I E C TS 62 446-3
®

Edition 1 .0 201 7-06

TE C H N I C AL
S P E C I F I C ATI ON

colour
i n sid e

P h oto vol tai c (P V) s ys tem s – Re q u i rem en ts for te s ti n g , d ocu m en tati on an d
m ai n te n an ce –

IEC TS 62446-3:201 7-06(en)

P art 3: P h otovol tai c m od u l e s an d pl an ts – O u td oor i n frared th erm og raph y


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I E C TS 62 446-3
®


Edition 1 .0 201 7-06

TE C H N I C AL
S P E C I F I C ATI ON

colour
i n sid e

P h otovol tai c (P V) s ys te m s – Req u i rem en ts for tes ti n g , d ocu m e n tati on an d
m ai n ten an ce –
P art 3: P h otovol tai c m od u l es an d pl an ts – Ou td oor i n frared th erm og raph y

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.1 60

ISBN 978-2-8322-4290-2

Warn i n g ! M ake s u re th a t you ob tai n ed th i s p u b l i cati on from an au th ori zed d i stri b u tor.

® Registered trademark of the International Electrotechnical Commission


–2–

I EC TS 62446-3:201 7 © I EC 201 7

CONTENTS
FOREWORD ... ... ... ... ... ... ... .. ... ... ... ... ... ... . .. ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... .. . ... ... ... ... ... ... .. ... ... ... 4

1
Scope . ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... ... ... ... ... . 6
2 Norm ative references ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... . .. ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... .. 6
3 Term s and definitions ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... . .. ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... .. 7
4 Requirements of inspection equipment ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... . .. ... ... ... ... ... ... ... .. 9
4. 1
General . ... .. ... ... ... ... ... ... ... ... ... ... ... ... . .. ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... ... 9
4. 2
M inimum requirements for I R-cameras used for inspecting PV plants ... ... .. ... ... ... ... . 9
4. 3
Requirements for photo cameras for docum entation of the findings . ... ... ... ... ... ... ... . 1 0
4. 4
Requirements for equipment to record the am bient conditions ... ... ... ... ... ... ... ... ... ... 1 0
5 I nspection procedure . ... ... ... ... ... ... ... ... ... ... ... .. ... .. . ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... 1 1
5. 1
General . ... .. ... ... ... ... ... ... ... ... ... ... ... ... . .. ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... . 1 1
5. 2
Visual inspection .. ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... . .. ... ... 1 2
5. 3
Environmental conditions .. ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... .. 1 2
5. 4
I maging procedure .. .. ... ... ... ... ... ... ... ... ... ... ... ... . .. ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. . 1 3
5. 4. 1
General . ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... . .. . 1 3
5. 4. 2
Using fast carriers for I R-cam era, e. g. aerial drones . ... ... ... ... ... .. ... ... ... ... ... ... .. 1 3
5. 4. 3
Emissivity ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... . .. ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... .. 1 4
6 Software for evaluation . ... ... ... ... ... ... ... ... ... ... .. ... ... . .. ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... .. . ... ... 1 5
7 Evaluation .. ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... .. . ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... 1 5

7. 1
General . ... .. ... ... ... ... ... ... ... ... ... ... ... ... . .. ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... . 1 5
7. 2
Evaluation of I R images . ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... .. 1 6
7. 3
Therm al abnorm alities . ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... . 1 7
7. 3. 1
General . ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... . .. . 1 7
7. 3. 2
Classes of abnormalities (CoA) .. ... ... ... ... ... ... ... ... ... ... ... ... ... .. .. . ... ... ... ... ... ... ... ... 1 7
7. 3. 3
Abnormalities of PV m odules ... ... ... ... ... ... ... ... .. ... ... ... ... ... .. . ... ... ... ... ... ... ... ... .. ... 1 7
7. 3. 4
Abnormalities of other BOS components . ... ... ... ... ... ... ... .. ... ... ... ... ... . .. ... ... ... ... .. 1 7
7. 4
Projection of tem perature differences to nom inal irradiance .. .. ... ... ... ... ... ... ... ... ... ... 1 8
7. 4. 1
General . ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... . .. . 1 8
7. 4. 2
Modules . ... ... ... ... ... ... ... ... .. ... ... ... ... ... . .. ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... .. . ... ... ... . 20
7. 4. 3
Other BOS components ... ... ... .. ... ... ... ... ... ... ... ... ... .. . ... ... ... ... ... .. ... ... ... ... ... ... ... .. 21
8 I nspection report .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... .. . ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... .. 21
Annex A (norm ative) I nspection procedure explanations ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... . .. . 24
Geom etric resolution of the cam era .. ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... .. . ... .. ... ... ... ... . 24
A. 1
A. 2
Angle of view .. ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... .. . ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 24
A. 3
Matrix for cell identification .. ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... ... ... ... ... .. 25

Annex B (norm ative) Qualification of personnel . ... ... ... ... ... ... ... ... ... .. ... ... ... .. . ... ... ... ... ... ... ... ... .. 27
Annex C (normative) Matrix for thermal abnormalities of PV m odules . ... ... ... ... ... ... ... ... ... ... .. . 28
Annex D (informative) Pol ygon m easurement as a method of evaluation ... .. ... ... ... ... ... ... ... ... . 32
Annex E (inform ative) Beaufort scale . ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... 34
Bibliograph y . ... ... ... ... ... ... ... .. ... ... ... ... .. . ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... . 36
Figure 1 – I m pact of camera m oving speed . ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... . 1 4
Figure 2 – Dependence of the em issivity of glass on the angle of view [1 0] . ... ... ... ... ... ... ... ... . 1 5
Figure 3 – Examples of influence of wind (left) and cloud m ovement (right) on
observed temperature pattern ... ... ... ... ... ... ... ... ... ... .. ... ... ... .. . ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... . 1 6


