SIST EN IEC 61400-12-5:2022
(Main)Wind energy generation systems - Part 12-5: Power performance - Assessment of obstacles and terrain (IEC 61400-12-5:2022)
Wind energy generation systems - Part 12-5: Power performance - Assessment of obstacles and terrain (IEC 61400-12-5:2022)
This part of IEC 61400 specifies the procedures for assessing the significance of obstacles and
terrain variations on a proposed power performance measurement site and applies to the
performance testing of wind turbines of all types and sizes connected to the electrical power
network as described in other parts of the IEC 61400 series. The procedure applies to the
performance evaluation of specific wind turbines at specific locations.
Windenergieanlagen - Teil 12-5: Leistungsverhalten - Bewertung von Hindernissen und Gelände (IEC 61400-12-5:2022)
Systèmes de génération d'énergie éolienne - Partie 12-5: Performance de puissance - Évaluation des obstacles et du terrain (IEC 61400-12-5:2022)
IEC 61400-12-5:2022 spécifie les procédures d'évaluation de l'importance des obstacles et des variations de terrain sur un site proposé pour le mesurage de la performance de puissance et s'applique aux essais de performance des éoliennes de tous types et de toutes tailles raccordées au réseau électrique comme cela est décrit dans d'autres parties de la série IEC 61400. La procédure s'applique à l’évaluation de la performance d'éoliennes spécifiques sur des sites spécifiques.
La présente première édition de l’IEC 61400-12-5 fait partie d'une révision structurelle qui annule et remplace les normes de performance IEC 61400-12-1:2017 et IEC 61400-12-2:2013. Cette révision structurelle ne contient aucune modification technique par rapport à l'IEC 61400‑12‑1:2017 et l'IEC 61400-12‑2:2013. Toutefois, les parties relatives aux mesurages du vent, au mesurage de l'étalonnage du site et à l'évaluation des obstacles et du terrain ont été extraites vers des normes distinctes.
Sistemi za proizvodnjo energije na veter - 12-5. del: Preskušanje zmogljivosti - Ocena ovir in terena (IEC 61400-12-5:2022)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN IEC 61400-12-5:2022
01-december-2022
Sistemi za proizvodnjo energije na veter - 12-5. del: Preskušanje zmogljivosti -
Ocena ovir in terena (IEC 61400-12-5:2022)
Wind energy generation systems - Part 12-5: Power performance - Assessment of
obstacles and terrain (IEC 61400-12-5:2022)
Windenergieanlagen - Teil 12-5: Leistungsverhalten - Bewertung von Hindernissen und
Gelände (IEC 61400-12-5:2022)
Systèmes de génération d'énergie éolienne - Partie 12-5: Performance de puissance -
Évaluation des obstacles et du terrain (IEC 61400-12-5:2022)
Ta slovenski standard je istoveten z: EN IEC 61400-12-5:2022
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
SIST EN IEC 61400-12-5:2022 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN IEC 61400-12-5:2022
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SIST EN IEC 61400-12-5:2022
EUROPEAN STANDARD EN IEC 61400-12-5
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2022
ICS 27.180
English Version
Wind energy generation systems - Part 12-5: Power
performance - Assessment of obstacles and terrain
(IEC 61400-12-5:2022)
Systèmes de génération d'énergie éolienne - Partie 12-5: Windenergieanlagen - Teil 12-5: Leistungsverhalten -
Performance de puissance - Évaluation des obstacles et du Bewertung von Hindernissen und Gelände
terrain (IEC 61400-12-5:2022)
(IEC 61400-12-5:2022)
This European Standard was approved by CENELEC on 2022-10-04. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61400-12-5:2022 E
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EN IEC 61400-12-5:2022 (E)
European foreword
The text of document 88/825/CDV, future edition 1 of IEC 61400-12-5, prepared by IEC/TC 88 "Wind
energy generation systems" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 61400-12-5:2022.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2023-07-04
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2025-10-04
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 61400-12-5:2022 was approved by CENELEC as a
European Standard without any modification.
2
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EN IEC 61400-12-5:2022 (E)
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1 Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cenelec.eu.
