SIST EN IEC 61400-26-1:2019

Wind energy generation systems - Part 26-1: Availability for wind energy generation systems (IEC 61400-26-1:2019)

IEC 61400-26-1:2019 defines an information model from which time-based, and production-based availability indicators for services can be derived and reported.
The purpose is to provide standardised metrics that can be used to create and organise methods for availability calculation and reporting according to the user’s needs.
The document provides information categories, which unambiguously describe how data is used to characterise and categorise the operation. The information model specifies category priority for discrimination between possible concurrent categories. Further, the model defines entry and exit criteria to allocate fractions of time and production values to the proper information category. A full overview of all information categories, exit and entry criteria is given in Annex.
The document can be applied to any number of WTGSs, whether represented by an individual turbine, a fleet of wind turbines, a wind power station or a portfolio of wind power stations. A wind power station is typically made up of all WTGSs, functional services and balance of plant elements as seen from the point of common coupling.
This first edition cancels and replaces IEC TS 61400-26-1:2011, IEC TS 61400-26-2:2014 and IEC TS 61400-26-3:2016.

Windenergieanlagen - Teil 26-1: Verfügbarkeit von Windenergieanlagen (IEC 61400-26-1:2019)

Systèmes de génération d'énergie éolienne - Partie 26-1: Disponibilité des systèmes de génération d'énergie éolienne (IEC 61400-26-1:2019)

l'IEC 61400-26-1:2019 définit un modèle d'informations à partir duquel peuvent être déduits et consignés les indicateurs de disponibilité temporelle et en production des services.
Il s'agit de fournir des mesures normalisées pouvant être utilisées pour créer et organiser des méthodes de calcul et de déclaration de la disponibilité en fonction des besoins de l'utilisateur.
Le présent document fournit des catégories d'informations, qui décrivent clairement la manière dont les données sont utilisées pour caractériser et catégoriser le fonctionnement. Le modèle d'informations spécifie une priorité de catégorie permettant de distinguer les différentes catégories concurrentes possibles. En outre, le modèle définit les critères d'entrée et de sortie permettant d'attribuer des fractions de temps et des valeurs de production à la catégorie d'informations adéquate. Une vue d'ensemble de toutes les catégories d'informations, des critères d'entrée et des critères de sortie est fournie à l'annexe.
Le présent document peut être appliqué à un certain nombre d'aérogénérateurs (éolienne individuelle, parc d'éoliennes, centrale éolienne ou ensemble de centrales éoliennes). Une centrale éolienne est généralement composée de l'ensemble des aérogénérateurs, services fonctionnels et éléments d'installation de production d'énergie, considérés par rapport au point de couplage commun (PCC).
Cette première édition annule et remplace l'IEC TS 61400-26-1:2011, l'IEC TS 61400-26-2:2014 and l'IEC TS 61400-26-3:2016.

Sistemi za proizvodnjo energije na veter - 26-1. del: Razpoložljivost sistemov za proizvodnjo energije na veter (IEC 61400-26-1:2019)

