Thermographic inspection

THERMOGRAPHIC INSPECTION (Radiometric analysis)

The analysis was carried out to monitor the thermographic equipment of a 1MW photovoltaic field located in Schifone (Italy). The inspection was accomplished with the aid of a UAV and a portable thermal camera to analyse the back panels.

The inspection was commissioned to control the proper functioning of the system following a decrease in production levels. The purpose was thus the identification of the nature of problems and the provision of information about the anomalies.

Acquisition of thermographic images for monitoring the infrastructure conditions.

Type of report supplied:

  • Qualitative
  • Quantitative

Qualitative Analysis

Method based on the analysis of thermal diagrams to disclose the existence, and location of potential anomalies, in order to allow their evaluation.

  • Detects IF there is an anomaly
  • Detects WHERE the anomaly is located
  • Usually carried out before the quantitative analysis to identify problems and, subsequently, assess the risk level.

Detailed analysis of radiometric parameters (Quantitative)

The quantitative thermography uses the temperature measurement as a principle to determine the seriousness of an anomaly and set out the repair priorities. Measurement carried out after duly correcting the panel emissivity and the reflected temperature value.

In order to classify the severity of the module anomaly, the temperature measured of the fault component was compared with that of the same component under correct operating conditions (Principle of ΔT), or rather in adjacent faultless areas.

The guidelines to classify the main anomalies within the photovoltaic field (German Thermography PV guidelines 2016) are listed here below:

  • Anomaly on the conductor track: ΔT > 3K – Module in-depth examination.
  • Overheated cell: ΔT > 20K – Module replacement.
  • Overheated connection box: ΔT > 3K – Box control.
  • Overheating of the string: 2K < ΔT < 7K – Module replacement.
  • Overheating of several modules in series: 2K < ΔT < 7K – Control modules connection.

For a clear identification of the critical situations detected during the inspection in question, the following classification on levels of criticality was adopted:

  • Critical level 1 - 0°C < ΔT < 10°C
  • Critical level 2 - 11°C < ΔT < 20°C
  • Critical level 3 - ΔT > 20°C

Note: the classification values are not standard but prescribed by an internal classification. Other parameters can be agreed with the customer depending on his maintenance procedures.