# Explainable Artificial Intelligence Approach for Improving Head-Mounted Fault Display Systems
## 3 Results and Discussion
### Fault Diagnosis  
The service record document failures highlight five critical electrical and mechanical components--namely, the gearbox, generator, generator bearing, transformer, and hydraulic unit. These failures occurred on various dates across multiple wind turbines. Additionally, the study incorporates reports detailing 22 errors in various turbine parts, including transformers, generators, and hydraulic groups. The failure observed for the turbine number 7 is detailed in Table 2.  
In what follows, we propose to discuss the relationships between the identified anomalies and reported faults to identify and locate faults. In Figure 8, the first reported error is marked with a vertical dashed line, and anomalies detected in each principal component are represented by dots using our approach. Before the error on 30 April 2016, multiple anomalies in the nacelle direction were detected, indicating a failure in regulating the turbine direction according to the wind. This could be due to natural wind direction irregularities in an offshore context or a mismatch in the regulation latency with wind direction variations, leading to asymmetrical stress on the blades and increased generator bearing temperature. \begin{table}
\begin{tabular}{c c c c} \hline
**Turbine ID** & **Component** & **Timestamp** & **Remarks** \\ \hline \multirow{5}{*}{T07} & GENERATOR\_BEARING & 30 April 2016 T12:40:00 & High temperature in generator bearing (replaced sensor) \\  & TRANSFORMER & 10 July 2016 T03:46:00 & High-temperature transformer \\  & TRANSFORMER & 23 August 2016 T02:21:00 & High-temperature transformer. \\  & HYDRAULIC\_GROUP & 17 June 2017 T11:35:00 & Off leakage in hub \\  & GENERATOR\_BEARING & 20 August 2017 T06:08:00 & Generator bearings damaged \\  & GENERATOR & 21 August 2017 T14:47:00 & Generator damaged \\ \hline \end{tabular}
\end{table} 
Table 2: Example maintenance records for turbine number 07. Figure 8: Detected anomalies before the first reported malfunction of the turbine T07 (generator bearing). Figure 9 shows the system issuing alerts for wind turbine components before detecting an oil leakage in the hub on 12 March 2019 (marked by a vertical dashed line). The hub, central to the rotor with attached blades, experienced oil leakage, suggesting a potential issue with the hydraulic system that uses oil to transmit power and pressure to actuators. An oil leakage can impair the hydraulic system's functionality and efficiency, causing damage to the components. Before the leakage, the system detected an anomaly in the hydraulic oil temperature, represented by blue dots on the graph. Maintaining optimal oil temperature is crucial for performance and viscosity. Deviations can affect fluid flow and pressure, leading to issues like cavitation, corrosion, and wear, potentially contributing to oil leakage. Additionally, alerts were issued for the generator SlipRing temperature, shown in red on the graph. The SlipRing enables electrical power and signal transmission between the rotating and stationary parts of the generator. Elevated SlipRing temperatures may indicate malfunctions or poor contact, leading to sparks, arcs, electrical noise, and generator damage. Such damage can affect oil quality and viscosity, potentially contributing to oil leakage from the generator [39]. Each parameter can be analyzed and compared to see which deviates the most according to the investigated anomaly (cf. Section 2.3.4). Two scenarios are considered in Figures 10 and 11. In Figure 10, the system alerted operators to a significant rise in the generator bearings' temperature. Conversely, Figure 11 shows a significant deviation in three wind turbine components: the transformer, generator bearings, and ambient temperature. Initially considered a warning anomaly, this could escalate to a critical anomaly if the deviations persist, according to Equation (13). Figure 9: Detected anomalies before the third reported malfunction of the turbine T07 (hydraulic group).