Publication Year Title EN/HD Year
IEC 61400-12-1 - Wind energy generation systems - Part 12- EN IEC 61400-12-1 -
1: Power performance measurement of
electricity producing wind turbines
IEC 61400-12-2 - Wind energy generation systems - Part 12- EN IEC 61400-12-2 -
2: Power performance of electricity
producing wind turbines based on nacelle
anemometry
IEC 61400-12-3 - Wind energy generation systems - Part 12- EN IEC 61400-12-3 -
3: Power performance - Measurement
based site calibration
IEC 61400-12-6 - Wind energy generation systems - Part 12- EN IEC 61400-12-6 -
6: Measurement based nacelle transfer
function of electricity producing wind
turbines
3
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SIST EN IEC 61400-12-5:2022
IEC 61400-12-5
®
Edition 1.0 2022-08
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 12-5: Power performance – Assessment of obstacles and terrain
Systèmes de génération d'énergie éolienne –
Partie 12-5: Performance de puissance – Évaluation des obstacles et du terrain
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-5603-9
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Symbols, units and abbreviated terms . 9
5 General . 9
6 Measurement sector procedure to be used for power performance measurements
according to IEC 61400-12-1 . 10
6.1 General . 10
6.2 Requirements regarding neighbouring and operating wind turbines . 11
6.3 Requirements regarding obstacles . 11
6.4 Method for calculation of sectors to exclude . 12
6.5 Special requirements for extended obstacles . 15
7 Measurement sector procedure to be used during the determination of the nacelle
transfer function (NTF) between free wind speed and nacelle anemometer wind
speed . 15
8 Measurement sector procedure to be used during the determination of the nacelle
power curve (NPC) . 15
8.1 General . 15
8.2 Requirements regarding neighbouring and operating wind turbines . 16
8.3 Requirements regarding obstacles . 16
8.4 Calculation of the excluded sector . 17
8.5 Self-consistency check procedure for the measurement sector . 18
9 Assessment of terrain at the test site . 19
10 Terrain classification for evaluation of NTF and NPC . 22
10.1 General . 22
10.2 RIX indices . 22
10.3 Average slope . 22
10.4 Determine terrain class . 23
10.5 Ridge formations . 24
Figure 1 – Sectors to exclude due to wakes of neighbouring and operating wind
turbines and significant obstacles . 13
Figure 2 – An example of sectors to exclude due to wakes of the wind turbine under
test, a neighbouring and operating wind turbine and a significant obstacle . 14
Figure 3 – Example of the result of a sector self-consistency check . 19
Figure 4 – Illustration of area to be assessed, top view . 20
Figure 5 – Example of determination of slope and terrain variation from the best-fit
plane: "2L to 4L" and the case "measurement sector" (Table 5, line 2) . 21
Figure 6 – Determination of slope for the distance "2L to 4L" and "8L to 16L" and the
case "outside measurement sector" (Table 5, line 3 and line 5). 21
Table 1 – Interfaces from other International Standards to this document . 10
Table 2 – Interfaces from this document to other International Standards . 10
Table 3 – Obstacle requirements: relevance of obstacles . 12
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Table 4 – Obstacle requirements: relevance of obstacles . 17
Table 5 – Test site requirements: topographical variations . 20
Table 6 – Slope terrain classification . 23
Table 7 – RIX terrain classification . 23
Table 8 – Final terrain class . 23
Table 9 – Maximum ridge step effects on terrain class . 24
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INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –
Part 12-5: Power performance –
Assessment of obstacles and terrain
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,
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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
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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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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
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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
members of its technical committees and IEC National Committees for any personal injury, property damage or
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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.
IEC 61400-12-5 has been prepared by IEC technical committee 88: Wind energy generation
systems. It is an International Standard.
This first edition of IEC 61400-12-5 is part of a structural revision that cancels and replaces the
performance standards IEC 61400-12-1:2017 and IEC 61400-12-2:2013. The structural revision
contains no technical changes with respect to IEC 61400-12-1:2017 and IEC 61400-12-2:2013,
but the parts that relate to wind measurements, measurement of site calibration and assessment
of obstacle and terrain have been extracted into separate standards.
The purpose of the re-structure was to allow the future management and revision of the power
performance standards to be carried out more efficiently in terms of time and cost and to provide
a more logical division of the wind measurement requirements into a series of separate
standards which could be referred to by other use case standards in the IEC 61400 series and
subsequently maintained and developed by appropriate experts.
