# Strategy Based on Two Stages for IR Thermographic Inspections of Photovoltaic Plants
## 3 Results
Figure 8 depicts the visual image and ground-level thermographic analysis with incidents in PV modules at positions AQ4 and AR4 (in array 2). The highest temperature in these modules at AQ4 and AR4, which are shaded by vegetation, is 49.6 \({}^{\circ}\)C. The top area with the diode case was not considered. The temperature difference compared to the previous case (module AV6) may be due to the separation from the vegetation that caused a moving shadow depending on the sun's position. Figure 6: 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. Figure 7: Thermographic analysis for an incident of partial shading: (**a**) aerial IR inspection, and (**b**) ground-level IR inspection. The red circles in (**a**) identify the affected PV modules. Figure 9a depicts the aerial thermographic analysis of the PV module at position AC12 (array 6), which reached a temperature of 63.7 \({}^{\circ}\)C. This overtemperature, or hotspot, was caused by the partial shading from metal fence posts on the perimeter and occurred in other PV modules in the bottom row of array 6 for the same reason. Figure 9b depicts the ground-level thermographic analysis with incidents in the PV module at position AC12 (array 6) that reaches a maximum temperature of 77.5 \({}^{\circ}\)C, where the average temperature of the hot cell is 56.2 \({}^{\circ}\)C. The difference in the maximum values obtained of nearly 15 \({}^{\circ}\)C between both thermographs may be due to the effect of concealment by the post. It could also be due to the fact that the shade moves with the movement of the sun so that the value changes over time. 3. Incidents involving PV module technology  
PV modules of type m-Si in array 1 reveal an irregular temperature pattern, reaching values of 53.5 \({}^{\circ}\)C, as shown in Figure 10a. This pattern is characteristic of a module in a short circuit according to IEC-62446-3. Remember that for the m-Si type module its \(\text{I}_{\text{sc}}=5.22\) A is less than \(\text{I}_{\text{mp}}=7.57\) A for the p-Si type module, so the series connection of both modules causes this situation. The heat pattern observed is characterised by a short circuit. The maximum temperature reached is 63.5 \({}^{\circ}\)C according to Figure 10b. In this case, the ground-level thermograph lets us see the irregular temperature pattern with higher resolution. Figure 8: Ground-level thermographic analysis with an incident involving partial shading: (**a**) visual image, and (**b**) ground-level IR inspection. Figure 9: Thermographic analysis with an incident of partial shading: (**a**) aerial IR inspection, and (**b**) ground-level IR inspection. The red circle in (**a**) identifies the affected PV module. 4. Incidents with open-circuit PV modules  
The modules with open circuits do not produce energy. All PV modules in the string that are observed in array 1 are in an open circuit with an overtemperature of some 5 \({}^{\circ}\)C with regard to operational PV modules, as depicted in the analysis lines in Figure 11a. All PV modules in the string that are observed in array 4 (bottom part) are also in an open circuit with an overtemperature of some 5 \({}^{\circ}\)C with regard to operational PV modules, as depicted in the analysis lines in Figure 10b. In this case, the ground-level thermograph is not necessary, as it does not provide any additional information. 5. Other incidents  
The modules can present open substrings, which limits their power generation. Figure 11a shows the aerial thermographic analysis in which some PV modules have substrings with temperature gradients of up to 5 \({}^{\circ}\)C with respect to adjacent substrings in the same module. This is seen in arrays 2, 3 and 4, as indicated by the analysis lines. Figure 12b shows the temperature gradient corresponding to open-circuit substrings from testing with ground-level thermography.