Abstract
In a recently published work, the characteristics of a new grounding device with spike rods (GDSR) with various arrangements of ground electrodes under high magnitude impulse currents (up to 16 kA), was investigated. In an earlier study, the ground electrodes were installed in low resistivity test media, with resistance at steady state (Rdc) values ranging from 11 Ω to 75 Ω. In practice, various soil resistivity, ranging from a few Ohm-metres to several kiloOhm-metres, have been reported in the standards. It is, therefore, necessary to investigate the characteristics of GDSR with different arrangements of ground electrodes in various soil resistivities under high impulse currents. In this present paper, six configurations of ground electrodes are used, installed at three different sites and subjected to high impulse conditions. Impulse test data of all the grounding systems are analyzed. The Finite Element Method (FEM) is used to compute the electric field values of the ground electrodes achieved. It is found that the highest electric field occurs in the presence of electrodes with the highest Rdc, soil resistivity and current magnitudes. This new data would be useful in bolstering the performance of GDSR in various types of soil resistivities, electrode arrangements and current magnitudes, which may allow for optimum design of grounding systems.
Highlights
There are two main parameters that affect the design of grounding systems; ground electrode configurations and soil resistivity
To provide a better analysis on the performance of these electrodes under high impulse currents and various factors, the results are presented in several sub-sections; time to peak current, time to discharge to the ground, and impulse resistance for various earth electrode configurations and soil resistivity
The effects of earth electrode configuration and soil resistivity on current rise time, time taken for current to discharge to ground and Zimpulse are investigated experimentally at field sites, using computational methods
Summary
There are two main parameters that affect the design of grounding systems; ground electrode configurations and soil resistivity. For the large grounding electrodes, 50 m × 52.5 m, and 0.8 m deep, Yang et al [12] reported a reduction in impulse grounding resistance with increasing currents for different response times and injection points All of these studies [5,6,7,8,9,10,11,12,13,14] showed that there are a few factors contributing to the impulse characteristics of grounding systems. This, in turn, can affect the ground potential rise (GPR), touch and step voltages This shows that it is important to include soil resistivity values correlating with impulse characteristics of grounding systems. Electric field distribution is computed using Finite Element Method (FEM) software for all the electrodes installed in different soil media
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