## 4 Conclusions  
The experimental test results concerning small-grid ground electrodes installed in natural soil, EM-treated soil and EM-treated soil with added water contents of 10 L, 20 L, 50 L and 100 L, depicted as ground electrode (i) GEN, (ii) GEM and (iii) GEM_10L, GEM_20L, GEM_50L and GEM_100L, respectively, are presented in this paper. The soil resistivity profile showed a small change in its values when the measurements were carried out before any groundwork and after placing the EM and pouring the WC. This minimal change in the soil properties occurred only within the working area where the grid electrode was installed, whereas the soil resistivity profile was measured over a larger ground area. On the other hand, significant changes were seen in the \(R_{DC}\) values for the same ground electrodes installed in natural and EM-treated soil with added water content, with an increase of more than 40%. This indicates that EM may be an effective material in reducing \(R_{DC}\) values. When all the ground electrodes were subjected to high-impulse conditions, an appreciable difference was seen for ground electrodes (ii) and (iii), where the voltage and current traces swung to the opposite polarity or overshot. Conversely, this overshoot phenomenon was not seen in ground electrode (i). The magnitude of the overshoot was found to be higher in instances of lower \(R_{DC}\) and increased with increasing applied voltage/current magnitudes. The simulation work confirmed that the overshoot resulted from the inductive test load, which became significant in the ground electrodes with low \(R_{DC}\) values (electrodes (ii) GEM and (iii) GEM_10L, GEM_20L, GEM_50L and GEM_100L). The impulse impedance values for all the ground electrodes were measured and found to be independent of current magnitudes in the ground electrodes with low \(R_{DC}\) values (electrodes (ii) and (iii)); however, a slight dependency of impulse impedance on current magnitude was seen in ground electrode (i). The time to peak current was measured and found to be close for all the ground electrodes and was independent of current magnitude and impulse polarity for all the ground electrodes. The current discharged times were found to be independent of current magnitude for ground electrodes (ii) and (iii). Higher current discharged times were found for ground electrode (i) due to its high \(R_{DC}\) value. Current discharged times for ground electrode (i) were found to decrease with increasing current magnitude and were influenced by impulse polarity. The slower current discharged times observed in positive-impulse polarity compared to negative-impulse polarity in electrode (i) and their dependency on current magnitudes were thought to be due to the conduction mechanism governed by the ionisation process in soil, since this process, which causes non-linear behaviour in soil, is known to be affected by voltage/current magnitudes and impulse polarity. On the other hand, for the other electrodes ((ii) and (iii)), high conduction in the soil was observed. A steady flow of current in these ground electrodes resulted in closely matched current discharged times, independent of the current magnitudes and impulse polarity. An important observation in this study is the increased significance of the inductive effect under high-impulse conditions in ground electrodes with low \(R_{DC}\) values. Hence, in fulfilling the design requirement of grounding systems, which is to reduce the low \(R_{DC}\), it is important to consider the inductive effect, which can be significant when subjected to high-impulse conditions. Conceptualization, U.M., F.A. and N.M.N. ; methodology, U.M., F.A. and N.M.N. ; PSPICE Student 9.1 software, N.M.N. ; validation, U.M. and F.A. ; formal analysis, U.M., F.A. and N.M.N. ; investigation, U.M., F.A. and N.M.N. ; resources, N.M.N. ; data curation, U.M. ; writing--original draft preparation, U.M. and N.M.N. ; writing--review and editing, N.M.N.N. ; visualization, U.M. and N.M.N.N; supervision, N.M.N. ; project administration, N.M.N.