I EC TS 62446-3: 201 7 © I EC 201 7

–3–

Figure 4 – Exam ple infrared thermogram s of a PV string com biner box with cables,
contacts, fuses and switches before (left) and after (right) m aintenance on a faulty
contact ... ... ... ... ... .. ... ... ... ... ... ... ... ... .. . ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... . 1 8
Figure 5 – Graphic representation of the correction factor for tem perature differences
to nom inal irradiance/load conditions as a function of the relative irradiance/load .. ... ... .. ... ... 1 9
Figure 6 – Example of image reporting ... ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 23
Figure A. 1 – Geom etric resolution of the I R cam era . ... ... ... ... ... ... ... ... ... .. ... ... ... ... .. . ... ... ... ... ... .. 24
Figure A. 2 – Angle of view ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... .. . ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... ... ... ... 25
Figure A. 3 – View for the designation of cell position, viewed from the front of a 60cell m odule, with the j unction box at the top (rear side) .. ... ... ... ... ... ... ... ... ... ... ... ... .. ... .. . ... ... ... . 26
Figure D.1 – Arithmetic mean value by pol ygon measurement ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... .. 32
Figure D.2 – Arithmetic mean and spot value by pol ygon measurement . ... .. ... ... ... ... ... ... ... ... . 33
Table 1 – Minimum requirem ents for I R-cam eras .. ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... .. . ... ... ... ... ... . 9
Table 2 – Requirements for equipm ent to record the ambient conditions ... .. ... ... ... ... ... ... ... ... . 1 1
Table 3 – Required inspection conditions . ... ... ... ... ... ... ... ... .. ... ... ... ... . .. ... ... ... ... ... ... ... ... ... ... .. ... . 1 2
Table 4 – Allocation in classes of abnorm alities . ... ... ... ... ... ... ... ... ... ... ... .. . .. ... ... ... ... ... ... ... ... ... .. 1 7

Table 5 – Example correction factors for tem perature differences to nom inal load
conditions based on formula above and Figure 5 . ... ... ... ... ... ... ... ... ... ... .. ... ... ... ... ... ... ... ... ... ... .. 20
Table E. 1 – Beaufort scale taken form World Meteorolgical Organization
(www. wmo.int) and Royal M eteorological Society (www.rm ets.org) . ... ... ... ... ... ... ... ... ... ... ... . .. .. 34


–4–

I EC TS 62446-3:201 7 © I EC 201 7

INTERNATI ONAL ELECTROTECHNI CAL COMMISSI ON
____________
P H O T O VO L T AI C ( P V) S YS T E M S –
RE Q U I RE M E N T S F O R T E S T I N G ,
D O C U M E N T AT I O N

P a rt 3 :

AN D M AI N T E N AN C E –

P h o t o vo l ta i c m o d u l e s a n d p l a n t s –

O u t d o o r i n fra re d th e rm o g ra p h y

FOREWORD
1 ) The I nternati on al Electrotech ni cal Comm ission (I EC) is a worl d wid e organization for stand ardization com prisin g
all nati on al el ectrotechnical comm ittees (I EC Nation al Comm ittees). The object of I EC is to prom ote
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8) Attention is drawn to the Norm ative references cited i n this publ ication. Use of the referenced publications is
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patent rig hts. I EC shall not be held responsibl e for identifyi ng any or al l such patent ri ghts.

The m ain task of I EC technical com mittees is to prepare I nternational Standards. I n

exceptional circum stances, a technical com mittee may propose the publication of a technical
specification when
•
•

the required support cannot be obtained for the publication of an I nternational Standard,
despite repeated efforts, or
the subject is still under technical development or where, for an y other reason, there is the
future but no immediate possibility of an agreem ent on an I nternational Standard.

Technical specifications are subj ect to review within three years of publ ication to decide
whether they can be transform ed into I nternational Standards.
I EC TS 62446-3, which is a technical specification, has been prepared by I EC technical
committee 82: Solar photovoltaic energ y systems.


I EC TS 62446-3: 201 7 © I EC 201 7

–5–

The text of this technical specification is based on the following documents:
Enqui ry draft

Report on votin g

82/1 1 88/DTS

82/1 242A/RVDTS

Full inform ation on the voting for the approval of this technical specification can be found in

the report on voting indicated in the above table.
This docum ent has been drafted in accordance with the I SO/I EC Directives, Part 2.
A list of all parts in the I EC 62446 series, published under the general title Photovoltaic (PV)
systems – Requirements for testing, documentation and maintenance , can be found on the

I EC website.

The committee has decided that the contents of this publication will rem ain unchanged until
the stability date indicated on the I EC website under "http: //webstore. iec.ch" in the data
related to the specific publication. At this date, the publication will be
•
•
•
•
•

transform ed into an I nternational standard,
reconfirmed,
withdrawn,
replaced by a revised edition, or
am ended.

A bilingual version of this publication m ay be issued at a later date.

I M P O RT AN T – T h e ' c o l o u r i n s i d e '
th at

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c o l o u r p ri n t e r.

of

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i ts

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c o n te n ts .

l og o
a re

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on

th e co ve r p ag e o f th i s

c o n s i d e re d
sh ou l d

to

t h e re fo re

be


p u b l i c ati o n

u s e fu l

p ri n t

th i s

fo r

i n d i c ate s

th e

d o cu m en t

c o rre c t
u si n g

a


–6–

I EC TS 62446-3:201 7 © I EC 201 7

P H O T O VO L T AI C ( P V) S YS T E M S –
RE Q U I RE M E N T S F O R T E S T I N G ,
D O C U M E N T AT I O N


P a rt 3 :

AN D M AI N T E N AN C E –

P h o t o vo l ta i c m o d u l e s a n d p l a n t s –

O u t d o o r i n fra re d th e rm o g ra p h y

1

S cop e

This part of I EC 62446 defines outdoor thermographic (infrared) inspection of PV m odules
and plants in operation. The inspection can include cables, contacts, fuses, switches,
inverters, and batteries. This inspection supports the preventive m aintenance for fire
protection, the availability of the system for power production , and the inspection of the
quality of the PV m odules. I ncluded in this document are the requirem ents for the
measurem ent equipm ent, am bient conditions, inspection procedure, inspection report,
personnel qualification and a m atrix for therm al abnorm alities as a guideline for the
inspection.
This document defines outdoor thermograph y on photovoltaic (PV) m odules and Balance-ofsystem (BOS) com ponents of PV power plants in operation, using passive techniques
(standard system operating conditions under natural sunlight, without an y external power or
irradiation sources). I EC 60904-1 2-1 covers general m ethods for laboratory or production -line
PV module thermographic im aging but not the specific details that are most relevant to
outdoor im aging of operational power plants including BOS components.
Two different levels of inspections are currentl y used:
a) A sim plified therm ographic inspection. This is a lim ited inspection to verify that the PV
m odules and BOS components are functioning, with reduced requirem ents for the
qualification of personnel. For exam ple, during a basic commissioning of a PV plant.

