## 3 Experimental Setup and Results
### Measurement System
#### 3.1.5 Supervisory Application for PD Monitoring
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Source Position**} & \multicolumn{2}{c}{**True Location**} & \multicolumn{2}{c}{**Estimated Location**} & \multirow{2}{*}{**Error (m)**} & \multirow{2}{*}{**Optimum PLE \(\alpha\)**} \\ \cline{2-2} \cline{5-7}  & \(\mathbf{X\) **(m)**} & \(\mathbf{Y\) **(m)**} & \(\mathbf{X\) **(m)**} & & \(\mathbf{Y\) **(m)**} & \\ \hline Position 1 & 13.50 & 4.50 & 12.37 & 4.49 & 1.13 & 1.75 \\ Position 2 & 4.50 & 4.50 & 5.99 & 5.02 & 1.57 & 2.15 \\ Position 3 & 4.50 & 13.50 & 5.41 & 13.76 & 0.94 & 3.45 \\ Position 4 & 13.50 & 13.50 & 10.94 & 15.48 & 3.23 & 4.25 \\ Position 5 & 10.00 & 6.00 & 12.65 & 6.95 & 2.81 & 1.60 \\ Position 6 & 6.00 & 8.00 & 6.60 & 8.50 & 0.78 & 2.05 \\ Position 7 & 8.00 & 12.00 & 7.89 & 13.89 & 1.90 & 3.30 \\ Position 8 & 12.00 & 10.00 & 13.16 & 10.86 & 1.45 & 2.60 \\ Position 9 & 4.5.0 & \(-\)4.50 & 3.14 & \(-\)6.43 & 2.36 & 2.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: PD source location estimation with seven sensors used, proposed method. Figure 9: Position 1 result of the estimated source location with seven receiving nodes. Table 3 shows that results have improved significantly in terms of localization accuracy and PLE optimizations. For all nine positions, the PLE values are from 1.55 to 3.35, with the majority between 2 to 3. The localization error for six position is less than two meters. For three positions it is between 2 to 3 m. This is an indication of how scalability can enhance the localization accuracy. The localization accuracy also means that PLE values are much closer to the average value of the free space propagation environment, i.e., 2 in this case. For position 1 the results are shown in Figure 10.  
For both field scenarios, the mean estimated error for the proposed algorithm can be summarized in Table 4 below:  
Table 4 shows that mean error was reduced from 1.80 m to 1.76 m, i.e., 0.04 m better localization accuracy with the addition of a single node. This implies that RSS based localization is a technique with better properties in PD localization due to its capability to offer scalability at any given time without any modifications in the overall system configuration except the addition of a receiving node. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **With 7 Sensors** & **With 8 Sensors** \\ \hline Mean Error (m) & 1.80 & 1.76 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mean error comparison for different arrangements of sensors. Figure 10: Position 1 result of the estimated source location with eight receiving nodes. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**True Location**} & \multicolumn{2}{c}{**Estimated Location**} & \multirow{2}{*}{**Error (m)**} & \multirow{2}{*}{**Optimum PLE \(\alpha\)**} \\ \cline{2-2}
**Source Position** & & & & & & \\ \cline{2-2}
**Position 1** & 13.50 & 4.50 & 12.44 & 4.45 & 1.06 & 1.75 \\ Position 2 & 4.50 & 4.50 & 5.73 & 5.22 & 1.43 & 2.20 \\ Position 3 & 4.50 & 13.50 & 4.12 & 14.72 & 1.28 & 2.80 \\ Position 4 & 13.50 & 13.50 & 11.35 & 15.24 & 2.77 & 3.55 \\ Position 5 & 10.00 & 6.00 & 12.58 & 7.20 & 2.85 & 1.55 \\ Position 6 & 6.00 & 8.00 & 5.63 & 9.68 & 1.72 & 2.50 \\ Position 7 & 8.00 & 12.00 & 8.95 & 13.86 & 2.08 & 2.95 \\ Position 8 & 12.00 & 10.00 & 13.18 & 10.83 & 1.44 & 2.70 \\ Position 9 & 4.5.0 & \(-\)4.50 & 3.97 & \(-\)5.63 & 1.24 & 2.85 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: PD source location estimation with eight sensors used, proposed method. Performance Evaluation of the Proposed Algorithm in Terms of Localization Error and PLE Optimization When Seven Measurement Sensors were Used  
The performance of the proposed algorithm was evaluated with ratio and search and least squares (LS) algorithms. All three algorithms use RSS for localization under an anonymous environment i.e., having no prior information of source transmitted power and path loss exponent.