IEC 62938:2020
(Main)Photovoltaic (PV) modules - Non-uniform snow load testing
Photovoltaic (PV) modules - Non-uniform snow load testing
IEC 62938:2020 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.
Modules photovoltaïques (PV) - Essais de charges de neige non uniformes
l'IEC 62938:2020 fournit une méthode pour déterminer le comportement mécanique d'un module photovoltaïque (PV) encadré sous l'effet de charges de neige non uniformes. Le présent document s'applique aux modules encadrés dont les cadres dépassent de la façade vitrée avant au niveau du rebord inférieur lorsqu'ils se trouvent dans la position de montage prévue, ce qui crée une barrière supplémentaire contre les glissements de neige accumulée sur les modules. Le présent document ne s'applique pas aux modules reposant sur d'autres constructions de cadre, par exemple les rails arrière qui sont mis en œuvre dans les cadres, sur les rebords latéraux, sur le rebord supérieur et sur le rebord inférieur, mais qui n'empêchent pas les glissements de neige. La méthode d'essai détermine la limite mécanique d'un module photovoltaïque encadré aux charges de neige non uniformes.
General Information
Standards Content (Sample)
IEC 62938 ®
Edition 1.0 2020-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Photovoltaic (PV) modules – Non-uniform snow load testing
Modules photovoltaïques (PV) – Essais de charges de neige non uniformes
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IEC 62938 ®
Edition 1.0 2020-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Photovoltaic (PV) modules – Non-uniform snow load testing
Modules photovoltaïques (PV) – Essais de charges de neige non uniformes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-8074-4
– 2 – IEC 62938:2020 IEC 2020
CONTENTS
FOREWORD . 3
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 6
4 Sampling . 6
5 Prerequisites . 7
6 Testing . 7
6.1 General . 7
6.2 Projections of the test results . 7
6.3 Test plan . 7
7 Test procedures . 9
7.1 Visual inspection . 9
7.2 Maximum power determination . 9
7.3 Insulation test . 9
7.4 Wet leakage current test . 9
7.5 Humidity-freeze test . 9
7.6 Electroluminescence imaging . 9
7.7 Non-uniform snow load test . 9
7.7.1 Purpose . 9
7.7.2 Load specification . 9
7.7.3 Apparatus . 11
7.7.4 Procedure . 13
8 Fail criteria . 15
9 Verification of the test results . 15
10 Statistical analysis . 15
10.1 General . 15
10.2 5 % fractile value with Student's distribution . 16
10.3 Safety factor . 16
10.4 Example. 16
10.5 Quantiles of the t distribution (Student's distribution) . 16
11 Test report . 17
12 Modifications . 18
Annex A (informative) Use of determined values . 19
A.1 Estimated snow loads and use of the determined resistance . 19
A.2 Calculate the bearable loads for different angles . 19
Bibliography . 20
Figure 1 – Test plan for inhomogeneous snow load test . 8
Figure 2 – Distribution of load on the test specimen at inclination . 10
Figure 3 – Simplified cross-sectional view of module width along bottom frame . 12
Figure 4 – Test procedure for the snow load test . 14
Figure 5 – Different deflection graphs under static load . 14
Table 1 – Applicable load in relation to angle of pitch of roof . 10
Table 2 – Quantiles of the t distribution (Student's distribution) . 17
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC (PV) MODULES –
NON-UNIFORM SNOW LOAD TESTING
FOREWORD
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62938 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this International Standard is based on the following documents:
FDIS Report on voting
82/1670/FDIS 82/1705/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
– 4 – IEC 62938:2020 IEC 2020
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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
– 6 – IEC 62938:2020 IEC 2020
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 is expressed in kN/m .
k
Note 2 to entry: The lowest value for S used in this document is 2,4 kN/m .
k
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 used in this document is 1,47 kN/m .
A
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 .
3.5
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
4 Sampling
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 electrical degradation at a load
below the determined maximum load bearing and one is used as a control module.
5 Prerequisites
The PV module type shall have passed the static mechanical load test (MQT 16) according to
IEC 61215-2 with a minimum positive test load of 5 400 Pa.
6 Testing
6.1 General
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 61215-2. 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.
– 8 – IEC 62938:2020 IEC 2020
NOTE The numbers in Figure 1 relate to the test references in IEC 61215-2:2016.