Ta del standarda IEC 61400 določa informacijski model, iz katerega je mogoče izpeljati časovne
in proizvodne kazalnike razpoložljivosti storitev ter o njih poročati.
Namen je zagotoviti standardizirane metrike, ki jih je mogoče uporabiti za ustvarjanje in urejanje metod za izračun razpoložljivosti ter poročanje glede na potrebe uporabnika.
Dokument vsebuje kategorije informacij, ki nedvoumno opisujejo, kako se podatki uporabljajo za karakterizacijo in kategorizacijo delovanja. Model informacij določa prednostne kategorije za razlikovanje med možnimi sočasnimi kategorijami. Nadalje model definira vstopna in izstopna merila za dodeljevanje časovnih ter proizvodnih vrednosti ustrezni kategoriji informacij. Popoln pregled vseh kategorij informacij, izhodnih in vstopnih meril je podan v dodatku A, glej sliko A.1.
Dokument je mogoče uporabiti za poljubno število proizvodnih sistemov vetrnih elektrarn ne glede na to, ali jih predstavlja posamezna turbina, serija vetrnih turbin, vetrna elektrarna ali nabor vetrnih elektrarn. Vetrna elektrarna je običajno sestavljena iz vseh proizvodnih sistemov vetrnih elektrarn, funkcionalnih storitev in ravnovesja elementov elektrarne, kot je razvidno iz skupne priključne točke.
Primeri so navedeni v informativnih dodatkih, v katerih so smernice za izračun kazalnikov razpoložljivosti:
• primeri izbirnih kategorij informacij, dodatek B;
• primeri uporabe kategorij informacij za določanje razpoložljivosti, dodatek C;
• primeri scenarijev uporabe, dodatek D;
• primeri metod za določanje potencialne proizvodnje, dodatek E;
• primeri, kako razširiti model na ravnovesje elementov elektrarne, dodatek F.
Ta dokument ne predpisuje načina izračunavanja kazalnikov razpoložljivosti. Standard ne določa načina pridobivanja informacij, kako oceniti proizvodne pogoje ali oblikovati podlago za meritve zmogljivosti krivulje moči – kar je cilj standarda IEC 61400-12.
Stopnja negotovosti je značilna tako za merjenje krivulje moči kot tudi za izračun potencialne proizvodnje energije. Zainteresirane strani naj bi se dogovorile o sprejemljivih parametrih negotovosti.

General Information

• Status: Published
• Publication Date: 19-Aug-2019
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: IEHT - Electrotechnics - Hydraulic turbins
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 25-Jul-2019
• Due Date: 29-Sep-2019
• Completion Date: 20-Aug-2019
• Ref Project: EN IEC 61400-26-1:2019 - Wind energy generation systems - Part 26-1: Availability for wind energy generation systems

Relations

• Replaces: SIST-TS CLC/TS 61400-26-2:2017 - Wind turbines - Part 26-2: Production-based availability for wind turbines (IEC/TS 61400-26-2:2014)
• Effective Date: 16-Jul-2019
• Replaces: SIST-TS CLC/TS 61400-26-1:2017 - Wind turbines - Part 26-1: Time-based availability for wind turbine generating systems (IEC/TS 61400-26-1:2011)
• Effective Date: 16-Jul-2019
• Replaces: SIST-TS CLC/TS 61400-26-3:2017 - Wind energy generation systems - Part 26-3: Availability for wind power stations (IEC/TS 61400-26-3:2016)
• Effective Date: 16-Jul-2019
• Revised: SIST-TS CLC/TS 61400-26-1:2017 - Wind turbines - Part 26-1: Time-based availability for wind turbine generating systems (IEC/TS 61400-26-1:2011)
• Effective Date: 03-Apr-2018
• Revised: SIST-TS CLC/TS 61400-26-2:2017 - Wind turbines - Part 26-2: Production-based availability for wind turbines (IEC/TS 61400-26-2:2014)
• Effective Date: 03-Apr-2018
• Revised: SIST-TS CLC/TS 61400-26-3:2017 - Wind energy generation systems - Part 26-3: Availability for wind power stations (IEC/TS 61400-26-3:2016)
• Effective Date: 03-Apr-2018

Overview

EN IEC 61400-26-1:2019 (Wind energy generation systems - Part 26-1: Availability) is a CLC / IEC standard that defines a formal information model for measuring, calculating and reporting availability of wind energy generation systems (WTGS). The standard supports both time‑based and production‑based availability indicators, gives unambiguous information categories for operational states, and specifies rules (entry/exit criteria and category priority) for assigning time and energy fractions to the correct category. It applies to a single turbine, a fleet, a wind power station or a portfolio of stations.

