Transient Behavior of Common Grounding Grids to Artificially Triggered Lightning

Electrical potential and distributed current of a specifically arranged remote common grounding grid subjected to triggered lightning currents were measured and analyzed. Although the measured waveforms of potential and distributed current were different, the peak of this potential displayed a linear relationship with the injected lightning currents. In the M-component process, waveforms of the measured potential and distributed current were similar to the injected current, but the common grounding grid potential may increase to as high as more than 5 kV. In the return-stroke process, the grounding potential had an average peak of 40 kV and a wider half-peak width compared to the injected current, which frequently damaged the surge protective devices connected to the grounding grids. The distributed current was found to be at an average low level of several kiloamperes in both processes. The ratio of distributed current to the injected current is proportional to the injected current. Moreover, the attenuation in amplitudes of distributed current is faster compared to the energy dissipation; the latter was primarily due to the widened half-peak width. It, thus, indicates the equal risks of both high peak and long duration of the surge currents in terms of the lightning protection.

I. Introduction

The common grounding grids, containing horizontal and vertical metal conductors, are widely used in electrical engineering applications by providing a low-impedance path for abnormal currents due to surge from such as lightning or power faults. In the meantime, such grids may also produce a high grounding potential rise (GPR) during the release of impulse currents, especially those with high frequency, amplitude, and gradient as lightning currents. The high GPR can cause damages to sensitive systems connected to the grounding systems.