• 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 Electrical Engineering and Technology
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• v.4 no.1
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• pp.98-105
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• 2009

This paper presents the characteristics of soil ionization for different water contents, and the parameters associated with the dynamic properties of a simple model grounding system subject to lightning impulse currents. The laboratory experiments for this study were carried out based on factors affecting the soil resistivities. The soil resistivities are adjusted with water contents in the range from 2 to 8% by weight. A test cell with a spherical electrode buried in the middle of the hemispherical container was used. As a result, the electric field intensity $E_c$ initiating ionization is decreased with the reduction of soil resistivities. Also, as the water content increased, the pre-ionization resistance $R_1$ and the post-ionization resistance $R_2$ became lower with increasing current amplitude. The time-lag to ionization $t_1$ and the time-lag to the second current peak $t_2$ at high applied voltages were significantly shorter than those of low applied voltages. It was found that the soil ionization behaviors are highly dependent on the water content and the applied voltage amplitude.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.47-50
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• 2003

In order to verify the extended theory, we have fabricated a two layers cable with the same twisting layer pitch. It was observed that almost all the operational current less than the critical current flowed on the outer layer because of its lower inductance. In case of operational current more than critical currents of layers, the flux flow resistances affect strongly current waveform and thereby the currents of layers were determined by the flux flow resistances. And we investigated withstand voltage, impulse voltage and breakdown characteristics of mini-model cable. In these test, the withstand voltage and impulse voltage test was satisfied and the breakdown voltage was 110kV.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2296-2298
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• 1999

The stationary ground resistance and the transient ground impedance of grounding system are very important parameters in the field of lightning and surge protection. But, it is very difficult to obtain correct values of them in large-scale grounding system. In this paper, the stationary and transient ground impedances of a large-scale grounding system have been measured and analyzed under impulse currents. In order to obtain correct values of them, we have described Z-v(impedance vs ground potential rise) distributions and Z-t waveforms. The transient ground impedance of 36 [m] long three-parallel grounding piles have showed the inductive aspects and the hysterisis region under impulse currents.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1724-1726
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• 2001

This paper deals with the characteristics of the potential rises of down-conductor due to lightning surge currents. Direct lightning strikes can cause high impulse currents to the lightning protection system(LPS) of a building. These high impulse currents have the front time as short as 1[${\mu}s$]. In this case, the induced voltages caused in a closed circuit inside the building can be very high and cause damage or submit people to electric hazard. So, the LPS has to be designed to ensure safety condition to person and acceptable levels of induced voltages to the electrical and electronic equipments. The results of the potential rises related to the bonding conditions between the grounding conductor and metal raceway and the type of down-conductors are introduced.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.12
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• pp.87-94
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• 2008

This parer presents the soil ionization phenomena and parameters associated to characterize the transient performances of grounding system under lightning impulse Currents. Ionization properties in occurring some soil media were experimentally investigated. The cylindrical test cell was employed in order to facilitate the analysis of soil breakdown field intensity and ionized radius. The soil breakdown field intensity, dependence of impedance on the amplitude of impulse current, V-I curves and transient impedances were discussed based on the voltage and current oscillograms. It was found that the ionization process and dynamic behaviors were strongly dependent on the types of soil and two current peaks were not observed in highly water-saturated soils. The results presented in this paper will provide useful information on the improvement of transient performance of a grounding system subjected to lightning impulse Current considering the soil ionization.

• 전기의세계
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• v.24 no.1
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• pp.63-69
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• 1975

This study investigated the characteristics of fatigue breakdown caused by the impulse voltage of heat treated polyethylene cables through fault currents. This study attempted to obtain the badic data on the insulation design by the repeated load of impulse voltage wave zone (1*40.mu.s) on heat treated polyethylene cables. Besides this study also analysed the data involving their durability by means of the Weibull distribution. An analysis of the breakdown characteristics based upon the repeated load of impulse voltage has revealed that worn out deteriorative breakdown existed at a high voltage near the initial breakdown voltage, and that random breakdown was discovered at a voltage somewhat lower than the initial breakdown voltage. These phenomena were more remarkable especially in the case of the higher temperature treated cables.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.12
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• pp.1290-1295
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• 1991

The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/x10S0-6Ts - 5cm/x10S0-6Ts, electric field intensity of 2kv/cm, predischarge current of 1.2-1.6A, the charges injected into the air gap of 11-40x10S0-6TC for 400-887kV impulse voltages.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2235-2237
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• 2005

This paper presents the transient impedance behaviors of grounding systems to lightning impulse current. The potential rise and effective impulse ground impedance of the test grounding electrodes were measured as a function of the rise time of impulse currents and lengths of down conductor. The transient ground impedances strongly depend on the configuration and size of grounding electrodes, the impulse current shapes and lengths of down conductor, and the inductance of reduce of grounding electrode inductance is an important factor to improve the transient ground impedance.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.05a
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• pp.328-331
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• 2009

This paper presents the behaviors of transient and conventional grounding impedances of a 30m counterpoise according to the injection point of lightning impulse currents. As a result, the trend of the conventional grounding impedances measured as a function of risetime of impulse current is similar to the transient grounding impedance of counterpoise. The injection point of impulse current greatly influences on the transient grounding impedance characteristics of counterpoise. The transient grounding impedances strongly depend on the injection point and the rising time of impulse current and the soil characteristics.