IEC 61643-31:2018

IEC 61643-31 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage surge protective devices –
Part 31: Requirements and test methods for SPDs for photovoltaic installations

Parafoudres basse tension –
Partie 31: Parafoudres pour usage spécifique y compris en courant continu –
Exigences et méthodes d'essai des parafoudres pour installations
photovoltaïques
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IEC 61643-31 ®
Edition 1.0 2018-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Low-voltage surge protective devices –

Part 31: Requirements and test methods for SPDs for photovoltaic installations

Parafoudres basse tension –
Partie 31: Parafoudres pour usage spécifique y compris en courant continu –

Exigences et méthodes d'essai des parafoudres pour installations

photovoltaïques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.240.01; 29.240.10 ISBN 978-2-8322-5211-6

– 2 – IEC 61643-31:2018 © IEC 2018
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions, acronyms and symbols . 9
3.1 Terms and definitions . 9
3.2 Acronyms / Symbols . 16
4 Service conditions . 17
4.1 Voltage . 17
4.2 Air pressure and altitude . 17
4.3 Temperatures . 17
4.4 Humidity . 18
5 Classification . 18
5.1 General . 18
5.2 SPD design . 18
5.3 Class I, II and III tests . 18
5.4 Location . 18
5.4.1 Indoor . 18
5.4.2 Outdoor . 18
5.5 Accessibility . 18
5.5.1 Accessible . 18
5.5.2 Inaccessible . 18
5.6 Disconnectors (including overcurrent protection) . 18
5.7 Degree of protection provided by enclosures according to IP-code of
IEC 60529 . 19
5.8 Temperature and humidity range . 19
5.9 Multipole SPD . 19
5.10 SPD failure mode . 19
5.11 PV earthing system . 19
6 Requirements . 19
6.1 General requirements . 19
6.1.1 Identification . 19
6.1.2 Marking . 21
6.2 Electrical requirements . 21
6.2.1 Protection against direct contact . 21
6.2.2 Residual current I . 21
PE
6.2.3 Voltage protection level U . 21
p
6.2.4 Operating duty . 21
6.2.5 Disconnectors and status indicators . 22
6.2.6 Insulation resistance . 23
6.2.7 Dielectric withstand . 23
6.2.8 Continuous current I . 23
CPV
6.2.9 Total discharge current I (for multipole SPDs) . 23
Total
6.3 Mechanical requirements . 23
6.3.1 Mounting . 23
6.3.2 Screws, current carrying parts and connections . 23

6.3.3 External connections . 23
6.3.4 Air clearances and creepage distances . 24
6.3.5 Mechanical strength. 24
6.4 Environmental and material requirements . 24
6.4.1 General . 24
6.4.2 Life test under damp heat . 24
6.4.3 Electromagnetic compatibility . 24
6.5 Additional requirements for specific SPD designs . 25
6.5.1 One-port SPDs with separate input/output terminals – Rated load
current I . 25
L
6.5.2 Environmental tests for outdoor SPDs . 25
6.5.3 SPDs with separate isolated circuits . 25
6.6 Additional parameter if declared by the manufacturer – Maximum discharge
current I . 25
max
7 Type tests . 25
7.1 General . 25
7.2 Testing procedures . 26
7.2.1 General . 26
7.2.2 Test impulses . 30
7.2.3 Characteristics of power sources for testing . 30
7.3 Indelibility of markings . 32
7.4 Electrical tests . 32
7.4.1 Residual current I . 32
PE
7.4.2 Operating duty test . 33
7.4.3 Disconnectors and safety performance of overstressed SPDs . 37
7.4.4 SPD failure mode behaviour test . 38
7.4.5 Dielectric withstand . 41
7.4.6 Continuous current I . 42
CPV
7.5 Mechanical tests . 42
7.5.1 Verification of air clearances and creepage distances . 42
7.5.2 Pass criteria . 42
7.6 Environmental and material tests . 45
7.6.1 Life test under damp heat . 45
7.6.2 Pass criteria . 45
7.7 Additional tests for specific SPD designs . 46
7.7.1 Test for one-port SPDs with separate input/output terminals . 46
7.7.2 Environmental tests for outdoor SPDs . 46
7.7.3 SPDs with separate isolated circuits . 46
8 Routine and acceptance tests . 46
8.1 Routine tests. 46
8.2 Acceptance tests . 47
Annex A (normative) Tests to determine the presence of a voltage-switching
component and the magnitude of the follow current of an SPD . 48
A.1 General . 48
A.2 Test to determine the presence of a voltage-switching component . 48
A.3 Test to determine the magnitude of the follow current . 48
Annex B (informative) Transient behaviour of the PV test source . 49
B.1 Transient behaviour of the PV test source according to 7.2.3.1 . 49

