Lightning and surge voltage protection for photovoltaic (PV) power supply systems

IEC TR 63227:2020 deals with the protection of PV power supply systems against detrimental effects of lightning strikes and surge voltages of atmospheric origin. In the event that a lightning and/or surge voltage protection is required to be erected, this document describes requirements and measures for maintaining the safety, functionality, and availability of the PV power supply systems.

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Status
Published
Publication Date
19-Oct-2020
Current Stage
PPUB - Publication issued
Completion Date
20-Oct-2020
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IEC TR 63227
Edition 1.0 2020-10
INTERNATIONAL
STANDARD
colour
inside
Lightning and surge voltage protection for photovoltaic (PV) power supply
systems
IEC TR 63227:2020-10(en)
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---------------------- Page: 2 ----------------------
IEC TR 63227
Edition 1.0 2020-10
INTERNATIONAL
STANDARD
colour
inside
Lightning and surge voltage protection for photovoltaic (PV) power supply
systems
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-8950-1

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TR 63227:2020 © IEC 2020
CONTENTS

FOREWORD ........................................................................................................................... 4

1 Scope .............................................................................................................................. 6

2 Normative references ...................................................................................................... 6

3 Terms and definitions ...................................................................................................... 7

4 Design principles ............................................................................................................. 8

4.1 Causes of damage and damages ............................................................................ 8

4.2 Galvanic coupling ................................................................................................... 8

4.3 Magnetic field coupling ........................................................................................... 9

4.4 Electric field coupling ............................................................................................ 10

4.5 Risk management ................................................................................................. 10

5 Lightning protection system (LPS) ................................................................................. 11

5.1 General ................................................................................................................. 11

5.2 External lightning protection .................................................................................. 12

5.3 Internal lightning protection ................................................................................... 14

5.4 Lightning equipotential bonding ............................................................................. 15

5.5 Lightning protection zone concept ......................................................................... 15

5.6 Selection of surge protective devices (SPDs) ........................................................ 15

5.6.1 General ......................................................................................................... 15

5.6.2 Class I tested SPD, lightning current-carrying capacity I .......................... 21

imp

5.6.3 Class II tested SPD, nominal impulse discharge surge current I ................... 23

5.7 Coordination of surge protective devices ............................................................... 23

5.8 Selection of surge protective devices for a functionally earthed line

conductor .............................................................................................................. 23

6 Routing and shielding of cables/lines ............................................................................. 23

7 Functional earthing/lightning equipotential bonding ........................................................ 25

8 Inspection and documentation ....................................................................................... 26

Annex A (informative) Shadowing ....................................................................................... 27

Annex B (informative) Tracking PV power supply system – External lightning

protection/down-conductors ........................................................................................... 29

Annex C (informative) Practical example: lightning protection for a PV power supply

system installed on a saddle roof building ...................................................................... 30

Annex D (informative) PV power supply system as a free-field system ................................ 32

D.1 General ................................................................................................................. 32

D.2 Earth screw foundations ........................................................................................ 32

D.3 Plate and strip or ring foundations ........................................................................ 33

D.4 Lightning current-carrying capacity of Class I tested SPDs for free-field

systems ................................................................................................................ 34

Annex E (informative) Metal roof and metal façade .............................................................. 36

E.1 Metal roof ............................................................................................................. 36

E.2 Metal façades ....................................................................................................... 36

Bibliography .......................................................................................................................... 38

Figure 1 – Examples of direct-axis components of voltage for galvanic coupling ..................... 9

Figure 2 – Voltages induced in loops by the steepness of the lightning current ..................... 10

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IEC TR 63227:2020 © IEC 2020 – 3 –

Figure 3 – High resolution full climatology (HRFC) ................................................................ 11

Figure 4 – Example for the design of the air-termination system for a PV power supply

system using the rolling sphere method ................................................................................ 12

Figure 5 – Maintaining the separation distance ..................................................................... 13

Figure 6 – Example for the design of the air-termination system for a PV power supply

system .................................................................................................................................. 14

