• Journal of the Korea Safety Management & Science
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• v.12 no.4
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• pp.73-80
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• 2010

The purpose of this study was to investigate the actual conditions of radiation safety supervision in animal clinics using inspection standard of X-ray generator for diagnosis. The surveys for inspection standard system, equipment condition, and safety supervision were carried out in 18 animal clinics randomly. The inspection standard included reproducibility of dose exposure, kVp, mAs, collimator accuracy test, collimator luminance test, X-ray view box luminance test, grounding system equipment test and external leakage current test. The surveys of equipment condition and safety supervision used one-on-one interview with 5 points measurement. As a result, 44.44% of reproducibility of dose exposure was proper, 81.25% of kVp test was good, and 100% of mAs test was appropriate. Also, 66.66% of collimator accuracy test was proper, 61.11% of collimator luminance test was good, 53.13% of X-ray view box luminance test was suitable. In addition, only 5.55% of grounding system equipment and ground resistance was proper, 63.64% of external leakage current test was appropriate in grounding system equipment test. The 100mA electric capacity of X-ray generator for diagnosis was popular with 44.44%, and its 55.56% was purchased used equipment. Monthly average of less than 50 times (61.11%) was top frequency in use, and no animal clinic had a thermo-luminescence dosimeter(TLD). The 16 animal clinics with radiation safety zone and 2 without radiation safety zone were appeared.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.100-108
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• 2008

The transient ground impedance depending on configuration, size, and material of grounding electrodes as well as the shapes of impulse currents, has a significant affect on the performance of the grounding system. This paper presents experimental results in regard to the analysis method of transient ground impedance using the lightning impulse and variable frequency currents. Also a new estimation method to replace the effective surge impedance for transient ground impedance was proposed. The ground electrodes used in this experiment are virtual ground electrodes including both resistance and inductance components, carbon ground electrode with 1[m] length, copper electrode with 9[m] length and counterpoise with 40[m] length. Ground impedances using the proposed method were measured respectively. Comparing with the ground impedance using variable frequency current the conventional ground impedance($Z_1$) calculated from the peak values of impulse voltage and impulse current is observed more correct method for evaluating the performance of ground electrode than the effective surge impedance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.6
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• pp.67-74
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• 2005

Grounding insures a reference potential point for electric devices and also provides a low resistance path for fault currents in the earth. The ground impedance as a function of frequency is necessary for determining its performance since fault currents could contain a wide range of frequencies. In this paper, the ground impedance of Magic rods which are commercially available has been measured in frequency ranging from 0[Hz] up to 100[kHz] and an equivalent circuit model, transfer function model of the ground impedance are identified from the measured values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.719-726
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• 1999

Multiconductor transmission line(MTL) equations are solved by FDTD method to examine the coupling between incident electromagnetic fields and multiconductor transmission lines. The measurement of induced voltages on UTP Category 5 and STP Category 5 cables which are used as LAN cables is carried out using a TEM cell where uniform and strong TEM fields can be established. The comparison between measured and simulated results shows good agreement. It is also found that grounding of shield foil at both terminations and small grounding resistance give good shielding effects for STP Category 5.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.4
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• pp.55-61
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• 1998

Generally, in the calculation of ground resistance in the grounding system, the method measuring ground potential rise which is caused by low frequency source injection is used. But both lightning and surge impulse re very harmful to electric equipment. In this connection, this paper presents the results of an experimental investigation of transient behavior of ground impedances when lightening current is injected to the electric rod the experimental results are agreement with the theoretical analysis. In addition, the states on the behavior of ground electrodes under impulse currents due to lighting strokes are presented. And the impulse impedance reductions caused by discharge in the soils are presented.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.847-853
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• 2010

This paper describes switching surge analysis for reclosing decision in 345kV combined transmission line with XLPE power cable. Reclosing operation should be decided based on the detailed technical analysis in combined transmission line because this line includes power cable section which is week on insulation. Insulation of power cable can be breakdown at the week point in case of reclosing moment. Therefore the detailed analysis has to be carried out by considering several conditions such as length ratio of power cable section, arrestor, inserting resistance, charging rate, grounding resistance, etc.. On the other hand sheath voltage on IJ(Insulated Joint) is analyzed to check dangerous condition on cable cover. Analysis is performed by EMTP/ATP. Analysis results show that reclosing can be operated as the single line-to-ground fault occurs on overhead line in 345kV combined transmission line, if the inserting resistance is considered before the operation of main circuit breaker.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.191-196
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• 2010

The electricity distribution system in Korea is adopting a multi-grounding system. Protection of this distribution system against lightning is performed by installing overhead ground wires over the high voltage wires, and connecting the overhead ground wires to the ground every 200 m. The ground resistance in this system is limited not to exceed $50\Omega$ and overhead ground wire and neutral wire are multiple parallel lines. Although overhead ground wire and neutral wire are installed in different locations on the same pole, this circuit configuration has duplicated functions of providing a return path for unbalanced currents and protecting the distribution system against induced lightning. Therefore, the purpose of this study is to analyze the induced lightning shielding effect according to the neutral wire installation structure of a 22.9kV distribution line in order to present a new 22.9kV distribution line structure model and characteristics. This study calculated induced lightning voltage by performing numerical analysis when an overhead ground wire is present in the multi-grounding type 22.9kV distribution line structure, and calculated the induced lightning shielding effect based on this calculated induced lightning voltage. In addition, this study proposed and analyzed an improved distribution line model allowing the use of both overhead wire and neutral wire to be installed in the current distribution lines. The result of MATLAB simulation using the conditions applied by Yokoyama showed almost no difference between the induced lightning voltage developed in the current line and that developed in the proposed line. This signifies that shielding the induced lightning voltage through overhead wire makes no difference between current and proposed distribution line structures. That is, this study found that the ground resistance of the overhead wire had an effect on the induced lightning voltage, and that the induced lightning shielding effect of overhead wire is small.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.247-250
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• 2004

A ground resistance is a good index of performance in a grounding system, but it does not reflect the performance in transient states. Recently long vertical ground rods in urban areas are often installed. But because of the inductance of long ground rods the ground impedance at high frequency might be greater than its resistance at low frequency. In this paper, a ground impedance of deeply driven ground rod has been measured in the frequency range from 10 kHz to 50 MHz. As a result, the ground impedances of a deeply driven ground rods are almost constant at the frequency range less than 100 kHz. However at high frequency the ground impedance showed the strong frequency dependance.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1811-1816
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• 2011

This paper describes switching surge analysis for reclosing decision in 345kV combined transmission line with GIL. Reclosing operation should be decided based on the detailed technical analysis in combined transmission line because this line includes power cable section which is week on insulation. Insulation of power cable can be breakdown at the week point in case of reclosing moment. Therefore the detailed analysis has to be carried out by considering several conditions such as charging rate, inserting resistance, arrester, length ratio of power cable section, grounding resistance, etc. Analysis is performed by EMTP/ATP.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.446-448
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• 2000

This paper discribes the modeling and transient analysis of cable in combined transmission line under high impedance fault(HIF). And also, transient characterstic analyzed on cable covering protection unit(CCPU) is presented. Modeling of the combined transmission line is established in PSCAD/EMTDC V3. The required data to analyze the transient phenomena is given from the actual system. The results show the HIF modeling in cable, fault current according to the value of fault resistance. And also when the value and method of grounding resistance is changed in CCPU, simulation results are presented.