## 2 Methodology
### Earthing Enhancing Compound (EC)  
The footing resistance has a linear relationship to soil resistivity. Soil resistivity is a fundamental parameter in the design of line earthing and is used to measure the fault current of the earth along a transmission line [38]. The effect of soil resistivity on earth impedance is generally greater compared with earthing electrode arrangements. It is an indicator of how much electric current is conducted, and it varies with soil type, moisture and temperature [39; 40; 41]. Previous studies showed that soil resistivity might be decreased  
Figure 4: Design A: Default design with counterpoise; (**a**) top view; (**b**) 3D view. Figure 5: Design B: Radial and ring electrodes; (**a**) top view; (**b**) 3D view. Figure 6: Design C: Diamond-style with counterpoise and vertical electrodes; (**a**) top view; (**b**) 3D view. by increasing the salt content, moisture and temperature of soil [41; 42; 43]. Therefore, implementing the EEC approach to substitute for an unsuitable soil content surrounding the electrodes is a simple method to reduce tower footing impedance. After several years of research and development, EEC brand A (later denoted as EEC) was developed and has been used very effectively in many locations around the world. The EEC is referred to as an ultra-conductive material containing a soil resistivity reducing agent that provides extremely minimal resistance to the flow of electrical conductivity and thus significantly improves the efficiency of the earthing. EEC is made of environmentally friendly, robust components and contains no heavy metals nor other harmful materials [44]. In this part of our study, the test was conducted according to the manufacturer's instructions, and the physical properties of EEC with prepared specimens were as in normal use, as shown in Table 3[44]. Subsequently, the modelling of EEC in CDEGS was developed by adding a coating to the surrounding electrode. The thickness of the EEC is one of the variables that influence the electrode resistance, and all parameters used in this study were based on the actual earthing system arrangement and the properties of EEC. Figure 7 illustrates a cross-sectional view of the EEC that was modelled by the CDEGS software. There are three parameters required in for modelling: the borehole radius, R borehole; the earth electrode radius, Relectrode; and the thickness of the outer electrode, which represents the thickness of the EEC surrounding the electrode. It can be calculated by the following equation:  
\[\text{R}_{\text{borehole}}-\text{R}_{\text{electrode}}=\text{EEC thickness}\]  
Table 3 indicates the soil resistivity parameter of the EEC, which was 0.6 \(\Omega\cdot\)m, and the thickness of the coating was 0.116698 m, as depicted in Table 4, and this was defined by selecting \"Define | Coating types\" on the characteristic menu in CDEGS. Table 4 shows also the details of EEC and its thickness required to fill a borehole. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Unit** & **Values** \\ \hline Visual appearance & - & Dark tan (powdered) \\ \hline Dry bulk density (average) & g/cm\({}^{3}\) & 1.07 \\ at 47.7 N compaction force & g/cm\({}^{3}\) & 1.07 \\ \hline Resistivity (average) at 100\% moisture content, & & \\ EEC mixed with water & \(\Omega\cdot\)m & 0.6 \\ (1:1 ratio by volume) & & \\ \hline Wet bulk density (average) & g/cm\({}^{3}\) & 1.49 \\ at 1:1 ratio by volume & & \\ \hline Conductivity (average) at 100\% moisture & & \\ content, EEC mixed with water & S/m & 1.7 \\ (1:1 ratio by volume) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Physical properties of the EEC. Figure 7: Cross-sectional view of the EEC modelled in the CDEGS software. In practice, each bag of 25 kg of EEC was mixed with 15-20 L of water (depending upon the level of dryness of the site) so that it assumed a slurry form.