IEC 63112:2021

Photovoltaic (PV) arrays - Earth fault protection equipment - Safety and safety-related functionality

IEC 63112:2021 is applicable to low voltage Photovoltaic Earth-Fault Protection Equipment (PV-EFPE) whose function is to detect, interrupt, and warn system operators of earth faults in solar photovoltaic arrays. This document specifies:
- the types and levels of the monitoring and protection functions that may be provided;
- the nature and timing of responses to earth faults;
- test methods for validating the monitoring and protection functions provided;
- requirements for functional safety and fault tolerance;
- requirements for product safety including construction, environmental suitability, markings, documentation, and testing.

Groupes photovoltaïques (PV) - Matériel de protection contre les défauts à la terre - Sécurité et fonctionnalités relatives à la sécurité

IEC 63112:2021 s'applique aux matériels de protection contre les défauts à la terre photovoltaïques (PV-EFPE) dont la fonction est de détecter, d'interrompre et de mettre en garde les opérateurs de réseau en cas de défauts à la terre dans les groupes photovoltaïques. Le présent document spécifie:
- les types et les niveaux des fonctions de surveillance et de protection qui peuvent être fournies;
- la nature et la chronologie des réponses aux défauts à la terre;
- les méthodes d'essai pour la validation des fonctions de surveillance et de protection fournies;
- les exigences en matière de sécurité fonctionnelle et de tolérance aux pannes;
- les exigences relatives à la sécurité du produit, y compris la construction, l'adaptation à l'environnement, les marquages, la documentation et les essais

General Information

• Status: Published
• Publication Date: 21-Jun-2021
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: WG 6 - TC 82/WG 6
• Current Stage: PPUB - Publication issued
• Start Date: 22-Jun-2021
• Completion Date: 18-Jun-2021

Overview

IEC 63112:2021 is an international standard published by the International Electrotechnical Commission (IEC) that establishes key safety and functionality requirements for earth fault protection equipment used in low voltage photovoltaic (PV) arrays. This standard provides essential guidelines for the design, operation, and testing of Photovoltaic Earth-Fault Protection Equipment (PV-EFPE). The equipment's primary purpose is to detect earth faults within solar PV arrays, to interrupt faulty circuits, and to alert system operators to prevent hazards such as electric shock or fire.

This standard covers:

• Types and levels of monitoring and protection functions provided by PV-EFPE
• Required responses and timing when earth faults occur
• Testing methodologies for validating these safety functions
• Functional safety and fault tolerance requirements
• Product safety including construction, environmental suitability, markings, and documentation

Adherence to IEC 63112:2021 enhances the reliability, safety, and fault management of photovoltaic installations, a critical consideration as solar power continues to grow globally.

Key Topics

PV Earth Fault Protection Functions

• Insulation Monitoring: Continuous checks of PV array insulation to earth ensure early fault detection.
• Residual Current Monitoring: Detection of earth currents that present shock or fire hazards.
• Fault Response Timing: Defined time frames for detecting and interrupting earth faults to minimize risk.
• Disconnection Mechanisms: Requirements for isolating and disconnecting faulty PV sub-arrays safely.

System Topology and Integration

• Adaptations of PV-EFPE depending on system configuration including isolated and non-isolated sub-arrays.
• Control mechanisms allowing PV-EFPE to command host system operation, managing disconnections or resets safely.

Safety and Fault Tolerance

• Standards for safe construction and environmental resilience of equipment.
• Functional safety assessments including risk analysis and fault tolerance tests.
• Software or firmware that performs safety-critical functions must undergo rigorous evaluation.

Testing Requirements

• Defined laboratory conditions for validation tests.
• Specific tests for insulation resistance, earth current monitoring, short circuit faults, and coordination functions.
• Routine production tests to assure consistent product quality.

Marking and Documentation

• Clear and complete equipment markings mandatory to convey safety ratings and operational status.
• Comprehensive instructions covering installation, operation, and maintenance for installers and end-users.

Applications

IEC 63112:2021 is essential for manufacturers, system designers, installers, and operators involved with low voltage solar PV arrays. Its applications include:

• Solar PV Array Safety: Ensuring rapid detection and isolation of earth faults mitigates risks of electric shock and fire hazards in residential, commercial, and industrial PV installations.
• System Reliability: By specifying fault tolerance and monitoring requirements, the standard helps maintain optimal PV system performance and longevity.
• Compliance and Certification: Facilitates product compliance with international electrical safety regulations, supporting market acceptance and regulatory approval.
• Maintenance and Operation: Provides guidelines for clear fault indication and safe resetting procedures, aiding in efficient system upkeep.

