IEC TS 62257-7-2:2022

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
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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

– 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

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

– 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

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

– 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
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-
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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
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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 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.

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.
– 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.

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 the use of a
small wind power system (SWPS) in a rural electrification project.
Only the hybrid collective electrification system (microgrid, isolated microgrid) including
SWT(s) is considered in this document. SWT in an isolated microgrid can be a single wind
turbine or multiple wind turbines. Isolated microgrid using only wind power generation is not
discussed in this document. General functional configuration of SWT(s) in an off-grid hybrid
power system is shown in Figure 1.

Figure 1 – General functional configuration of SWT(s)
in an off-grid hybrid power system
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.
It describes the minimum safety requirements and does not claim to be an exhaustive
instruction manual or design specification.
Compliance with this document does not exempt any person, organization, or corporation
from the responsibility to comply with all other relevant regulations.
This document gives recommendations for the single SWT with a swept area smaller than or
equal to 200 m , or multiple SWTs with other power sources of total capacity up to 100 kW in
an off-grid hybrid power system.
The design life of a good quality modern wind turbine is 20 years. The real lifetime of a SWT
is subjected to quite extreme loads throughout its life. This mostly depends on its designed

– 10 – IEC TS 62257-7-2:2022 © IEC 2022
structure and reliability of moving parts, because the power in the wind increases with the
cube of the speed.
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 60038:2009, IEC standard voltages
IEC 60038:2009/AMD1:2021
IEC 60287 (all parts), Electric cables – Calculation of the current rating
IEC 60721-2-1:2013, Classification of environmental conditions – Part 2-1: Environmental
conditions appearing in nature – Temperature and humidity
IEC 61140, Protection against electric shock – Common aspects for installation and
equipment
IEC 61400-2:2013, Wind turbines – Part 2: Small wind turbines
IEC 61400-12-1, Wind energy generation systems – Part 12-1: Power performance
measurements of electricity producing wind turbines
IEC TS 62257-2, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 2: From requirements to a range of electrification systems
IEC TS 62257-4, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 4: System selection and design
IEC TS 62257-5, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 5: Protection against electrical hazards
IEC TS 62257-6, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 6: Acceptance, operation, maintenance and replacement
IEC TS 62257-9-1, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-1: Integrated systems – Micropower systems
IEC TS 62257-9-2, Recommendations for renewable energy and hybrid systems for rural
electrification – Part 9-2: Integrated systems – Microgrids
ISO 3864-1:2011, Graphical symbols – Safety colours and safety signs – Part 1: Design
principles for safety signs and safety markings
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
Annual Energy Production
AEP
calculated total energy that would be produced during a one-year period at an average wind
speed of 5,0 m/s at hub height, assuming a Rayleigh wind speed distribution, 100 %
availability, and the power curve derived from IEC 61400-12-1
SEE: 3.28.
3.2
annual average
mean value of a set of measured data of sufficient size and duration to serve as an estimate
of the expected value of the quantity
3.3
annual average wind speed
Vave
wind speed averaged according to the definition of annual average
3.4
brake
device capable of reducing the rotor speed or stopping rotation of a wind turbine system
3.5
collective electrification system