– 4 – IEC 61643-31:2018 © IEC 2018
B.2 Test setup using a semiconductor switch to determine the transient
behaviour of a PV test source . 49
B.3 Alternative test setup using a fuse . 50
Bibliography . 53

Figure 1 – I/U characteristics . 31
Figure 2 – Flow chart of the operating duty test . 33
Figure 3 – Example of test setup for operating duty test . 34
Figure 4 – Operating duty test timing diagram for test classes I and II . 35
Figure 5 – Additional duty test timing diagram for test class I . 36
Figure 6 – Operating duty test timing diagram for test class III . 36
Figure 7 – Example of sample preparation for SPD failure mode behaviour test . 39
Figure B.1 – Test setup using an adjustable semiconductor switch to determine the
transient behaviour of a PV test source . 49
Figure B.2 – Time behaviour of voltage and current during disconnection operating
time of a semiconductor switch at a PV-source I = 4 A, open-circuit voltage = 640 V . 49
SC
Figure B.3 – Semiconductor disconnection behaviour (normalized) with intersection
point i(t) / u(t) . 50
Figure B.4 – I/U-characteristic of the PV test source calculated from the normalized
current and voltage records in Figure B.3 . 50
Figure B.5 – Test setup using a fuse to determine the transient behaviour of a PV test
source . 51
Figure B.6 – Normalized disconnection behaviour during operation of a fuse rated
0,1 x I at a PV test source with intersection point i(t) and u(t) . 51
SCPV
Figure B.7 – I/U-characteristic of the PV test source calculated from the normalized
current and voltage records in Figure B.6 . 52

Table 1 – List of acronyms and symbols . 17
Table 2 – Compliant termination and connection methods . 24
Table 3 – Environmental and material requirements . 24
Table 4 – Type test requirements for SPDs . 28
Table 5 – Common pass criteria for type tests . 29
Table 6 – Specific power source characteristics for operating duty tests . 31
Table 7 – Specific power source characteristics for failure mode tests . 32
Table 8 – Dielectric withstand . 41
Table 9 – Air clearances for SPDs . 43
Table 10 – Creepage distances for SPDs . 44
Table 11 – Relationship between material groups and classifications . 45
Table 12 – Test conductors for rated load current test . 46

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

Part 31: Requirements and test methods
for SPDs for photovoltaic installations

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
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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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.
International Standard IEC 61643-31 has been prepared by subcommittee 37A: Low-voltage
surge protective devices, of IEC technical committee 37: Surge arresters.
The text of this standard is based on the following documents:
FDIS Report on voting
37A/306/FDIS 37A/310/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – IEC 61643-31:2018 © IEC 2018
A list of all parts of the IEC 61643 series can be found, under the general title Low-voltage
surge protective devices, on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
INTRODUCTION
This part of IEC 61643 addresses safety and performance tests for surge protective devices
(SPDs) to be installed on the DC side of photovoltaic installations to protect against induced
and direct lightning effects.
There are three classes of tests:
1) The Class I test is intended to simulate partial conducted lightning current impulses. SPDs
subjected to Class I test methods are generally recommended for locations at points of
high exposure, e.g., line entrances to buildings protected by lightning protection systems.
2) SPDs tested to Class II or Class III test methods are subjected to impulses of shorter
duration.
3) SPDs are tested on a “black box” basis as far as possible.
Tests take into account that photovoltaic generators:
• behave like current generators,
• that their output current depends on the incident light intensity and temperature,
• that their short-circuit current is slightly higher than the operating output current,
• are connected in series and/or parallel combinations leading to a great variety of voltages,
currents and powers from a few hundreds of W (in residential installations) to several MW
(photovoltaic fields).
The specific electrical parameters of PV installations on the DC side require specific test
requirements for SPDs.
IEC 61643-32 addresses the selection and application principles of SPDs in practical
situations for PV application (work in progress).

