IEC TS 62257-9-2:2016

Recommendations for renewable energy and hybrid systems for rural electrification - Part 9-2: Integrated systems - Microgrids

IEC TS 62257-9-2:2016(E) specifies microgrids made of overhead lines because of technical and economical reasons in the context of decentralized rural electrification. The microgrids covered by this part of IEC 62257 are low voltage AC, three-phase or single-phase, with rated capacity less than or equal to 100 kVA. They are powered by a single micropower plant. The main technical changes with regard to the previous edition are as follows: changing the voltage range covered by the technical specification to AC nominal voltage below 1 000 V and DC nominal voltage below 1 500 V.
This publication is to be read in conjunction with IEC 62257 series.

General Information

• Status: Published
• Publication Date: 26-Sep-2016
• ICS: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION
• ICS: 27.160 - Solar energy engineering
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Drafting Committee: JWG 1 - TC 82/JWG 1
• Current Stage: PPUB - Publication issued
• Start Date: 15-Nov-2016
• Completion Date: 27-Sep-2016

Relations

• Revises: IEC TS 62257-9-2:2006 - Recommendations for small renewable energy and hybrid systems for rural electrification - Part 9-2: Microgrids
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC TS 62257-9-2 ®
Edition 2.0 2016-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural
electrification –
Part 9-2: Integrated systems – Microgrids

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

IEC Central Office Tel.: [phone]
3, rue de Varembé Fax: [phone]
CH-1211 Geneva 20 [e-mail]
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished
Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: [e-mail].
IEC TS 62257-9-2 ®
Edition 2.0 2016-09
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural

electrification –
Part 9-2: Integrated systems – Microgrids

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-3586-7

– 2 – IEC TS 62257-9-2:2016 © IEC 2016
CONTENTS
FOREWORD. 5
INTRODUCTION . 7
1 Scope . 8
2 Normative reference . 8
3 Terms and definitions . 8
4 General . 10
4.1 Limits of a microgrid . 10
4.2 Voltage drops . 10
4.3 Composition of a microgrid . 10
5 Protection against electric shocks . 12
6 Protection against overcurrents . 12
7 Selection and erection of equipment. 12
7.1 Equipment installation . 12
7.2 Operational conditions and external influences . 12
7.2.1 Ambient temperature . 12
7.2.2 Sources of heat . 12
7.2.3 Presence of water . 12
7.2.4 Risk of penetration of solid bodies . 13
7.2.5 Corrosive or polluting substance presence . 13
7.2.6 Mechanical requirements . 13
7.2.7 Equipment and supporting structures . 13
7.2.8 Vibration . 13
7.2.9 Other mechanical constraints for underground microgrid sections . 13
7.2.10 Presence of flora, mold or fauna . 14
7.2.11 Solar radiation . 14
7.3 Characteristics of lines . 14
7.3.1 General . 14
7.3.2 Installation modes . 14
7.3.3 Minimum height of conductors . 14
7.3.4 Proximity to other services . 14
7.4 Cables . 14
7.5 Poles . 15
7.5.1 General . 15
7.5.2 Characteristics of poles . 15
7.6 Cable anchorage . 17
7.7 Connections and accessories . 18
7.7.1 General . 18
7.7.2 Connections between conductors, connections to other equipment . 18
7.7.3 Connection points for individual service connections . 18
7.7.4 Connection equipment . 18
7.8 Where poles are used for other purposes . 19
7.8.1 Public lighting points . 19
7.8.2 Telecommunication lines . 19
7.9 Isolation and switching . 20
7.9.1 Overcurrent protection device . 20

7.9.2 Isolating devices . 21
7.10 Earthing arrangement, protective conductors and protective bonding
conductors . 21
8 Verification and acceptance . 22
8.1 General . 22
8.2 Supervision of works . 22
8.3 Verification before commissioning (on site acceptance) . 23
8.4 Operation tests . 23
Annex A (informative) Characteristics of cables . 24
Annex B (informative) Maximum circuit length . 26

Figure 1 – Microgrid limits . 10
Figure 2 – Microgrid consisting of a single phase feeder . 11
Figure 3 – Three phase system output, single phase distribution or three phase
service provided where needed . 11
Figure 4 – Three phase system output, single phase distribution . 11
Figure 5 – Diagram showing installation of twinned wooden poles forming an angle . 16
Figure 6 – Examples of different pole arrangements . 17
Figure 7 – Example of an overhead line . 17
Figure 8 – Connection mode diagram . 19
Figure 9 – Microgrid earthing scheme . 21
Figure B.1 – Maximum lengths as a function of active power (1 phase) for 16 mm
cable and 6 % voltage drop with loads at end of cable . 27
Figure B.2 – Maximum lengths as a function of active power (1 phase) for 16 mm
cable and 6 % voltage drop with loads spread across cable . 28
Figure B.3 – Maximum lengths as a function of active power (1 phase) for 25 mm
cable and 6 % voltage drop with loads at end of cable . 29
Figure B.4 – Maximum lengths as a function of active power (1 phase) for 25 mm
cable and 6 % voltage drop with loads spread across cable . 30
Figure B.5 – Maximum lengths as a function of active power (3 phase) for 35 mm
cable and 6 % voltage drop with loads at end of cable . 31
Figure B.6 – Maximum lengths as a function of active power (3 phase) for 35 mm
cable and 6 % voltage drop with loads spread across cable . 32
Figure B.7 – Maximum lengths as a function of active power (3 phase) for 35 mm
cable and 3 % voltage drop with loads at end of cable . 33
Figure B.8 – Maximum lengths as a function of active power (3 phase) for 50 mm
cable and 6 % voltage drop with loads at end of cable . 34
Figure B.9 – Maximum lengths as a function of active power (3 phase) for 50 mm
cable and 6 % voltage drop with loads spread across cable . 35
Figure B.10 – Maximum lengths as a function of active power (3 phase) for 50 mm
cable and 3 % voltage drop with loads at end of cable . 36
Figure B.11 – Maximum lengths as a function of active power (3 phase) for 70 mm
cable and 6 % voltage drop with loads at end of cable . 37
Figure B.12 – Maximum lengths as a function of active power (3 phase) for 70 mm
cable and 6 % voltage drop with loads spread across cable . 38
Figure B.13 – Maximum lengths as a function of active power (3 phase) for 70 mm
cable and 3 % voltage drop with loads at end of cable . 39

– 4 – IEC TS 62257-9-2:2016 © IEC 2016
Table 1 – Maximum values of voltage drops . 10
Table 2 – Fuse ratings for protection from short-circuiting in 230 V (and 240 V) a.c.
microgrids (overhead lines) . 20
Table 3 – Fuse ratings for protection from short-circuiting in 120 V a.c. microgrids
(overhead lines) . 20
Table 4 – Circuit breaker ratings for protection from short-circuiting in microgrids
(overhead lines) . 20
Table 5 – Characteristics of earthing components .
...