• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.69-77
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• 2000

In this paper, the effects of the positions of the potential and current probes on the measurements of the ground resistance and potential gradients with the fall-of-potential method are described and the testing techniques to minimize the measuring errors are proposed. The fall-of-potential method is theoretically based on the potential and current measuring principle and the measuring error is primarily caused by the position and ground resistance of the measuring probes. The ground resistance is calculated by applying the 61.8% and rule in the fall-of-potential method, and then the potential probe is located on the straight line between the grounding electrode to be measured and the current probe. However, sometimes the grounding electrode to be measured and the measuring probes in on-site test might not be arranged on the straight line with adequate distance because there are building, road block, construction and other establishments. Provided that the grounding electrode to be measured and the measuring probes ar out of position on the straight line or have inadequate distance, the measurement of the ground resistance classically falls into an error and the measured ground resistance should be corrected. Measurements were focused on the grounding electrode system made by the ground rods of 2.4m long. It was found that the suitable separation between the grounding electrode to be measured and the current probe is more than 5 times of the length of the grounding electrode to be measured.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.230-236
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• 2015

In this paper, the electric potential of electrode surface is investigated by assuming them as two dimensional sets of point current sources. And, the simulated water tank is manufactured as a reduced scale of the earth. Henceforth, the adequate model electrode for test is decided to decrease experimental errors relevant to the limitation of the size of the water tank. The one of important things of this work, the deduction method of the potential interference factor is proposed, which used as the criterion of the potential interference according to the shape of conductors and the laying conditions, when multiple grounding conductors are situated at the same resistance grounding area. Also, the validity of this theory is verified from a numerical simulation of the grounding electrode to be used in experiments, and this study is realized by the verified theory and the simulated experiments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.5
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• pp.92-98
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• 2006

This paper deals with the potential interferences between ground rods. To propose a method for reducing the potential interference caused by grounding electrodes, the theoretical analysis and the reduced scale model tests, which we related to the measurement and computation of ground potential rise and potential interference caused by actual-sized grounding electrodes where current is injected, were carried out. The ground potential rise and potential interference coefficients were measured by using the hemispherical water tank grounding simulator and calculated by CDEGS software as a function of the distance between grounding electrodes. The ground potential rises and potential interference coefficients strongly depend on the distance between grounding electrodes, and the measured results were compared with the computer calculated data and were known in good agreement.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.66-71
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• 2003

Electronic equipments made from integrated circuits and small-sized semiconductors is protected by surge protective devices(SPDs) such as ZnO varistors, Zener diode and gas discharge tube from lightning overvoltages. However the clamping voltage of SPDs is greatly influenced by the method of installing the SPDs. In this paper, the protective effects of SPDs according to types of system groundings were experimentally investigated. The separate grounding is a particularly undesirable way to install SPDs. The effectiveness of the common grounding point for ZnO varistors is more pronounced than that for gas discharge tubes. The common grounding at the terminal of SPDs is recommended as a best method of installing SPDs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.587-593
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• 2021

Since 2017, a total of 29 fire accidents have occurred in energy storage systems (ESSs) as of June 2020. The common mode voltage (CMV) is one of the electrical hazards that is assumed to be a cause of those fire accidents. Several cases of CMV that violate the allowable insulation level of a battery section are being reported in actual ESS operation sites with △-Y winding connections. Thus, this paper evaluates the characteristics of CMV. An ESS site was modeled with an AC grid, PCS, and battery sections using PSCAD/EMTDC software. As a result of a simulation based on the proposed model, it was confirmed that characteristics of CMV vary significantly and are similar to actual measurements, depending on the grounding method of the internal transformer for PCS. The insulation level of the battery section may be severely degraded as the value of CMV exceeds the rated voltage in case of a grounding connection. It was found that the value of CMV dramatically declines when the internal transformer for PCS is operated as non-grounding connection, so it meets the standard insulation level.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.12
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• pp.595-601
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• 2000

This paper describes the improvement method of distance relaying algorithm for the underground transmission cables. Distance relaying algorithms have been mainly developing to protect the overhead transmission lines than the underground cables. If the cable systems are directly protected using distance relaying algorithm developed for overhead line without any improvement, there will be really occurred many misoperation in cable systems, because the cable systems consist of the conductor, the sheath, several grounding method, cable cover protection units(CCPUs), and grounding wire. Accordingly, the complicated phenomena are occurred, if there is a fault in cable systems. Therefore, to develope a correct distance relaying algorithm, such cable characteristics should be taken into account. This paper presents the process to improve distance relaying algorithm which is now used. REal cable system was selected to establish modeling in EMTP and ATP Draw. It was discovered through the detailed simulation during the fault that the large error existed between impedance measured at the relay point and real impedance is due to the resistance of grounding wire in each grounding method. And also compensation factor obtained by the simulation is proposed in this paper. It is proved that the factor proposed can fairly improve the accuracy of impedance at the relay point. It is evaluated that the protective ability will be really much improved, if the algorithm proposed in this paper is applied for cable systems of utility.

• Proceedings of the KIEE Conference
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• 2002.07a
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• pp.330-332
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• 2002

There are a lot errors and little accuracy when calculating the grounding resistance with the transposition methods in the equivalent surface of hemisphere electrode. Therefore we should calculate the grounding resistance by using the mesh factor. In this paper, we would estimated the grounding value of mesh electrode with water tank model & estimation method using the reduced scale ratio of mesh electrode based on the theory of model electrode & proportional factor according to the reduced scale ratio. And also we have confirmed the accuracy of the empirical formula of model electrode by using by regression analysis.

• 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.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.29-33
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• 2002

There are a lot of errors and little accuracy when calculating the grounding resistance with the transposition methods in the equivalent surface of hemisphere electrode. Therefore we should calculate the grounding resistance by using the mesh factor, In this paper, we would estimate the grounding value of mesh electrode with water tank model & estimation method using the reduced scale ratio of mesh electrode based on the theory of model electrode & proportional factor according to the reduced scale ratio. And also we have confirmed the accuracy of the empirical formula of model electrode by using the regression analysis.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.10
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• pp.489-492
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• 2001

The connection method of CCPU has been changed from connection between sheath and grounding to connection between sheaths without grounding since 1997. In domestic, there is so many cases that cables circuits were installed before 1997, added in same route after that, operated as multi-connecting systems of CCPU in same route. This paper examine the problem of multi-connecting system by EMTP simulation, and presents methods to improve the system characteristics.