IEC TS 62548:2013

Photovoltaic (PV) arrays - Design requirements

IEC/TS 62548:2013(E) sets out design requirements for photovoltaic (PV) arrays including d.c. array wiring, electrical protection devices, switching and earthing provisions. The scope includes all parts of the PV array up to but not including energy storage devices, power conversion equipment or loads. The object of this Technical Specification is to address the design safety requirements arising from the particular characteristics of photovoltaic systems. Attention is drawn to a project in the IEC 60364 series under joint development between IEC TCs 64 and 82, which will, when published, cancel and replace the present technical specification.

General Information

• Status: Replaced
• Publication Date: 25-Jul-2013
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 3 - TC 82/WG 3
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 28-Sep-2016

Relations

• Replaced By: IEC 62548:2016 - Photovoltaic (PV) arrays - Design requirements
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC/TS 62548
®

Edition 1.0 2013-07
TECHNICAL
SPECIFICATION

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Photovoltaic (PV) arrays – Design requirements

IEC/TS 62548:2013(E)

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IEC/TS 62548

®


Edition 1.0 2013-07




TECHNICAL



SPECIFICATION








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inside










Photovoltaic (PV) arrays – Design requirements




























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ELECTROTECHNICAL

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– 2 – TS 62548 © IEC:2013(E)
CONTENTS
FOREWORD . 5
1 Scope and object . 7
2 Normative references . 7
3 Terms and definitions, symbols and abbreviations . 9
3.1 Terms, definitions and symbols . 9
4 Compliance with IEC 60364 . 15
5 PV array system configuration . 16
5.1 General . 16
5.1.1 Functional configuration of a PV system . 16
5.1.2 PV system architectures . 16
5.1.3 Array electrical diagrams . 16
5.1.4 Use of PCE with multiple d.c. inputs . 21
5.1.5 Series-parallel configuration . 22
5.1.6 Batteries in systems . 22
5.1.7 Considerations due to prospective fault conditions within a PV array . 22
5.1.8 Considerations due to operating temperature . 23
5.1.9 Performance issues . 23
5.2 Mechanical design . 24
5.2.1 General . 24
5.2.2 Thermal aspects . 24
5.2.3 Mechanical loads on PV structures . 24
5.2.4 Wind . 24
5.2.5 Material accumulation on PV array . 24
5.2.6 Corrosion. 24
6 Safety issues . 25
6.1 General . 25
6.2 Protection against electric shock . 25
6.3 Protection against overcurrent . 25
6.3.1 General . 25
6.3.2 Requirement for overcurrent protection . 25
6.3.3 Overcurrent protection in PV systems connected to batteries . 25
6.3.4 Requirement for string overcurrent protection . 26
6.3.5 Requirement for sub-array overcurrent protection . 26
6.3.6 Overcurrent protection sizing . 26
6.3.7 Overcurrent protection location . 28
6.4 Requirements for PV arrays operating at DVC-B and DVC-C voltages . 29
6.4.1 Detection and alarm requirements . 29
6.4.2 Earth fault alarm . 31
6.5 Protection against effects of lightning and overvoltage . 32
6.5.1 General . 32
6.5.2 Protection against overvoltage . 32
7 Selection and erection of electrical equipment . 32
7.1 General . 32
7.2 PV array maximum voltage . 33
7.3 Component requirements . 33
7.3.1 General . 33

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TS 62548 © IEC:2013(E) – 3 –
7.3.2 PV modules . 34
7.3.3 PV array and PV string combiner boxes . 34
7.3.4 Circuit breakers . 34
7.3.5 Disconnectors and switch-disconnectors. 35
7.3.6 Cables . 35
7.3.7 Segregation of a.c. and d.c. circuits . 38
7.3.8 Plugs, sockets and connectors . 38
7.3.9 Wiring in combiner boxes . 39
7.3.10 Fuses . 39
7.3.11 Bypass diodes . 39
7.3.12 Blocking diodes . 39
7.4 Location and installation requirements. 40
7.4.1 Disconnecting means . 40
7.4.2 Earthing and bonding arrangements . 42
7.4.3 Wiring system . 46
8 Acceptance . 47
9 Operation/maintenance . 47
10 Marking and documentation . 48
10.1 Equipment marking . 48
10.2 Requirements for signs . 48
10.3 Identification of a PV installation . 48
10.4 Labelling of PV array and PV string combiner boxes . 48
10.5 Labelling of disconnection devices . 48
10.5.1 General . 48
10.5.2 PV array disconnecting device . 48
10.6 Documentation . 49
Annex A (informative) Examples of signs . 50
Annex B (informative) Examples of system functional earthing configurations in PV
arrays . 51
Annex C (informative) Blocking diode . 53
Annex D (informative) Arc fault detection and interruption in PV arrays . 57
Annex E (informative) DVC limits . 59
Bibliography . 60