– 8 – IEC 61643-31:2018 © IEC 2018
LOW-VOLTAGE SURGE PROTECTIVE DEVICES –

Part 31: Requirements and test methods
for SPDs for photovoltaic installations

1 Scope
This part of IEC 61643 is applicable to Surge Protective Devices (SPDs), intended for surge
protection against indirect and direct effects of lightning or other transient overvoltages.
These devices are designed to be connected to the DC side of photovoltaic installations rated
up to 1 500 V DC.
These devices contain at least one non-linear component and are intended to limit surge
voltages and divert surge currents. Performance characteristics, safety requirements,
standard methods for testing and ratings are established.
SPDs complying with this standard are exclusively dedicated to be installed on the DC side of
photovoltaic generators and the DC side of inverters.
SPDs for PV systems with energy storage (e.g. batteries, capacitor banks) are not covered.
SPDs with separate input and output terminals that contain specific series impedance
between these terminal(s) (so called two-port SPDs according to IEC 61643-11:2011) are not
covered.
SPDs compliant with this standard are designed to be permanently connected where
connection and disconnection of fixed SPDs can only be done using a tool. This standard
does not apply to portable SPDs
NOTE 1 In general SPDs for PV applications do not contain a specific series impedance between the input/output
terminals due to power efficiency considerations.
NOTE 2 Wherever reference is made to the electric power system or the power system within this document, this
refers to the DC side of the photovoltaic installation.
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 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60068-2-78:2012, Environmental testing – Part 2-78: Tests – Test Cab: Damp heat,
steady state
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests

IEC 61000-6-3, Electromagnetic compatibility (EMC) – Part 6-3: Generic standards –
Emission standard for residential, commercial and light-industrial environments
IEC 61180-1, High-voltage test techniques for low-voltage equipment – Part 1: Definitions,
test and procedure requirements
IEC 61643-11:2011, Low-voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 62475:2010, High-current test techniques – Definitions and requirements for test currents
and measuring systems
3 Terms, definitions, acronyms and symbols
For the purposes of this document, the following terms, definitions and abbreviated terms
apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
Surge Protective Device
SPD
device that contains at least one nonlinear component that is intended to limit surge voltages
and divert surge currents
Note 1 to entry: An SPD is a complete assembly, having appropriate connecting means.
[SOURCE: IEC 61643-11:2011, 3.1.1]
3.1.2
one-port SPD
SPD having no intended series impedance
Note 1 to entry: A one-port SPD may have separate input and output connections
Note 2 to entry: Overcurrent protection devices e.g fuses or circuit breakers are not considered as specific
intended series impedance.
[SOURCE: IEC 61643-11:2011, 3.1.2, modified (Note 2 to entry added)]
3.1.3
voltage-switching SPD
SPD that has a high impedance when no surge is present, but can have a sudden change in
impedance to a low value in response to a voltage surge
Note 1 to entry: Common examples of components used in voltage-switching SPDs are spark gaps, gas tubes and
thyristors. These are sometimes called "crowbar-type" components.
[SOURCE: IEC 61643-11:2011, 3.1.4, modified (original term referred to "voltage switching
type SPD")]
– 10 – IEC 61643-31:2018 © IEC 2018
3.1.4
voltage-limiting SPD
SPD that has a high impedance when no surge is present, but will reduce it continuously with
increased surge current and voltage
Note 1 to entry: Common examples of components used in voltage-limiting SPDs are varistors and avalanche
breakdown diodes. These are sometimes called "clamping-type" components.
[SOURCE: IEC 61643-11:2011, 3.1.5, modified (original term referred to "voltage limiting
type SPD")]
3.1.5
combination SPD
SPD that incorporates both voltage-switching components and voltage-limiting components.
The SPD may exhibit voltage-switching, limiting or both
[SOURCE: IEC 61643-11:2011, 3.1.6, modified (original term referred to "combination type
SPD")]
3.1.6
mode of protection
an intended current path between terminals, that contains one or more protective
components, for which the manufacturer declares a protection level
Note 1 to entry: Additional terminals may be included within this current path.
[SOURCE: IEC 61643-11:2011, 3.1.8, modified (original term referred to "mode of protection
of an SPD", Note 1 to entry added)]
3.1.7
nominal discharge current
I
n
crest value of the current through the SPD having a current waveshape of 8/20
[SOURCE: IEC 61643-11:2011, 3.1.9, modified (original term referred to "nominal discharge
current for class II test)]
3.1.8
impulse discharge current for class I test
I
imp
crest value of a discharge current through the SPD with specified charge transfer Q and
specified energy W/R in the specified time
[SOURCE: IEC 61643-11:2011, 3.1.10]
3.1.9
maximum discharge current
I
max
crest value of a current through the SPD having an 8/20 waveshape and magnitude according
to the manufacturers specification
Note 1 to entry: I is equal to or greater than I .
max n
[SOURCE: IEC 61643-11:2011, 3.1.48]
3.1.10
maximum continuous operating voltage for PV application
U
CPV
maximum DC voltage which may be continuously applied to the SPD’s mode of protection