Key topics and technical requirements

• Information model: core structure from which availability metrics are derived (basic model, services, service delivery layers).
• Information categories: standardized states such as INFORMATION AVAILABLE, OPERATIVE (FULL/ PARTIAL PERFORMANCE, READY STANDBY), OUT OF SERVICE (technical standby, out of environmental/electrical specification, requested shutdown), NON‑OPERATIVE (scheduled maintenance, planned corrective action, forced outage, suspended), FORCE MAJEURE, and INFORMATION UNAVAILABLE.
• Category priority: clear rules to resolve concurrent conditions and assign the correct category for overlapping events.
• Entry and exit criteria: defined conditions and thresholds to allocate time and production to categories (detailed overview in Annex A).
• Indicator examples and verification: Annex C provides examples of time‑based and production‑based availability indicators (operational and technical availability); Annex D contains verification scenarios.
• Scalability: can model multiple services, individual components or complete wind power stations (including balance of plant and point of common coupling).
• Supersedes: replaces earlier IEC TS 61400‑26 series (2011–2016).

Practical applications & users

This standard is essential for:

• Wind farm owners and asset managers - for consistent availability reporting and benchmarking.
• Operations & maintenance (O&M) teams - to classify outages, schedule maintenance and compute technical availability.
• Turbine OEMs and integrators - to specify performance and validate contractual availability.
• Developers, investors and portfolio managers - for due diligence, performance guarantees and financial models.
• Grid operators and regulators - to harmonize reporting and understand generation availability.
• Data analysts and SCADA engineers - for implementing measurement logic, data tagging and automated reporting pipelines.

Related standards

• IEC 61400 series (wind turbine design and testing), notably IEC 61400‑1 (design requirements).
• IEC 61400‑25 series (data exchange for wind turbine monitoring) referenced as harmonized documents.
• EN IEC 61400‑26‑1 aligns European and international availability reporting practices.

Keywords: EN IEC 61400-26-1:2019, wind energy availability, availability indicators, information model, WTGS, time-based availability, production-based availability.

Standards Content (Sample)

SLOVENSKI STANDARD
01-oktober-2019
Nadomešča:
SIST-TS CLC/TS 61400-26-1:2017
SIST-TS CLC/TS 61400-26-2:2017
SIST-TS CLC/TS 61400-26-3:2017
Sistemi za proizvodnjo energije na veter - 26-1. del: Razpoložljivost sistemov za
proizvodnjo energije na veter (IEC 61400-26-1:2019)
Wind energy generation systems - Part 26-1: Availability for wind energy generation
systems (IEC 61400-26-1:2019)
Windenergieanlagen - Teil 26-1: Verfügbarkeit von Windenergieanlagen (IEC 61400-26-
1:2019)
Systèmes de génération d'énergie éolienne - Partie 26-1: Disponibilité des systèmes de
génération d'énergie éolienne (IEC 61400-26-1:2019)
Ta slovenski standard je istoveten z: EN IEC 61400-26-1:2019
ICS:
27.180 Vetrne elektrarne Wind turbine energy systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61400-26-1

NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2019
ICS 27.180 Supersedes CLC/TS 61400-26-1:2017,
CLC/TS 61400-26-2:2017,
CLC/TS 61400-26-3:2017
and all of their amendments and corrigenda (if any)
English Version
Wind energy generation systems - Part 26-1: Availability for wind
energy generation systems
(IEC 61400-26-1:2019)
Systèmes de génération d'énergie éolienne - Partie 26-1: Windenergieanlagen - Teil 26-1: Verfügbarkeit von
Disponibilité des systèmes de génération d'énergie Windenergieanlagen
éolienne (IEC 61400-26-1:2019)
(IEC 61400-26-1:2019)
This European Standard was approved by CENELEC on 2019-07-03. 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,
Turkey 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
© 2019 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61400-26-1:2019 E

European foreword
The text of document 88/665/CDV, future edition 1 of IEC 61400-26-1, prepared by IEC/TC 88 "Wind energy
generation systems" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national level by (dop) 2020-04-03
publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2022-07-03
document have to be withdrawn
This document supersedes CLC/TS 61400-26-1:2017, CLC/TS 61400-26-2:2017 and
CLC/TS 61400‑26‑3:2017 and all of their amendments and corrigenda (if any).
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.

