IEC TS 62257-7-2:2022

Recommendations for renewable energy and hybrid systems for rural electrification - Part 7-2: Generator set - Off-grid wind turbines

IEC TS 62257-7-2:2022 applies to all small wind turbines (SWTs) with a swept area smaller than or equal to 200 m2, and designed for supplying electrical power to isolated sites used in systems as described in IEC TS 62257-2.
This document is not an exhaustive resource for the design, installation, operation or maintenance of small wind turbines and wind power systems, but is more focused on recommendations to provide strategies on selection and criteria which may affect the use of a small wind power system (SWPS) in a rural electrification project.
The aim of this document is to provide users with the appropriate levels of reliability and safety of the equipment during its estimated service lifespan.

General Information

• Status: Published
• Publication Date: 15-Mar-2022
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 82 - Solar photovoltaic energy systems
• Current Stage: PPUB - Publication issued
• Completion Date: 16-Mar-2022

Standards Content (sample)

IEC TS 62257-7-2
Edition 1.0 2022-03
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural
electrification –
Part 7-2: Generator set – Off-grid wind turbines
IEC TS 62257-7-2:2022-03(en)
---------------------- Page: 1 ----------------------
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IEC TS 62257-7-2
Edition 1.0 2022-03
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for renewable energy and hybrid systems for rural
electrification –
Part 7-2: Generator set – Off-grid wind turbines
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-1087-2

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62257-7-2:2022 © IEC 2022
CONTENTS

FOREWORD ........................................................................................................................... 6

INTRODUCTION ..................................................................................................................... 8

1 Scope .............................................................................................................................. 9

2 Normative references .................................................................................................... 10

3 Terms and definitions .................................................................................................... 10

4 Symbols and abbreviated terms ..................................................................................... 15

4.1 Abbreviated terms ................................................................................................. 15

4.2 Symbols ................................................................................................................ 16

5 Wind turbine (WT) ......................................................................................................... 16

5.1 Types of wind turbines .......................................................................................... 16

5.1.1 Horizontal axis wind turbine (HAWT) .............................................................. 16

5.1.2 Vertical axis wind turbine (VAWT) .................................................................. 17

5.1.3 SWT classes.................................................................................................. 18

5.2 General characteristics of SWT ............................................................................. 18

5.2.1 Basic technical characteristics ....................................................................... 18

5.2.2 Most important technical characteristics ........................................................ 19

5.3 Working conditions of SWT ................................................................................... 20

6 Off-grid Small Wind Power Systems (SWPS) ................................................................. 20

6.1 General ................................................................................................................. 20

6.2 Major components in SWPS .................................................................................. 20

6.2.1 SWT .............................................................................................................. 20

6.2.2 Tower ............................................................................................................ 21

6.2.3 Controller ...................................................................................................... 22

6.2.4 Brake ............................................................................................................. 22

6.2.5 Inverter .......................................................................................................... 23

6.2.6 Storage system .............................................................................................. 23

6.2.7 Dump load ..................................................................................................... 23

6.3 Design Procedure of SWPS .................................................................................. 23

6.3.1 General ......................................................................................................... 23

6.3.2 Wind resource assessment ............................................................................ 23

6.3.3 Site assessment ............................................................................................ 24

6.3.4 Determine the capacity of the SWPS ............................................................. 24

6.3.5 Select SWT ................................................................................................... 24

6.4 Configuration of SWPS ......................................................................................... 24

6.4.1 General ......................................................................................................... 24

6.4.2 Layout SWT(s) on site ................................................................................... 28

7 Selection of SWPS ........................................................................................................ 28

7.1 General ................................................................................................................. 28

7.2 Selection criteria ................................................................................................... 29

7.2.1 General factors in selection of SWT ............................................................... 29

7.2.2 Rule of thumb ................................................................................................ 29

7.2.3 Wind turbine height ........................................................................................ 29

7.2.4 Turbulence .................................................................................................... 30

7.3 Design of a microgrid or Isolated Microgrid with SWT ........................................... 30

7.3.1 Meet national rural grid standards.................................................................. 30

7.3.2 Design microgrid and wiring into households ................................................. 30

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IEC TS 62257-7-2:2022 © IEC 2022 – 3 –

8 Safety issues ................................................................................................................. 30

8.1 General ................................................................................................................. 30

8.2 General ................................................................................................................. 30

8.3 Personal safety ..................................................................................................... 31

8.3.1 Safety training and regulation following ......................................................... 31

8.3.2 Basic safety guidelines .................................................................................. 31

8.4 Equipment safety .................................................................................................. 32