Figure 1 – Test plan for inhomogeneous snow load test
7 Test procedures
7.1 Visual inspection
This test is performed according to IEC 61215-2 MQT 01.
7.2 Maximum power determination
This test is performed according to IEC 61215-2 MQT 02 after initial stabilization according to
IEC 61215-2 MQT 19. 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 61215-2 MQT 03.
7.4 Wet leakage current test
This test is performed according to IEC 61215-2 MQT 15.
7.5 Humidity-freeze test
This test is performed according to IEC 61215-2 MQT 12.
7.6 Electroluminescence imaging
Accompanying the visual inspection, electroluminescence according to IEC 60904-13 imaging
could be performed optionally on the electrical verification module to visualize cell cracking.
7.7 Non-uniform snow load test
7.7.1 Purpose
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.
– 10 – IEC 62938:2020 IEC 2020
Figure 2 – Distribution of load on the test specimen at inclination
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 , the module angle of
k
inclination α = 37° ± 1°, the shape coefficient µ as a substitute value for pitch roofs, and the
i
linear load generated from S as a function of an assumed specific snow weight of
E
γ = 3 kN/m .
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).
Table 1 – Applicable load in relation to angle of pitch of roof
Angle of pitch of roof α 0°< α ≤ 30° 30°< α < 60° α ≥ 60°
µ 0,8 0,8 · (60° – α) / 30° 0,0
i
At a test angle of 37°, µ = 0,61 applies (this is considered as the most critical angle for snow
i
slides).
The lower edge of the PV modules represent the eaves of a roof and hence this case needs to
be considered in this document. The minimum of S is 0,72 kN/m.
E
S = S / γ
E A
where
S is the snow load of the overhang depending on eaves, in kN/m;
E
S is the snow load on the roof, in kN/m (S = µ · S );
A A i K
γ is the specific snow weight, in kN/m .
The weight elements for S are distributed over the bottom area of the inclined module over a
A
length of approximately, but not greater than, 2/3 of the vertical length of the module (l).
The weight elements for S are distributed over the bottom area of the inclined module over a
E
length of approximately, but not greater than, 1/2 of the vertical length of the module (l).
Quasi- triangle PV for the hipped and/or broach roof, and roof shingle PV which has very short
vertical length are out of scope, because it is assumed less impact of snow slide.
The subsequent load increases shall be applied as angle-dependent loads per area. Each load
corresponds to the angle-dependent pressure given the shape coefficient (example: in the first
2 2
step, 2,4 kN/m corresponds to an angle-dependent pressure of 1,47 kN/m at 37° (±1°)
inclination angle, as defined in Formula (1).
S = S · µ (1)
A K i
The linear load S is then calculated and increased according Formula (2):
E
S = (S /γ) (2)
E A
To calculate the force which can then distributed inhomogeneously according
to Figure 2, the result needs to be multiplied with the factors out of Figure 2 and the bottom
length of the module L .
b
S
A
Example: Additional force for the bottom segment = 0,4⋅⋅ L
b
γ
The initial load with which all tests begin is derived from the minimum design qualification of
PV modules according to the static mechanical load test (MQT 16) of IEC 61215-2.
The initial load corresponds to the combination of characteristic snow load S of 2 400 Pa and
K
linear load S . In this example:
E
S = 2,4 kN/m (3)
K
S = angle-dependent load at 37° = 1,47 kN/m (4)
A
S = 0,72 kN/m (5)
E
The weight elements used shall be able to slide on the surface of the module with as little
friction as achievable. For example, a polytetrafluoroethylene, PTFE surface on the weight
elements is suitable.
For each total load, it shall be ensured that the individual weight elements be placed according
to the distribution shown in Figure 2. Further weight elements (e.g. weight disks) are placed on
the bottom half of the module to form the linear load S per Figure 2, in order to ensure a
E
simulated "bulging" snow accumulation. A deviation of the distribution of up to ±10 % can be
tolerated.
7.7.3 Apparatus
The test bench has a substructure on which PV modules can be mounted at 37° ± 1° as specified
by the manufacturer.
