# Design, Modeling, and Analysis of IEEE Std 80 Earth Grid Design Refinement Methods Using ETAP
## 5 Conclusions  
In this study, various substation earth grid design refinement methods adapted from the IEEE's standard IEEE Std 80-2013 Guide for Safety in AC Substation Grounding were modeled, simulated, and analyzed. The methods assessed included the current limiting method, the current diversion method, and the touch and step voltage increment method. From the studies, it was observed that each of these methods influenced the design parameters and performance of the substation earth grid. From the current limiting method, the use of neutral earth resistors was implemented, and the results show that the NERs significantly reduce the fault current being injected into the substation earth grid. As a result, the ground potential rise is reduced, which is a critical design element tested for earth grid compliance. The current diversion method proved effective when applied as it partially reduced the fault current injected into the earth grid. This was achieved by applying the separation factor in the simulation; in practice, however, it is computed by applying [PERSON]'s current law to obtain the current division factor between the substation earth grid resistance and the input impedance of each circuit (conductors or overhead lines) [15]. Lastly, the touch and step voltage increment method was implemented by varying the fault current clearance time. The simulation results show that reducing the fault clearance time greatly increases the tolerable limits of the touch and step voltages. This method could be suited for all power systems with reliable high-speed protection relays. Additionally, using the results of the refined earth grid designs, optimal design analyses were conducted for all the methods. The simulation results show that, out of all the methods applied, the current limiting method was the most effective and easy-to-apply method. By limiting the fault current, all the other design parameters are greatly impacted \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{5}{c}{**Optimized Earth Grids Based on Refinement Methods**} \\ \hline
**Refinement Method** & **Group Potential Rise (V)** & **Touch Voltage (V)** & \multicolumn{2}{c}{**Step Voltage (V)**} \\ \hline  & & **Calculated** & **Tolerable** & **Calculated** & **Tolerable** \\ \hline Current Division & 4841.4 & 1131 & 1144.3 & 312.8 & 4026.9 \\ Fault Duration & 7784.1 & 1313 & 1321.3 & 518 & 4649.9 \\ Current Limitation & 153.9 & 47.9 & 1144.3 & 9.9 & 4026.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Comparison of optimized earth grids based on the refinement methods and their impact on the safety limits. as the earth grid becomes capable of complying with both the design criteria as set out in IEEE Std 80, with far fewer earth grid conductors and electrodes in size and quantity, and the required surface area for the earth grid. As a result, this would greatly reduce the procurement and construction costs associated with the design and application of substation earth grids. This study, therefore, concludes that, when designing a substation earth grid with limited design options, it is essential to first assess which of the design refinement methods would be applicable for that specific case. As a starting point, the current limiting method and the touch and step voltage increment methods are the best options to be explored first. Conceptualization, V.M.N.D. ; methodology, V.M.N.D. ; software, V.M.N.D. ; validation, V.M.N.D., A.F.N., and R.P.T. ; formal analysis, V.M.N.D. ; investigation, V.M.N.D. ; resources, V.M.N.D. and A.F.N. ; data curation, V.M.N.D. ; writing--original draft preparation, V.M.N.D. ; writing--review and editing, A.F.N. and R.P.T. ; visualization, V.M.N.D. ; supervision, A.F.N. and R.P.T. ; project administration, V.M.N.D. ; funding acquisition, V.M.N.D. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. The ETAP model and detailed results obtained from the simulations are readily available upon request.