IEC TS 63209-1:2021

Photovoltaic modules - Extended-stress testing - Part 1: Modules

IEC TS 63209-1:2021 is intended to provide information to supplement the baseline testing defined in IEC 61215, which is a qualification test with pass-fail criteria. This document provides a standardized method for evaluating longer term reliability of photovoltaic (PV) modules and for different bills of materials (BOMs) that may be used when manufacturing those modules. The included test sequences in this specification are intended to provide information for comparative qualitative analysis using stresses relevant to application exposures to target known failure modes.

General Information

• Status: Published
• Publication Date: 26-Apr-2021
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 2 - TC 82/WG 2
• Current Stage: PPUB - Publication issued
• Start Date: 27-Apr-2021
• Completion Date: 27-May-2021

Overview

IEC TS 63209-1:2021 - "Photovoltaic modules - Extended-stress testing - Part 1: Modules" is a Technical Specification from IEC that standardizes a set of extended stress test sequences to supplement baseline qualification (IEC 61215). It is intended to evaluate longer-term PV module reliability and compare different bills of materials (BOMs) using stresses relevant to field failure modes. This document provides a common, comparative framework (not pass‑fail certification) to identify vulnerabilities and rank-order module designs qualitatively.

Key topics and requirements

• Purpose: Provide standardized extended-stress sequences to reveal weaknesses not covered by IEC 61215 baseline tests.
• Test sequences: Five principal sequences are included (summarized in the TS):
  • Thermal fatigue (thermal cycling)
  • Mechanical stress (static loads combined with cycling)
  • Sequential testing including UV exposure to the module back (to stress polymeric components)
  • Damp heat (moisture/temperature exposure)
  • Potential‑Induced Degradation (PID) testing
• Characterization & diagnostics: Pre- and post-test measurements such as visual inspection, electroluminescent (EL) imaging, wet leakage current, insulation testing, thermal cycling and humidity‑freeze checks are specified to document effects.
• Comparative, qualitative results: The TS emphasizes rank ordering and failure-mode identification rather than lifetime prediction. It explicitly notes limitations (e.g., limited duration for front‑side UV acceleration, potential for false positives/negatives).
• Design constraints: Test durations are chosen for practical turnaround; some long-term mechanisms (e.g., slow UV-induced discoloration) may not be fully captured. Annexes discuss weaknesses and background rationale (e.g., thermal cycling 600 cycles ≈ 3× IEC 61215; damp heat 2000 h ≈ 2× IEC 61215).

Applications

• Benchmarking and comparative reliability testing of PV modules and BOM variants
• R&D and accelerated durability screening for materials and module designs
• Supplier qualification and component selection based on comparative risk
• Root‑cause and failure‑mode analysis using standardized stress sequences
• Harmonizing test data across test labs to reduce redundant testing and cut costs/time

Who should use it

• Module manufacturers (design validation, BOM comparisons)
• Test laboratories and independent engineering firms (standardized protocols)
• Project owners, asset managers and procurement teams (comparative risk assessment)
• Research organizations and failure‑analysis teams

Related standards

• IEC 61215 - Crystalline silicon PV module qualification (baseline tests)
• IEC 61730 - PV module safety qualification
• IEC 63209 series - other parts covering extended‑stress testing

Note: IEC TS 63209-1 is a Technical Specification for information and alignment; it is not a pass/fail certification standard and should be used alongside baseline IEC standards and engineering judgment when assessing PV module durability and field performance.

Standards Content (Sample)

IEC TS 63209-1 ®
Edition 1.0 2021-04
TECHNICAL
SPECIFICATION
Photovoltaic modules – Extended-stress testing –
Part 1: Modules
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IEC TS 63209-1 ®
Edition 1.0 2021-04
TECHNICAL
SPECIFICATION
Photovoltaic modules – Extended-stress testing –

