• Proceedings of the KSR Conference
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• 2005.11a
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• pp.736-741
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• 2005

This paper presents electric characteristics analysis and safe configuration for extension power supply between existent 6.6kV ungrounded distribution system and establishment and improvement 22.9kV direct grounding distribution system. For this, we model 6.6kV ungrounded and 22.9kV direct grounding distribution system of urban underground, ground region. and rural electrical, unelectrical region using PSCAD/EMTDC and analyze voltage drop, charging current, ground and short fault through simulation. To analyze electric characteristics of extension power supply, we simulate extension power supply of overhead line of 6.6kV ungrounded system and underground line of 22.9kV direct grounding system of rural electrical region and propose operation condition for safe extension power supply through result of analysis. Characteristics of voltage drop, charging current, ground and short fault appear almost similarly with electrical characteristic of direct power supply. However, because unbalance of phases may cause relay's malfunction of ungrounded system and ground fault current of direct grounding system may demage facilities of ungrounded system, we propose safe system configuration such as impedance grounding system of neutral point.

• 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.49-56
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• 2011

Grounding system insures a reference potential point for electric devices and also provides a low impedance path for fault currents or transient currents in the earth. The ground impedance as function of frequency is necessary for determining its performance since fault currents could contain a wide range of frequencies. In this paper, the grounding resistance, grounding impedance and transient grounding impedance are measured by using 3-point fall-of-potential method in order to analyse grounding characteristics of the copper and concrete rod grounding electrodes. An equivalent transfer function model of the ground impedance and transient grounding impedance are identified from the measured values by using ARMA method and evaluated by comparing the conventional grounding impedance.

• Electric Engineers Magazine
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• v.228 no.8
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• pp.52-57
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• 2001

Presently the Korean grounding system uses TN system, multi-grounding method with IT independent grounding method. Nevertheless TN system can't exist with TT system in the technological terms. If they coexist, it causes ground-fault circuit not to operate, and brings about different electrical potential rise by customer system. It brings about serious problems for safety. This paper aims for improving method of grounding system based on the technical analysis on instances in foreign countries and Korea. Almost standards and construction manner were apt to be internationalized after WTO/TBT agreement was concluded. The internal grounding systems should meet the international criteria and reliability for safety, and be provided with technologically impeccable standards.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.3
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• pp.331-337
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• 2014

The Korean distribution system consists of overhead ground wire (OHGW), phase conductors and neutral wire. Especially, OHGW is installed over the phase conductors to protect distribution system from the lightning surge. The flashover rate and the magnitude of lightning overvoltage on distribution system can be affected by grounding condition of OHGW such as grounding resistance and grounding interval. In this paper, we conduct an analysis of lightning overvoltage and flashover rate according to the grounding condition of OHGW. The distribution system and lightning surge are modeled by using ElectroMagnetic Transient Program (EMTP). Also, the Monte Carlo method is applied to consider random characteristics of lightning, and the flashover rate is calculated based on IEEE std. 1410. The simulations are performed by changing the grounding resistance and interval of OHGW and the simulation results are analyzed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.3
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• pp.57-65
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• 2005

No matter how well the equally spaced grounding grid is designed, there we questions keep rising, such as leakage of current from comer conductor, high voltage of touch voltage in comers of grid than in center, and high material cost for grounding grid. The best-fitted design for unequally spaced grounding grid is a part that must be considered. Explain advantages of unequally spaced grounding grid and lead formula by dividing the number of grid division, j, into 20, instead of 7. Then, present Dij, which is optimum rate for unequally spaced grounding grid and verify safety and economy of the unequally spaced grounding grid by computer simulation with a poly-nominal function form.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.7
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• pp.41-48
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• 2009

Grounding impedance depends on the frequency of current flowing into a grounding system lightning in particular has a broad frequency spectrum from some tens of Hz to a few MHz. So the grounding impedance related to transient currents such as lightning should be measured. In this paper, the grounding impedances of vertically-driven ground rods of 10, 30 and 48[m] long are measured and analyzed as functions of the frequency of injected current and the feeding point. As a result, the longer the ground rod is, the lower the steady-state ground resistance is. However the grounding impedance of a vertically-driven ground rod at a high frequency is significantly increased. It is not always true that low grounding impedance follows from a low steady-state ground resistance. It is important to evaluate the high frequency performance of grounding systems for protection against lightning.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.108-114
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• 2011

In order to mitigate the possible hazards from electric shock due to the touch and step voltages, the high resistivity material such as gravel is often spread on the earth's surface in substations. When the grounding electrode is installed in two-layer soil structures, the surface layer soil resistivity is different with the resistivity of the soil contacted with the grounding electrodes. The design of large-sized grounding systems is fundamentally based on assuring safety from dangerous voltages within a grounding grid area. The performance of the grounding system is evaluated by tolerable touch and step voltages. Since the floor surface conditions near equipment to be grounded are changed after a grounding system has been constructed, it may be difficult to determine the tolerable touch and step voltage criteria. In this paper, to propose an accurate and convenient method for evaluating the protective performance of grounding systems, the propriety of the method for evaluating the current flowing through the human body around on a counterpoise buried in two-layer soils is presented. As a result, it is reasonable that the grounding system performance would be evaluated by measuring and analyzing the current flowing through the human body based on dangerous voltages such as the touch or step voltages and the contact resistance between the ground surface and feet.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2352-2354
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• 1999

The purpose of substation grounding system is to provide reference potential with power system and protect field workers from electrical shock resulted from unsymetrical power system faults. For this purpose, grounding grid should be designed to maintain max, touch voltage under safety criteria in fault conditions. It is difficult, however, to design a safe grounding grid at very resistive or narrow area. This paper describes an example of substation grounding grid design procedures in such areas with very severe design conditions. By using grounding conductors, which is located close to earth surface, earth surface potential could be controlled effectively, so that maximum touch voltages is to be maintained under safety criteria.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1738-1740
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• 2003

This paper deals with the characteristic analysis of multi-grounding system. In order to assess the effectiveness of bonding two grounding systems, the scale model grounding simulation system and grid grounding conductors which were downsized as a scale factor of 100:1 were designed and fabricated. A profile of GPR(Grounding Potential Rise) of each case was measured. Also the measured results were compared with the analysis results.