IEC 62938-2020 Photovoltaic (PV) modules – Non-uniform snow load testing (IEC 62938:2020).
The PV module type shall have passed the static mechanical load test (MQT 1 6) according to
IEC 61 21 5-2 with a minimum positive test load of 5 400 Pa.
These test specifications describe a test method for determining the direct load-bearing capability of framed PV modules under the effects of inhomogeneous snow loads.
6.2 Projections of the test results
Failure of the (adhesive) bond between module frame and glass/laminate can lead to
• deformation of the module rail or frame,
• glass breakage,
• displacement of rail or frame parts,
• fracture of rail or frame parts,
• loss of adhesion strength in adhesive bonds , and
• breakage or displacement of mounting parts.
In addition, this can impact electrical performance due to:
• interruption of the module’s electrical insulation,
• cell breakage and junction box failure, and
• power degradation.
6.3 Test plan
Figure 1 shows the test flow where the numbers in the boxes represent the test references in IEC 61 21 5-2. Five modules undergo the mechanical testing until failure as defined in Clause 8 occurs. A sixth module shall be used to determine the highest load bearing at which no power degradation > 5,0 % occurs.
7 Test procedures
7.1 Visual inspection
This test is performed according to IEC 61 21 5-2 MQT 01 .
7.2 Maximum power determination
This test is performed according to IEC 61 21 5-2 MQT 02 after initial stabilization according to IEC 61 21 5-2 MQT 1 9. For intermediate and final control measurements, further stabilization steps might be required dependent on the module technology. The maximum power determination is a relative measurement only; the measurements do not need to be performed at standard test conditions (STC).
7.3 Insulation test
This test is performed according to IEC 61 21 5-2 MQT 03.
7.4 Wet leakage current test
This test is performed according to IEC 61 21 5-2 MQT 1 5.
7.5 Humidity-freeze test
This test is performed according to IEC 61 21 5-2 MQT 1 2.
7.6 Electroluminescence imaging
Accompanying the visual inspection, electroluminescence according to IEC 60904-1 3 imaging could be performed optionally on the electrical verification module to visualize cell cracking.
7.7 Non-uniform snow load test
This test specification describes a method for determining the direct load-bearing capability of inclined, framed PV modules under the effects of inhomogeneous snow loads.
7.7.2 Load specification
The inhomogeneous load distribution of the weights is determined by the diagram showed in Figure 2.
The load to be applied to the PV module and its distribution by means of separate weight elements is determined as a function of the characteristic snow load S k , the module angle of inclination α = 37° ± 1 °, the shape coefficient µ i as a substitute value for pitch roofs, and the linear load generated from S E as a function of an assumed specific snow weight of γ = 3 kN/m 2 . Here, it is assumed that the snow can slide off unhindered. For mono pitch roofs or PV modules, where the snow is not prevented from sliding off the roof, the values showed in Table 1 can be used (see also Annex A).IEC 62938 pdf download.