Part 1: Modules
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-9728-5

– 2 – IEC TS 63209-1:2021 © IEC 2021
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 7
4 Selection of test samples . 8
5 Characterization and stabilization techniques to be applied . 8
5.1 General . 8
5.2 Physical measurement . 8
5.3 Visual inspection . 8
5.4 Initial stabilization . 8
5.5 Performance . 8
5.6 Insulation test . 8
5.7 Wet leakage current . 9
5.8 Electroluminescent imaging . 9
5.9 Insulation thickness test . 9
5.10 Thermal cycling. 9
5.11 Humidity freeze . 9
5.12 Final stabilization . 9
6 Data collection and stress application . 9
6.1 General . 9
6.2 Initial characterization . 9
6.3 Test sequence 1: Thermal fatigue . 10
6.4 Test sequence 2: Mechanical stress . 10
6.5 Test sequence 3: Sequential testing including UV stress to module back . 11
6.6 Test sequence 4: Damp heat . 12
6.7 Test sequence 5: Potential-Induced Degradation (PID) testing . 12
7 Report . 13
8 Test flow and procedures . 14
Annex A (informative) Appropriate use of IEC TS 63209-1 – Potential weaknesses of
the included test sequences . 15
A.1 General . 15
A.2 False negatives/false positives . 15
A.3 Approximations to service life . 16
A.4 Design to test. 16
Annex B (informative) Background on IEC TS 63209-1 . 17
B.1 General . 17
B.2 Sequence 1: Thermal fatigue – Thermal cycling 600 cycles = 3x IEC 61215
(similar to other extended stress protocols) . 17
B.3 Sequence 2: Mechanical stress (adds static load to sequence similar to
other extended stress protocols) . 17
B.4 Sequence 3: Combines UV, moisture and temperature/mechanical cycling to
stress polymeric components . 17
B.5 Sequence 4: Damp heat moisture exposure – DH 2 000 h = 2x IEC 61215
(similar to other extended stress protocols) . 18
B.6 Sequence 5: Potential-Induced Degradation (PID) testing . 18
Bibliography . 19

Figure 1 – Full test flow – Each box refers to the corresponding MQT in IEC 61215-2 . 14

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC MODULES – EXTENDED-STRESS TESTING –

Part 1: Modules
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 63209-1 has been prepared by IEC technical committee 82: Solar photovoltaic energy
systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
DTS Report on voting
82/1820/DTS 82/1873/RVDTS
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
A list of all parts in the IEC 63209 series, published under the general title Photovoltaic modules
– Extended-stress testing, can be found on the IEC website.
The language used for the development of this Technical Specification is English.

– 4 – IEC TS 63209-1:2021 © IEC 2021
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
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.
INTRODUCTION
Existing qualification test standards such as IEC 61215 standard series have been very useful
for identifying module designs that avoid most early field failures, but are not intended or able
to demonstrate long term performance in all locations within the scope of those documents. In
order to assess the risk of product failure it has become industry practice for the different
stakeholders to require results of test protocols beyond baseline type approval and safety tests
according to the IEC 61215 standard series and IEC 61730 standard series. These extended
stress test protocols primarily contain aforementioned baseline tests in different sequences
and/or increased test duration or number of cycles. They originate from the various experiences
made by third parties such as test institutes/ independent engineering firms/ owners engineers
and aim to cause aging that would be seen after long term use of PV modules, or apply a “test
to failure” approach, aimed to identify weaknesses rather than to replicate field performance.
They do not provide detailed reliability or durability predictions/estimates, but have been useful
to reveal deficiencies.
With many variants of extended stress test protocols in use, a standardized approach is desired.
The included set of extended stress test sequences is intended to standardize the various
approaches used by different industry participants, with a benefit of a common data set for
reliability reviews, and a practical benefit to module manufacturers who are faced with the
challenge of running (and maintaining after product changes) a number of very similar test
protocols in parallel.
This global reference comparative document utilizes a common denominator approach
considering all the sequences of the variants, and adds to this subset sequences that are
uniquely positioned to capture special failure modes, while excluding sequences where test
conditions and durations do not show results that are useful for assessing module field
performance. This document is intended to align extended test protocols, in order to make
results from different institutes more directly comparable and to reduce test costs and time lines
for the industry.
This document is intended to provide a set of data to be used for qualitative reliability risk
analysis, highlighting potential failure modes and areas possibly in need of improvement. It is
only useful for rank ordering modules and materials for special cases, for very large differences
in performance, or with respect to specific understood failure modes and mechanisms. A robust
module level rank ordering or service life prediction is beyond the scope of this document. A
series of component test suites is in development to complement the module level testing in
this specification.
– 6 – IEC TS 63209-1:2021 © IEC 2021
PHOTOVOLTAIC MODULES – EXTENDED-STRESS TESTING –