Figure 1 – General functional configuration of a PV powered system . 16
Figure 2 – PV array diagram – single string case . 17
Figure 3 – PV array diagram – multiple parallel string case . 18
Figure 4 – PV array diagram – multiple parallel string case with array divided into sub-
arrays . 19
Figure 5 – PV array using a PCE with multiple MPPT d.c. inputs . 20
Figure 6 – PV array using a PCE with multiple d.c. inputs internally connected to a
common d.c. bus . 21
Figure 7 – Example of a PV array diagram where strings are grouped under one over-
current protection device per group . 27
Figure 8 – Reinforced protection of wiring . 38
Figure 9 – PV array exposed-conductive parts functional earthing/bonding decision tree . 43
Figure 10 – Exposed conductive parts earthing in a PV array . 44

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– 4 – TS 62548 © IEC:2013(E)
Figure 11 – PV string wiring with minimum loop area . 46
Figure A.1 – Example of sign required on PV array combiner boxes (10.4) . 50
Figure A.2 – Example of switchboard sign for identification of PV on a building . 50
Figure B.1 – System functional earthing/grounding . 51
Figure B.2 – Examples different PV configurations in common use . 52
Figure C.1 – Effect of blocking diode at short circuit in PV string . 54
Figure C.2 – Effect of blocking diode where there is an earth fault on a system with
earthing on the minus side . 54
Figure C.3 – Effect of blocking diode where there is an earth fault on a system with
positive side earthing . 55
Figure D.1 – Examples of types of arcs in PV arrays . 57

Table 1 – Nominal overcurrent rating of functional earth fault interrupter . 28
Table 2 – Requirements for different system types based on PCE isolation and PV
array functional earthing . 29
Table 3 – Minimum insulation resistance thresholds for detection of failure of
insulation to earth . 30
Table 4 – Response time limits for sudden changes in residual current . 31
Table 5 – Voltage correction factors for crystalline and multi-crystalline silicon PV
modules . 33
Table 6 – Minimum current rating of circuits . 36
Table 7 – Disconnection device requirements in PV array installations . 41
Table E.1 – Summary of the limits of the decisive voltage classes . 59

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TS 62548 © IEC:2013(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

PHOTOVOLTAIC (PV) ARRAYS –
DESIGN REQUIREMENTS

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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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
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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
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The main task of IEC technical committees is to prepare International Standards. In
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• the required support cannot be obtained for the publication of an International Standard,
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• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62548, which is a technical specification, has been prepared by IEC technical committee
82: Solar photovoltaic energy systems.

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– 6 – TS 62548 © IEC:2013(E)
The present Technical Specification is intended to be withdrawn as soon as an International
Standard in the IEC 60364 series, under joint development by IEC technical committees 64
and 82, will be published.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/746/DTS 82/765A/RVC

Full information on the voting for the approval of this technical specification 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.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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.

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TS 62548 © IEC:2013(E) – 7 –
PHOTOVOLTAIC (PV) ARRAYS –
DESIGN REQUIREMENTS



1 Scope and object
This Technical Specification sets out design requirements for photovoltaic (PV) arrays
including d.c. array wiring, electrical protection devices, switching and earthing provisions.
The scope includes all parts of the PV array up to but not including energy storage devices,
power conversion equipment or loads.
The object of this Technical Specification is to address the design safety requirements arising
from the particular characteristics of photovoltaic systems. Direct current systems, and PV
arrays in particular, pose some hazards in addition to those derived from conventional a.c.
power systems, including the ability to produce and sustain electrical arcs with currents that
are not greater than normal operating currents.
In grid connected systems the safety requirements of this Technical Specification are however
critically dependent on the inverters associated with PV arrays complying with the
requirements of IEC 62109-1 and IEC 62109-2.
Installation requirements are also critically dependent on compliance with IEC 60364 series
(see Clause 4).
PV arrays of less than 100 W and less than 35 V d.c. open circuit voltage at STC are not
covered by this Technical Specification.
Attention is drawn to Annex D describing arc fault detection and interruption in PV arrays. It is
expected that requirements for the use of this type of equipment will be included in this
Technical Specification when reliable commercial equipment for detection of arcs in PV
systems is available.
NOTE 1 This Technical Specification covers the protection requirements of PV arrays which develop as a result of
the use of batteries in PV systems.
NOTE 2 Additional requirements may be needed for more specialized installations e.g. concentrating systems,
tracking systems or building integrated PV.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60228:2004, Conductors of insulated cables
IEC 60269-6, Low-voltage fuses – Part 6: Supplementary requirements for fuse-links for the
protection of solar photovoltaic energy systems
IEC 60287 (all parts), Electric cables – Calculation of the current rating
IEC 60332-1-2:2004, Tests on electric and optical fibre cables under fire conditions – Part 1-
2: Test for vertical flame propagation for a single insulated wire or cable – Procedure for 1 kW
pre-mixed flame