Figure 7 – Use of SPDs in PV power supply systems ............................................................ 16

Figure 8 – Situation A) The surge voltage protection concept for a PV power supply

system on a building without external lightning protection ..................................................... 17

Figure 9 – Situation B) Surge voltage protection concept for a PV power supply system

on a building with external lightning protection, the separation distance s is maintained ........ 17

Figure 10 – Situation C) Surge voltage protection concept for a PV power supply

system on a building with external lightning protection, the separation distance s is not

maintained ............................................................................................................................ 18

Figure 11 – Situation C) Surge voltage protection concept for a PV power supply

system on a building with external lightning protection, the separation distance s is not

maintained, use of a shield able to carry the lightning current ............................................... 18

Figure 12 – Flow chart for the selection of protective measures ............................................ 20

Figure 13 – Example of a structure with two down-conductors of the external lightning

protection system.................................................................................................................. 22

Figure 14 – Reduction of the effects of induction by shielding and line routing ...................... 24

Figure 15 – Example for the shielding of the generator main lines by closed metal

cable channels ...................................................................................................................... 25

Figure 16 – Functional earthing of the module racks in case no external lightning

protection is available or the separation distance is not maintained ...................................... 26

Figure 17 – Lightning equipotential bonding at the module racks in case the separation

distance is not maintained .................................................................................................... 26

Figure A.1 – Shadowing of a PV module by a lightning rod ................................................... 27

Figure A.2 – Minimum distance between the lightning rod or lightning line and the

PV module required to prevent an umbra .............................................................................. 28

Figure C.1 – Saddle roof building – Meshed air-termination systems of lightning

protection level III, the PV power supply system spans several meshes ................................ 30

Figure C.2 – Example for the calculation of the separation distances for lightning

protection level III ................................................................................................................. 31

Figure D.1 – Connection of module tables to the earthing system for pile-driven

foundations and earth screw foundations .............................................................................. 33

Figure D.2 – Connection of module tables to the earthing system for strip foundations ......... 34

Figure D.3 – Earthing concept and arrangement of the SPDs for a free field ......................... 35

Table 1 – Selection of the SPD test class (type) and minimum cross-section of the

equipotential bonding ............................................................................................................ 16

Table 2 – Selection of the minimum discharge capacity of voltage limiting SPDs of

Class I tested (voltage limiting type) or combined SPDs of Type 1 (series connection of

voltage limiting type and voltage switching type) ................................................................... 21

Table 3 – Selection of the minimum discharge capacity of voltage switching class I

tested SPDs (voltage switching) or combined class I tested SPDs (parallel connection

of voltage limiting and voltage switching) .............................................................................. 22

Table A.1 – Minimum distance of air-termination systems required to avoid an umbra .......... 28

Table D.1 – Minimum discharge capacity of voltage limiting or combined Class I tested

SPDs and voltage switching type class I tested SPDs ........................................................... 35

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– 4 – IEC TR 63227:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LIGHTNING AND SURGE VOLTAGE PROTECTION
FOR PHOTOVOLTAIC (PV) POWER SUPPLY SYSTEMS
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

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

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

in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,

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

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

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

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

indispensable for the correct application of this publication.

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

rights. IEC shall not be held responsible for identifying any or all such patent rights.

IEC TR 63227 has been prepared by IEC technical committee 82: Solar photovoltaic energy

systems. It is a Technical Report.
The text of this Technical Report is based on the following documents:
Draft Report on voting
82/1501/DTR 82/1554A/RVDTR

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this Technical Report is English.