3.1.11
continuous current for PV application
I
CPV
current flowing through the plus and minus terminals of the SPD while energized at U
CPV
3.1.12
residual current
I
PE
current flowing through the PE-terminal of the SPD while energized at U
CPV
[SOURCE: IEC 61643-11:2011, 3.1.4,modified (different reference test voltage referred to)]
3.1.13
follow current
I
f
peak current supplied by the electrical power system and flowing through the SPD after a
discharge current impulse
Note 1 to entry: The follow current is significantly different from the continuous current I .
CPV
[SOURCE: IEC 61643-11:2011, 3.1.12, modified (Note 1 to entry added)]
3.1.14
rated load current
I
L
maximum continuous rated DC current that can be supplied through the input/output terminals
of an SPD
[SOURCE: IEC 61643-11:2011, 3.1.13, modified (modified definition)]
3.1.15
voltage protection level
U
p
maximum voltage to be expected at the SPD terminals due to an impulse stress with defined
voltage steepness and an impulse stress with a discharge current with given amplitude and
waveshape
Note 1 to entry: The voltage protection level is given by the manufacturer and may not be exceeded by:
– the measured limiting voltage, determined for front-of-wave sparkover (if applicable) and the measured limiting
voltage, determined from the residual voltage measurements at amplitudes up to I and / or I respectively for
n imp
test classes II and / or I;
– the measured limiting voltage determined for the combination wave measurements up to U for test class III.
OC
[SOURCE: IEC 61643-11:2011, 3.1.14, modified (modified Note 1 to entry)]
3.1.16
measured limiting voltage
highest value of voltage that is measured across the terminals of the SPD during the
application of impulses of specified waveshape and amplitude
[SOURCE: IEC 61643-11:2011, 3.1.15]
3.1.17
residual voltage
U
res
crest value of voltage that appears between the terminals of an SPD due to the passage of
discharge current
[SOURCE: IEC 61643-11:2011, 3.1.16]

– 12 – IEC 61643-31:2018 © IEC 2018
3.1.18
1,2/50 voltage impulse
voltage impulse with a nominal virtual front time of 1,2µs and a nominal time to half-value of
50µs.
Note 1 to entry: Clause 8 of IEC 60060-1: 2010 defines the voltage impulse definitions of front time, time to half
value and waveshape. IEC 61643-1 defines specific tolerance values.
[SOURCE: IEC 61643-11:2011, 3.1.20]
3.1.19
8/20 current impulse
current impulse with a nominal virtual front time of 8µs and a nominal time to half-value of
20µs
Note 1 to entry: Clause 10 of IEC 62475: 2010 defines the current impulse definitions of front time, time to half
value and waveshape. IEC 61643-11 defines specific tolerance values.
[SOURCE: IEC 61643-11:2011, 3.1.21]
3.1.20
combination wave
wave characterized by defined voltage amplitude (U ) and waveshape under open-circuit
OC
conditions and a defined current amplitude (I ) and waveshape under short-circuit
CW
conditions
Note 1 to entry: The voltage amplitude, current amplitude and waveform that is delivered to the SPD are
determined by the combination wave generator (CWG) impedance Z and the impedance of the DUT.
f
[SOURCE: IEC 61643-11:2011, 3.1.22]
3.1.21
open-circuit voltage
U
OC
open-circuit voltage of the combination wave generator at the point of connection of the
device under test
[SOURCE: IEC 61643-11:2011, 3.1.23]
3.1.22
combination wave generator short-circuit current
I
CW
prospective short-circuit current of the combination wave generator, at the point of connection
of the device under test
Note 1 to entry: When the SPD is connected to the combination wave generator, the current that flows through
the device is generally less than I .
CW
[SOURCE: IEC 61643-11:2011, 3.1.24]
3.1.23
thermal stability
state of an SPD if, after heating up during the operating duty test, its temperature decreases
with time while energized at specified maximum continuous operating voltage and at specified
ambient temperature conditions
[SOURCE: IEC 61643-11:2011, 3.1.25]