Endorsement notice
The text of the International Standard IEC 61400-26-1:2019 was approved by CENELEC as a European
Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 61400-25-2:2006 NOTE Harmonized as EN 61400-25-2:2007 (not modified)
IEC 61400-25-3:2006 NOTE Harmonized as EN 61400-25-3:2007 (not modified)
IEC 61400-25-4:2008 NOTE Harmonized as EN 61400-25-4:2008 (not modified)

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 60050-415 -  International Electrotechnical Vocabulary - - -
Part 415: Wind turbine generator systems
IEC 61400-1 -  Wind energy generation systems - Part 1: EN IEC 61400-1 -
Design requirements
IEC 61400-26-1 ®
Edition 1.0 2019-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –

Part 26-1: Availability for wind energy generation systems

Systèmes de génération d'énergie éolienne –

Partie 26-1: Disponibilité des systèmes de génération d'énergie éolienne

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-6797-4

– 2 – IEC 61400-26-1:2019 © IEC 2019
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 12
2 Normative references . 12
3 Terms, definitions and abbreviated terms . 13
3.1 Terms and definitions . 13
3.2 Abbreviated terms . 15
4 Information model . 18
4.1 Basic model . 18
4.2 Information categories . 18
4.3 Information category priority . 19
4.4 Services . 20
4.5 Service delivery layers . 21
4.5.1 General . 21
4.5.2 Time layer . 21
4.5.3 Actual service delivery layer . 21
4.5.4 Potential service delivery layer . 21
4.5.5 Lost service . 22
4.6 Modelling multiple services . 22
4.7 Determination of information categories for the WPS . 24
4.8 Application of the information model to components of the WEGS. 25
5 Information categories . 25
5.1 INFORMATION AVAILABLE . 25
5.2 OPERATIVE . 26
5.3 IN SERVICE . 26
5.3.1 General . 26
5.3.2 FULL PERFORMANCE . 26
5.3.3 PARTIAL PERFORMANCE . 27
5.3.4 READY STANDBY . 27
5.4 OUT OF SERVICE . 28
5.4.1 General . 28
5.4.2 TECHNICAL STANDBY . 28
5.4.3 OUT OF ENVIRONMENTAL SPECIFICATION . 28
5.4.4 REQUESTED SHUTDOWN . 29
5.4.5 OUT OF ELECTRICAL SPECIFICATION . 29
5.5 NON-OPERATIVE . 30
5.5.1 General . 30
5.5.2 SCHEDULED MAINTENANCE . 30
5.5.3 PLANNED CORRECTIVE ACTION . 30
5.5.4 FORCED OUTAGE . 31
5.5.5 SUSPENDED. 31
5.6 FORCE MAJEURE . 32
5.7 INFORMATION UNAVAILABLE . 32
Annex A (informative) Entry and exit conditions overview for WEGS . 33
Annex B (informative) Optional information categories for WEGS information model –
illustrative explanation and examples . 34