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.
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IEC TR 63227:2020 © IEC 2020 – 5 –

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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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– 6 – IEC TR 63227:2020 © IEC 2020
LIGHTNING AND SURGE VOLTAGE PROTECTION
FOR PHOTOVOLTAIC (PV) POWER SUPPLY SYSTEMS
1 Scope

This document deals with the protection of PV power supply systems against detrimental effects

of lightning strikes and surge voltages of atmospheric origin. In the event that a lightning and/or

surge voltage protection is required to be erected, this document describes requirements and

measures for maintaining the safety, functionality, and availability of the PV power supply

systems.
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 60364-4-44:2007/AMD1:2015, Low-voltage electrical installations – Part 4-44: Protection

for safety – Protection against voltage disturbances and electromagnetic disturbances

IEC 60364-7-712:2017, Low voltage electrical installations – Part 7-712: Requirements for

special installations or locations – Solar photovoltaic (PV) power supply systems

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 61643-21, Low voltage surge protective devices – Part 21: Surge protective devices

connected to telecommunications and signalling networks – Performance requirements and

testing methods

IEC 61643-31, Low-voltage surge protective devices – Part 31: Requirements and test methods

for SPDs for photovoltaic installations
IEC 62305-1, Protection against lightning – Part 1: General principles
IEC 62305-2, Protection against lightning – Part 2: Risk management

IEC 62305-3:2010, 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 62561-1, Lightning Protection System Components (LPSC) – Part 1: Requirements for

connection components

IEC 62561-2, Lightning Protection System Components (LPSC) – Part 2: Requirements for

conductors and earth electrodes
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IEC TR 63227:2020 © IEC 2020 – 7 –

IEC 62561-3, Lightning Protection System Components (LPSC) – Part 3: Requirements for

isolating spark gaps (ISG)

IEC 62561-4, Lightning protection system components (LPSC) – Part 4: Requirements for

conductor fasteners
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
photovoltaic
relating to the conversion of light directly into electrical energy
[SOURCE: IEC 62109-1:2011, 3.55]
3.2
PV module

smallest complete and environmentally protected assembly of interconnected PV cells

[SOURCE: IEC 60364-7-712:2017, 712.3.2]
3.3
PV inverter
device which converts DC voltage and DC current into AC voltage and AC current
3.4
PV string

circuit in which PV modules are connected in series to a PV sub-generator in order to achieve

the specified output voltage
3.5
PV sub-generator

mechanically and electrically assembled combination of PV modules and other necessary

components in order to form a DC power supply unit
3.6
PV generator
combination of PV sub-generators
3.7
surge protective device
SPD

device that contains at least one non-linear component and 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]
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– 8 – IEC TR 63227:2020 © IEC 2020
3.8
voltage switching type 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 type SPDs are spark gaps, gas tubes,

and thyristors. These are sometimes called “crowbar type” components.
[SOURCE: IEC 61643-11:2011, 3.1.4]
3.9
voltage limiting type 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 type SPDs are varistors and avalanche

breakdown diodes. These are sometimes called “damping type” components.
[SOURCE: IEC 61643-11:2011, 3.1.5]
3.10
combination type SPD

SPD that incorporates both voltage switching components and voltage limiting components

Note 1 to entry: The SPD can exhibit voltage switching (e.g. spark gap), voltage limiting (e.g. varistor) or both.

These components can be connected in series as well as in parallel.

[SOURCE: IEC 61643-11:2011, 3.1.6, modified – Second sentence of definition moved to the

note to entry. Second sentence of note to entry has been added.]
4 Design principles
4.1 Causes of damage and damages

The lightning current of a lightning discharge can be injected into PV power supply systems in

different ways:
– by galvanic coupling;
– by magnetic field coupling;
– by electric field coupling.

The respective type of coupling is influenced by lightning protective measures (e.g. earthing,

equipotential bonding, shielding of the structure, shielding of the electric lines as well as layout

and type of these lines).
4.2 Galvanic coupling

A prerequisite for galvanic coupling is for the lightning current or at least part of it to be injected

directly. The (partial) lightning current generates a direct-axis component of voltage at the

impedances of the lines it passes through. When a structure is struck by lightning, the current

flowing to earth normally generates a voltage magnitude of some hundred kilovolts at the

effective conventional earth impedance.