3.1.24
degradation (of performance)
undesired permanent departure in the operational performance of equipment or a system from
its intended performance
[SOURCE: IEC 61643-11:2011, 3.1.26]
3.1.25
short-circuit current rating of the SPD
I
SCPV
maximum prospective short-circuit current from the power system for which the SPD, in
conjunction with the disconnector specified, is rated
[SOURCE: IEC 61643-11:2011, 3.1.27, modified (term originally referred to as I )]
SCCR
3.1.26
SPD disconnector (disconnector)
device for disconnecting an SPD, or part of an SPD, from the power system in the event of
SPD failure
Note 1 to entry: This disconnecting device is not required to have isolating capability for safety purposes. It is to
prevent a persistent fault on the system and is used to give an indication of an SPD’s failure. Disconnectors can be
internal (built in) or external (required by the manufacturer). There may be more than one disconnector function, for
example an over-current protection function and a thermal protection function. These functions may be in separate
units.
[SOURCE: IEC 61643-11:2011, 3.1.28]
3.1.27
degree of protection of enclosure
IP
classification preceded by the symbol IP indicating the extent of protection provided by an
enclosure against access to hazardous parts, against ingress of solid foreign objects and
possibly harmful ingress of water
[SOURCE: IEC 61643-11:2011, 3.1.29]
3.1.28
type test
conformity test made on one or more items representative of the production
[SOURCE: IEC 60050-151:2001, 151-16-16]
3.1.29
routine test
test made on each SPD or on parts and materials as required to ensure that the product
meets the design specifications
[SOURCE: IEC 60050-151:2001, 151-16-17]
3.1.30
acceptance tests
contractual test to prove to the customer that the item meets certain conditions of its
specification
[SOURCE: IEC 60050-151:2001, 151-16-23]

– 14 – IEC 61643-31:2018 © IEC 2018
3.1.31
impulse test classification
3.1.31.1
class I tests
tests carried out with the impulse discharge current I , with an 8/20 current impulse having
imp
a crest value equal to the crest value of I , and if relevant, with a 1,2/50 voltage impulse
imp
[SOURCE: IEC 61643-11:2011, 3.1.34.1, modified (addition of "if relevant)]
3.1.31.2
class II tests
tests carried out with the 8/20 nominal discharge current I , and if relevant, with a
n
1,2/50 voltage impulse
[SOURCE: IEC 61643-11:2011, 3.1.34.2, modified (addition of "if relevant)]
3.1.31.3
class III tests
tests carried out with the 1,2/50 voltage – 8/20 current combination wave generator
[SOURCE: IEC 61643-11:2011, 3.1.34.3]
3.1.32
sparkover voltage or trigger voltage of a voltage-switching SPD
maximum voltage value at which the sudden change from high to low impedance starts for a
voltage-switching SPD
[SOURCE: IEC 61643-11:2011, 3.1.36]
3.1.33
specific energy for class I test
W/R
energy dissipated by a unit resistance of 1 Ώ with the impulse discharge current I
imp
Note 1 to entry: This is equal to the time integral of the square of the current (W/R = ∫ i dt ) .
[SOURCE: IEC 61643-11:2011, 3.1.37]
3.1.34
prospective short-circuit current
I
P
current which would flow at a given location in a circuit if it were short-circuited at that
location by a link of negligible impedance
[SOURCE: IEC 61643-11:2011, 3.1.38, modified (removal of "of a power supply" from
original term and removal of Note to entry)]
3.1.35
status indicator
device that indicates the operational status of an SPD, or a part of an SPD
Note 1 to entry: Such indicators may be local with visual and/or audible alarms and/or may have remote signalling
and/or output contact capability.
[SOURCE: IEC 61643-11:2011, 3.1.41]

3.1.36
output contact
contact included in a circuit separate from the main circuit of an SPD, and linked to a
disconnector or status indicator.
[SOURCE: IEC 61643-11:2011, 3.1.42]
3.1.37
multipole SPD
type of SPD with more than one mode of protection, or a combination of electrically
interconnected SPDs offered as a unit
[SOURCE: IEC 61643-11:2011, 3.1.43]
3.1.38
total discharge current
I
Total
current which flows through the earth conductor of a multipole SPD during the total discharge
current test
Note 1 to entry: The aim is to take into account cumulative effects that occur when multiple modes of protection of
a multipole SPD conduct at the same time.
Note 2 to entry: I is particularly relevant for SPDs tested according to test class I, and is used for the purpose
Total
of lightning protection equipotential bonding according to IEC 62305 series.
[SOURCE: IEC 61643-11:2011, 3.1.44, modified ("PE or PEN conductor" replaced by "earth
conductor")]
3.1.39
voltage for clearance determination
U
max
highest measured voltage during surge applications according to 8.3.3.1 of
IEC 61643-11:2011
[SOURCE: IEC 61643-11:2011, 3.1.47]
3.1.40
Open-Circuit Failure
...