically. Accurate estimation of subsurface resistivity distribution has an absolute influence on calculating touch voltage, step voltage and ground potential rise (GPR) which are related with grounding design standard for human safety. In this study, thirty-three electrical sounding surveys were made in Yongdam Power Station to obtain detailed subsurface resistivity distribution and the sounding data were interpreted quantitatively using multi-layered model. The results of the quantitative resistivity models were adopted practically to calculate grounding resistance values. Analytical asymptotic equations and CDEGS program were used in grounding resistance calculation and the results were compared and reviewed in the study.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.295-297
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• 1998

This paper shows characteristics of fault current division factor $S_f$, which is a ratio of earth- return current to total fault current, at a substation fed exclusively by power cables under unsymmetrical fault condition, such as single line-to-ground fault. In substation grounding system design, $S_f$ is a very important factor determining GPR, touch and step voltage at a substation under fault condition. In case of substations fed by overhead lines, 40-60% of $S_f$ has been typically used, although it is a very conservative value with no other network conditions considered. It is authors' hope that $S_f$ presented in this paper could hopefully be a basic reference in designing of substation grounding system, especially for a substation fed exclusively by power cables.

• Economic and Environmental Geology
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• v.36 no.2
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• pp.123-131
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• 2003

Geophysical surveys(electrical resistivity, self-potential, seismic refraction, GPR) were conducted to investigate the physical properties of the subsurface, and to delineate the flow channel of leachate from a AMD(acid mine drainage), buried rock wastes and tailings, and drainage pipes at an abandoned mine(Kwangyang mine). Especially in rainy season the sites appear to be abundant in AMD leachate, characterized by electrical conductivities of 0.98-1.10 ms/S. Electrical resistivity sections indicate that the leachate flows running in two directions at southern part rise up through the narrow fracture zones at the central part and contaminates the surrounding soil and stream. Such schematic features at the anomalous zone are well correlated with negative peaks in self-potential data, the limited penetration depth in GPR data and low velocity zone in seismic refraction data. Shallow high-resistivity zone is associated with the buried rock wastes which cause the diffractions in GPR image. In addition, the events at depth of approximately 1-1.25 m in GPR sections must be the metal pipes through which AMD is drained off to the inner bay.