micro-power plant and micro-grid that supplies electricity to multiple consumption points using
a single or multiple energy resource points
3.6
consumer label
label for the benefit of consumers consisting of two parts: the label itself, and a test summary
report made available by a web site
3.7
control system
sub-system that receives information about the condition of the wind turbine system and/or its
environment and adjusts the turbine in order to maintain it within its operating limits
3.8
start-up wind speed
wind speed at which the rotor first begins to turn after being at rest once spinning, wind
turbine rotors can coast to lower wind speeds than those necessary to start the rotor revolving
3.9
cut-in wind speed
Vin
lowest mean hub height wind speed bin value at which the wind turbine system produces a
net positive power output. The turbine does not produce power between start up wind speed
and cut in wind speed.
3.10
cut-out wind speed
Vout
highest mean wind speed at hub height at which the wind turbine system is designed to
produce power
– 12 – IEC TS 62257-7-2:2022 © IEC 2022
3.11
downwind
in the main direction of wind flow
3.12
emergency shutdown
rapid shutdown of the wind turbine system triggered by a protection system or by manual
intervention
3.13
external condition
factor affecting the operation of a wind turbine system including the environmental conditions
(temperature, snow, ice, etc.) and the electrical network conditions that are not part of the
wind turbine system
3.14
extreme wind speed
highest average wind speed, averaged over t seconds, that is likely to be experienced within
a specified time period (recurrence period) of T years
3.15
fail-safe
design property of an item which prevents its failures from resulting in critical faults
3.16
hybrid power system
HPS
power system including generators from different technologies
3.17
horizontal axis wind turbine
HAWT
type of wind turbine in which the axis of the rotor's rotation is nominally parallel to the
horizontal ground surface
3.18
hub
fixture for attaching the blades or blade assembly to the rotor shaft of a wind turbine system
3.19
hub height
height of the geometric center of the swept area of the wind turbine rotor above the terrain
surface
3.20
mean wind speed
statistical mean of the instantaneous value of the wind speed averaged over a given time
period which can vary from a few seconds to 1 year
Note 1 to entry: Though wind speed varies over a continuum, measurements used to develop power curves group
power measurements into separate discrete registers or bins, for wind speed in m/s, typically 0,5m/s wide. The 5
m/s bin, for example, would represent winds from 4,75 to 5,25 m/s.
3.21
nacelle
housing which contains the drivetrain and other elements on top of a horizontal axis wind
turbine tower
3.22
noise label
defined graphical and textual representation of the acoustic noise data pertaining to a small
wind turbine system
3.23
overspeed control
action of a control system, or part of such system, which prevents excessive rotor speed
3.24
power form and voltage
physical characteristics which describe the form in which power produced by the wind turbine
system is made deliverable to the load (e.g. 230 V AC, 50 Hz, 1 ph; or e.g. 48 V DC)
3.25
protection system
system which ensures that a wind turbine generator system remains within the design limits
3.26
rated power
maximum continuous electrical output power which a wind turbine system is designed to
achieve at the connection facilities under normal operation
Note 1 to entry: The rated power of SWT is its output at 11 m/s at standard sea-level condition.
Rated power of SWT varies roughly proportionally to the swept area of the rotor. Blade design and technology
developments are therefore one of the keys to increasing wind turbine capacity output. By doubling the rotor
diameter, the swept area and therefore power output is increased by a factor of four.
3.27
rated wind speed
wind speed at which a wind turbine system’s rated power is achieved. The distribution
depends on one adjustable parameter – the scale parameter, which controls the average wind
speed.
3.28
maximum design wind speed
highest allowable wind speed for turbine operations
Note 1 to entry: It is expressed in m/s.
3.29
swept area
projected area perpendicular to the wind direction that a rotor will describe during one
complete rotation
Note 1 to entry: It is expressed in m .
3.30
Rayleigh distribution
probability distribution function often used for wind speeds
3.31
reference annual energy
calculated total energy that would be produced during a one-year period at an average wind
speed of 5,0 m/s at hub height, assuming a Rayleigh wind speed distribution, 100 %
availability, and the power curve derived from IEC 61400-12-1 (where it is referred to as
Annual Energy Production (AEP))
Note 1 to entry: The AEP from IEC 61400-12-1 is either the “AEP-measured” or the “AEP-extrapolated”, and is
either “sea-level normalised” or “site-specific”.