Related Standards

IEC 63112:2021 complements and relates to other IEC standards and industry best practices in the photovoltaic and electrical safety domain, such as:

• IEC 61730 - Photovoltaic (PV) module safety qualification
• IEC 62446 - Grid-connected PV systems - Documentation, commissioning tests, and inspection
• IEC 60364-7-712 - Electrical installations of buildings - Specific requirements for PV power supply systems
• IEC 61010 - Safety requirements for electrical equipment for measurement, control, and laboratory use

Together, these standards provide a comprehensive framework for the safe and effective deployment of photovoltaic energy technologies worldwide.

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Keywords: IEC 63112:2021, photovoltaic arrays, earth fault protection, PV-EFPE, solar PV safety, insulation monitoring, residual current detection, functional safety, PV system fault tolerance, solar array fault testing, PV equipment standards

Standards Content (Sample)

IEC 63112 ®
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Photovoltaic (PV) arrays – Earth fault protection equipment – Safety and safety-
related functionality
Groupes photovoltaïques (PV) – Matériel de protection contre les défauts à la
terre – Sécurité et fonctionnalités relatives à la sécurité

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IEC 63112 ®
Edition 1.0 2021-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Photovoltaic (PV) arrays – Earth fault protection equipment – Safety and safety-

related functionality
Groupes photovoltaïques (PV) – Matériel de protection contre les défauts à la

terre – Sécurité et fonctionnalités relatives à la sécurité

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.160 ISBN 978-2-8322-9872-5

– 2 – IEC 63112:2021 © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, symbols and abbreviated terms . 10
4 Requirements relating PV-EFP to system topology . 12
4.1 General . 12
4.2 PV-EFP functions for different system topologies . 16
4.3 PV-EFPE control over host system operation . 18
4.3.1 General . 18
4.3.2 Types of PV-EFPE requiring host system control . 18
4.3.3 Methods of control of the host system operation . 18
4.4 Disconnection under fault conditions . 19
4.4.1 General . 19
4.4.2 Disconnecting means . 19
4.4.3 High impedance connections . 19
4.4.4 Indirect disconnection . 19
4.5 Systems with more than one sub-array (informative) . 20
4.5.1 General . 20
4.5.2 Isolated sub-arrays . 20
4.5.3 Non-isolated sub-arrays . 20
5 PV array to earth insulation monitoring . 20
5.1 General . 20
5.2 Array insulation monitoring requirements . 21
5.3 Array insulation fault response requirements. 21
5.4 Provisions for reset . 22
5.5 Insulation monitoring function adjustability . 22
6 PV array residual or earth current monitoring. 22
6.1 General . 22
6.2 Required PV-EFP current monitoring functions . 22
6.3 Shock hazard current monitoring . 23
6.3.1 General . 23
6.3.2 Limits and response. 23
6.3.3 Provisions for reset . 23
6.3.4 Shock hazard current monitoring – adjustability . 24
6.3.5 Fault tolerance of shock hazard current monitoring . 24
6.4 Fire hazard (continuous) current monitoring by electronic means . 24
6.4.1 Overview . 24
6.4.2 General . 24
6.4.3 Settings and response . 24
6.4.4 Provisions for reset . 25
6.4.5 Fire hazard current monitoring function adjustability . 25
6.4.6 Fault tolerance of fire hazard current monitoring by electronic means . 25
6.5 Fire hazard current monitoring by an overcurrent protective device in the
functional earthing conductor . 25
6.5.1 Overview . 25