– 12 – IEC 62938:2020 IEC 2020
As seen in Figure 3, the effective length of a weight element acting on the frame is designated
by the symbol L .
a
The width of the PV module is designated by the symobl L .
b
To achieve a sufficiently high homogeneity of the surface load (weight element/module area)
and a sufficiently high number of contact points (weight element/frame), the following conditions
shall be fulfilled:
L
∑ a
Homogeneity of the surface load: ≥ 90 % (6)
L
b
L
b
Number of contact points: ≥ 5 (7)
L
a
Figure 3 – Simplified cross-sectional view of module width along bottom frame
The weight elements shall be designed such that the load is introduced in planar form,
homogeneously and without torque to the modules surface.
The contact between the module frame and the weight element shall be form-fitted.
It shall be ensured that the downhill-slope force is transmitted to the module bottom frame
member.
The contact of the bottom of the weight element and the module surface shall be realised with
as little friction as possible.
Two neighbouring weight elements shall be placed with sufficient space in-between them to
avoid them getting stuck to each other when the frame bends and the module surface deflects.
Abrasion or scratching of the module surface due to weight elements sliding shall be avoided.
For safety reasons, the weight elements shall be secured against falling down. The fixation of
the loads shall not hinder the loads to fully lie on the PV module.
The test apparatus shall be equipped with means to monitor movements in the joint between
frame and laminate (bending of the frame).
7.7.4 Procedure
The module to be loaded is mounted on the test bench as specified in the instruction manual of
the supplier. Installations with clamping along the long frame side usually use cross bars as the
substructure. Bending of the module under load may cause the backsheet to touch the
substructure. This real condition shall be represented in the test set-up (no free bending on the
test bench, if in reality such bending is prevented by the sub-structure).
The environmental conditions for performing the tests are 25 °C ± 5 °C.
As most adhesives will perform worse under elevated temperatures, room temperature is
considered to be a worst case condition for testing. If the adhesive used for a particular module
type is known to perform better at room temperature, the test shall be performed at 0 °C ± 5 °C.
The test procedure shall be as followed (see also Figure 4).
Apply an initial load of S = 2 400 Pa for at least 24 h. After these 24 h, three cases are
K
distinguished:
– Case 1: no movement in the frame is visible since the initial setting. The load shall be
increased to the next load step for at the least 30 min. Once no movement is visible for at
least 15 min, the load shall be increased further. Repeat this procedure until the module
fails. Then start with next module with the initial load.
– Case 2: the deflection over time graph (see Figure 5) shows a change in gradient within the
24 h but is stable for at least 15 min towards the end. If no movement is visible for at least
15 min, the next load step shall be applied for at least 1 h. Repeat this procedure waiting at
th
least 1 h for stabilization for each load step and 4 h for each 5 load step, until the module
fails. Then start with next module with the initial load.
– Case 3: movement in the frame is still visible. Wait until movement stops. If no stable
situation arises and the module fails, the test series shall be stopped. If no movement is
visible for at least 15 min, the next load step shall be applied for at least 1 h. Repeat this
th
procedure waiting for stabilization for at least 1 h for each load step and 4 h for each 5
load step, until the module fails. Then start with next module with the initial load.
Examples for case 1, case 2 and case 3 movement over time are given in Figure 5. Furthermore,
the following steps shall be followed:
a) document the test setup in unloaded condition and at each load step with a photograph;
b) determine the load distribution as defined in 7.7.2;
c) document the date and time for the impression of the load steps;
d) record movements with an accuracy of at least ±0,5 mm at least every five minutes during
the first and last hour for the initial 24 h load application, and continuously for subsequent
load steps;
e) the load increments shall be applied in steps of S + 200 Pa.
K
A visible change is defined as a change of at least 1,0 mm measured at any of the following
points:
• ½ · L of the bottom frame member, in the direction of the module plane;
b
• on the left and the right ends of the bottom frame member, in the direction of the module
plane.
– 14 – IEC 62938:2020 IEC 2020
Figure 4 – Test procedure for the snow load test
NOTE Due to different frame adhesive techniques, different reactions to a static load are possible. Three example
graphs are shown in Figure 5, representing the three reaction cases introduced in Figure 4.
Figure 5 – Different deflection graphs under static load
If failure occurs while a new load level is being applied, the previous load level qualifies as the
failure limit.
This test sequence is performed on a total of at least 5 modules.