IEC 61400-26-1:2019 © IEC 2019 – 3 –
B.1 General . 34
B.2 PARTIAL PERFORMANCE – optional categories . 34
B.2.1 Introduction of optional categories . 34
B.2.2 Derated . 34
B.2.3 Degraded. 35
B.3 OUT OF ENVIRONMENTAL SPECIFICATION – optional categories . 36
B.3.1 Introduction of optional categories . 36
B.3.2 Calm winds . 36
B.3.3 Other environmental . 36
B.4 PLANNED CORRECTIVE ACTION – optional categories . 37
B.4.1 Introduction of optional categories . 37
B.4.2 Retrofit . 37
B.4.3 Upgrade . 37
B.4.4 Other planned corrective action . 37
B.5 FORCED OUTAGE – optional category . 38
B.5.1 Introduction of optional categories . 38
B.5.2 Response . 38
B.5.3 Diagnostic . 39
B.5.4 Logistic . 39
B.5.5 Repair . 39
B.6 SUSPENDED – optional categories. 40
B.6.1 Introduction of optional categories . 40
B.6.2 Suspended scheduled maintenance . 40
B.6.3 Suspended planned corrective action . 40
B.6.4 Suspended forced outage . 40
B.7 Considerations of competing assignment of lost service . 41
Annex C (informative) Examples of availability indicators . 42
C.1 General . 42
C.1.1 Introduction to the scope of this annex . 42
C.1.2 Time-based availability . 42
C.1.3 Production-based availability . 42
C.1.4 Mapping of availability and unavailability . 43
C.2 Time-based availability . 43
C.2.1 General . 43
C.2.2 Time-based availability – "operational availability" . 43
C.2.3 Time based availability – "technical availability" . 45
C.3 Production-based availability . 46
C.3.1 General . 46
C.3.2 Production-based availability – "operational availability" . 46
C.3.3 Production-based availability – "technical availability". 47
C.4 Capacity factor and other performance indicators . 48
C.4.1 General . 48
C.4.2 Capacity factor . 49
C.4.3 Production ratio . 49
C.4.4 Mean-value based information . 49
Annex D (informative) Verification scenarios – examples . 50
D.1 General . 50
D.2 Time-based scenarios for a WTGS . 50
D.2.1 Introduction to verification scenarios . 50

– 4 – IEC 61400-26-1:2019 © IEC 2019
D.2.2 Scenario 1 – communication aspects . 51
D.2.3 Scenario 2 – partial operational aspects . 52
D.2.4 Scenario 3 – maintenance aspects . 53
D.2.5 Scenario 4 – operational aspects . 54
D.2.6 Scenario 5 – grid/electrical network aspects . 57
D.2.7 Scenario 6 – environmental aspects . 58
D.3 Production-based scenarios for a WTGS . 60
D.3.1 Introduction to verification scenarios . 60
D.3.2 Scenarios under FULL PERFORMANCE . 60
D.3.3 Scenarios under PARTIAL PERFORMANCE . 62
D.3.4 Scenarios under READY STANDBY . 64
D.3.5 Scenarios under TECHNICAL STANDBY . 65
D.3.6 Scenarios under OUT OF ENVIRONMENTAL SPECIFICATION . 66
D.3.7 Scenarios under REQUESTED SHUTDOWN . 67
D.3.8 Scenarios under OUT OF ELECTRICAL SPECIFICATION . 68
D.3.9 Scenarios under SCHEDULED MAINTENANCE . 69
D.3.10 Scenarios under PLANNED CORRECTIVE ACTION . 69
D.3.11 Scenarios under FORCED OUTAGE . 70
D.3.12 Scenarios under SUSPENDED . 71
D.3.13 Scenarios under FORCE MAJEURE . 72
D.4 Production-based scenarios for a WTGS – calculation of lost production . 72
D.4.1 Introduction to verification scenarios . 72
D.4.2 Production-based availability algorithm based on mandatory information

