Visual inspections are important to detect major problems, like broken fuses, obvious panel issues, etc. Nevertheless this method only allows detecting few issues. As an example after a hailstorm only a few modules were exhanged at a solar power plant. Detailed investigations showed that a lot more modules were affected by the hailstorm.
This technique is most used for inspection of PV plants. It requires Know-How for executionand analysis of the measurements. Often drones or airplanes are used and the power plant needs to be in full operation (heat). It allows detection of different kind of faults and to find broken components.
- Mismatch losses are not detected
- PID can not be detected
- Cell cracks can not be detected
This technique is mainly done in laboratories. Modules will get activated by current injection. Measurements are done without solar radiation (by night). It allows detailed analysisof PV panels. Nevertheless mobile measurement systems to analyse whole PV strings are not available yet. The systems require high power for signal injection.