8 Fail criteria
The following types of damages are considered to be a test failure:
a) broken, cracked, or torn external surfaces, including superstrates, substrates, frames, rails
and junction boxes;
b) bent or misaligned external surfaces (permanent deformation), including superstrates,
substrates, frames, rails and junction boxes to the extent that the installation and/or
operation of the module would be impaired;
c) loss of mechanical integrity, to the extent that the installation and/or operation of the module
would be impaired.
d) failure of the sixth module (used for the determination of the electrical degration in the right
leg of Figure 1) to meet the requirements of IEC 61215-2 MQT 03 and MQT 15. as well as
exceeding a maximum power degradation of 5 % following the formula given in
IEC 61215-1:2016, 7.2.2.
9 Verification of the test results
The load limit values X are determined according to the calculation rules defined in Clause 10
and converted to the 5 % fractile value X . This fractile value is then divided by a safety factor
5 %
of 1,5.
At a fractile value of 5 %, for example, only 5 % of the components fail to attain the minimum
strength.
The inhomogeneous load test is performed on a sixth PV module for at least 24 h with the
computed load value (5 % fractile value divided by the safety factor). In addition, before and
after the inhomogeneous snow load test, the diagnostic measurements of IEC 61215-2 are
performed (insulation test, wet leakage current test, determination of output power). The
maximum permitted degradation of maximum output power from before to after the
inhomogeneous load test is 5,0 %.
If the power loss is greater than 5,0 %, or the modules fails in the diagnostic insulation test or
wet leakage current the test may be repeated on another PV module that was also pre-
conditioned with the humidity-freeze test. A higher safety factor shall then be applied, however.
The following safety factor shall be increased in steps of 0,25 until no failure occurs.
10 Statistical analysis
10.1 General
The following computational steps shall be performed for the statistical analysis of the
component test.
– 16 – IEC 62938:2020 IEC 2020
10.2 5 % fractile value with Student's distribution
Formula (8) shall be used to determine the load limit at which statistically 5 % of the specimens
fail:
S
X =xt− ⋅ (8)
5% n,−1α
n
where
t is the factor of the Student's distribution at α = 0,95;
n,−1α
n is the number of samples (5);
S is the standard deviation.
10.3 Safety factor
For measuring the actual load capacity, the 5 % fractile value shall be divided by a safety factor.
For this document, as components susceptible to vibrations and subject to dynamic loads, a
safety factor of 1,5 is used, unless a higher safety factor is needed per Clause 9.
10.4 Example
The load bearing determination sequence test determined the following values (the given values
are assumption from a fictive project):
• 3 652 Pa;
• 2 700 Pa;
• 4 025 Pa;
• 3 700 Pa;
• 4 250 Pa.
Mean value = 3 665 Pa.
Standard deviation = S = 530 Pa.
t = 2,13
n – 1,α
5 % fractile value = 3 160 Pa t .
n – 1α
Division by the safety factor of 1,5 gives a final load value of 2 107 Pa.
Verification of the test results per Clause 9 is performed at this final load value.
10.5 Quantiles of the t distribution (Student's distribution)
The degree of freedom to be read off corresponds to the number of the tests (n – 1) at the
required confidence interval of 0,95 (see Table 2).
Table 2 – Quantiles of the t distribution (Student's distribution)
(t ) at (t ) at
n – 1,α n – 1,α
Degree of freedom Degree of freedom
α = 0,95 α = 0,95
1 (with 2 test specimens) 6,314 11 (with 12 test specimens) 1,796
2 (with 3 test specimens) 2,920 12 (with 13 test specimens) 1,782
3 (with 4 test specimens) 2,353 13 (with 14 test specimens) 1,771
4 (with 5 test specimens) 2,132 14 (with 15 test specimens) 1,761
5 (with 6 test specimens) 2,015 15 (with 16 test specimens) 1,753
6 (with 7 test specimens) 1,943 16 (with 17 test specimens) 1,746
7 (with 8 test specimens) 1,895 17 (with 18 test specimens) 1,740
8 (with 9 test specimens) 1,860 18 (with 19 test specimens) 1,734
9 (with 10 test specimens) 1,833 19 (with 20 test specimens) 1,729
10 (with 11 test specimens) 1,812 20 (with 21 test specimens) 1,725
Corresponding to the number of test samples used for the load bearing determination sequence,
the value of (t ) shall be chosen from Table 2 to be used in Formula (8).