Authoritative conclusions regarding module quality are not possible with this inspection,
and exam ples of abnormalities are provided to aid the inspector.
b) A detailed thermographic inspection and anal ysis. This may include thermal signatures
which differ from the exam ples provided, and therefore requires a deeper understanding of
the therm al abnormalities. For exam ple, it m ay be used for periodic inspections according
to the I EC 62446 series and for trouble-shooting the cause of underperform ing system s.
Absolute tem perature measurem ents m ay be made. An authorized expert in PV plants,
together with therm ograph y experts can perform the inspection .
2

N o rm a t i ve re fe re n c e s

The following docum ents are referred to in the text in such a way that some or all of their
content constitutes requirem ents of this docum ent. For dated references, onl y the edition
cited applies. For undated references, the latest edition of the referenced document (including
an y amendments) applies.
I EC 60050-1 31 , International Electrotechnical Vocabulary – Part 131: Circuit theory
I EC 6021 6-2, Electrical insulating materials – Thermal endurance properties – Part 2:

Determination of thermal endurance properties of electrical insulating materials – Choice of
test criteria
I EC 6021 6-5, Electrical insulating materials – Thermal endurance properties – Part 5:

Determination of relative thermal endurance index (RTE) of an insulating material


I EC TS 62446-3: 201 7 © I EC 201 7

–7–


I EC 60269-1 , Low-voltage fuses – Part 1: General requirements
I EC 61 095, Electromechanical contactors for household and similar purposes
IEC 61 21 5-1 , Terrestrial photovoltaic (PV) modules – Design qualification and type approval –
Part 1: Test requirements
IEC 61 439-1 , Low-voltage switchgear and controlgear assemblies – Part 1: General rules
IEC 61 724-1 , Photovoltaic system performance – Part 1: Monitorin g
IEC 61 730-1 , Photovoltaic (PV) module safety qualification –Part 1: Requirements for

construction

IEC 61 730-2, Photovoltaic (PV) module safety qualification –Part 1: Requirements for testing
IEC TS 61 836, Solar photovoltaic energy systems – Terms, definitions and symbols
I EC 621 09-1 , Safety of power converters for use in photovoltaic power systems – Part 1:

General requirements

IEC 62446-1 , Photovoltaic (PV) systems – Requirements for testing, documentation and

maintenance – Part 1: Grid connected systems – Documentation, commissioning tests and
inspection
IEC 62446-2: –, Photovoltaic (PV) systems – Requirements for testing, documentation and

maintenance – Part 2: Grid connected photovoltaic (PV) systems – Maintenance of PV
systems 1
I EC 62930: –, Electric cables for photovoltaic systems with a voltage rating of 1, 5 kV d.c. 1
I SO 9488, Solar energy – Vocabulary
I SO 971 2, Non-destructive testing — Qualification and certification of NDT Personnel
VATh- Directive, Electrical Infrared Inspections – Low Voltage. Planning, execution and
documentation of infrared surveys on electrical sys te ms a n d com p on e nts ≤1 kV


(http: //www. vath. de/docs/richtlinien/VATh-Richtlinie_Elektro_N S+PV_engl_web. pdf)

EN 1 671 4-3, Non-destructive testing – Thermographic testing of electric installations
EN 501 1 0-1 , Operation of electrical installations – Part 1: General requirements
DGU V BGV/GU V-V A3 E, Accident prevention regulations, Electrical installations and

equipment
3

Terms and definitions

For the purposes of this docum ent, the term s and definitions given in I EC TS 61 836,
I SO 9488, I EC 60050-1 31 and the following appl y.
___________
1

To be publ ished.


–8–

I EC TS 62446-3:201 7 © I EC 201 7

I SO and I EC maintain term inological databases for use in standardization at the following
addresses:
I EC Electropedia: available at http://www. electropedia.org/
I SO Online browsing platform : available at http: //www. iso. org/obp

•
•

3. 1

a b n o rm a l t h e rm a l b e h a v i o r

thermal signature of an element that cannot be explained by its operating condition or its
technical design, e. g. position of load resistors
[SOU RCE:I EC 60050-903: 201 3, Am endment 1 : 201 4, 903-01 -22; m odified: adapted to therm al
behavior]
3. 2
re fl e c t e d

T

t e m p e ra t u re

m ean apparent tem perature of the am bient that is reflected by the object towards the I Rcamera
re fl

Note 1 to entry: Measured i n Celsius (° C).
Note 2 to entry: Som e m anufactures of I R cam eras use the term : am bient tem perature.
3. 3
a t m o s p h e ri c a i r t e m p e ra t u re

defined in Celsius (°C) for the geographic installation location as measured and documented
by meteorological services for this geographic location
3. 4
B e a u fo rt ( s c a l e )
B ft

quantifies wind speed by phenomenological criteria, e. g. movem ent of branches and trees

SEE: Annex E.
3. 5
cl o u d

c o v e ra g e

for the inspection two types of clouds are to differ: Cumulus and Cirrus. The cloud coverage
should be given in okta (part of eight of cloud coverage)
SEE: I SO 1 5469:2004[1 8] 2 .
3. 6
e m i s s i v i t y o f th e o b j e ct

ε

ratio of the thermal radiation that is em itted by the surface of an object compared to a black
bod y radiator both at the sam e tem perature
3. 7
I n s tan tan eo u s F i e l d

o f Vi e w

IFOV

field of view of one pixel of an I R-cam era-lens com bination
Note 1 to entry: Measured i n m illiradian (m rad ).

___________
2

Num bers in sq uare brackets refer to the Bi bliography.



I EC TS 62446-3: 201 7 © I EC 201 7

–9–

3. 8
N o i s e E q u i v a l e n t T e m p e ra t u re D i ffe re n c e
N ETD

smallest temperature difference detectable by an I R-camera
Note 1 to entry: Measured i n m illikelvin (m K).
3. 9
t h e rm a l

s te a d y s tat e co n d i ti o n s

usable m easurem ent conditions, which show stable tem peratures and temperature differences
4

4. 1

Re q u i re m e n t s o f i n s p e c t i o n e q u i p m e n t

G e n e ra l

This clause states the m inim um requirements for equipm ent used for thermographic (infrared)
inspection within the scope of this docum ent. I t includes requirements for the infrared (I R)
cam era, the photo cam era and equipment to record am bient conditions.
All equipm ent shall be date and time synchronized prior to use, to easily match im ages to

system conditions, for exam ple the in plane irradiation, and DC-load of the plant.
4. 2

Minimum

re q u i re m e n t s fo r I R - c a m e ra s u s e d fo r i n s p e c t i n g

P V pl an ts

The specifications of the infrared cam era shall fulfil the m inimum requirem ents according to
Table 1 .
Tabl e 1

– Minimum

re q u i re m e n t s fo r I R - c a m e ra s

F e a t u re s

Minimum

a

Spectral response

b

Tem peratu re-sensiti vity an d calibration –20 ° C to +1 20 °C
range (object tem perature range)


c

Operatin g am bient air tem perature
range

–1 0 ° C to +40 °C

d

Therm al sensiti vity

NETD ≤ 0, 1 K at 30 °C

e

Geom etric resolution

1)
2)

re q u i re m e n t s

2 µ m to 5 µm (m id wavelen gth ) or 8 µ m to 1 4 µ m (long
wavel ength) 1

PV m odule: m ax. 3 cm of the m odule ed ge per pi xel 2
Electrical con nections: Th e geom etrical resol ution (Real
m easurem ent spot 3 ) h as to m atch the sm allest object area to
be verifi ed.


