IEC TS 62257-9-4:2016

IEC TS 62257-9-4 ®
Edition 2.0 2016-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural
electrification –
Part 9-4: Integrated systems – User installation

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IEC TS 62257-9-4 ®
Edition 2.0 2016-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural

electrification –
Part 9-4: Integrated systems – User installation

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-3588-1

– 2 – IEC TS 62257-9-4:2016 © IEC 2016
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative reference . 7
3 Terms and definitions . 8
4 General considerations . 9
4.1 General . 9
4.2 Installation limits . 9
4.3 User interface . 9
5 Protection against electric shock . 9
5.1 Requirements for d.c. parts of installation . 9
5.2 Requirements for a.c. parts of installation . 9
5.2.1 General . 9
5.2.2 Neutral earthing system . 9
6 Protection against overcurrent . 11
7 Protection against effect of lightning. 11
7.1 Installation supplied from a microgrid . 11
7.2 Standalone installation . 11
8 Selection and erection of electrical equipment . 12
8.1 Wiring system . 12
8.1.1 General . 12
8.1.2 Voltage drops . 12
8.1.3 Cross-sectional area of conductors . 12
8.1.4 Connections . 13
8.1.5 Installation method . 14
8.1.6 Selection and erection of wiring systems in relation to external
influences . 15
8.1.7 Specific rules to wiring systems buried in earth . 17
8.1.8 Circuits identification . 18
8.2 Isolation and switching . 18
8.2.1 Overcurrent protective devices . 18
8.2.2 Residual current devices . 18
8.3 Surge protective devices . 18
8.4 Earthing arrangement, protective conductors and protective bonding . 18
8.5 User interface . 18
9 Verification . 19
9.1 Pre-commissioning checks . 19
9.1.1 General information . 19
9.1.2 Verification by inspection . 19
9.1.3 Verification by tests . 20
10 Operation and maintenance . 20
Annex A (informative) Maximum possible length of circuits with different cables and
conductors to handle maximum voltage drops (ambient temperature 30 °C) . 21

Figure 1 – Installation limits . 9

Figure 2 – Protection of persons in an installation supplied from a microgrid according
to a TN-C-S system . 10
Figure 3 – Protection of persons in a combined d.c. and a.c. system . 11
Figure A.1 – Maximum possible length of circuit as a function of current for a voltage
drop of 3 % in a.c. system in a cable HO5VVF . 22
Figure A.2 – Maximum possible length of circuit as a function of current for a voltage
drop of 15 % in d.c. system in a cable 1000RO2V . 23

Table 1 – Maximum design current of circuits depending on voltages . 11
Table 2 – Maximum acceptable voltage drop values in installations . 12
Table 3 – Cross-sectional area for copper conductors in fixed installations . 13
Table 4 – Selection of wiring systems . 14
Table 5 – Installation of wiring systems . 14
Table 6 – Fuses/circuit breakers rating and selection for overcurrent protection . 18

– 4 – IEC TS 62257-9-4:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 9-4: Integrated systems – User installation

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, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising 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
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
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5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
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6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• 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 62257-9-4, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

This second edition cancels and replaces the first edition issued in 2006. It constitutes a
technical revision.
The main technical changes with regard to the previous edition are as follows:
• Changing the voltage range covered by the technical specification to a.c. nominal voltage
below 1 000 V and d.c. nominal voltage below 1 500 V (introduction).
• Including 240 V and 220 V 1-Ø in the voltage levels (scope).
• Introduced requirement that conductor used for lightning protection must be minimum
16 mm (7.2).
This part of IEC 62257 is to be used in conjunction with the IEC 62257 series.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
82/1031/DTS 82/1090/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 document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 62257 series, published under the general title Recommendations
for renewable energy and hybrid systems for rural electrification, can be found on the IEC
website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
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
• 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.
– 6 – IEC TS 62257-9-4:2016 © IEC 2016
INTRODUCTION
The IEC 62257 series intends to provide to different players involved in rural electrification
projects (such as project implementers, project contractors, project supervisors, installers,
etc.) documents for the setting up of renewable energy and hybrid systems with a.c. nominal
voltage below 1 000 V, and d.c. nominal voltage below 1 500 V.
These documents are recommendations:
• to choose the right system for the right place,
• to design the system,
• to operate and maintain the system.
These documents are focused only on rural electrification concentrating on but not specific to
developing countries. They should not be considered as all inclusive to rural electrification.
The documents try to promote the use of renewable energies in rural electrification; they do
not deal with clean mechanisms developments at this time (CO emission, carbon credit, etc.).
Further developments in this field could be introduced in future steps.
This consistent set of documents is best considered as a whole with different parts
corresponding to items for safety, sustainability of systems and at the lowest life cycle cost as
possible. One of the main objectives is to provide the minimum sufficient requirements,
relevant to the field of application that is: small renewable energy and hybrid off-grid systems.