8.4.1 SWT .............................................................................................................. 32

8.4.2 System current and voltage ........................................................................... 32

8.4.3 Wiring and disconnection requirements ......................................................... 32

8.4.4 Grounding...................................................................................................... 32

8.4.5 Other safety issues and anti-theft .................................................................. 33

8.5 SWPS safety for isolated microgrid ....................................................................... 33

8.5.1 System safety ................................................................................................ 33

8.5.2 Extreme climate proof .................................................................................... 34

8.5.3 High elevation for electronics ......................................................................... 34

8.6 Protection against electric shock and fire .............................................................. 34

9 SWT and SWPS installation ........................................................................................... 34

9.1 General ................................................................................................................. 34

9.1.1 Overview ....................................................................................................... 34

9.1.2 General installation methods ......................................................................... 35

9.1.3 Rooftop installation ........................................................................................ 35

9.1.4 Verticality ...................................................................................................... 35

9.2 Installation of SWPS of isolated microgrid ............................................................. 36

9.2.1 Transportation ............................................................................................... 36

9.2.2 Preparations .................................................................................................. 36

9.2.3 Infrastructure ................................................................................................. 36

9.2.4 Civil works ..................................................................................................... 37

9.2.5 Installation of equipment ................................................................................ 38

10 Tests and acceptance .................................................................................................... 40

10.1 General ................................................................................................................. 40

10.2 Individual equipment test ...................................................................................... 40

10.3 System self-test .................................................................................................... 40

10.4 Acceptance test .................................................................................................... 40

10.4.1 General ......................................................................................................... 40

10.4.2 Preparation .................................................................................................... 41

10.4.3 Documentation .............................................................................................. 41

10.4.4 Commissioning .............................................................................................. 41

10.4.5 Agreement ..................................................................................................... 42

11 Operation and maintenance ........................................................................................... 42

11.1 General ................................................................................................................. 42

11.2 Safety ................................................................................................................... 42

11.3 Operation and maintenance procedures ................................................................ 42

11.4 General inspection, routine and troubleshooting.................................................... 43

11.4.1 Inspection ...................................................................................................... 43

11.4.2 Check list ...................................................................................................... 43

11.5 Troubleshooting .................................................................................................... 43

12 Marking and documentation ........................................................................................... 44

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– 4 – IEC TS 62257-7-2:2022 © IEC 2022

12.1 Markings and signs ............................................................................................... 44

12.1.1 General ......................................................................................................... 44

12.1.2 Equipment marking ........................................................................................ 44

12.1.3 Requirements for signs .................................................................................. 44

12.2 Labelling ............................................................................................................... 44

12.2.1 Labelling of SWT ........................................................................................... 44

12.2.2 Labelling of disconnection devices ................................................................. 44

12.3 Documentation ...................................................................................................... 44

Annex A (informative) Main characteristics of an off-grid wind turbine .................................. 45

A.1 Example of battery charging horizontal axis SWT’s characteristics, see

Table A.1 .............................................................................................................. 45

A.2 Example of battery charging vertical axis SWT’s characteristics, see

Table A.2 .............................................................................................................. 46

Annex B (informative) Wind shear exponent, α .................................................................... 47

Annex C (informative) Example of labelling .......................................................................... 48

Annex D (informative) Example of inspection and maintenance schedule ............................. 49

D.1 General ................................................................................................................. 49

D.2 Example of inspection and maintenance schedule for a SWPS with HAWT ........... 49

D.3 Checklist for inspections ....................................................................................... 49

Annex E (informative) Example of troubleshooting for a SWPS with HAWT SWT ................. 51

Annex F (informative) Example of commissioning records sheet for SWT ............................ 53

Annex G (informative) Case study of SWPS design ............................................................. 55

G.1 Basic information .................................................................................................. 55

G.2 Local renewable energy resource – Wind resource ............................................... 55

G.3 Required wind power capacity in the HPS ............................................................. 55

G.4 Select wind turbine (s) .......................................................................................... 55

G.5 Calculate the power output of unit SWT based upon local wind resource and

power curve of selected SWT ................................................................................ 56

Annex H (informative) Example of oscillation method to determine natural frequency

and tension .................................................................................................................... 57

H.1 General ................................................................................................................. 57

H.2 Oscillation method for tensioning guy cables ......................................................... 57

Bibliography .......................................................................................................................... 58

Figure 1 – General functional configuration of SWT(s) in an off-grid hybrid power

system .................................................................................................................................... 9

