IEC 62938 pdf – Photovoltaic (PV) modules – Non-uniform snow load testing
This document provides a method for determining how well a framed PV module performsmechanically under the influence of inclined non-uniform snow loads. This document isapplicable for framed modules with frames protruding beyond the front glass surface on thelower edge after intended installation and as such creates an additional barrier to snow sliding
down from modules. For modules with other frame constructions, such as backrails formed in
frames,on the side edges,on the top edge and on the lower edge not creating an additionalsnow slide barrier, this document is not applicable.
The test method determines the mechanical non-uniform-load limit of a framed PV module.
The loads specified in this document apply exclusively to natural snow load distributions.Any expected artificial accumulations (e.g. from snow removal or redistribution) are consideredseparately.
Methods to eliminate or counteract the occurence of inhomogeneous snow accumulation, suchas a steep installation angle (more than 60″), are not included in this document.This documentassumes a relationship between ground snow-cover and module snow-cover which may not be
applicable in locations where the snow does not completely melt between snow falls. Thisdocument does not consider the effect of snow cover on power generation.
While the test method includes a wait time between load steps, the document does not providea complete assessment of the fatigue behaviour of the materials of the module, such as frontglass.
Because typical field failures of PV modules caused by snow load show glass breakage andframe bending, the test method aims at reproducing the load under which such failures occur.
The following documents are referred to in the text in such a way that some or all of their contentconstitutes requirements of this document. For dated references, only the edition cited applies.
For undated’ references，the latestedition of the referenced document(including anyamendments) applies.
IEC TS 60904-13 :2018，Photovoltaic devices – Part 13: Electroluminescence of photovoltaicmodules
IEC 61215-1:2016,Terrestrial photovoltaic (PV) modules – Design qualification and typeapproval- Part 1: Test requirements
IEC 61215-2:2016,Terrestrial photovoltaic(PV) modules – Design qualification and typeapproval- Part 2: Test procedures
IEC TS 61836,Solar photovoltaic energy systems – Terms, definitions and symbols
IEC TS 62915,Photovoltaic(PV)modules -Type approval,design and safety qualification -Retesting
3Terms and definitions
For the purposes of this document，the terms and definitions given in IEC TS 61836 and thefollowing apply.
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characteristic snow loadsK
characteristic value of snaw on the ground
Noke 1 to entry:sis experessedin kNm a.
Note 2 to entry: The lowest value for 5k used in this dacument is 2,4 kN/m 2.
characteristic value of snow loadangle dependent snow load
product of the characteristic snow load on the ground and the snow load shape coefficient
Note 1 to entry: The lowest value for ss used in this document is 1,47 kNm 2.
snow load shape coefficientpuri
ratio of the snow load on the roof or PV module to the undrifted snow load on the ground
specific snow weight
weight per unit volume of snow
Note 1 to entry: The specific snow weight v is considered to be 3 ktNm x.3.5
snow load of the overhangSE
load vertical to the eaves applied in addition to the uniform load on a roof
lower or upper bounds of a distribution function (Student’s distribution, normal distribution, lognormal distribution, etc.) which represents, in construction, strenghts or impacts
At least seven PV modules are used for testing. Five or more modules are used to determine
the maximum load bearing; one is used for determination of electricaldegradation at a loadbelow the determined maximum load bearing and one is used as a control module.