The text of this International Standard is based on the following documents:
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SIST EN IEC 61400-12-5:2022
IEC 61400-12-5:2022 © IEC 2022 – 5 –
Draft Report on voting
88/825/CDV 88/870/RVC
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 International Standard 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 61400 series, published under the general title Wind energy
generation systems, 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 document 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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INTRODUCTION
The purpose of this part of IEC 61400 is to describe procedures to determine a measurement
sector that is not influenced by turbines or other obstacles for a specific wind turbine. The
measurement sector is used to assess the terrain and determine if a site calibration is required.
This measurement sector can be used to evaluate wind turbine power performance.
Clause 6 describes a procedure to determine one or more sectors which are not usable for a
power performance measurement because the flow at the wind turbine under test and/or the
flow at the position of the wind measurement equipment (WME: a meteorological mast or a
remote sensing device) might be affected by an operating wind turbine and/or by an obstacle.
Clause 7 describes a procedure for establishing the measurement sector during the
determination of the nacelle transfer function.
Clause 8 describes a procedure for establishing the measurement sector during the
determination of the nacelle power curve.
Clause 9 describes a procedure to assess the terrain surrounding the site and to determine if it
is sufficiently complex to require site calibration. The purpose of site calibration is generally to
measure the change in the boundary layer as it follows the orography, which is generally
attached flow, whereas obstacles often generate more turbulent wakes associated with them,
which are affected by sharp edges and vertical surfaces that can trigger flow separation.
Clause 10 describes a procedure to classify the terrain in order to apply the nacelle transfer
function for a nacelle power curve measurement. The classification is used to estimate the
uncertainty of the nacelle transfer function (NTF) and nacelle power curve (NPC) and also to
determine under what terrain condition the NTF can be used for the NPC.
The creation of this new standard was mandated with the restriction that no technical changes
to the content copied from the source documents (IEC 61400-12-1 and IEC 61400-12-2) would
be allowed. Therefore, in this first edition of the new standard IEC 61400-12-5, there are some
obvious areas of technical disagreement (e.g. assessment of terrain in Clauses 9 and 10) where
a choice needs to be made depending on whether the intended use case is as an input to a
IEC 61400-12-1 or to a IEC 61400-12-2 power curve evaluation. It is recommended that future
revisions of this document aim to harmonise the technical content.
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IEC 61400-12-5:2022 © IEC 2022 – 7 –
WIND ENERGY GENERATION SYSTEMS –
Part 12-5: Power performance –
Assessment of obstacles and terrain
1 Scope
This part of IEC 61400 specifies the procedures for assessing the significance of obstacles and
terrain variations on a proposed power performance measurement site and applies to the
performance testing of wind turbines of all types and sizes connected to the electrical power
network as described in other parts of the IEC 61400 series. The procedure applies to the
performance evaluation of specific wind turbines at specific locations.
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 61400-12-1, Wind energy generation systems – Part 12-1: Power performance
measurements of electricity producing wind turbines
IEC 61400-12-2, Wind energy generation systems – Part 12-2: Power performance of electricity
producing wind turbines based on nacelle anemometry
IEC 61400-12-3, Wind energy generation systems – Part 12-3: Power performance –
Measurement based site calibration
IEC 61400-12-6, Wind energy generation systems – Part 12-6: Measurement based nacelle
transfer function of electricity producing wind turbines
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
complex terrain
terrain surrounding the test site that features significant variations in topography and terrain
obstacles (refer to 3.10) that may cause flow distortion
3.2
cut-in wind speed
lowest wind speed at which a wind turbine will begin to produce power
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3.3
data set
collection of data sampled over a continuous period
3.4
flow distortion
change in air flow caused by obstacles, topographical variations, or other wind turbines that
results in the wind speed at the measurement location to be different from the wind speed at
the wind turbine location
3.5
free stream wind speed
horizontal wind speed measured upstream of the rotor of the wind turbine generator that is
unaffected by rotor aerodynamics
3.6
hub height
height of the centre of the swept area of the wind turbine rotor above the
ground at the tower
Note 1 to entry: For a vertical axis wind turbine the hub height is defined as the height of the centroid of the swept
area of the rotor above the ground at the tower.