Futher details can be found in Clauses A. 1 and A. 2.
f

Absolute error of m easurem ent

<±2K

g

Adjustabl e param eters

Em issivity ( ε ), reflected tem perature ( Trefl )

h

Adjustabl e functions

Focus, tem peratu re level an d span

i

Measurem ent functions

Measuri ng spot, m easuring area with average and m axim um
tem peratu re


– 10 –
Featu res


I EC TS 62446-3:201 7 © I EC 201 7
M i n im u m req u i rem en ts

j

Cali bration

The m easuri ng system (cam era, lens, aperture an d filter): Th e
therm ographic cam era shall be traceably cal ibrated at least every
two years. The cali brati on has to be d ocum ented. I f the cam era is
not com pliant (absol ute tem perature an d/or tem perature
differences), it m ay be readj usted by the m anufacturer.

k

Docum entation

Storin g of the i nfrared pictu re with all radiom etric inform ation to be
able to determ ine absolute temperatu res. Non-radiom etric pictures
can onl y provid e pattern an d eventuall y tem perature d ifferences.

1

Cam eras operati ng in wavel ength rang e of 2 µ m to 5 µ m shall on ly be used for therm ography of el ectrical
BOS com ponents, e. g. fuses. Due to th e transparency of g lass in the ran ge of 3 µ m the use of that rang e on
PV m odules can l ead to m easurem ent errors.

2

3 cm length of ed ge per pi xel equals 5 x 5 pi xel on a 6“ PV cell.


3

The real m easuring spot m ostly is defin ed as 3 x 3 pi xel, for high -q uality optics.

Use of an I R camera with re s o l u ti o n ≥ 320 x 240 pixels and a separate photo cam era are
recom mended, with m onitor and remote control or a swivelling display.
4. 3

Req u i rem en ts for ph oto cam eras for d ocu m entation of th e fin din gs

Visual photos documenting the state of the module/plant are recom mended, however visual
photos of an y thermal abnorm ality are required. One photo of every safety relevant
abnorm ality (see Table 4) shall be taken.
The resolution of the visual photo shall be significantl y higher than the I R im age and shall
have a sim ilar field of view to sufficientl y capture all details of the object (e.g. , busbars,
ribbons of a solar cell, broken front glass, fuse and fuse holder). I t shall be ensured that I R
and visual photo capture the same area of interest while fulfilling the resolution requirem ent.
A separate photo camera and I R camera are recom mended, in order to ensure sufficient
resolution of visual photo (typicall y at least 30 times higher).
NOTE I n m any cases, th e basic photo cam era which is i ntegrated i nto th e i nfrared cam era is not abl e to provi de
the requested resol ution. For an I R cam era of 640 x 480 pi xel a separate ph oto cam era with at least 9 M pi x is
suitable.

4. 4

Req u i rem ents for equ i pment to record th e ambi ent cond iti on s

To detect thermographic abnormalities correctl y, certain am bient conditions have to be m et.
Equipm ent to m easure these conditions should be com pliant to the minim um requirements in

Table 2.


I EC TS 62446-3: 201 7 © I EC 201 7

– 11 –

T a b l e 2 – R e q u i re m e n t s fo r e q u i p m e n t t o re c o rd
th e a m b i e n t co n d i ti o n s

P a ra m e t e r

Eq u i pm en t

Ac c u ra c y

a

I rradiance

I rradiance sensor (crystalli ne
silicon cell or pyranom eter)

Cali bration: ± 5 %

b

Am bient (air) tem peratu re

Tem peratu re sensor (shiel ded

from direct lig ht and win d)

Cali bration: ± 2 K

c

Wind speed

Bft scale (visual) or anem om eter

Estim ation

d

Cl ou d coverag e

Photo cam era

Estim ation

e

Deg ree of soili ng

Photo cam era

Estim ation
Estim ation can be done usi ng
procedu re accordi ng to
I EC 61 724-1


f
1

5

5. 1

Modul e or string cu rrent

DC (cl am p) am pere m eter (or
inverter readin g 1

Cali bration: ± 2 %

Note that the i nverter readin g m ay not gi ve accu rate resu lts or be calibrated. Though it m ay be usefu l for
som e BOS com ponents, it m ay also not h ave resoluti on for PV string-l evel current m easurem ent.

I n s p e c t i o n p ro c e d u re

G e n e ra l

An inspection of the PV plant should be done during the commissioning and operation of the
power plant, in accordance with applicable health and safety regulations. The recomm ended
interval for periodic therm ograph y inspections is four years but the applied intervals for a
specific installation shall be agreed upon with the owner / operator, or they m ight be defined
by national electric codes and safety regulations for electrical installations.
The owner, operator or an authorized person shall give the inspector(s) an introduction into
the safety specific regulations of the PV plant to be inspected , including details of the plant
and electrical layout. A second person should be present during inspection, and m ay be

required by local safety regulations. At least one of the persons perform ing the inspection
shall have technical knowledge of the specific system , and of PV plants in general.
I nspections shall be done following applicable safety regulations, for exam ple in accordance
to EN 501 1 0-1 or DGU V BGV/GU V-V A3 E.
The detailed inspection scope shall be defined prior to the inspection and agreed in writing
between the involved parties.
The plant shall be under operating conditions. The part of the system under evaluation shall
be in therm al stead y state condition and free of partial shading (if possible). Soiling should be
low (less than 1 0 % operating current I m pp loss) and hom ogeneous, without causing partial
shading (e. g. , by bird droppings, leaves, vegetation) to avoid therm al effects. I f strong soiling
or partial shading due to, for exam ple bird droppings, is observed on the PV modules, it is
recom mended to clean the entire system prior to inspection. N ote that the perform ance of the
system m ay change as a result of the cleaning. Ensure modules are at therm al stead y state
after cleaning prior to perform ing infrared im aging inspection.
For quantification of soiling, it is recom mended to conduct m easurements according to
IEC 61 724-1 . This might be helpful to compare m easurem ents from periodic inspections.
Collecting I R images can be done in different ways, e. g. , using tripods, by hand or drones.
Care shall be taken that the method selected still m eets the resolution requirem ents, and to
ensure understanding of the m ethod used (e. g. , reflections). An y known deviations or
limitations shall be noted in the inspection report.