– 14 – IEC TS 62257-7-2:2022 © IEC 2022
Note 2 to entry: In this document reference annual energy is AEP-measured and sea-level normalised.
Note 3 to entry: The reference annual energy is defined for the purposes of comparing wind turbine systems.
3.32
reference wind speed
V
ref
basic parameter for wind speed used for defining SWT classes
Note 1 to entry: Other design related climatic parameters are derived from the reference wind speed and other
basic SWT class parameters.
Note 2 to entry: A turbine designed for a SWT class with a reference wind speed, V , is designed to withstand
ref
climates for which the extreme 10 min average wind speed with a recurrence period of 50 years at turbine hub
height is lower than or equal to V .
ref
3.33
resonance
phenomenon appearing in an oscillating system, in which the period of a forced oscillation is
very close to that of free oscillation
3.34
rotor centre
geometric centre of the wind turbine rotor
3.35
rotor speed
rotational speed of a wind turbine rotor about its axis
3.36
scheduled maintenance
preventive maintenance carried out in accordance with an established time schedule
3.37
Small Wind Power System
SWPS
includes the wind turbine itself including support structures, the turbine controller, the charge
controller / inverter (if required), wiring and disconnects, the installation and operation
manual(s) and other documentation
3.38
Small Wind Turbine
SWT
(IEC 61400-2)
wind turbine with a rotor swept area smaller than or equal to 200 m
3.39
swept area
projected area perpendicular to the wind direction that a rotor will describe during one
complete rotation
3.40
turbulence intensity
ratio of the wind speed standard deviation to the mean wind speed, determined from the same
set of measured data samples of wind speed, and taken over a specified period of time
3.41
upwind
in the direction opposite to the main direction of wind flow

3.42
Vertical Axis Wind Turbine
VAWT
wind turbine system whose rotor axis is substantially perpendicular to the wind flow
3.43
Weibull distribution
probability distribution function often used for wind speeds
3.44
wind speed distribution
probability distribution function, used to describe the distribution of wind speeds over an
extended period of time
3.45
wind shear
variation of wind speed across a plane perpendicular to the wind direction
3.46
wind speed
velocity of air at a specified point in space wind profile
3.47
wind profile
wind shear law mathematical expression for assumed wind speed variation with height above
ground
Note 1 to entry: Commonly used profiles are the logarithmic profile (1) or the power law profile (2).
ln (𝑍𝑍⁄𝑍𝑍0)
𝑉𝑉 =𝑉𝑉 ×  (1)
(𝑍𝑍) (𝑍𝑍𝑍𝑍)
ln (𝑍𝑍𝑍𝑍/𝑍𝑍0)
𝛼𝛼
𝑍𝑍
𝑉𝑉 =𝑉𝑉 ×� � (2)
(𝑍𝑍) (𝑍𝑍𝑍𝑍)
𝑍𝑍𝑍𝑍
where
V is the wind speed at height z;
(z)
z is the height above ground;
z is a reference height above ground used for fitting the profile;
r
z is the roughness length;
α is the wind shear (or power law) exponent.
3.48
yaw mechanism
yaw system is the component responsible for the orientation of the wind turbine rotor towards
the wind
4 Symbols and abbreviated terms
4.1 Abbreviated terms
AEP annual energy production
EHS extra high strength
HAWT horizontal axis wind turbine
HPS hybrid power system
O&M operation and maintenance
QC quality control
– 16 – IEC TS 62257-7-2:2022 © IEC 2022
RPM revolution(s) per minute
SWPS small wind power system
SWT small wind turbines
VAWT vertical-Axis wind turbine
VOM Volt-Ohm-Milliammeter, another name for a multimeter
WT wind turbines
4.2 Symbols
Cp power coefficient, a measure of wind turbine efficiency
D diameter of rotor
H0 reference height
height
H
capacity descent factor
Ki
P rated capacity of an electronic component at normal conditions
Pi equivalent capacity at high elevation
V voltage
measured wind speed at the height H
V0 0
α wind shear exponent
5 Wind turbine (WT)
5.1 Types of wind turbines
5.1.1 Horizontal axis wind turbine (HAWT)
HAWT mainly consists of the following parts: rotor (blades), generator, speed regulating
mechanism, direction regulating mechanism (yaw system), brake mechanism and tower.
Normally HAWT has three blades, but can also have two blades or multiple blades. Typically
a small HAWT uses a tail vane assembly for its direction regulating mechanism, while for a
large HAWT, a transmission device consisting of a sensor element and a servo motor is used.
Figure 2a) is tail vane direction regulating type, or called passive yaw regulation type, which
is widely used in small wind turbines; while Figure 2b) is electrical tr
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