The insulation resistance test is an electrical safety test and shows whether a solar module offers adequate insulation.
What does the insulation resistance test measure?
With an insulation resistance test, manufacturers, installers and quality testers can assess if a solar panel has adequate insulation between its electricity-conducting components and the module's frame or, in case of a frameless panel, the outside world.
Badly designed pv modules may have insulation problems. Common causes for insufficient insulation are for instance solar cells that are too closely positioned to the frame. Another common cause of insufficient insulation resistance is material weakness, such as modules that were poorly laminated with low quality encapsulates.
How is the insulation resistance test set up?
During the test, a dielectric strength tester is used to apply DC voltage of up to 1000 V, plus twice the maximum system voltage, to the module. To pass this test, the PV module should not show any surface tracking, nor any functional breakdown or development of leakage paths.
Current leakage may occur on the edges of the solar panel or through the backsheet.
For standard solar panels (modules with an area larger than 0.1 m2), the resistance should not be less than 40Ω for every square meter.
Nowadays solar panel manufacturers use advanced flash test machines that also test the insulation resistance of the solar panel.
As this is an important safety aspect of the pv module, according to IEC 61215 standard the insulation resistance test needs to be installed at every manufacturer's assembly line.