• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1861-1868
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• 2009

A ground electrode subjected to lightning surge current shows the transient impedance behaviors. The ground electrode for protection against lightning should be evaluated in view of the transient grounding impedance and conventional grounding impedance, not ground resistance. The transient impedance characteristics of ground electrodes are influenced by the shape of ground electrode and the soil characteristics, as well as the waveform of lightning surge current. In order to propose a simulation method of analyzing the transient impedance characteristics of the grounding system in practical use, this paper suggests a theoretical analysis method of distributed parameter circuit model to simulate the transient impedance characteristics of counterpoise subjected to lightning surge current. EMTP and Matlab programs were employed to compute the transient grounding impedances of three counterpoises with different lengths. As a consequence, the simulated results using the proposed distributed parameter circuit model are in good agreement with the measured results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.352-355
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• 2009

The ground resistance has been used as a method of estimating the capability of counterpoise. When transient currents blow through a ground electrode, it is reasonable to evaluate the performance of ground electrode system as a ground impedance instead of ground resistance. However, the measurement method of ground impedance for counterpoise is not clearly presented. This paper describes the measurement method of ground impedance considering the earth mutual resistances and AC mutual coupling. When we measure the ground impedance, the error due to earth mutual resistances depends on the distance between the auxiliary electrodes and the electrode under test. The measurement accuracy of high frequency ground impedance is mainly influenced by the location of the current electrode and the potential electrode.

• 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.27 no.2
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• pp.54-61
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• 2013

This paper presents transient response behavior and frequency-dependent ground impedance of a single carbon ground electrode. The ground impedance of the carbon ground electrode was measured as a function of frequency of injected currents and simulated by using the distributed parameter circuit model with due regard to the frequency-dependent soil parameters, and the transient response behavior of the carbon ground electrode against impulse currents were investigated. As a consequence, the frequency-dependent ground impedance of the carbon ground electrode showed the capacitive behavior, that is, the ground impedance decreases with increasing the frequency of injected currents and lowers at the fast front time of impulse current. It was found that the carbon ground electrode is effective in grounding system for lightning protection. The ground impedance simulated with due regard to the frequency-dependent soil parameters was in good agreement with the measured data. The adequacy of the simulation technique and the distributed parameter circuit model for the carbon ground electrode was verified. It is expected that the simulation methodology, which analyzes the frequency-dependent ground impedance of the carbon ground electrode proposed in this work, can be used in the design of a grounding system for protection against lightning.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.253-257
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• 2004

In order to analyze the frequency dependance of ground impedance in grounding grids for lightning and surge protection, a novel method for measuring the ground impedance as a function of frequency were experimentally investigated. The experiments were carried out in rectangular grounding grids with $6{\times}8$ conductors of 22 $mm^2$ buried at a depth of 0.5 m. The test current was injected by the variable frequency inverter whose frequency is linearly controlled for the established period in the range of 5∼500 KHz. The amplitude and phase of ground impedance were calculated from the waveforms of the test current and ground potential rise measured by the band-pass filter tuned in a specific frequency. The frequency dependence of ground impedance was mainly caused by the inductive current flowing through grounding conductors over the frequency of 100 KHz. The proposed measurement method of ground impedance would be applicable to evaluate the transient response characteristics in lightning protection grounding systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1223-1228
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• 2008

While a high frequency source is used for measuring the ground impedance, there are several factors having an effect on the measured value. A primary factor of the measurement error is the ac mutual coupling between current and potential test leads. The mutual coupling causes the test current to induce a voltage into the potential test lead that adds to the actual ground potential rise and produces a significant measurement error as the length of the test leads paralleled is prolonged. In order to avoid the mutual coupling, it is recommended that the ground impedance be measured by angled arrangement of test leads. The mutual impedance due to the inductive coupling with an angle of $90^{\circ}$ was calculated at $0^{\circ}$ by Campbell/Foster Method. With an angle of $180^{\circ}$, the mutual impedance was calculated large value enough to introduce a fairly large margin of error, however, the measured value of ground impedance was close to the value at $90^{\circ}$.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.47-52
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• 2016

This paper describes the design and fabrication of high frequency ground impedance measuring system for assessment of grounding system for Lightning protection. The ground impedance measuring system has been designed and fabricated which makes it possible to assess the ground impedance by frequency ranges from 100 Hz to 1 MHz. The effective grounding systems having a very low impedance to electromagnetic disturbance such as lightning surges and noises in microelectronics and high-technology branches are strongly required. In order to analyze the dynamic characteristic of grounding system impedances in lightning and surge protection grounding systems, it is highly desirable to assess the ground impedances as a measure of performance of grounding system in which lightning and switching surge currents with fast rise time and high frequency flow. The measuring system is based on the variable frequency power supply and consists of signal circuit part, main control part, data acquisition and processing unit, and voltage and current probe system. The ground impedance measuring system can be used to assess grounding system during occurrence of lightning.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.4
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• pp.62-69
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• 2014

This paper deals with the fundamental characteristics of transient and conventional ground impedances associated with soil discharges when the lightning impulse voltage was applied to a small-sized ground rod. The potential rise responses of the test ground rod to impulse currents were observed. The current-voltage (I-V)curves, transient and conventional ground impedance curves were examined.. To analyze the transient behaviors of ground rod attendant upon soil discharges, the impulse responses of ground rod were compared with those of non-inductive resistor. As a consequence, the potential rise and impedance of ground rod were reduced and the currents dispersed into the earth were increased due to soil discharges near the ground rod. Soil discharges are classified into two regimes; ionization and breakdown phenomena. The potential rise and impulse impedance of ground rod are significantly decreased by breakdown processes in soil.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1489_1490
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• 2009

Ground impedance is changed according to frequency of the current injected into the grounding system. Because the lightning surge gives a broad frequency spectrum from some ten Hz to a few MHz, frequency dependance of ground impedance must be evaluated. In this paper, we have constructed 10m, 30m, 50m counterpoise and evaluated frequency dependance of ground impedance. Also we have evaluated frequency dependance of ground impedance according to current injection point. As a result, long counterpoises have low ground resistance, but ground impedances of those are significantly increased in the range of high frequency. In the case that currents are injected into the center of counterpoise, the ground impedance is most lower than any other injection point. Also, additory ground rod of 1.8m long affect ground impedance decrease.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.227-230
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• 2007

In this paper, we have analyzed the change characteristics of induced noise due to the impedance change of the ground in both ends of telecommunication line. As what affects the induced noise, there are power influence or longitudinal transverse voltages and its weighted filtered voltage. In the result of measurement, we can see the noise level change due to the change of the ground impedance, that is, as the ground impedance at either end of the telecommunication line become grower, the noise level is increased, and as the ground impedance at either end of the telecommunication line become smaller, the noise level is decreased. However, we can't define the relation between ground impedance size and PIF in these measurement results, so we will have to carry out the measurement more deeply and more practically with various conditions in environmental viewpoint and/or experimental viewpoint to establish the definition between ground impedance size and PIF.