# Strategy Based on Two Stages for IR Thermographic Inspections of Photovoltaic Plants
## 3 Results  
IR thermographic inspection was done by centring the thermographic log on a time interval starting at noon and ending at 1.30 p.m. In this time range, the sun's position expressed by solar elevation/azimuth was at the start time: 30.18\({}^{\circ}\) N/\(-\)18.81\({}^{\circ}\) W; and at the end time: 32.42\({}^{\circ}\) N/\(-\)2.59\({}^{\circ}\) W. The results are presented by classifying them by the type of incidents or faults detected, showing aerial IR thermography and ground-level IR thermography. The analysis of results was done by considering this classification of standard incidents:  
1. Incidents with broken glass in PV module. 2. Incidents involving partial shading. 3. Incidents involving PV module technology. 4. Incidents with open-circuit PV modules. 5. Other incidents. 1. Incidents with broken glass in PV module  
Figure 5a depicts the aerial thermographic analysis of the PV module with a broken front cover (array 5, position E10), which reaches a temperature of 57.0 \({}^{\circ}\)C. The temperature difference with respect to the adjacent PV module is around 19 \({}^{\circ}\)C. Figure 5b shows the ground-level thermographic analysis for the same module. In this case, the maximum temperature of the PV module at position E10 is 86.6 \({}^{\circ}\)C. This abnormality is one-time and is obtained in the cell indicated in the analysis chart. The average temperature of this cell is 63.7 \({}^{\circ}\)C. The difference in the results obtained for maximum values is nearly 30 \({}^{\circ}\)C between both thermographs. This difference is due to the fact that the abnormality is a one-off with a size smaller than the cell, and thus, the aerial inspection distance provides a spatial resolution that is insufficient for this type of fault. Figure 6a depicts another PV module with a broken front cover (array 6, position AK11), which reaches a temperature of 66.0 \({}^{\circ}\)C. Figure 6b shows the ground-level thermographic analysis for the same PV module. The top temperature in the PV module with position AK11 is 89.6 \({}^{\circ}\)C and is reached in the indicated cell via an analysis chart as a one-off abnormality. The difference in the results obtained for maximum values is nearly 33 \({}^{\circ}\)C between both thermographs. Like in the previous case, this difference is due to the  
Figure 4: Coding system for identification of PV modules and cells. (**a**) Identification matrix of plant PV modules, and (**b**) the cells in each PV module from a front view. Figure 5: Thermographic analysis for an incident of broken glass: (**a**) aerial IR inspection, and (**b**) ground-level IR inspection. The red circle in (**a**) identifies the affected PV module. fact that the abnormality is a one-off with a size smaller than the cell, and thus, the aerial inspection distance provides a spatial resolution that is insufficient for this type of fault. 2. Incidents involving partial shading  
Figure 7a shows the thermographic analysis with incidents due to partial shading in cell AV6 in array 3. A maximum temperature of 68.6 \({}^{\circ}\)C was reached in this PV module. Figure 7b shows the ground-level thermographic analysis for the same PV module. The temperature in this PV module (location AV6) for the cell to the right attained values up to 111.8 \({}^{\circ}\)C and an average temperature of 88.6 \({}^{\circ}\)C. The cell on the left reached values of 108.4 \({}^{\circ}\)C and an average temperature of 85.9 \({}^{\circ}\)C. The temperature was not homogenous in either shaded cell. The high temperature value may be due to the fact that the vegetation has no appreciable separation over the module, so that the shading effect on the cells is fixed, without influence from the sun's position. The PV modules at cell positions AQ4 and AR4 (in array 2) in Figure 7a are hidden behind the vegetation, so that no overtemperature of these PV modules is observed due to obstruction by the object.