6.5.2 General . 25
6.5.3 Ratings . 26
6.5.4 Response . 26
6.5.5 Provisions for reset . 26
6.5.6 Overcurrent protective device adjustability and replacement . 26
7 Construction . 27
7.1 General . 27
7.2 Environmental considerations . 27
8 PV-EFP Fault Indication . 28
8.1 General . 28
8.2 Integral fault indication . 28
8.3 Remote fault indication . 28
8.3.1 General . 28
8.3.2 Observability . 28
8.3.3 Remote fault indication means . 28
8.4 Resetting of the fault indication . 28
9 Testing . 29
9.1 General requirements for the tests in 9.2 through 9.5 . 29
9.1.1 Tests required . 29
9.1.2 DC sources . 29
9.1.3 AC sources . 30
9.1.4 Laboratory conditions . 30
9.1.5 Monitoring the PV-EFPE means of control of the host system . 30
9.1.6 Control of the PV-EFPE state . 30
9.1.7 Test setup . 31
9.2 Tests for PV array insulation monitoring functions . 32
9.2.1 Setup . 32
9.2.2 Sequence of tests . 33
9.2.3 Test for R above setting during system start-up . 34
iso
9.2.4 Test for R below setting during system start-up . 34
iso
9.2.5 Test for R dropping below setting during operation . 34
iso
9.2.6 Test for short circuit earth fault during system start-up . 35
9.2.7 Test for short circuit earth fault during operation – non-earth-referenced
PV arrays . 35
9.2.8 Tests for PV array mid-point fault detection . 36
9.2.9 24 h timer test . 36
9.3 Tests for residual or earth current monitoring functions: . 36
9.3.1 Setup . 36
9.3.2 Sequence of tests . 37
9.3.3 Tests for shock hazard current monitoring . 37
9.3.4 Tests for fire hazard current monitoring by electronic means . 39
9.3.5 Fault-tolerance of shock hazard current monitoring and fire hazard
current monitoring by electronic means. 41
9.3.6 Tests for fire hazard current monitoring by an overcurrent protective
device in the functional earthing conductor . 42
9.4 Test for short circuit earth fault during operation . 42
9.4.1 General . 42
9.4.2 Short circuit earth fault test procedure . 42
9.4.3 Short circuit earth fault test pass/fail criteria . 42

– 4 – IEC 63112:2021 © IEC 2021
9.5 Tests for coordination of PV-EFP functions . 43
9.6 Product safety tests . 44
10 Software or firmware performing safety critical functions . 44
10.1 General . 44
10.1.1 Overview . 44
10.1.2 Risk analysis . 44
10.1.3 Integrated PV-EFPE . 45
10.2 Evaluation methods . 45
10.2.1 General . 45
10.2.2 Testing with features disabled . 45
10.2.3 Functional safety analysis . 45
11 Marking and documentation . 46
11.1 Equipment markings . 46
11.1.1 General . 46
11.1.2 Marking content . 46
11.2 Installation and operating instructions . 48
11.2.1 General . 48
11.2.2 General content . 49
11.2.3 Information related to installation . 49
11.2.4 Information related to operation . 51
11.2.5 Information related to maintenance . 52
12 Routine (production) tests. 52
12.1 General . 52
12.2 Routine dielectric tests . 52
12.3 Routine EFP function tests . 52
12.3.1 General . 52
12.3.2 Shock hazard current monitoring . 53
12.3.3 Electronic fire hazard current monitoring . 53
12.3.4 Residual current device test function . 53
12.3.5 PV array insulation monitoring function . 53
Annex A (informative) Examples of system topologies with respect to PV Earth Fault
Protection . 54
A.1 General . 54
A.2 Functionally earthed (FE) system with FE current monitoring . 54
A.3 Functionally earthed (FE) system with a functionally earthed conductor fault . 55
A.4 Functionally earthed (FE) system with residual current monitoring . 56
A.5 Non-separated system with residual current monitoring on PV+/- . 57
A.6 Non-separated system with residual current monitoring on the AC side . 58
A.7 Non-earth-referenced system with continuous insulation monitoring . 59
Annex B (informative) Background and rationale for PV Earth Fault Protection
requirements . 60
B.1 Purpose . 60
B.2 PV earth faults – scope and meaning . 60
B.3 PV-EFP goals . 61
B.4 PV-EFP challenges . 61
B.4.1 Characteristics of PV systems that affect PV-EFP approaches . 61
B.4.2 PV-EFP “blind spots” and coordination of protective measures . 63
B.4.3 Relation between PV-EFP protection settings and PV system size . 65
B.5 Current and historical standards covering PV Earth Fault Protection . 68