Figure 2 – Example of wind turbine with active yaw system................................................... 17

Figure 3 – Rotors with different number of blades of a HAWT ............................................... 17

Figure 4 – Four typical VAWTs ............................................................................................. 17

Figure 5 – Variety of tower options ........................................................................................ 22

Figure 6 – AC bus system ..................................................................................................... 25

Figure 7 – DC bus system ..................................................................................................... 25

Figure 8 – Obstruction of the wind by a building or a tree...................................................... 30

Figure 9 – Pads for tilt-up tower ............................................................................................ 38

Figure 10 – Acceptance test procedure of SWPS .................................................................. 41

Figure C.1 – Sample label in English ..................................................................................... 48

Figure C.2 – Sample label, bilingual (English and French) .................................................... 48

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IEC TS 62257-7-2:2022 © IEC 2022 – 5 –

Figure G.1 – Annual monthly average wind speed pattern ..................................................... 55

Figure G.2 – Power curve of selected SWT ........................................................................... 56

Figure G.3 – Power output from one 10 kW SWT .................................................................. 56

Table 1 – Basic parameters for SWT classes ........................................................................ 18

Table 2 – Equipment having a nominal voltage below 750 V DC ........................................... 26

Table 3 – Equipment having a nominal voltage below 750 V DC ........................................... 27

Table 4 – AC systems having a nominal voltage between 100 V and 1 000 V inclusive

and related equipment .......................................................................................................... 28

Table 5 – Installation methods of different SWPSs ................................................................ 35

Table A.1 – Example of battery charging horizontal axis SWT’s characteristics ..................... 45

Table A.2 – Example of battery charging vertical axis SWT’s characteristics ......................... 46

Table B.1 – Surface roughness and lengths and the wind hear exponents α ......................... 47

Table E.1 – Example of troubleshooting guide for SWT ......................................................... 51

Table F.1 – Acceptance of wind generators .......................................................................... 53

Table F.2 – Example of commissioning records sheet for SWT operation .............................. 54

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– 6 – IEC TS 62257-7-2:2022 © IEC 2022
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RECOMMENDATIONS FOR RENEWABLE ENERGY AND
HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –
Part 7-2: Generator set – Off-grid wind turbines
FOREWORD

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

IEC TS 62257-7-2 has been prepared by IEC technical committee 82: Solar photovoltaic

energy systems. It is a Technical Specification.
The text of this Technical Specification is based on the following documents:
Draft Report on voting
82/1956/DTS 82/1995/RVDTS

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 Specification is English.

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IEC TS 62257-7-2:2022 © IEC 2022 – 7 –

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.

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.

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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– 8 – IEC TS 62257-7-2:2022 © IEC 2022
INTRODUCTION

The IEC 62257 series of publications 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 AC

voltage below 500 V, DC voltage below 750 V and power below 100 kW.
These publications provide recommendations for:
• choosing the right system for the right place;
• designing the system;
• operating and maintaining the system.

These publications are focused only on rural electrification concentrated in, but not specific to,

developing countries. They are not considered as all-inclusive of rural electrification. The

publications try to promote the use of renewable energies in rural electrification. They do not

deal with clean mechanism developments at this time (CO2 emission, carbon credit, etc.).

Further developments in this field could be introduced in future steps.

This consistent set of publications is best considered as a whole, with different parts

corresponding to items for the safety and sustainability of systems at the lowest possible life-

cycle cost. One of the main objectives of the series is to provide the minimum sufficient

requirements relevant to the field of application, i.e. for small renewable energy and hybrid

off-grid systems.

The purpose of this document is to provide guidance for the deployment of small wind

turbines (a wind turbine with a rotor swept area smaller than or equal to 200 m , see

IEC 61400-2: 2013) used in off-grid hybrid power system in rural electrification.

This document is a general introduction followed by more specific documents dedicated to the

generation technologies which are the most currently used in rural electrification projects.

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IEC TS 62257-7-2:2022 © IEC 2022 – 9 –
RECOMMENDATIONS FOR RENEWABLE ENERGY AND
HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –
Part 7-2: Generator set – Off-grid wind turbines
1 Scope

This document applies to all small wind turbines (SWTs) with a swept area smaller than or

equal to 200 m , and designed for supplying electrical power to isolated sites used in systems

as described in IEC TS 62257-2.

This document is not an exhaustive resource for the design, installation, operation or

maintenance of small wind turbines and wind power systems, but is more focused on

recommendations to provide strategies on selection and criteria which may affect
...