# Design, Modeling, and Analysis of IEEE Std 80 Earth Grid Design Refinement Methods Using ETAP
## 2 Literature Review
### Increasing the Tolerable Safety Limits of Touch and Step Voltage
#### 2.2.2 Surface Material Usage  
In addition to the fault clearance time, the surface material used has a significant impact on the tolerable limits of touch and step voltage. A study conducted by [PERSON] et al. [14] showed that, by varying the types of surface materials, the performance of the  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Method** & \multicolumn{2}{c}{**Advantages**} & \multicolumn{2}{c}{**Disadvantages**} \\ \hline Solid & \(\bullet\) & Low overvoltage occurrence risk & \(\bullet\) & The power system must trip on the occurrence of the first fault \\  & \(\bullet\) & The usage of equipment with normal & \(\bullet\) & It results in extremely high fault currents \\  & & phase-earth insulation levels & \(\bullet\) & High risk of exposing personnel to dangerous touch voltages \\  & & & phase-earth insulation levels & \(\bullet\) & It requires additional reliable time coordination protection to \\  & & \(\bullet\) & Significantly reduces fault currents & clear the fault as quickly as possible \\  & & \(\bullet\) & Dampens elevated voltage levels & \\ Resistive & \(\bullet\) & Allows for functionality of protection devices & \(\bullet\) & It trips on the first fault \\  & & without any requirements & \\  & & \(\bullet\) & Requires less maintenance & \\  & & \(\bullet\) & Limits fault currents & \(\bullet\) & Protection devices require a higher operating fault current \\ Reactance & \(\bullet\) & Arching grounds are avoided & \(\bullet\) & Compared to resistive \\  & & \(\bullet\) & Does not dissipate high levels of heat & \(\bullet\) & It trips on the first fault \\  & & \(\bullet\) & Does not dissipate high levels of heat & \(\bullet\) & May cause elevated voltage levels under fault conditions \\  & & \(\bullet\) & Provides continuous power; it only trips on the & \(\bullet\) & High risk of elevated voltages; requires reinforcement of \\ High-impedance & & second fault (provided that the fault level & \(\bullet\) & Equipment insulation \\  & & would not endanger personnel and equipment) & \(\bullet\) & It requires insulation monitoring \\  & & & would not endanger personnel and equipment & \(\bullet\) & It is difficult to implement protection schemes after the \\  & & & occurrence of the first fault \\ \hline \hline \end{tabular}
\end{table}
Table 1: Advantages and disadvantages of each method and how they compare against each other.  
safety limits of touch voltage and step voltage in an earth grid is greatly affected. The study showed that, by using crusher-run granite stones, the touch and step voltage are relatively low compared to when other available surface materials are used. The study further showed that, by varying the depth at which the surface material is buried, the safety limits are also affected, the deeper the applied surface material is buried, the higher the magnitude of the safety limits, and, vice versa, the shallow the applied surface material is buried, the lower the magnitude of the safety limits; however, care must be taken to ensure that they are adequately and solidly laid below the surface without the risk of being washed off by heavy rains or the movement of heavy machinery [14].