– 12 –

I EC TS 62446-3:201 7 © I EC 201 7

National regulations and laws may apply to using I R cam eras and other equipm ent like
drones.
The inspection results verify the status at the time of inspection. I ssues of interm ittent or
changing nature may or may not be captured at the tim e of inspection.


5.2

Visual inspection

Prior to the therm ographic inspection of the PV plant, it is recomm end to do a visual
inspection to determine whether the requirem ents of 5. 1 are m et. Observations such as bird
droppings, strong soiling, burn spots on modules or other Balance of System (BOS)
components shall be documented by photos and location prior to the therm ographic
inspection. I f possible, those findings should be resolved (e. g. by cleaning) prior to the
therm ographic inspection especiall y during comissioning. Photos post-cleaning (pre-imaging)
should be documented. However, it m ay be desireable to conduct the therm ograph y
inspection without cleaning, e. g. for a root-cause analysis for a poor performing PV power
plant.
Upon observation of therm al anom alies, it is desireable to visuall y inspect the component and
visuall y observe an y abnormal conditions in the area. The PV module visual inspection
procedures in I EC 61 21 5-1 and I EC 61 730-2 may be useful references. A visual photo shall
be captured for every therm al abnorm ality type.

5.3

Environmental conditions

The inspection should be perform ed under the conditions specified in Table 3.

Table 3 – Required inspection conditions
Parameter
a

I rradiance


Limits
•
•

Min im um 600 W/m 2 in the plan e of the PV m odule for PV m odule inspection
Measured operati ng current shall be a m inim um of 30 % of rated system current
within th e inspected current path (typicall y > 30 % of PV m odule nam e plate I sc at
STC (eq uals typically > 300W/m 2 in the plan e of the PV m odul es) for i nspection of
other electrical com pon ents (e. g. cabl es, connectors, con nections). Recom m ended
for inspection are > 600 W/m 2 .

NOTE Exam ple for singl e stri ng with no parall el conn ection: 30 % of STC I sc current.
I sc to be taken from PV m odul e nam e plate an d not to be m easured on PV plants.
b

Wind speed

Maxim um 4 Bft or 28 km /h (see Annex E)

c

Clou d coverag e

Maxim um 2 okta of sky covered by cum ulus clou ds

d

Soiling


No or low. Cleani ng recom m end, e. g. if bird d roppin gs exist.

NOTE For cloud coverag e, fin d furth er i nform ation in I SO 1 5469: 2004.

After change in operating conditions, for example load or irradiance (due to e. g. cirrus clouds)
of >1 0 % per m inute, a waiting time of 1 5 m in is recomm ended to regain the stead y state
measurem ent conditions.
The cloud coverage should not consist of more than 2 okta of cum ulus clouds, because of
misleading reflections on the modules.


I EC TS 62446-3: 201 7 © I EC 201 7
5. 4

5. 4. 1

I m ag i n g

– 13 –

p ro c e d u re

G e n e ra l

The distance between the inspected object and the I R-cam era shall fulfil the geometrical
resolution, specified in 4. 2, while required safety distances according to safety regulations are
met. (See Clauses A. 1 and A. 2)
The I R-cam era im age shall be taken as perpendicular to the PV module surface as possible.
At the sam e time, self-reflection of m easuring personnel and I R-camera apparatus, and
reflection of heated obj ects like sun, near-by buildings and trees shall be avoided. I n cases

where the im age cannot be taken perpendicular to the PV m odule surface, e. g. a sm all
installation with lim ited ability to raise the cam era, the angle between the cam era and the PV
module plane should still be greater than 30° (see Clause A. 2).
Adjust the camera em issivity based on surface conditions of the obj ect under investigation
(e. g. soiling of m odule front glass or dust on shi ny parts of e.g. fuse holders).
The DC-load of the plant shall be monitored and recorded to avoid measurem ents under
undefined load conditions due to grid events (e.g. strings are open circuit or short circuit).
Together with the thermographic im age, a photo of the sam e area shall be taken for each type
of thermal finding. The exact position of all the findings in the inspected system shall be
documented, as well as the operating conditions including local DC load and environm ental
conditions.
Two different levels of quality of examinations are currentl y used:
a) Simplified inspection:
The simplified thermographic inspection with reduced requirements for the qualification of
personnel (see Annex B). This is for a lim ited inspection to test the basic functioning of the
PV modules. For exam ple, during the comm issioning of system s. Authoritative conclusions
regarding m odule quality are not possible. No absolute tem peratures are determined,
therefore therm al pattern s are used to evaluate the abnormalities. Refer to the exam ples
in Annex C.
b) Detailed inspection:
The detailed thermographic inspection and anal ysis, which may include thermal patterns
which differ from the examples in the Annexes. This may be useful for trouble-shooting
and for periodic inspections according to I EC 62446-1 and future I EC 62446-2. Absolute
temperature m easurements are determ ined during this detailed inspection. An authorized
expert for PV plants, together with therm ographic experts, shall have advanced
qualifications as per Annex B.
5. 4. 2

Using


fa s t c a rri e rs fo r I R - c a m e ra ,

e.g.

a e ri a l d ro n e s

Aerial drones are increasingly being used as part of the tool kit for fault detection and
localization in PV plants. I t should be noted that while drones help scale, automate and
accelerate detection of faulty areas within a large power plant, such techniques can lack the
resolution to detect fine com ponent artifacts or identify specific failure modes. Such an
inspection by drones is classified as sim plified inspection procedure of the whole PV array in
order to find PV sub arrays/strings/modules with obvious noticeable problems.
In the case where im aging is perform ed usi ng a fast carrier, the moving speed of the cam era
should always be chosen with respect to the time constant of the cam era’s I R-detector to
avoid sm earing effects (com pare the following pictures in Figure 1 ). Smearing influences
visual pattern and absolute and relative tem peratures. Relevant sm earing effects on common
IR cam era bolom eter detectors, when used for PV-modules and system s, m ay alread y appear
at a m oving speed of 3 m /s.