Part 1: Modules
1 Scope
This document is intended to provide information to supplement the baseline testing defined in
IEC 61215, which is a qualification test with pass-fail criteria. This document provides a
standardized method for evaluating longer term reliability of photovoltaic (PV) modules and for
different bills of materials (BOMs) that may be used when manufacturing those modules. The
included test sequences in this specification are intended to provide information for comparative
qualitative analysis using stresses relevant to application exposures to target known failure
modes.
A significant constraint imposed was that the test duration was limited, recognizing that
customers of the test will proceed with decisions before the test results are available, if the test
takes too long. With this business-relevant limitation, some known failure modes cannot be
accurately addressed, most notably those related to long-term ultra-violet light (UV) exposures.
While failure modes related to UV stress are known to occur on both front and back side of PV
modules, the testing time required to achieve a dose of UV stress that causes changes observed
in the field during the module’s intended lifetime without overstressing is beyond the scope of
this document. The included backside UV stress sequence gives increased confidence for some
backsheets with regard to backside cracking, and a frontside UV stress sequence is not
included at all, leaving gaps for failure modes, such as encapsulant discoloration, frontside
backsheet cracking, frontside delamination, etc.
Other limitations of extended stress testing are described in Annex A. This document identifies
vulnerabilities without attempting to gather the information needed to make a service-life
prediction, which would require identifying failure mechanisms and their dependencies on all of
the stresses. Annex B contains a brief background of the origins of the tests.
Out of scope for this document is its use as a pass-fail criterion. The same module deployed in
two different locations may fail/degrade in different ways, so a single test protocol cannot be
expected to simultaneously exactly match both results, and will depend upon where and how
the product is deployed. Additionally, both false positives and false negatives may occur: due
to the highly accelerated and extended nature of some of the stress exposures, the tests may
cause some changes that do not occur in the field for some module designs, and degradation
which is difficult to accelerate will be missed.
This document was developed with primary consideration for c-Si modules, as reflected in the
targeted failure modes. However, the applied stresses are based on the service environment,
and as such are relevant to generalized PV modules. Interpretation of the data resulting from
these tests should always include the possibility that a design change may cause a new failure
to occur. In particular, modules with different form factors (e.g. made without the standard glass
frontsheet) may be found to differ in the way they fail. In every case, the data collected in this
extended-stress test procedure is used as input to an analysis that may then identify the need
for additional testing, to more fully assess module performance relative to the intended
deployment conditions.
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 60904-1-2, Photovoltaic devices – Part 1-2: Measurement of current-voltage
characteristics of bifacial photovoltaic (PV) devices
IEC TS 60904-13, Photovoltaic devices – Part 13: Electroluminescence of photovoltaic modules
IEC 61215-1, Terrestrial photovoltaic (PV) modules – Design qualification and type approval –
Part 1: Test requirements
IEC 61215-1-1:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 1-1: Special requirements for testing of crystalline silicon photovoltaic (PV)
modules
IEC 61215-1-2, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-2: Special requirements for testing of thin-film Cadmium Telluride (CdTe) based
photovoltaic (PV) modules
IEC 61215-1-3, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
– Part 1-3: Special requirements for testing of thin-film amorphous silicon based photovoltaic
(PV) modules
IEC 61215-1-4, Terrestrial photovoltaic (PV) modules – Design qualification and type approval
based photovoltaic
– Part 1-4: Special requirements for testing of thin-film Cu(In,GA)(S,Se)
(PV) modules
IEC 61215-2:2021, Terrestrial photovoltaic (PV) modules – Design qualification and type
approval – Part 2: Test procedures
IEC 61730 (all parts): Photovoltaic (PV) module safety qualification
IEC 61730-2, Photovoltaic (PV) module safety qualification – Part 2: Requirements for testing
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC TS 62782, Photovoltaic (PV) modules – Cyclic (dynamic) mechanical load testing
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions in IEC TS 61836 apply, as well as
the following.
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
Module Quality Test
MQT
Module Quality Test in accordance with IEC 61215-2
3.2
Module Safety Test
MST
Module Safety Test in accordance with IEC 61730-2

