September 2015 - Failure Analysis at a PV-plant - several PID damages found

PID

A PV plant with an installed nominal power of 60kWp had delivered significantly less energy than expected.  Since no plant monitoring had been installed at the plant in the Middle East, the inverter data, retrieved directly from the inverters had to be verified. It became apparent, that the voltage of all PV strings was different and in general much too low (even when the high ambient temperatures were taken into account).
 

The infrared camera showed images of several hundred PV modules with PID damages. The effect was observed on the whole installation. Results were verified with the curve tracer on a few strings as well as on single PV panels. After a few trials with anti-PID boxes, which were partially successful, the PV panels were exchanged, Apparently the combination of a certain EVA foil together with the high ambient temperature and the high humidity, were the root cause of the problem. Technical backround note on PID...