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– 8 – TS 62548 © IEC:2013(E)
IEC 60364 (all parts), Low-voltage electrical installations
IEC 60364-4-41:2005, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60364-5-54:2011, Low-voltage electrical installations – Part 5-54: Selection and erection
of electrical equipment – Earthing arrangements and protective conductors
IEC 60364-7-712:2002, Electrical installations of buildings – Part 7-712: Requirements for
special installations or locations – Solar photovoltaic (PV) power supply systems
IEC 60529, Degrees of protection provided by enclosures (IP Code)
IEC 60898-2, Circuit-breakers for overcurrent protection for household and similar
installations – Part 2: Circuit-breakers for a.c. and d.c. operation
IEC 60947-1, Low-voltage switchgear and controlgear – Part 1: General rules
IEC 60947-2, Low-voltage switchgear and controlgear – Part 2: Circuit breakers
IEC 60947-3, Low-voltage switchgear and controlgear – Part 3: Switches, disconnectors,
switch-disconnectors and fuse-combination units
IEC 61215:2005, Crystalline silicon terrestrial photovoltaic (PV) modules − Design
qualification and type approval
IEC 61646, Thin-film terrestrial photovoltaic (PV) modules − Design qualification and type
approval
IEC 61730-1:2004, Photovoltaic (PV) module safety qualification − Part 1: Requirements for
construction
IEC 61730-2:2004, Photovoltaic (PV) module safety qualification − Part 2: Requirements for
testing
IEC 62109-1:2010, Safety of power converters for use in photovoltaic power systems – Part 1:
General requirements
IEC 62109-2, Safety of power converters for use in photovoltaic power systems – Part 2:
Particular requirements for inverters
IEC 62305-2, Protection against lightning – Part 2: Risk management
IEC 62305-3, Protection against lightning – Part 3: Physical damage to structures and life
hazard
IEC 62305-4, Protection against lightning – Part 4: Electrical and electronic systems within
structures
IEC 62446, Grid connected photovoltaic systems – Minimum requirements for system
documentation, commissioning tests and inspection
EN 50521, Connectors for photovoltaic systems – Safety requirements and tests

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TS 62548 © IEC:2013(E) – 9 –
3 Terms and definitions, symbols and abbreviations
3.1 Terms, definitions and symbols
For the purposes of this document, the following terms and definitions apply.
3.1.1
blocking diode
diode connected in series with module(s), panel(s), sub-arrays and array(s) to block reverse
current into such module(s), panel(s), sub-array(s) and array(s)
3.1.2
bonding conductor
conductor provided for functional or protective equipotential bonding
3.1.3
bypass diode
diode connected across one or more cells in the forward current direction to allow the module
current to bypass shaded or broken cells to prevent hot spot or hot cell damage resulting from
the reverse voltage biasing from the other cells in that module
3.1.4
cable
assembly of one or more conductors and/or optical fibres, with a protective covering and
possibly filling, insulating and protective material
[SOURCE: IEC 60050-151:2001,151-12-38]
3.1.5
cable core
the conductor with its insulation but not including any mechanical protective covering
3.1.6
Class A: General access, hazardous voltage, hazardous power applications
modules rated for use in this application class may be used in systems operating at greater
than 50 V d.c. or 240 W, where general contact access is anticipated. Modules qualified for
safety through IEC 61730-1 and IEC 61730-2 within this application class are considered to
meet the requirements for safety class II.
[SOURCE: IEC 61730-1:2004]
3.1.7
Class B: Restricted access, hazardous voltage, hazardous power applications
modules rated for use in this application class are restricted to systems protected from public
access by fences, location, etc. Modules evaluated within this application class provide
protection by basic insulation, are considered to meet the requirements for safety class 0.
[SOURCE: IEC 61730-1:2004]
3.1.8
Class C: Limited voltage, limited power applications
modules rated for use in this application class are restricted to systems operating at less than
50 V d.c. and 240 W, where general contact access is anticipated. Modules qualified for
safety through IEC 61730-1 and IEC 61730-2 within this application class are considered to
meet the requirements for safety class III.
Note 1 to entry: Safety classes are defined in IEC 61140.

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– 10 – TS 62548 © IEC:2013(E)
[SOURCE: IEC 61730-1:2004]
3.1.9
competent person
a person, who has acquired, through training, qualification or experience or a combination of
these, the knowledge and skill enabling that person to perform the required task correctly
3.1.10
disconnector
mechanical switching device which provides, in the open position, an isolating distance in
accordance with specified requirements.
Note 1 to entry: A disconnector is capable of opening and closing a circuit when either negligible current is
broken or made, or when no significant
...