3.7
measured power curve
table and graph that represent the measured, corrected and normalized net power output of a
wind turbine as a function of measured wind speed, measured under a well-defined
measurement procedure
3.8
measurement sector
sector of wind directions from which data are selected for the measured power curve
3.9
nacelle transfer function
NTF
transfer function applied to estimate the free stream wind speed from the nacelle anemometer
wind speed
3.10
obstacle
obstruction that blocks and distorts the flow of the wind, such as a building or tree
3.11
power performance
measure of the capability of a wind turbine to produce electric power and energy
3.12
test site
location of the wind turbine under test and its surroundings
3.13
uncertainty in measurement
parameter, associated with the result of a measurement, which characterizes the dispersion of
the values that could reasonably be attributed to the measurand
[SOURCE: IEC 60050-415:1999, 415-05-13]
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3.14
wind measurement equipment
meteorological mast or remote sensing device
4 Symbols, units and abbreviated terms
Symbol or Description Unit
abbreviated term
D rotor diameter [m]
D equivalent rotor diameter [m]
e
D rotor diameter of neighbouring and operating wind turbine [m]
n
d distance from turbine to point in terrain for worst case scenario of slope [m]
i
H hub height of wind turbine [m]
h height of obstacle [m]
L distance between the wind turbine and the wind measurement equipment [m]
L
distance between the wind turbine or the wind measurement equipment and an [m]
e
obstacle
L distance between the wind turbine or the wind measurement equipment and a [m]
n
neighbouring and operating wind turbine
l height of obstacle [m]
h
l width of obstacle [m]
w
RIX Ruggedness index
VP wind speed evaluated from the power output [m/s]
V measured nacelle wind speed, corrected with nacelle transfer function [m/s]
free
WME wind measurement equipment
z height above ground [m]
z terrain elevation at point of the worst-case scenario for slope [m]
i
5 General
For a power performance measurement carried out according to IEC 61400-12-1 or
IEC 61400-12-2, the wind speed experienced at the measurement location and at the test
turbine location can be influenced both by obstacles (e.g. buildings, forests, other turbines) in
the surroundings and by the terrain (severity of terrain slopes and deviations within the terrain).
The presence of such influences should be checked and the valid direction sector reduced
accordingly in the case of obstacles or a site calibration (according to IEC 61400-12-3) carried
out in the case of sufficiently complex terrain. Clause 6 and Clause 8 describe procedures to
determine one or more sectors which are not usable for the test because the flow at the wind
turbine under test and/or the flow at the position of the wind measurement equipment (WME: a
meteorological mast or a remote sensing device) might be affected by an operating wind turbine
and/or by an obstacle. Clause 9 describes the criteria to assess terrain to determine if a site
can be considered flat (no site calibration required) or complex (site calibration required).
Clause 10 describes the criteria to classify terrain as required for the application of an NTF.
As this method is closely related to both IEC 61400-12-1 and IEC 61400-12-2, both standards
are referred to frequently in this document.
For this document, the interfaces are defined in Table 1 and Table 2; in order to facilitate the
correct interpretation of the interfaces, a short description of the use of the interface has been
added as well.
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Table 1 – Other International Standards which refer to this document
References to this document in Short use
Interface description Format
other International Standards description
Filtering the data
Measurement sector IEC 61400-12-1:2022, Clause 6 From [degree] to [degree]
set
Measurement sector Filtering the data
IEC 61400-12-2:2022, Clause 7 From [degree] to [degree]
(NTF) set
Measurement sector Filtering the data
IEC 61400-12-2:2022, Clause 8 From [degree] to [degree]
(NPC) set
Determination of
Terrain assessment IEC 61400-12-1:2022, Clause 9 site calibration Complex or not complex
requirement
Reporting of the
IEC 61400-12-2:2022, Clause 10 Terrain class
Terrain class transfer function
IEC 61400-12-6:2022, Clause 10 [1; 2; 3; 4; 5]
validity
Table 2 – Interfaces from this document to other International Standards
Interface Relevant content Reference to other Short use Format
description in this document standards description
Terrain assessment Clause 9 IEC 61400-12-1:2022 Input to the wind Operational
speed characteristics of
measurement anemometer
uncertainty dependent on
calculation for complexity of
the power curve terrain or
site-specific data
Terrain class Clause 10 IEC 61400-12-2:2022 Input to the wind Terrain class
speed [1; 2; 3; 4; 5]
measurement
uncertainty
calculation for
the nacelle
transfer function
(NTF)
6 Measurement sector procedure to be used for power performance
measurements according to IEC 61400-12-1
6.1 General
Claus
...
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