• Journal of the Society of Disaster Information
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• v.18 no.1
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• pp.19-28
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• 2022

Purpose: One of the methods for preventing disasters such as fire, explosion, and electric shock caused by electricity is to perform grounding. In case of the grounding current includes a frequency component having a high, it is preferable to measure grounding impedance rather than grounding resistance. This study proposes countermeasures to reduce grounding impedance to suppress an ground potential rise due to a grounding current having a frequency component of several kHz or more. Method: General grounding rods and needles-typed grounding rods were buried in the ground, and grounding resistance and grounding impedance were measured, respectively. The characteristics of grounding impedance according to frequency were identified. Result: There was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range lower than 62.5kHz, there was little difference in the measurement results of the grounding resistance between general grounding rods and needles-typed grounding rods. In a frequency range higher than 62.5kHz, the grounding impedance of needles-typed grounding rods was reduced by about 15% than the grounding impedance of general grounding rods. Conclusion: In the commercial frequency domain, it is effective to connect several grounding rods (common grounding) to lower the grounding resistance value. In the frequency domain of several kHz or more, it is expected that needles-typed grounding rods can effectively reduce the ground potential rise due to the grounding current.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.211-215
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• 2008

This paper deals with the transient ground impedance of small-sized needle-rod installed in a test field, Impulse voltage generator was used to inject lightning impulse on a ground electrode and modified fall-of potential method was proposed to measure the high ground potential rise. Transient ground impedance was analysed with impedance curve and I-V curve as respects the resistivity of soil. Soil ionization near the ground electrode is activated in high resistivity soil and have an effect on the reduction of transient ground impedance significantly.