Figure 1 shows examples of galvanic couplings at an equipotential bonding line carrying a

(partial) lightning current and at the conventional earth impedance. This type of coupling is also

present where a (partial) lightning current passes through a line’s cable screen. In that case,

the (partial) lightning current causes a direct-axis component of voltage at the coupling

impedance of the cable screen, which appears between the cable screen and the inner

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IEC TR 63227:2020 © IEC 2020 – 9 –

conductor. This direct-axis component of voltage U can jeopardize the electric or electronic

systems connected at the two line ends.
Key

U Direct-axis component of voltage at the cable screen the current flows through

U Direct-axis component of voltage at the voltage equalizing cable U = L di/dt
2 2
U Voltage at the conventional earth impedance RE (U = i R )
3 3 E
PAS Equipotential bonding bar
HPAS Main earthing bar
Figure 1 – Examples of direct-axis components of voltage for galvanic coupling
4.3 Magnetic field coupling

The process at which the magnetic field H(t) of a lightning discharge passes through conductor

loops is referred to as magnetic field coupling or magnetic induction (see Figure 2). If the

conductor loops are open (idle motion), voltages u will result in proportion to dH/dt; however,

ind

where the conductor loops are short-circuited currents, i will result in proportion to H(t).

ind
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– 10 – IEC TR 63227:2020 © IEC 2020
Figure 2 – Voltages induced in loops by the steepness of the lightning current

Magnetic injections can be reduced considerably by increasing the distance of air-termination

systems and down-conductors to the PV modules. A minimum value of 0,5 m is recommended

for the distance of air-termination systems and down-conductors to the PV modules. The

separation distance s can differ from this value (see Annex C).
4.4 Electric field coupling

A prerequisite for electric field coupling is an “electrically effective aerial” (e.g. the module

frame). The electric field strength resulting from the leader approaching reaches up to 500 kV/m

at a distance of a couple hundred metres to the prospective striking point. As soon as the main

discharge starts, the electric field breaks down. During that process, field changes dE/dt can

appear at a magnitude of 500 (kV/m)/µs.

The effect of electric field coupling to equipment installed within and outside a structure is

generally very small compared to that of magnetic field coupling.
4.5 Risk management

A lightning protection system (LPS) designed to comply with class III meets the regular

requirements for PV power supply systems.

In special cases, e.g. for objects of cultural value or requirements for an increased availability

of the system, it should be checked in accordance with IEC 62305-2 whether additional

measures or a different LPS class is required.

The lightning protection measures for the PV power supply system are adapted to the LPS class

of the structure. The LPS class of the building is determined by factors as its use, values and

others as well as the area-specific lightning activity (Figure 3). The area-specific lightning

activity should be also taken into account to decide on lightning protection measures for ground-

mounted systems.
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IEC TR 63227:2020 © IEC 2020 – 11 –

(Source: https://ghrc.nsstc.nasa.gov/pub/lis/climatology/LIS-OTD/HRFC/browse/HRFC_COM_FR_V2.3.2015.png)

Figure 3 – High resolution full climatology (HRFC)
5 Lightning protection system (LPS)
5.1 General

The erection of conventional PV power supply systems on or at buildings does not change the

lightning strike risk. It is recommended to design and harmonize the PV power supply and

lightning protection systems before erection.

The PV generator delivers current and voltage even at low amounts of solar irradiance. This

has to be taken into account for mounting and troubleshooting purposes.

Suitable measures of external lightning protection are supposed to catch direct lightning and

feed them into an earthing system such that no galvanically coupled currents can have an effect

on metal building installations and the PV power supply system.

In addition to that, measures of internal lightning protection are used to prevent impacts that

lightning strikes and potential differences may have onto and inside the building.

The purpose of these measures is to prevent damage to the building (mechanical damages up

and including fire and its effects) as well as damage to the PV power supply system (supply

networks, controls and electrical protective equipment). Where the legislator requires lightning

protective measures as part of the preventive fire protection, these shall not be affected by

PV power supply systems.
For lightning protection, the IEC 62305 series applies.

For the erection of PV power supply systems, the IEC 60364 series and, in particular,

IEC 60364-7-712 apply.
In order for a lightning prot
...

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