B.5.1 General . 68
B.5.2 NFPA 70 – the US National Electrical Code (NEC) . 68
B.5.3 UL1741 and related documents . 68
B.5.4 VDE 0126-1-1 . 69
B.5.5 IEC 62109-2 . 70
B.5.6 IEC 60364-7-712 . 71
B.5.7 IEC 62548 . 71
B.5.8 Conclusions . 72
Bibliography . 73

Figure 1 – Examples of functionally earthed system topologies . 14
Figure 2 – Examples of non-earth-referenced system topologies. 15
Figure 3 – Examples of non-separated system topologies . 16
Figure 4 – Example setup for PV-EFPE testing . 32
Figure 5 – Example setup for PV-EFPE testing of array mid-point faults . 33
Figure A.1 – Functionally earthed (FE) system with current monitoring in the FE
conductor . 54
Figure A.2 – Functionally earthed (FE) system with a functionally
earthed conductor fault . 55
Figure A.3 – Functionally earthed (FE) system with residual current monitoring . 56
Figure A.4 – Non-separated 3-phase system with residual current monitoring on PV+/- . 57
Figure A.5 – Non-separated 1-phase system with residual current monitoring
on the AC side . 58
Figure A.6 – Non-earth-referenced system with continuous insulation monitoring. 59

Table 1 – PV-EFP functions based on system topology and earthing . 17
Table 2 – Example PV array to earth insulation resistance limits . 21
Table 3 – Shock hazard – Sudden current change limits and response times . 23
Table 4 – Example continuous current limits and response times . 24
Table 5 – Example trip current of overcurrent protection in the functional earthing
conductor . 26
Table B.1 – Sudden change residual current limits . 70

– 6 – IEC 63112:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PHOTOVOLTAIC (PV) ARRAYS –
EARTH FAULT PROTECTION EQUIPMENT –
SAFETY AND SAFETY-RELATED FUNCTIONALITY

FOREWORD
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International Standard IEC 63112 has been prepared by IEC technical committee 82: Solar
photovoltaic energy systems.
The text of this International Standard is based on the following documents:
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Full information on the voting for its approval can be found in the report on voting indicated in
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contents. Users should therefore print this document using a colour printer.

– 8 – IEC 63112:2021 © IEC 2021
INTRODUCTION
This document specifies the safety requirements that are applicable to Photovoltaic Earth-Fault
Protection (PV-EFP) equipment (PV-EFPE) whose function is to detect, interrupt, and warn PV
system operators of earth faults in solar photovoltaic arrays. A stand-alone standard on this
topic is deemed necessary and appropriate because PV-EFPE may be designed as stand-alone
equipment or may be integrated into other equipment such as PV inverters, charge controllers,
combiner boxes, etc. Therefore it is not appropriate to continue the current standardization
approach in which the PV-EFPE requirements are located only in an end-product standard
specific to inverters: IEC 62109-2:2011. It is intended that in coordination with the publication
of this document, IEC 62109-2 will be revised to refer to this document and to remove
overlapping and conflicting requirements. With this approach, the PV-EFPE requirements will
be more visible and will be usable for PV-EFPE that is not part of an inverter.
It is also desirable that in coordination with the publication of this document, the applicable IEC
system and installation standards for PV arrays will be amended to refer to this document, to
specify required functions and to remove overlapping and conflicting requirements. This work
will be managed by TC82 for IEC 62548 and jointly by TC82 and TC64 through JWG32 for
IEC 60364-7-712.
The appropriate functions, settings, responses, and timing for PV-EFP functions are dependent
on the size and topology of the overall PV system. These array details are not known at the
time the PV-EFPE is being evaluated to this product standard; therefore the required PV-EFP
functions and settings need to be provided by local and international system and installation
standards. As a result, this document does not require all PV-EFPE to implement all possible
functions, and does not generally contain the required settings for the functions. The functions,
settings, and ranges of adjustment that are claimed by the equipment manufacturer are tested
and evaluated, and the documentation for the installer and user specifies what functions are
and are not provided.
As well as requirements for the PV-EFP functions, this document includes product safety
requirements covering the construction, environmental suitability, markings, documentation,
and testing of the equipment. Since PV-EFPE is related to, and often integral to, PV power
conversion equipment, references are made to product safety requirements in IEC 62109-1.
However, those requirements may overlap or conflict with existing IEC standards for certain
types of equipment related to PV-EFP (for example insulation monitoring devices and residual
current monitoring equipment). Therefore, for some aspects, this document provides options
for equipment to comply with those standards, where such standards exist.
NOTE Further information on the intent of this document and special aspects of PV earth faults are summarized in
the (informative) Annex B.
PHOTOVOLTAIC (PV) ARRAYS –
EARTH FAULT PROTECTION EQUIPMENT –
SAFETY AND SAFETY-RELATED FUNCTIONALITY