– 8 – IEC TS 63209-1:2021 © IEC 2021
4 Selection of test samples
This document describes data collection methodology. Sample selection, number of samples,
and or sample sets are left to the user, based on the purpose of the data collection. The number
of samples used in each test may vary between the test sequences and may be selected to
emphasize the stresses anticipated in the current application. The confidence in the test results
will be greater for a larger number of test samples, and inclusion of multiple samples is
encouraged.
5 Characterization and stabilization techniques to be applied
5.1 General
The characterization methods are as described in published standards, such as the IEC 61215
standard series, including the technology-specific portions of these. Baseline characterization
shall be completed before application of stress, and repeated after subsequent applications of
stress to establish the trend of response to that stress. Additional intermediate tests may be
included between application of stresses at the customer’s request. For example, additional
characterization may be beneficial after mechanical stress is applied.
5.2 Physical measurement
Physical module measurements shall include weight, length, width, and thickness (depth) of
frame. Additionally, the cell dimensions shall be recorded. Photographs of module and example
cells shall be recorded.
5.3 Visual inspection
Observations are completed as defined in IEC 61215-2, MQT 01. All observations shall be
recorded and reported as part of the final report. Photographs shall be used to document any
changes and included in the final report.
For the visual inspection of the backsheet after UV exposure, magnification of 10X or greater
is recommended using an illumination of at least that specified in IEC 61215-2, MQT 01.
5.4 Initial stabilization
Initial stabilization shall be completed as defined in IEC 61215-2, MQT 19.1. All measurements
(as defined in 5.5) shall be recorded after each stabilization step. These data shall be included
in the final report.
5.5 Performance
The performance at Standard Test Conditions shall be measured as defined in IEC 61215-2,
MQT 06.1. The performance at low-irradiance conditions shall be measured as defined in
IEC 61215-2 MQT 07. If the test lab does not have the capability to accurately measure at low
irradiance, the low irradiance measurement may be omitted. In both cases, the measurements
shall be recorded including V , I , V and I in addition to the maximum power.
oc sc mp mp
Performance of bifacial modules shall be characterized using IEC TS 60904-1-2 with Standard
Test Conditions applied to both the front side and the back side for initial and final
characterizations. Additionally (and for intermediate measurements), bifacial modules shall be
characterized under bifacial nameplate irradiance (BNPI) as defined in IEC 61215-1. All
measurements shall be included in the final report.
5.6 Insulation test
The insulation shall be tested as defined in IEC 61215-2, MQT 03. The insulation resistance
measurement shall be recorded and reported as part of the final report.

5.7 Wet leakage current
The wet leakage current shall be measured as defined in IEC 61215-2, MQT 15. The measured
leakage current shall be recorded and reported in the final report.
5.8 Electroluminescent imaging
Electroluminescent imaging shall be completed as defined in IEC TS 60904-13, using both low
and high injection levels for the initial characterization for all tests. For the post-stress
characterization, the low-injection imaging is optional for test sequences 1-4. The low-injection
image is required after the PID stress in test sequence 5. All high-injection images and
conditions used for their measurement shall be included in the final report. Low-injection images
shall be included in the final report for the PID test sequence 5, but may be omitted for the final
report for the other test sequences if they are indistinguishable from the high-injection images.
5.9 Insulation thickness test
For modules being stressed according to sequence 3, the final insulation thickness shall be
measured on any polymeric insulation sheets using the procedure described in IEC 61730-2,
MST 04. The measured thicknesses shall be reported. No pass-fail criteria are applied.
5.10 Thermal cycling
Thermal cycling shall be performed according to IEC 61215-2, MQT 11 with applied current
defined in the technology specific subclauses of IEC 61215-1-x. For bifacial modules, current
applied during MQT 11 shall be that defined in IEC 61215-1-1:2021: the peak power current at
bifacial stress irradiance (BSI).
5.11 Humidity freeze
Humidity freeze shall be performed according to IEC 61215-2, MQT 12 with any t
...