categories ("operational availability") . 72
D.4.3 Production-based availability algorithm – including optional categories
("technical availability") . 75
D.5 Production-based scenarios for a WPS . 76
D.5.1 Introduction to verification scenarios . 76
D.5.2 Example 1: Normal operation – all WPS . 76
D.5.3 Example 2: Normal operation – part of WPS . 77
D.5.4 Example 3: Contaminated WTGSs blades – all WPS . 78
D.5.5 Example 4: Contaminated WTGSs blades – part of WPS . 79
D.5.6 Example 5: BOP limitations – all WPS . 80
D.5.7 Example 6: BOP limitations – part of WPS . 81
D.5.8 Example 7: "Spinning reserve" – part of WPS . 82
D.5.9 Example 8: "Spinning reserve" – all WPS . 83
D.5.10 Example 9: Noise restrictions – warranty related . 84
D.5.11 Example 10: Noise restrictions – environmentally related . 86
D.5.12 Example 11: Ice storm on grid – all WPS . 87
Annex E (informative) Possible methods for determination of potential WEGS energy
production . 89
E.1 General . 89
E.2 Specific power curve and velocities methods . 89
E.2.1 General . 89
E.2.2 Nacelle anemometer wind measurement with power curve . 89
E.2.3 Upstream wind measurement with power curve . 90
E.2.4 Met mast wind measurement with correction factors and power curve. 90
E.3 Power-based methods . 91
E.3.1 General . 91

IEC 61400-26-1:2019 © IEC 2019 – 5 –
E.3.2 Average production of WPS . 91
E.3.3 Average production of representative comparison WTGSs . 92
E.3.4 Data acquisition with comparison chart/database . 93
E.3.5 Average wind speed of WPS . 93
E.4 Determination of potential production for a WPS – examples . 94
E.4.1 Overview . 94
E.4.2 Primary service . 94
E.4.3 Secondary services . 94
Annex F (informative) Balance of plant integration . 96
F.1 WPS functions and services . 96
F.2 Externally required functions and services . 96
F.3 Internally required functions and services . 96
F.4 Expansion of the information model for BOP functions and services . 97
Bibliography . 98

Figure 1 – Data stakeholders for a wind energy generation system . 10
Figure 2 – Information category overview . 19
Figure 3 – Information category priority . 20
Figure 4 – Three-layer information model . 21
Figure 5 – Information categories, definitions for layer 2 and layer 3, mandatory
categories . 23
Figure 6 – Examples of an information model representing active energy, reactive
energy, high and low frequency response services . 24
Figure A.1 – Overview of the entry and exit conditions of all mandatory information
categories described in this document . 33
Figure B.1 – Information category overview – mandatory and optional . 35
Figure B.2 – Workflow breakdown structure . 38
Figure B.3 – Example of simultaneous degrading and derating . 41
Figure E.1 – Step 1: Calculation of wind speed based on working WEGS 1 to n . 93
Figure E.2 – Step 2: Estimation of lost production for WEGS not in FULL
PERFORMANCE . 94

Table C.1 – Example of mapping of available and unavailable information categories . 43
Table D.1 – Verification scenarios – time allocation to information categories . 50
Table D.2 – Verification scenarios – communication aspects . 51
Table D.3 – Verification scenarios – partial operational aspects . 52
Table D.4 – Verification scenarios – maintenance aspects . 53
Table D.5 – Verification scenarios – operational aspects . 54
Table D.6 – Verification scenarios – grid / electrical network aspects . 57
Table D.7 – Verification scenarios – environmental aspects . 58
Table D.8 – FULL PERFORMANCE: By definition, actual energy production is equal to

the potential energy production . 60
Table D.9 – FULL PERFORMANCE: Actual energy production is less than potential
energy production but within agreed uncertainty . 61
Table D.10 – FULL PERFORMANCE: Actual energy production greater than potential
energy production . 61
Table D.11 – PARTIAL PERFORMANCE – derated: Grid constraint . 62