– 14 –

I EC TS 62446-3:201 7 © I EC 201 7

For large-area im aging such as through use of drones, consider irradiance and system
stability, especiall y if im ages will be stitched together and not individually m apped to system
perform ance (instantaneous DC string current).
Ensure the geometric resolution requirem ents are met, especiall y if the distance between the
I R camera and PV module is large. I f the requirem ents are not met, it is a deviation to the
procedure.

NOTE A typical approach is to do this sim plified i nspection at the whol e PV array to find PV m odules or strin gs
with n oticeable problem s. Afterwards a detailed inspection i s done at these PV m odul es. This partial or detail ed
inspection can be agreed in a contract, al ong with the th resholds for d ecidin g what sort of issue in the sim plified
procedure wou ld warrant the d etailed approach described i n this docum ent.

IEC
a)

P i c t u re c a p t u re d
speed

wi th

s l o w c a m e ra m o v i n g

wi th o u t n o ti c e a b l e

s m e a ri n g

F i g u re 1

5. 4. 3

IEC
b)

P i c tu re c a p tu re d
wi th

– I m p a c t o f c a m e ra m o v i n g


at hi gh

c a m e ra m o vi n g

speed

u n a c c e p t a b l e s m e a ri n g

speed

E m i s s i vi ty

Estimating the em issivity of the exam ined surface is the responsibility of the qualified
thermographer, particularl y in the case of detailed inspection. The emissivity of a surface
depends on m an y factors. Man y of them are less relevant for the given task (such as the
exact spectral range of the (LW)-I R-cam era, surface and ambient temperature, surface
geom etry, etc. ).
For the simplified inspection, the m ost im portant dependencies and som e comm on values are
given for com m on surface and am bient tem peratures, surfaces without holes and (LW)-I Rcam eras (note that less common MW-I R-cameras differ significantl y):
For the practice of thermograph y on PV modules and BOS components, it is im portant to
understand the following three dependencies: first m aterial, second surface (includes soiling)
and third angle of view. Dependencies and values are given by examples.
a) Materials such as unoxidised m etal (parts made out of stainless steel), polished
aluminium parts and some BOS components have very low emissivities around ε = 0, 1 to
ε = 0, 3, therefore an accurate tem perature determ ination is not possible.
b) Most insulation synthetics and ceram ics have em issivity around ε = 0,9.
c) Rough oxidated aluminium of m odule frames and mounting clamps and som e BOS
components typicall y show values above unoxidised m etal, but below glass, typicall y
about ε = 0,4 to ε = 0, 7.

d) Materials like glass have higher emissivities around ε = 0,85. Glass with a rough surface,
such as textured glass or glass with high degree of soiling m ay have an em issivity up to
ε = 0, 9.


I EC TS 62446-3:201 7 © I EC 201 7

– 15 –

e) On non-ferrous glass the em issivity decreases with the angle of view, so at around 45° the
em issivity will be around ε = 0, 8 and at 30° it can be around ε = 0, 75 or lower.
(See Figure 2 and also Clause A.2.)

Emissivity

Angle of view on m odule

at T refl

=

–50 °C

at T refl

=

250 °C

IEC


Figure 2 – Dependence of the emissivity of
glass on the angle of view [1 0]

6

Software for evaluation

Using software, it is possible to transfer the radiation density values measured by the I Rcamera into absolute temperature values. The calculations may be done directl y using the I Rcam era software, which updates the tem perature labels on the display screen and in the
saved file. Care shall be taken when interpreting an y temperature values, as they m ay not be
absolute temperatures if the correct parameters were not set. To obtain temperature values, it
is necessary to set specific param eters, in particular:
a)
b)
c)
d)

em issivity, ε ,
reflected tem perature, Trefl,
tem perature level and span,
different m easuring tools (e.g. spot m easurement, pol ygons) under specification of
minim um , m axim um and arithm etic mean value for the temperature data.

7

Evaluation

7.1

General


The following measurements and observations are important for evaluation or validation:
a)
b)
c)
d)

maximum temperatures,
temperature differences,
temperature profiles,
cloud, cloud movem ent, cloudiness (see exam ple in Figure 3 right),


– 16 –
e)
f)
g)
h)
i)

I EC TS 62446-3:201 7 © I EC 201 7

wind speed and direction (see exam ple in Figure 3 left),
previous mechanical stress from installation history logfile,
soiling,
visual inspection,
irradiance and/or DC load of system .

Results and recomm endations of previous inspections should also be taken into
consideration.

During a sim plified thermographic inspection of a PV plant no exact tem peratures are
determ ined. Here the m ain focus is onl y on evaluating certain therm ographic pattern s as
shown in Annex C. To evaluate absolute tem perature and tem perature differences, a detailed
inspection shall be done with appropriate qualified person el (see Annex B). General guidance
can be found in EN 1 671 4-3 and VATh-Directive.

IEC

F i g u re 3 – E x a m p l e s o f i n fl u e n c e o f w i n d
o n o b s e rv e d

7. 2

IEC

( l e ft )

an d

c l o u d m o v e m e n t ( ri g h t )

t e m p e ra t u re p a t t e rn

E va l u ati o n o f I R i m a g e s

This subclause introduces several techniques to evaluate I R images. Other procedures exist
and can be applied also.
a) Patterns (Simplified inspection, see Annex C)
The abnorm aity is classified and evaluated by a known thermal pattern. Measurement of
absolute and relative tem perature values are not neccesary but can supplem ent therm al

patterns as plausibility check.
b) Temperatures of point abnormalities (Detailed inspection, see Annex D)
Use an algorithm to determ ine highest tem perature in the image. This can be done using
different types of tools such as “freehand spot” or “m axim um spot within an area” in the
camera and image processing software.
c) Extended areas (Detailed inspection, see Annex D)
Use different types of tools such as “rectangle”, “circle” or “polygon areas” to calculate the
m ean tem peratures of the areas, using the cam era and image processing software.
d) Relative tem peratures (Detailed inspection, see Annex D)
Can be calculated between point abnorm alities and/or the mean values of extended areas,
with consideration of the uncertainty of measurement.
e) Absolute temperatures (Detailed inspection, see Annex D)
Can be measured at point abnormalities and the mean values of extended areas, with
consideration of the uncertainty of measurem ent.


I EC TS 62446-3: 201 7 © I EC 201 7

– 17 –

Attention: Absolute tem peratures on PV generators vary due to wind and convection
differences with tim e and position in the PV array and plant.