RECOMMENDATIONS FOR RENEWABLE ENERGY
AND HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 9-4: Integrated systems – User installation

1 Scope
This part of IEC 62257, which is a technical specification, specifies the general requirements
for the design and the implementation of a user's installation.
This part of IEC 62257 applies to single phase user's electrical installations with maximum
power of 500 VA, in Decentralized Rural Electrification Systems (DRES).
NOTE For installations above 500 VA in decentralized electrification systems, IEC TS 62257-5 applies.
This part of IEC 62257 is applicable to installations supplied by an a.c microgrid (120 V or
220 V or 230 V or 240 V) and to installations encompassing their own single-unit a.c.
micropower plant (120 V or 220 V or 230 V or 240 V) or d.c micropower plant (12 V or 24 V).
The part of IEC 62257 applies neither to the electric power production and distribution
installations described in the clauses concerning micropower plants and microgrids, nor to
user electrical equipment. It details the rules governing the design and construction of
consumer’s electrical installations for the purpose of ensuring the safety of persons and
property, and satisfactory operation in accordance with the purpose for which the installations
are designed.
It applies to new installations and modifications of existing installations.
2 Normative reference
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 (all parts), Low-voltage fuses
IEC 60364-5-52, Electrical installations of buildings – Part 5-52: Selection and erection of
electrical equipment – Wiring systems
IEC 62257 (all parts), Recommendations for renewable energy and hybrid systems for rural
electrification
IEC TS 62257-5, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC TS 62257-7 (all parts), Recommendations for renewable energy and hybrid systems for
rural electrification – Part 7: Generators
IEC TS 62257-7-1, Recommendations for small renewable energy and hybrid systems for
rural electrification – Part 7-1: Generators – Photovoltaic generators

– 8 – IEC TS 62257-9-4:2016 © IEC 2016
IEC TS 62257-9-3, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-3: Integrated systems – User interface
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
protective conductor
identification: PE
conductor provided for purposes of safety, for example protection against electric shock
Note 1 to entry: In an electrical installation, the conductor identified PE is normally also considered as protective
earthing conductor.
[SOURCE: IEC 60050-195:1998, 195-02-09]
3.2
PEN conductor
conductor combining the functions of a protective earthing conductor and a neutral conductor
[SOURCE: IEC 60050-195:1998, 195-02-12]
3.3
equipotential bonding
provision of electric connections between conductive parts, intended to achieve
equipotentiality
Note 1 to entry: The role of the equipotential bonding is to decrease the difference in potential that can exists
between two exposed-conductive parts of an installation.
3.4
surge arrester
device designed to protect the electrical apparatus from high transient overvoltages and to
limit the duration and frequently, the amplitude of the follow-on current
3.5
supply point
contractual limit between the grid and the user’s installation
Note 1 to entry: In rural electrification systems, it is generally located on the input terminals (microgrid side) of
the user’s interface.
3.6
Surge Protective Device
SPD
device intended to protect the electrical apparatus from transient overvoltages and divert
surge current; it contains at least one non-linear component

4 General considerations
4.1 General
User installations shall be designed to ensure protection of persons, animal and equipment in
compliance with IEC TS 62257-5.
Specific requirements for generators associated with stand-alone user installations are
provided in the relevant part of the IEC TS 62257-7 series.
4.2 Installation limits
Installation limits are illustrated in Figure 1.
Production Distribution User
sub-system sub-system sub-system
Microgrid Installation
Micropowerplant
Other
User interface
Generator
equipment
IEC
Figure 1 – Installation limits
4.3 User interface
See IEC TS 62257-9-3.
5 Protection against electric shock
5.1 Requirements for d.c. parts of installation
Simple separation, at least, shall be provided between the d.c. side and the a.c. side of a
stand-alone installation (for a PV array, see also IEC TS 62257-7-1).
5.2 Requirements for a.c. parts of installation
5.2.1 General
The characteristics of the protective devices shall be such that if a fault of negligible
impedance occurs anywhere in the in
...