IEC 62938:2020 pdf download

IEC 62938:2020 pdf download.Photovoltaic (PV) modules – Non-uniform snow load testing
1 Scope
This document provides a method for determining how well a framed PV module performs mechanically under the influence of inclined non-uniform snow loads. This document is applicable for framed modules with frames protruding beyond the front glass surface on the lower 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 additional snow 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 considered separately. Methods to eliminate or counteract the occurence of inhomogeneous snow accumulation, such as a steep installation angle (more than 60°), are not included in this document. This document assumes 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. This document 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 provide a complete assessment of the fatigue behaviour of the materials of the module, such as front glass. Because typical field failures of PV modules caused by snow load show glass breakage and frame bending, the test method aims at reproducing the load under which such failures occur.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC TS 60904-13 :2018, Photovoltaic devices – Part 13: Electroluminescence of photovoltaic modules IEC 61215-1:2016, Terrestrial photovoltaic (PV) modules – Design qualification and type approval – Part 1: Test requirements IEC 61215-2:2016, Terrestrial photovoltaic (PV) modules – Design qualification and type approval – 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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC TS 61836 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp 3.1 characteristic snow load S K characteristic value of snow on the ground Note 1 to entry: S k is expressed in kN/m 2 . Note 2 to entry: The lowest value for S k used in this document is 2,4 kN/m 2 . 3.2 characteristic value of snow load angle dependent snow load S A product of the characteristic snow load on the ground and the snow load shape coefficient Note 1 to entry: The lowest value for S A used in this document is 1,47 kN/m 2 . 3.3 snow load shape coefficient µ i ratio of the snow load on the roof or PV module to the undrifted snow load on the ground 3.4 specific snow weight γ weight per unit volume of snow Note 1 to entry: The specific snow weight γ is considered to be 3 kN/m 3 . 3.5 snow load of the overhang S E load vertical to the eaves applied in addition to the uniform load on a roof 3.6 fractile value lower or upper bounds of a distribution function (Student’s distribution, normal distribution, log normal distribution, etc.) which represents, in construction, strenghts or impacts