n – 1,α
11 Test report
Following determination of the non-homogeneous load limit, a report of the tests, with measured
performance characteristics and details of any failures and re-tests, shall be prepared by the
test laboratory. The report shall contain the detail specification for the module. Each test report
shall include at least the following information:
a) a title;
b) name and address of the test laboratory and location where the tests were carried out;
c) unique identification of the test report (each page);
d) name and address of client, where appropriate;
e) description and identification of the item tested;
f) characterization and condition of the test item;
g) date of receipt of test item and date(s) of test, where appropriate;
h) reference to sampling procedure, where relevant;
i) photo documentation;
j) information about the relevant components or dimensions:
• frame (type designation, material, dimensions, manufacturer);
• backsheet (type designation, material, manufacturer);
• glass (type designation, material, dimensions, manufacturer);
• adhesive between glass and frame (type designation, material, dimensions,
manufacturer);
• clamps or screws being used to mount the module (type / dimensions);
• mounting system or method (type designation, material, dimensions, manufacturer);
• clamping or mounting points;
k) time for each load step (impression of the loads and load);
l) applied pressure at point of failure of each sample, in Pascal;
m) angle at which the test was performed and angle/load combinations as determined
according to Clause A.2;
– 18 – IEC 62938:2020 IEC 2020
n) final load value;
o) any deviations from, additions to or exclusions from the test method, and any other
information relevant to specific tests, such as environmental conditions;
p) a statement of the estimated uncertainty of the test results (where relevant);
q) a signature and title, or equivalent identification of the person(s) accepting responsibility for
the content of the report, and the date of issue;
r) where relevant, a statement to the effect that the results relate only to the items tested;
s) a statement that the report shall not be reproduced except in full, without the written
approval of the laboratory.
A copy of this report shall be kept by the manufacturer for reference purposes.
12 Modifications
Changes in material selection, components and manufacturing process can impact the
qualification of the modified product.
Retesting shall be performed according to IEC TS 62915. The recommended test sequences
have been selected to identify adverse changes to the modified product.
The number of samples to be included in the retesting program and the pass/fail criteria are to
be taken from the relevant clauses/subclauses of this document.
Annex A
(informative)
Use of determined values
A.1 Estimated snow loads and use of the determined resistance
The estimated local snow load is commonly described in the national annexes of the structural
standards or through references in local building codes. The load value determined from this
inhomogeneous snow load test can be used in static calculations for the resistance side if
accepted by the local code authority.
In absence of national requirements, the European code EN 1991-1-3 can act as a guideline.
Here, snow loads are defined as a function of the local altitudes above sea level (in m).
Alternatively, corresponding snow loads can be obtained from regional snow load maps for the
area where PV modules will be installed.
A.2 Calculate the bearable loads for different angles
To calculate the bearable load for other angles, the following formulae shall be used:
final load
For α: 0° ≤ α ≤ 30°: · 0,8 (A.1)
0,61
60°– angle
final load ( )
For α: 30° < α < 60°: · 0,8 · (A.2)
0,61 30
final load
For α: α ≥ 60°: (A.3)
0,61
– 20 – IEC 62938:2020 IEC 2020
Bibliography
EN 1991-1-3:2010, Eurocode 1 – Actions on structures – Part 1-3: General actions – Snow
loads
___________
– 22 – IEC 62938:2020 IEC 2020
SOMMAIRE
AVANT-PROPOS . 23
1 Domaine d'application . 25
2 Références normatives . 25
3 Termes et définitions . 26
4 Echantillonnage . 27
5 Conditions préalables . 27
6 Essais . 27
6.1 Généralités . 27
6.2 Projections des résultats d'essai . 27
6.3 Plan d'essai . 27
7 Procédures d'essai . 29
7.1 Examen visuel . 29
7.2 Détermination de la puissance maximale . 29
7.3 Essai diélectrique . 29
7.4 Essai de courant de fuite en milieu humide . 29
7.5 Essai humidité-gel . 29
7.6 Imagerie par électroluminescence . 29
7.7 Essai de charges de neige non uniformes . 29
7.7.1 Objet . 29
7.7.2 Spécification de la charge . 29
7.7.3 Appareillage . 32
7.7.4 Procédure . 33
8 Critères de rejet . 35
9 Vérification des résultats d'essai. 35
10 Analyse statistique .
...
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