– 6 – IEC 61400-26-1:2019 © IEC 2019
Table D.12 – PARTIAL PERFORMANCE – derated: Grid constraint, actual energy
production less than requested . 62
Table D.13 – Partial performance – derated: Output constraint due to excessive noise

of the WTGS . 63
Table D.14 – PARTIAL PERFORMANCE – derated: Dirt on blades constrained
performance . 63
Table D.15 – PARTIAL PERFORMANCE – derated: Ice accumulated on blades has
been detected, WTGS is allowed to operate although the power performance is
‘derated’ . 64
Table D.16 – PARTIAL PERFORMANCE – degraded: WTGS deterioration known to the
WTGS user . 64
Table D.17 – READY STANDBY: Avian detection system . 64
Table D.18 – READY STANDBY: Automatic generation control – Var support . 65
Table D.19 – TECHNICAL STANDBY: WTGS is cable unwinding . 65
Table D.20 – OUT OF ENVIRONMENTAL SPECIFICATION – calm winds . 66
Table D.21 – OUT OF ENVIRONMENTAL SPECIFICATION – high winds . 66
Table D.22 – OUT OF ENVIRONMENTAL SPECIFICATION – temperature too high . 66
Table D.23 – REQUESTED SHUTDOWN: ice on blades is detected and WTGS user
requests shutdown of the WTGS . 67
Table D.24 – REQUESTED SHUTDOWN: Sector management . 67
Table D.25 – REQUESTED SHUTDOWN: Noise nuisance – warranty claim . 68
Table D.26 – OUT OF ELECTRICAL SPECIFICATION: Low voltage . 68
Table D.27 – SCHEDULED MAINTENANCE: WTGS is under scheduled maintenance
work by the WTGS manufacturer or maintenance provider within the time allowance
agreed by the maintenance contract . 69
Table D.28 – PLANNED CORRECTIVE ACTION: WTGS manufacturer or maintenance
provider performs corrective action to the WTGS at his discretion outside the time

allowance of scheduled maintenance . 69
Table D.29 – FORCED OUTAGE: Short circuit . 70
Table D.30 – FORCED OUTAGE: Corrosion . 70
Table D.31 – FORCED OUTAGE: Overheating . 71
Table D.32 – SUSPENDED: Suspended repair work due to storm with lightning . 71
Table D.33 – FORCE MAJEURE: No access to the WTGS due to flooding impacting
infrastructure . 72
Table D.34 – Production-based availability algorithm based on mandatory information
categories only ,‘operational availability’ . 73
Table D.35 – Production-based availability algorithm – including optional categories,

‘technical availability’ . 75
Table D.36 – Scenario, Example 1: Normal operation – all WPS . 77
Table D.37 – Scenario, Example 2: Normal operation – part of WPS . 78
Table D.38 – Scenario, Example 3: Contaminated WTGSs blades – all WPS . 79
Table D.39 – Scenario, Example 4: Contaminated WTGSs blades – part of WPS . 80
Table D.40 – Scenario, Example 5: BOP limitations – all WPS . 81
Table D.41 – Scenario, Example 6: BOP limitations – part of WPS . 82
Table D.42 – Scenario, Example 8: ‘Spinning reserve’ – part of WPS . 83
Table D.43 – Scenario, Example 7: ‘Spinning reserve’ – all WPS . 84
Table D.44 – Scenario, Example 9: Noise restrictions – all WPS . 85

IEC 61400-26-1:2019 © IEC 2019 – 7 –
Table D.45 – Scenario, Example 10: Noise restrictions – all WPS . 86
Table D.46 – Scenario, Example 11: Ice storm on grid – all WPS . 87
Table E.1 – Examples on how to determine potential production . 95

– 8 – IEC 61400-26-1:2019 © IEC 2019
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 26-1: Availability for wind energy generation systems

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
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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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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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) 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.
International Standard IEC 61400-26-1 has been prepared by IEC technical committee 88:
Wind energy generation systems.
This first edition cancels and replaces IEC TS 61400-26-1:2011, IEC TS 61400-26-2:2014 and
IEC TS 61400-26-3:2016.
The text of this International Standard is based on the following documents:
CDV Report on voting
88/665/CDV 88/705/RVC
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

