Inspection Objectives

• Identify temperature anomalies that cannot be explained by normal operation or system design

• The focus is on identifying potential defects rather than merely measuring temperature

Inspection Conditions

• The system shall be in operation during inspection

• The system shall reach a stable state

• Avoid significant fluctuations in irradiance and load

Environmental Requirements

• Irradiance ≥ 500 W/m²

• Wind speed ≤ approximately 4 m/s

• Cloud cover ≤ 2/8

• Modules should be kept clean

Scope of Inspection

• 100% of PV modules

• Electrical equipment (cabling, combiner boxes, inverters, etc.)

Image Acquisition Requirements

• IR images should be captured as perpendicular to the module surface as possible

• Avoid reflections and angular errors

• UAVs or ground-based thermal cameras may be used

Analysis Methodology

• Calculate the mean temperature of the region

• More accurate than single-point measurements

Temperature Difference Evaluation (ΔT)

• Use the temperature difference between the module and its surroundings as the evaluation criterion

• Environmental and load conditions shall be taken into account

Anomaly classification

• Hot spot

• Module anomaly

• Overheating at electrical connections

• String anomaly

Trend Analysis

• Use ΔT for long-term comparison

• Used for degradation monitoring and fault prediction

Inspection Report Requirements

• Personnel and equipment information

• Inspection date, time, and location

• Environmental conditions (irradiance, temperature, wind speed, cloud cover)

• Locations of anomalies and corresponding thermal images

• Defect classification and maintenance recommendations

Personnel Qualifications

• Personnel shall possess knowledge of electrical systems and PV systems

• Possess the ability to interpret thermal images

Conclusion

IEC TS 62446-3 emphasizes that inspections shall be conducted under stable operating conditions, utilizing area-based temperature analysis and temperature differential (ΔT) evaluation to ensure comprehensive assessment, engineering reliability, and international consistency of the results.