# Explainable Artificial Intelligence Approach for Improving Head-Mounted Fault Display Systems
## 3 Results and Discussion
### Persistent Feature Selection  
To identify the impact of individual features, we conduct a correlation study between the 81 available features and the recorded problems as detailed in Section 2.3.3. Figure 12 presents a heat map illustrating the correlation between each feature (\(x\)-axis) and problems related to specific components (\(y\)-axis).  
The heat map reveals a high correlation between problems related to the generator bearing and the recorded temperature of the generator bearing. Consequently, for this example, all features that do not meet a minimum correlation threshold with our targets are omitted from the rest of the study to refine the findings.  
These initial insights indicate that certain variables are more influential than others. Highly correlated variables are directly related to the occurrence of errors, making the results intuitive and explainable. By applying an arbitrary threshold, we streamline the detection model, reducing the number of variables from 81 to 21 (Table 3).  
Figure 11: Detection and explanation of a rise in the transformer’s temperature.  
Figure 10: Detection and explanation of a significant rise in the generator bearings’ temperature.  
Figure 12: Correlations between each feature and instances of system malfunction. (**a**) For each component. (**b**) Zoom display with the generator bearing component.  
\begin{table}
\begin{tabular}{c c c c l} \hline \hline
**Feature ID** & **Component** & **Feature Descriptor** & **Unit** & **Feature Description** \\ \hline
01 & Generator & Gen\_RPM\_Max & [rpm] & Maximum generator rpm in latest average period \\
02 & Generator & Gen\_RPM\_Std & [rpm] & Std. generator rpm in latest average \\
03 & Generator & Gen\_Phase1\_Temp\_Avg & [°C] & Average temperature inside generator in stator windings \\  & & & & phase 1 \\
04 & Generator & Gen\_Phase3\_Temp\_Avg & [°C] & Average temperature inside generator in stator windings \\  & & & & phase 3 \\
05 & Generator & Hyd\_Oil\_Temp\_Avg & [°C] & Oil Average temperature in Humidification system \\
06 & Rotor & Rtr\_RPM\_Avg & [ rpm] & Average speed of the Rotor \\
07 & Production & Prod\_LatestAvg\_ActPwrGen0 & [WH] & Active power - generator disconnected (yaw motor \\  & & & hydraulic motor etc.) \\
08 & Production & Prod\_LatestAvg\_ActPwrGen1 & [WH] & Active power - generator connected in delta \\
09 & Production & Prod\_LatestAvg\_ActPwrGen2 & [Wh] & Active power - generator connected in star \\
10 & Transformer & HYTrafo\_Phase1\_Temp\_Avg & [°C] & Average temperature in HV transformer phase L1 \\
11 & Transformer & HVTrafo\_Phase2\_Temp\_Avg & [°C] & Average temperature in HV transformer phase L2 \\
12 & Grid & Grd\_InverterPhase1\_Temp\_Avg & [°C] & Average temperature measured by the IGBT-driver on the grid side inverter \\
13 & Spinner & Spin\_Temp\_Avg & [°C] & Average temperature in the nose cone \\
14 & Blades & Blds\_PitchAngle\_Min & [°C] & Average angle \\
15 & Controller & Cont\_VCP\_WrTemp\_Avg & [°C] & Average temperature on the VCP-board \\
16 & Grid & Grd\_Prod\_ReactPwr\_Max & [KVAr] & Maximum grid reactive power \\
17 & Grid & Grd\_Prod\_P\_P\_P\_Max & [KV] & Maximum possible grid active power \\
18 & Grid & Grd\_Prod\_P\_P\_P\_P\_heldel\_Max & [KVar] & Maximum possible inductive reactive power \\
19 & Grid & Grd\_Prod\_P\_P\_P\_P\_P\_heldel\_Max & [KVar] & Maximum possible capacitive reactive power \\
20 & Grid & Grd\_Prod\_CurPhse2\_Avg & [A] & Averaged current in phase 2 \\
21 & Grid & Grd\_Prod\_CurPhse3\_Avg & [A] & Averaged current in phase 3 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The 21 st top variables required for the test [11].