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.

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Status
Published
Publication Date
26-Apr-2021
Current Stage
PPUB - Publication issued
Completion Date
27-Apr-2021
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IEC TS 63209-1
Edition 1.0 2021-04
TECHNICAL
SPECIFICATION
Photovoltaic modules – Extended-stress testing –
Part 1: Modules
IEC TS 63209-1:2021-04(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
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

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 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

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IEC TS 63209-1:2021 © IEC 2021 – 3 –
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

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international

co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and

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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with

may participate in this preparatory work. International, governmental and non-governmental organizations liaising

with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for

Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

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.

---------------------- Page: 5 ----------------------
– 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.
---------------------- Page: 6 ----------------------
IEC TS 63209-1:2021 © IEC 2021 – 5 –
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.
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– 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.
---------------------- Page: 8 ----------------------
IEC TS 63209-1:2021 © IEC 2021 – 7 –

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
---------------------- Page: 9 ----------------------
– 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.
---------------------- Page: 10 ----------------------
IEC TS 63209-1:2021 © IEC 2021 – 9 –
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 technology

specific modifications made consistent with IEC 61215-1-x.
5.12 Final stabilization

Final stabilization shall be applied according to MQT 19.2 in IEC 61215-1 and the technology-

specific parts of the IEC 61215 series. In sequence 4 (damp heat) of this document, each final

stabilization shall include the stress-specific stabilization for B-O LID, as specified in MQT 19.3

of IEC 61215-2:2021.
6 Data collection and stress application
6.1 General

The individual stress application methods (without pass-fail criteria) are as described in

IEC 61215 series and IEC 61730 series, including the technology-specific parts of these. This

document describes which characterization tools to apply after each interval of stress

application. The sequences are summarized in Clause 8.
6.2 Initial characterization

Physical measurements shall be recorded as described in 5.2 to identify variations from sample

to sample and to precisely define the properties of the test samples for further comparison. In

the final report, these measurements shall be reported and compared with any corresponding

values found on the product specifications sheet.

All modules shall be characterized before application of stress using the methods described in

5.2 to 5.8.
---------------------- Page: 11 ----------------------
– 10 – IEC TS 63209-1:2021 © IEC 2021
Modules are subjected to five types of test sequences.
6.3 Test sequence 1: Thermal fatigue

Test sequence 1 is intended to test for thermal fatigue-related failures, such as solder bond

failure. It follows sequence D of IEC 61215-1 and is then extended to repeat the sequence two

additional times, with characterization at intermediate steps. Initially, the modules shall be

characterized as described in 6.2. The stresses and characterizations are completed according

to:
– Stress:
• IEC 61215-2 MQT 11 Thermal cycling (200 cycles, 5.10)
– Post-stress characterization:
• IEC 61215-2 MQT 01 Visual inspection (5.3)
• IEC 61215-2 MQT 19.2 Final stabilization (5.12)

• IEC 61215-2 MQT 06.1 Performance at STC and MQT 07 Performance at low irradiance

(5.5)
• IEC 61215-2 MQT 03 Insulation test (5.6)
• IEC 61215-2 MQT 15 Wet leaka
...

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