7.3
7.3.1

Thermal abnormalities
General

This subclause applies in particular for detailed inspection.


7.3.2

Classes of abnormalities (CoA)

For the allocation into classes of abnormalities (CoA), the specific patterns and measured
tem peratures have to be compared with the examples of therm ographic im ages and
differences in tem perature shown in Annex C. Table 4 introduces three classes of
abnormalies and their follow up action. This is im portant since there might be imminent
danger (electric shock or fire) to peronal and property.

Table 4 – Allocation in classes of abnormalities
Cl ass of Abnorm ality (CoA) 1 (n o abnorm alities – OK)

2 (therm al abnorm ality – tA) 3 (safety relevant therm al
abnorm ality – dtA)

Recom m endation for
actions

Checkin g the cause an d, if Prom pt interrupti on of
necessary, rectification i n a operati on, checkin g the
reasonable period.
cause an d rectificati on in a
reasonable period.

No im m inent action

I t is not always possible to classify thermal abnormalities without an y doubt using
thermograph y inspection alone. I n this case additional appropriate inspections shall be

applied.

7.3.3

Abnormalities of PV modules

Thermal images and resulting tem perature differences shall always be evaluated in the
context of the am bient conditions, type of mounting, and module assembl y (glass-glass
m odule, glass-foil m odule, integrated pol ym ers, etc.).
I f a doubtless classification from the front side of a PV m odule is not possible, a back side
view (optical and therm ographic) or further m easurement techni ques shall be utilized or a
more qualified personnel (therm ograph of level 2 or equivalent) shall become involved.
Suggested actions for further m easurements and rectification are described in Annex C.

7.3.4

Abnormalities of other BOS components

The BOS component inspection includes, but is not limited to, cables, contacts, fuses,
switches, inverters and batteries. An exam ple is given for a faulty (abnorm al) contact.
Classification of abnormalities will depend on the BOS component. N o specific PV
requirements are developed, yet. For the time being, refer to the applicable product standards
and general electro thermograph y techniques for electrical components and their defined
requirements. See Figure 4.


– 18 –

I EC TS 62446-3:201 7 © I EC 201 7


IEC

Figure 4 – Example infrared thermograms of a PV string combiner box
with cables, contacts, fuses and switches before (left) and after (right)
maintenance on a faulty contact
7.4
7.4.1

Projection of temperature differences to nominal irradiance
General

The following gives guidance for the extrapolation of the m easured tem perature difference
between functioning and non/partial-functioning com ponents under actual conditions, to the
expected tem perature difference under nom inal in plane irradiance of the PV m odule, defined
as 1 000 W/m 2 . This applies for PV m odules and for other BOS com ponents for an y therm al
abnormality, and does not consider other conditions such as wind speed which are separatel y
reported.
Here, therm al abnorm alities are differentiated between:
a) point abnormalies (e. g. localized hot-spots in solar cells or a fuse), and
b) extended area abnorm ality (e. g. an entire warm/hot solar cell or a heat sink plate).
For tem perature difference extrapolation the following formula shall be used:
∆푇2

푥

퐺

= � 퐺2 � ∆ 푇1
1


NOTE 1 Reference for the form ula: Gui deli nes to th erm ographic i nspection of el ectrical install ations; Thom as
Perch-Niel sen; J ens Christian Sorensen; 1 994 [1 ].

where
∆T

is the temperature difference between functional and non-functioning components
under identical irradiance condition i
G
is the irradiance or load (DC current) at condition i
I ndex i = 1 is the value at actual/partial irradiance/load (see Table 3 for m inim um required
partial irradiance/load conditions);
I ndex i = 2 is the value at nominal load/tem perature (1 00 % irradiance/load condition);
x
is the exponential factor, considering different shapes of abnormalities. For im pact
of x see Figure 5.
i

;

i

;

Since DC current load generated by the PV m odules is proportional to irradiance and if the
nom inal current load at 1 000 W/m 2 is known, DC current load m ay be substituted for
irradiance in the above formula and Table 5.


I EC TS 62446-3:201 7 â I EC 201 7

ã

19 –

For a point abnorm ality (point heat source with radial heat transport – typicall y up to a
couple of square m illim etres in size and m uch sm aller than a cell – for example, for
a 6” c-Si cell a point abnorm ality is typicall y less than 3 m m 2 ) the following applies:
exponential factor x is typicall y between 1 , 5 and 1 , 8, where x = 2, 0 represents onl y current
induced heat from a point spot, without an y heat dissipation by radiation.

NOTE 2 "6 inch cell" is an expression currently used in the PV in dustry; 6'' correspon ds to 1 5, 24 cm . However,
other sim ilar sizes are used in the PV industry as well.
•

For extended area abnormality (lateral extended heat source – typicall y of the size of one
or m ore cells) the following applies:
exponential factor x is typicall y x = 1 and therefore represents a linear dependence of
tem perature on irradiance / current load.
1 2, 0

Correction factor

1 0, 0

Linear x = 1
Factor x = 1 , 6

8, 0

Factor x = 2, 0

6, 0
4, 0
2, 0
0
20

30

40

50

60

70
80
Load (%)

90

1 00

110

1 20
IEC

Figu re 5 – Graphi c representation of the correction factor for temperature
differen ces to nomin al i rrad i an ce/load cond iti ons as a fun ction of
the rel ative i rrad i an ce/l oad


For convenience, the exponential factor x and the irradiance/load terms can be combined into
a “correction factor”, to directl y extrapolate ∆ T from the m easured to the nominal condition .
Values for these correction factors for point abnormalities and extended area abnormalities of
PV m odules and BOS components can be found in the corresponding columns of Table 5 and
graphicall y showin in Figure 5.
푐푐 푐푐푐 푐푐푐푐 푐 푓푓푐푐푐 푐

퐺

= � 퐺2 �
1

푥


– 20 –

I EC TS 62446-3:201 7 © I EC 201 7

Table 5 – Example correction factors for temperatu re differences
to nominal load conditions based on formula
above and Figure 5
Fraction of rated
irradian ce /
curren t load

Point abnormality

extended area abnormali ty

( x = 1 , 0)

%

7.4.2

PV modules

Other BOS

PV modules

Other BOS

( x = 1 , 5)

( x = 1 , 6)