1 Scope
This document is applicable to low voltage Photovoltaic Earth-Fault Protection Equipment (PV-
EFPE) whose function is to detect, interrupt, and warn system operators of earth faults in solar
photovoltaic arrays.
NOTE 1 In the context of this document, the PV array may include connected wiring and equipment. The required
coverage of the monitoring and protection is defined in PV installation codes and standards, including aspects such
as whether or not the coverage is required to include battery circuits, the DC outputs of DC-DC converters, etc.
NOTE 2 The IEC definition of low voltage is 1 000 V or less for AC systems and 1 500 V or less for DC systems.
PV-EFPE may be stand-alone or integrated into other equipment such as PV power conversion equipment, a PV
combiner, etc.
This document specifies:
– the types and levels of the monitoring and protection functions that may be provided;
– the nature and timing of responses to earth faults;
– test methods for validating the monitoring and protection functions provided;
– requirements for functional safety and fault tolerance;
– requirements for product safety including construction, environmental suitability, markings,
documentation, and testing.
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 60269-6, Low-voltage fuses – Part 6: Supplementary requirements for fuse-links for the
protection of solar photovoltaic energy systems
IEC 60417, Graphical symbols for use on equipment – 12-month subscription to regularly
updated online database comprising all graphical symbols published in IEC 60417
IEC 60664-1, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 60730-1:2013, Automatic electrical controls – Part 1: General requirements
IEC 60730-1:2013/AMD1:2015
IEC 60730-1:2013/AMD2:2020
IEC 60947-2:2016, Low-voltage switchgear and controlgear – Part 2: Circuit-breakers
IEC 60947-2:2016/AMD1:2019
IEC 61008-1:2010, Residual current operated circuit-breakers without integral overcurrent
protection for household and similar uses (RCCBs) – Part 1: General rules
IEC 61008-1:2010/AMD1:2012
IEC 61008-1:2010/AMD2:2013
– 10 – IEC 63112:2021 © IEC 2021
IEC 61439-1, Low-voltage switchgear and controlgear assemblies – Part 1: General rules
IEC 61557-8, Electrical safety in low voltage distribution systems up to 1 000 V a.c. and
1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures – Part 8:
Insulation monitoring devices for IT systems
IEC TS 61836, Solar photovoltaic energy systems – Terms, definitions and symbols
IEC 62109-1:2010, Safety of power converters for use in photovoltaic power systems – Part 1:
General requirements
IEC 62109-3:2020, Safety of power converters for use in photovoltaic power systems – Part 3:
Particular requirements for electronic devices in combination with photovoltaic elements
IEC TS 63053, General requirements for residual current operated protective devices for DC
system
ISO 3864 (all parts), Graphical symbols – Safety colors and safety signs
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in IEC TS 61836 and the
following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1
closed electrical operating area
room or location for electrical equipment to which access is restricted to skilled or instructed
persons by the opening of a door or the removal of a barrier by the use of a key or tool and
which is clearly marked by appropriate warning signs
3.2
DC-only system
PV system where all energy sources and power conversion is DC, with no inverter and no AC
connection in the system
3.3
earth fault
ground fault (US)
occurrence of an accidental conductive path between a live conductor and the Earth
Note 1 to entry: The conductive path can pass through a faulty insulation, through structures (e.g. poles,
scaffoldings, cranes, ladders), or through vegetation (e.g. trees, bushes) and can have a significant impedance.
[SOURCE: IEC 60050-195:1998,195-04-14]
3.4
host equipment
equipment that integrated PV-EFPE is intended to be used with or installed in (see also 3.7)

