## 3 Experimental Setup and Results
### Measurement System
#### 3.1.5 Supervisory Application for PD Monitoring  
Supervisory application for PD monitoring has three main parts, which include:  
* A data collection module
* A monitoring module
* A location algorithm  
The data collection module collects data by interacting with a wirelessHART unit and stores it into a database. The monitoring module is a database system that is based on Indusoft web studio. The full details are described in [36]. The location algorithm uses the received signal and estimates the location of the PD source. To obtain the measurements, eight measurement nodes have been used and arranged as shown in Figure 6. Each measurement sensor is an individual radiometer. The locations of the measurement sensors were kept the same and the location of the source was changed. The received signal was in millivolts (mV) that was converted into d\(Bm\). The average-step voltage signal was converted into d\(Bm\) as an input to the location algorithm. The signal was converted as below:  
\[\mathrm{d}Bm=20 log_{10}\left(U^{2}\right)+30 \tag{18}\]  
and is shown in Table 1 for each node and all positions. Table 1 shows the values in d\(Bm\) for each position of the source for each node. For each position, several measurements were performed and Table 1 shows the average of all measurements performed. From the measurements, it is clear that receiving nodes closer to the source have higher signal strength than the ones that are far from the source. For example, position \(1\)\((13.5,\ 4.5)\) has the closest nodes \(4\), \(5\), \(7\) and \(8\). All four nodes have the strongest received signal than other nodes in the receiving system. Nodes \(1\) and \(2\) that are farthest have the least strength of the received signal. PD source localization was performed by using two scenarios:  
* Scenario 1: PD source localization using seven sensors  
In Scenario 1, seven measurement sensors were used and PD source location was estimated for all nine positions. Table 2 shows the estimated location, error and path loss exponent. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Source Position** & **Node 1** & **Node 2** & **Node 3** & **Node 4** & **Node 5** & **Node 6** & **Node 7** & **Node 8** \\ \hline Position 1 & \(-12.49\) & \(-12.69\) & \(-12.32\) & \(-4.35\) & \(-4.56\) & \(-8.98\) & \(-3.58\) & \(-6.27\) \\ Position 2 & \(-13.10\) & \(-14.38\) & \(-  
Table 2 shows results for the estimated location as well as the optimum path loss exponent which is from 1.60 to 3.45 for the majority of the positions with an exception for position 4 where it is 4.25 m. The calculated error is reasonably low for the majority of the positions as well. For two positions it is less than one meter, for four positions it is between 1 to 2 m and for three positions it is more than 2 m. Estimated location for position 1 when seven measurement nodes were used is shown in Figure 9.  
\(\bullet\) Scenario 2: PD source localization by using eight sensors  
When eight measurement sensors were used, the estimated coordinates of the source, error calculations and optimum value of path loss exponent for each position are shown in Table 3.