IEC 61400-26-1:2019 © IEC 2019 – 9 –
A list of all parts of the IEC 61400 series, under the general title Wind energy generation
systems, 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.
Mandatory information categories defined in this document are written in capital letters;
optional information categories are written in bold letters.
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
• 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.
– 10 – IEC 61400-26-1:2019 © IEC 2019
INTRODUCTION
The intention of this International Standard is to define a common basis for exchange of
information on availability metrics between stakeholders in the wind power generation
business such as owners, utilities, lenders, operators, manufacturers, maintenance providers,
consultants, regulatory bodies, certification bodies and insurance companies. From this
diverse group of stakeholders, a number of external and internal interfaces arise in the
operation and delivery of power. Some of these are energy related and many are
informational. Since the intention is for a common basis of informational exchange, many of
these interfaces are illustrated in Figure 1, which identifies external and internal elements
related to energy production and asset management and which also benefit from a defined set
of terms. This is achieved by providing an information model specifying how time designations
shall be split into information categories.

Figure 1 – Data stakeholders for a wind energy generation system
Throughout the document, reference is made to wind energy generation systems (WEGS);
however, the document may be used for a single wind turbine (WTGS), as well as for any
number of WTGSs combined with additional components to represent a complete wind power
station (WPS). The designation WEGS used throughout the document thus shall be
understood as the specifications being applicable to individual wind turbines as well as for
wind power stations.
IEC 61400-26-1:2019 © IEC 2019 – 11 –
The information model specifies the terminology for reporting availability indicators.
Availability indicators include time-based and production-based availability. A WEGS includes
all equipment up to the point of interconnection , or in case of a single WTGS in a WPS, the
interconnection point defined by the user. Availability indicators are based upon fractions of
time and the amount a service is providing or capable of providing within the time fractions,
taking internal and external aspects into account. Internal aspects will include the WEGS’
components and their condition. External aspects are wind and other weather conditions, as
well as grid and substation conditions.

___________
Defined in IEC 60050-415:1999, Definition 415-04-01.

– 12 – IEC 61400-26-1:2019 © IEC 2019
WIND ENERGY GENERATION SYSTEMS –

Part 26-1: Availability for wind energy generation systems

1 Scope
This part of IEC 61400 defines an information model from which time-based, and production-
based availability indicators for services can be derived and reported.
The purpose is to provide standardised metrics that can be used to create and organise
methods for availability calculation and reporting according to the user’s needs.
The document provides information categories, which unambiguously describe how data is
used to characterise and categorise the operation. The information model specifies category
priority for discrimination between possible concurrent categories. Further, the model defines
entry and exit criteria to allocate fractions of time and production values to the proper
information category. A full overview of all information categories, exit and entry criteria is
given in Annex A, see Figure A.1.
The document can be applied to any number of WTGSs, whether represented by an individual
turbine, a fleet of wind turbines, a wind power station or a portfolio of wind power stations. A
wind power station is typically made up of all WTGSs, functional services and balance of plant
elements as seen from the point of common coupling.
Examples are provided in informative annexes which provide guidelines for calculation of
availability indicators:
• examples of optional information categories, Annex B;
• examples of application of the information categories for determination of availability,
Annex C;
• examples of application scenarios, Annex D;
• examples on methods for determination of potential production, Annex E;
• examples of how to expand the model to balance of plant elements, Annex F.
This document does not prescribe how availability indicators shall be calculated. The standard
does not specify the method of information acquisition, how to estimate the production terms
or to form the basis for power curve performance measurements – which is the objective of
IEC 61400-12.
A degree of uncertainty is inherent in both the measurement of a power curve and the
calculation of potential energy production. The stakeholders should agree upon acceptable
uncertainty parameters.
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 60050-415, International Electrotechnical Vocabulary – Part 415: Wind turbine generator
systems
IEC 61400-26-1:2019 © IEC 2019 – 13 –
IEC 61400-1, Wind energy generation systems – Part 1: Design requirements
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-415 and the
following apply
...