3.5
host system
system in which the PV-EFPE is connected, consisting of at least a PV array, the PV-EFPE,
and the load(s) for the PV system, such as PCE, energy storage equipment, DC loads, etc.
3.6
indicate
annunciate that a fault has occurred in a manner that can be locally and remotely observed
Note 1 to entry: Requirements for fault indication are given in detail in 8.1 through 8.3.
3.7
integrated PV-EFPE
PV-EFPE that is integrated into, intended to be integrated into, or specified to be exclusively
used with particular host equipment (see 3.4) that has intended function(s) other than PV earth
fault protection, and that the PV-EFPE is evaluated and tested with (for example a PCE, a PV
combiner box, etc.)
3.8
I
SC-PR-MAX
PV-EFPE rating, applicable to any terminal intended for connection to an external power
system, specifying the absolute maximum prospective short circuit fault current allowed to be
available at the PV-EFPE terminals if a fault of negligible impedance is applied at the PV-EFPE
terminals
Note 1 to entry: This is a general term applicable to all ports connecting to external sources of supply.For the PV
port, the specific term is I as defined in 3.9.
SC PV
3.9
I
SC PV
PV-EFPE maximum rated prospective short circuit current (see 3.8) at the PV input terminals;
i.e. the absolute maximum current the PV input to the PV-EFPE is designed to withstand or
carry under normal and fault conditions
Note 1 to entry: At the system design level, this rating would typically be coordinated with the total I of the
sc
connected PV strings, adjusted for temperature, excess irradiance, etc., as required by installation standards (i.e.
not simply the sum of the marked I ratings of the connected PV modules, since those markings are based on short-
sc
circuit conditions under standard test conditions (STC), and may be exceeded in actual use).
Note 2 to entry: This is a particular case of the general definition of I in 3.8, and is aligned with IEC 62109-1.
sc-pr-max
3.10
PV-EFP
photovoltaic earth fault protection
3.11
PV-EFPE
photovoltaic earth fault protection equipment
3.12
power conversion equipment
PCE
electrical device converting one kind of electrical power from a voltage or current source into
another kind of electrical power with respect to voltage, current and frequency
Note 1 to entry: Examples include AC-DC converters, DC-AC inverters, DC-DC charge controllers, frequency
converters, etc.
[SOURCE: IEC 62109-1:2010, 3.66]

– 12 – IEC 63112:2021 © IEC 2021
3.13
R
iso
symbol representing the insulation resistance (isolation) between the PV array and earth
3.14
routine test
conformity test made on each individual item during or after manufacture
[SOURCE: IEC 60050-151:2001, 151-16-17]
3.15
safe state
condition which continues to preserve safety
[SOURCE: IEC 60050-821:2017, 821-12-49]
3.16
stand-alone PV-EFPE
PV-EFPE that is self-contained, and therefore not integrated PV-EFPE in accordance with 3.7,
is for use in unspecified systems or with unspecified equipment, and is tested independently of
any particular host equipment
3.17
system, functionally-earthed
system in which the PV array has one conductor intentionally connected to earth for purposes
other than safety, by means not complying with the requirements for protective bonding
Note 1 to entry: Examples of functionally-earthed systems include earthing one conductor of the PV array through
an impedance, relay, or overcurrent protective device, or systems in which the array is not permanently earthed
(opening the earth connection periodically or under fault conditions).
Note 2 to entry: Examples of design elements that are not functional earthing include the use of varistors or other
surge protection devices between a circuit and earth, and the use of a resistive network connected between the array
and earth to measure the array insulation resistance (impedance monitoring). Neither of these examples creates a
functionally-earthed system, as the impedance of such connections is normally very high.
Note 3 to entry: For examples of the various system types, refer to Figure 1 through Figure 3.
3.18
system, non-earth-referenced
system that has none of its conductors intentionally referenced to earth either directly or through
the power conversion equipment (PCE)
3.19
system, non-separated
system in which the PV array is connected to an intentionally earth-referenced system, through
a PCE without at least simple separation
4 Requirements relating PV-EFP to system topology
4.1 General
The following aspects of the system topology affect the approaches needed to protect against
earth faults in the PV array:
– the PV system may or may not have separation between the PV array and the AC mains or
other earthed power system;
– the PV array may or may not be functionally-earthed;

– the AC mains or other power system that the PV system output connects to may or may not
be an earthed system.
In consideration of the above aspects, this document uses the following system types, for which
examples are given in Figure 1 through Figure 3, to define requirements for protection against
earth faults:
• functionally-earthed systems, as per 3.17 and Figure 1
• non-earth-referenced systems, as per 3.18 and Figure 2
...