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Direct measurement of frequency domain impedance characteristics of grounding system

Although DC ground resistance is a good index of performance for a grounding system, it does not reflect the grounding performance during the transient states. Besides, impulse ground impedance, which is defined by a ratio of the peak value of transient ground potential rise to the peak value of impulse current, cannot be an absolute performance index due to its dependence on impulse current shape. In this paper, a ground impedance of mesh-type ground grid has been measured in the frequency range from 0.1 Hz to several hundred kHz. A transfer function of the ground grid is identified from the measured values of ground impedance in the frequency domain. An EMTP simulation has been performed to verify the usefulness of the transfer function of the ground grid.