How do you troubleshoot bypass diode failure in solar PV modules using a multimeter or an infrared camera?

bypass diode is a bridging element connected in parallel to a series of solar cells or strings to reduce the risks of overheating and mitigate the power loss due to current mismatch between the solar cells.

Bypass diodes are important because they allow a portion of the cells be shaded, damaged, or compromised without affecting the entirety of the solar module's performance.

To troubleshoot bypass diode failure in solar PV modules using a multimeter, measure the voltage across each diode in the module. A failed diode will show an open circuit or unexpected voltage drop. For an infrared camera, inspect the module for hotspots or uneven temperature distribution; a failed bypass diode will cause localized heating. Compare temperature readings across the panel to identify abnormal hot spots indicating diode issues. In both methods, confirm the failure by testing with a replacement diode and verifying improved performance.

Using an infrared camera one can see a temperature differential on the bypassed cells. Using a voltage meter one can see a reduction is open circuit voltage.

1- overheating of the connected string (in case of short-circuit) 2- Hotspots and extreme module temperature (in case of open-circuit) 3- voltage drop on the module (almost 33%)

Yeah, open circuit voltage for that panel will reduce by a third in most of the solar panel, as 3 diodes are normally fitted every 18 or 24 cells. So the failure of just one of those diodes, will make the whole string of the cells, connected in series, so generally lowering Voc to 2 thirds of the original output. I prefer a multimeter straight test results in number ratherthan relaying on the guess of a thermal imaging camera. And I would definitely not use an infrared temp gun!

main sources can be distinguished as: 1- improper choice of diodes 2- long time operation which leads tin increased diode temperature 3- improper soldering 4- fatigue in solder point due to thermal-cycling 5- extreme reverse current (e.g. lightning)

connect the multimeter to the junctions, in case you monitor a voltage drop, a diode is defected. You can check them in the junction box separately to distinguish the short-circuit or open circuit failures by setting the voltage

Utility scale solar facility asset management is assisted by a drone carrying an infrared camera. A failed bypass diode often shows up in the cell temperatures. A string of cells running hotter than the adjacent strings often occurs because a diode is bypassing that string. From there one needs to determine why that diode is bypassing the cell string. Often its because of shading, soiling, or...you guessed it - a failed diode.

A bypassed section (typ called a substring) is open-circuited. If illuminated like its neighboring, normally operating substrings, the bypassed one will be hotter, not cooler. A pair of power balance free-body diagrams, one around a bypassed substring and one around a normal substring will show why. A normally operating section is converting 10-20% of the absorbed sun into dc electricity, while a stalled area in open-circuit can only dissipate all of the absorbed sunlight via heat transfer. Translation: it'll be hotter than the operating one.

you need to chose a sunny day. In case that the bypass diode is in operation, the temperature rise up. You can apply shading to the related string to see whether the temperature of bypass diode rises. Otherwise, you have a bypass diode which is disconnected. A short-circuited bypass diode leads to a higher temperature on the solar cells, as they operate in short-circuit

In case that the Junction box is filled with potting, the easiest way is to use a multi meter to check the output voltage of the module. If you see around 33% or higher loss, then the bypass diode has a short circuit. Otherwise, you can apply shading on the module and test the output current but it might not be that accurate. EL and flash test are the best ways to test them indoor and Thermography helps you to trouble shoot it outdoor.

Troubleshooting bypass diode failure in solar PV modules involves project management coordination. Using a multimeter, measure voltage across diodes to identify faulty ones. With an infrared camera, detect temperature anomalies indicating diode malfunction. Project management ensures efficient diagnosis, replacement, and documentation, minimizing downtime and optimizing system performance.