# Strategy Based on Two Stages for IR Thermographic Inspections of Photovoltaic Plants
## 5 Conclusions  
Aerial IR thermographic inspection of operational PV plants is a powerful and versatile tool for detecting abnormalities that affects its operation. Its application to large PV plants entails a significant saving of time and cost compared to ground-level IR thermographic inspection. However, some incidents may not be observed or may be misinterpreted when the inspection is done in the air. One-off thermal abnormalities of sizes smaller than the cell are determined with greater resolution and precision when the thermographic inspection is at ground level. Further, the problem of obstacles such as vegetation or a perimeter fence can be avoided with ground-level inspections. The existence of solar heat reflections can also be captured more easily from the air.  
Applying a two-stage thermographic inspection improves maintenance if the advantages of both techniques are employed. Stage one with aerial IR thermographic inspection will detect incidents and faults, as well as their locations, quickly and reliably. Additionally, stage two with ground-level IR thermographic inspection, applied only to relevant incidents from the previous stage, assures greater precision and resolution in the results. This two-stage thermographic inspection strategy will improve the diagnosis conducted.  
The integration of the proposed approach in the flight planning of automatic detection systems can have a significant advantage in the maintenance of large PV plants and in the reduction of the corresponding execution time. This innovative approach may be the subject of future research.  
Conceptualisation, [PERSON] and [PERSON]; methodology, [PERSON] and [PERSON]; validation, [PERSON]-T. and [PERSON]; formal analysis, [PERSON]; investigation, [PERSON] and [PERSON]; data curation, [PERSON] and [PERSON]; writing--original draft preparation, [PERSON]-T.; writing--review and editing, [PERSON]-T. and [PERSON]; visualisation, [PERSON]-T. and [PERSON]; supervision, [PERSON] and [PERSON]; project administration, [PERSON]-T. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Incident Type** & **Affected** & **Temperature Value** & **Irradiance Value** & \multicolumn{2}{c}{**Temperature Value**} & \\
**PV Modules** & **(°C)** & **(W/m\({}^{2}\))** & **Extrapolated at** & **Comment** \\ \hline  & AF6 & 55.6 & 890 & 61.2 & Required \\ Broken cover & E10 & 86.6 & 922 & 94.6 & replacement of \\  & AK11 & 89.6 & 940 & 97.9 & PV modules \\ \hline  & AL12 & 60.2 & 921 & 66.2 & Post \\  & AV6 & 111.8 & 941 & 118.5 & Vegetation \\ Partial shade & AQ4 & 49.6 & 941 & 54.6 & Vegetation \\  & AK4 & 49.6 & 941 & 54.6 & Vegetation \\  & AC12 & 77.5 & 945 & 85.3 & Post \\  & Several array 6 & - & - & - & Post \\ \hline PV module & All m-Si type & 63.5 & 944 & 69.9 & Measurement of \\ technology & PV modules & & & & max. temperature \\ \hline Open circuit & String in & 2 to 7 °C for & & 2 to 7 °C for & Electrical \\  & arrays 1, 4 and 5 & operational & & operational & verification required \\  & & PV modules & & PV modules & & \\ \hline Open-circuit & Many p-Si type & 2 to 7 °C for & & 2 to 7 °C for & Electrical \\  & & PV modules & adjacent substring & - & adjacent substring & verification required \\ \hline \hline \end{tabular}
\end{table}
Table 1: Summary of incidents detected during inspection.