• 조명전기설비학회논문지
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• 제25권5호
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• pp.54-60
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• 2011

This paper presents characteristics of frequency-dependent grounding impedance and transient grounding impedance for the carbon compound grounding electrode used in the installation of computerized electronic equipment and lightning protection system. The frequency-dependent grounding impedances were measured by applying sinusoidal currents in the frequency range from 100 [Hz] to 10[MHz], and the transient grounding impedances were examined by subjecting the impulse current with the front-time between 1~80[${\mu}s$]. As a result, the ground resistance of the carbon compound grounding electrode is less than that of another type grounding electrodes. The transient grounding impedance is relatively low and the conventional grounding impedance is rather lower than the ground resistance. The frequency-dependent grounding impedance of the carbon compound grounding electrode is capacitive and the grounding impedance is decreased with increasing the frequency of injected currents. Therefore in the case that the carbon compound grounding electrode is jointly used with large-scaled grounding electrodes, it is possible to reduce the high frequency grounding impedance of the integrated grounding electrode system.

• 전기학회논문지
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• 제59권6호
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• pp.1103-1108
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• 2010

A grounding electrode has the transient grounding impedance characteristics against lightning surges. So the performance of grounding electrodes should be evaluated as a grounding impedance as well as the ground resistance. The frequency-dependent grounding impedance is varied with the shape and size of grounding electrode and is divided into both inductive and capacitive behaviors. This paper presents a theoretical analysis for the grounding impedance determined by the size of grounding electrode using the distributed parameter circuit model. EMTP and Matlab programs were used in calculating the frequency-dependent grounding impedances of vertical grounding electrodes. It was found that the frequency-dependent grounding characteristics of vertical grounding electrodes are characterized by the distributed parameters which are changed in the dimension of grounding electrodes.

• 한국재난정보학회 논문집
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• 제18권1호
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• pp.19-28
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• 2022

연구목적: 전기로 인한 화재·폭발·감전 등의 재해를 예방하기 위한 방법 중의 하나가 접지를 시행하는 것이다. 접지전류가 높은 주파수 성분을 포함하는 경우에는 접지저항보다는 접지임피던스를 측정하는 것이 바람직하다. 본 연구에서는 수 kHz 이상의 주파수 성분을 가지는 접지전류에 의한 대지전위상승을 억제하기 위한 접지임피던스를 줄이는 방안을 제시하고자 한다. 연구방법: 대지에 접지동봉과 접지침봉을 매설하여 각각 접지저항과 접지임피던스를 측정하였고, 주파수에 따른 접지임피던스의 특성을 파악하였다. 연구결과: 접지동봉과 접지침봉의 접지저항 측정 결과는 거의 차이가 없었다. 62.5kHz 보다 낮은 주파수 영역에서는 접지동봉이나 접지침봉의 접지임피던스 측정 결과는 거의 차이가 없었으며, 62.5kHz 보다 높은 주파수 영역에서는 접지침봉의 접지임피던스가 접지동봉의 접지임피던스보다 약 15% 정도의 저감효과가 있었다. 결론: 상용주파수 영역에서 접지저항 값을 낮추기 위하여 다수의 접지극을 공통으로 접지하는 것이 효과적이고, 접지임피던스가 낮은 접지침봉을 설치하는 경우 수 kHz 이상의 주파수 성분을 가지는 접지전류에 의한 대지전위상승을 효과적으로 억제할 수 있을 것으로 보인다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권5호
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• pp.224-226
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• 2005

In this paper, the secular changes of buried grounding electrodes was investigated; the electrodes are such facilities as grounding grid, grounding connector, grounding terminal and grounding rod etc.. The corrosiveness of removed substation grounding electrodes after commercial operation more than 50 years was measured and its conductivity deterioration trend was analyzed. The measuring results using three experimental methods were compared, finally the consideration for safe and economic grounding design were shown. As the result, it shows the maintenance necessity of grounding systems.

• 조명전기설비학회논문지
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• 제25권6호
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• pp.100-107
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• 2011

Since transmission and distribution neutral wires are connected with a substation grounding grid, it is very difficult to measure grounding resistance of isolated substation grounding grid after the substation is energized. It is impractical to isolate the grounding grid from other parallel connections such as distribution line neutrals and overhead ground wires for grounding resistance measurement only. In this paper, we proposed and demonstrated a novel measurement method of grounding resistance of isolated substation grounding grid. For this method, grounding current division factor and conventional FOP(Fall-Of-Potential) profiles were measured at power supplying 154[kV] substation. The obtained FOP profile was processed with the measured grounding current division factor to produce the grounding resistance of isolated grounding grid. Simulated FOP profile agreed well with the measured one showing the validity of the proposed method.

• 대한전기학회논문지:전력기술부문A
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• 제49권6호
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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.

• 조명전기설비학회논문지
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• 제25권6호
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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.

• International Journal of Safety
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• 제9권2호
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• pp.1-5
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• 2010

In order to analyze the potential rise of ground surface of grounding grid installed in buildings, the grounding simulator has been designed and fabricated as substantial and economical measures. This paper describes the study of touch and step voltages with grounding grid where earth leakage current is injected. To assess risk voltage of grounding grid, the grounding simulator and CDEGS program were used to obtain measured data and theoretical results of this study. The grounding simulator was composed of an electrolytic tank, AC power supply, a movable potentiometer, and test grounding electrodes. The potential rise was measured by grounding simulator, and the touch and step voltages were computed by CDEGS program. As a consequence, the touch voltage and step voltage above the grounding grid were very low, but were significantly increased near the edge of grounding grid.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.94-100
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• 2010

접지시스템은 전기설비의 기준 전위점을 확보할뿐만 아니라 낮은 대지저항으로 고장전류나 과도 전류를 흐르게 한다. 접지임피던스는 주파수에 대한 함수로 고장이나 과도전류가 넓은 범위의 주파수 성분을 포함하기 때문에 접지성능을 평가하는데 중요한 역할을 한다. 본 논문에서는 스테인리스강판 접지전극의 접지특성을 파악하기 위하여 3점 전위강하법으로 접지저항, 접지임피던스와 과도접지임피던스를 측정하였다. 측정된 데이터를 이용하여 접지임피던스와 과도접지임피던스의 등가 전달함수 모델은 ARMA 기법으로 모델링 되었고, 규약접지임피던스로 비교하여 평가하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권11호
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• pp.717-723
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• 1999

The transient characteristics of grounding systems play a major role in the protection of power equipments, electronic circuits and info-communication facilities against surges which arise from lightning or ground faults. Electronic devices are very weak against lightning surges injected from grounding systems and can be damaged. The malfunction and damage of electronic circuits bring about bad operation performances, a lot of economical losses, and etc. Therefore, in order to obtain the effective protection measure of electronic devices from overvoltages and lightning surges, the analysis of the transient grounding impedances in essential. One of this work is to examine the transient behaviors of grounding impedances under steplike currents for various grounding systems. And the other of this work is to evaluate the transient behaviors of a grid with rods under impulse currents and to investigate the effect of grounding lead wire. Transient grounding impedances of a grid with rods under impulse current waves have been measured as a parameter of the length of the grounding leads. Z-t, Z-i and V-i curves of transient grounding impedance under impulse current waveforms have been measured and analyzed. It was found that the grounding impedance gives the inductive, resistive and capacitive aspects under steplike current. Transient grounding impedance characteristics were very different with shapes, geometries of ground electrodes. Also, they were dependent on the waveform and magnitude of impulse current.