30

NA

6, 9

NA

3, 3

40
50


NA

4, 3

NA

2, 5

NA

3, 0

NA

2, 0

60

1 ,7

2, 3

1 ,7

1 ,7

70

1 ,4


1 ,8

1 ,4

1 ,4

80

1 ,3

1 ,4

1 ,3

1 ,3

90

1 ,1

1 ,2

1 ,1

1 ,1

1 00

1 ,0


1 ,0

1 ,0

1 ,0

110

0, 9

0, 9

0, 9

0, 9

1 20

0, 8

0, 8

0, 8

0, 8

M odules

For a sim plified inspection, 7. 4 does not appl y since onl y I R patterns as given in Annex C

shall be used for interpretation of abnorm alities.
For a m ore detailed inspection absolute temperatures are im portant. For a detailed inspection ,
maximum tem peratures, tem perature differences and tem peratures gradients shall be
evaluated. Qualified personel are required as per Annex B.
Guidance for norm alizing temperature differences for m odule abnorm alities is given in 7. 4.
A clear differentiation shall be m ade between point and extended area abnormalities.
The detailed evalutation shall consider also addititional observations such as DC current load
measured at the abnorm ality, soiling (homogenious or partial), possible mechanical stress
(e. g. due to installation, therm al cycling, or snow loads), previous inspections, and material
properties of the components.
At least the following normative references shall be taken into account, e. g. for operating
conditions, expected temperatures and tem perature limits given by the used materials:
•
•

•

I EC 61 730-1 , Photovoltaic (PV) module safety qualification – Part 1: Requirements for

construction

I EC 6021 6-2, Electrical insulating materials – Thermal endurance properties – Part 2:
Determination of thermal endurance properties of electrical insulating materials – Choice
of test criteria
I EC 6021 6-5, Electrical insulating materials – Thermal endurance properties – Part 5:
Determination of relative thermal endurance index (RTE) of an insulating material

Based on the results, a classification of each abnormality according to 7. 3 and Table 4 shall
be done. Exam ples of corrective actions for PV m odules are specified in Annex C.



I EC TS 62446-3: 201 7 © I EC 201 7
7 . 4. 3

– 21 –

O th e r B O S co m p o n e n ts

The BOS component inspection includes, but is not lim ited to, cables, contacts, fuses,
switches, inverters and batteries.
General guidance for normalizing temperatures for BOS com ponents is given in 7. 4. A clear
differentiation shall be done between point and extended area abnorm alities. For evaluation
the com ponent shall be stressed with at least 30 % of its nom inal m axim um rating in its
application, recommended is more than 60 %, per Table 3.
Based on the results, a classification of each component according to 7. 3 and Table 4 shall
be done. Corrective actions for BOS components depend on com ponent. Guidance can be
found in the following references and in manufacturers documentation :
•

Cables:
– Future I EC 62930, Electric cables for photovoltaic systems with a voltage rating of 1, 5

kV d.c.

•

•

Fuses:
– I EC 60269-1 , Low-voltage fuses – Part 1: General requirements

I nverters:
– I EC 621 09-1 , Safety of power converters for use in photovoltaic power systems –

Part 1: General requirements
– I EC 61 095, Electromechanical contactors for household and similar purposes

•

Switchgear:
– I EC 61 439-1 , Low-voltage switchgear and control gear assemblies – Part 1: General

rules

– I EC 61 095, Electromechanical contactors for household and similar purposes
8

I n s p e c t i o n re p o rt

The inspection report shall contain the following inform ation:
a)
b)
c)
d)
e)

name of the PV expert, thermographer and of the attending persons,
type, including m ake and models, of the cam era system ,
day and tim e of the inspection,
location of the inspection,
scope of inspection as contracted:

1 ) with type designation of components,
2) efficiency of PV m odule, nom inal rating of BOS component,
3) listing of all inspected components,
4) m ounting:
i) Modules: type of m ounting (e. g. roof mounted: parallel, tilted, in roof; greenfield
installation; orientation; inclination).
ii) BOS com ponent location (e. g. roof, conduit, open-air).

NOTE M od ules with hig her efficiency wi ll reach lower n orm al operati ng absolute tem peratu re valu es.

f) environm ental conditions:
1 ) air temperature, in °C,
2) wind speed, in Bft or m/s and direction,
3) cloud coverage, in okta and type of cloud,
4) irradiance in plane of m odule, in W/m²,


– 22 –

I EC TS 62446-3:201 7 © I EC 201 7

g) soiling of component (mainl y important for PV modules) with photos as evidence,
h) description of the inspection procedure,
i) listing of the identified thermal noticeable spots with identification of their position inside
the PV plant, using at least 2 of the possible identifications for each item :
1 ) PV modules:
i) serial num ber,
ii) a photograph which shows the position of the m odule in the array (for small
installations onl y),
iii) X-Y coordinates with clear identification of column and row,

iv) m arking in the system documentation (string or table/roof plan),
v) permanent m arking of the module on site.
2) Other BOS:
i) serial number,
ii) marking on a photograph clearl y indicating the location within the photo, and
clearl y identifying the location of the photo,
iii) X-Y coordinates with clear identification ,
iv) marking in the system docum entation,
v) permanent m arking of the component on site,
j) recom m endation for the next periodic inspection, if different from the 4 year cycle,
k) recom m ended actions based on classification of the abnorm alities,
l) summ ary of the results.
For thermal abnorm alities within a module, the thermographic image shall show at m inimum
one whole m odule, pointing out the position of the junction box and the lower edge within the
installation. Additional thermographic im ages of detailed views m ay be added for further
clarification (See Clause A. 3).
The following details shall be given for every therm ographic image:
m)
n)
o)
p)
q)

exact description of the object,
file name, date and tim e of taking the thermographic im age,
cam era system with serial num ber and lens,
used em issivity and recorded reflected-tem perature ( Trefl ),
exact description of the location in the PV plant, which allows the custom er the clear
identification of the abnormality,
r) in case immediate action is required (see 7. 3), a photo with sufficient resolution to visuall y

distinguish the details in the therm ographic im age shall be provided ,
s) for detailed inspections, tem peratures ( Tatm , objects) or temperature difference at the
thermal abnorm ality, preferabl y in com parison to the temperature of an regular spot,
t) conclusions and recommendations for further actions.
An example including a pol ygon evaluation is given in Figure 6. The details may be recorded
within the image file itself, or separately.


I EC TS 62446-3:201 7 © I EC 201 7

– 23 –

IEC

Key
rig ht: color schem e of tem peratu re, center: I R im age, left: im age inform ation like fi le n am e, date, tim e, used
equi pm ent with setting, am bient conditi ons like Trefl , Tatm , i rradiance, wi nd speed and proj ect inform ation such as
m odule efficiency

Figure 6 – Example of image reporting