IEC TS 61400-28:2025

IEC TS 61400-28 ®
Edition 1.0 2025-03
TECHNICAL
SPECIFICATION
Wind energy generation systems –
Part 28: Through-life management and life extension of wind power assets

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IEC TS 61400-28 ®
Edition 1.0 2025-03
TECHNICAL
SPECIFICATION
Wind energy generation systems –

Part 28: Through-life management and life extension of wind power assets

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180  ISBN 978-2-8327-0295-6

– 2 – IEC TS 61400-28:2025 © IEC 2025
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 10
2 Normative references . 10
3 Terms, definitions and abbreviated terms . 11
3.1 Terms and definitions . 11
3.2 Abbreviated terms . 16
4 User guidance: Concept of through-life management and lifetime extension . 18
4.1 Overview. 18
4.2 Data management . 24
4.3 Reading guideline . 24
5 Data management, requirements and uncertainty . 28
5.1 Preamble . 28
5.2 Data management . 28
5.3 Data and information definition . 29
5.4 Data / information sources . 30
5.4.1 Design information . 30
5.4.2 Meteorological data . 31
5.4.3 Wind data from nacelle . 31
5.4.4 Extreme site conditions . 32
5.4.5 SCADA data . 32
5.4.6 Instrumentation . 33
5.4.7 Operational experience . 33
5.4.8 Maintenance and field history . 33
5.4.9 Inspection history . 33
5.5 Data requirements for components in the primary load path . 34
5.6 Data uncertainty. 35
5.7 Classification of uncertainty . 36
5.8 Data requirements for new wind farms . 36
6 Risk management process . 36
6.1 General approach . 36
6.2 Scope of risk assessment . 38
6.3 Life extension risk assessment . 39
7 Wind farm operation, maintenance and inspections . 39
7.1 Name plate and design class requirements . 39
7.2 Replacement of structural or major components . 40
7.3 Operation and maintenance . 40
7.4 Physical inspections . 42
7.5 Scheduling of physical inspections . 42
7.5.1 General . 42
7.5.2 Early life inspections (15 % to 25 % through operational life) . 43
7.5.3 Mid-life inspections (45 % to 55 % through operational life) . 43
7.5.4 Life extension preparation inspections (70 % to 80 % through
operational life) . 43
8 Condition and structural health monitoring . 44
8.1 Purpose . 44

8.2 CMD minimum necessary requirement . 46
8.2.1 General . 46
8.2.2 Vibration monitoring system (VMS) . 46
8.2.3 Temperature monitoring . 46
8.2.4 Oil and grease wear particle analysis. 47
8.2.5 Site (wind) condition monitoring . 48
8.3 Structural health and load monitoring . 48
8.4 Data acquisition . 48
8.5 Integration to asset management . 49
8.5.1 General . 49
8.5.2 Documentation . 49
8.5.3 Business procedures . 49
9 Health and safety information . 50
10 Analytical assessment of turbine lifetime . 50
10.1 Overview. 50
10.2 Methods to determine loads . 50
10.2.1 General . 50
10.2.2 Relative assessment . 51
10.2.3 Absolute assessment . 51
10.3 Model data, input data and their uncertainties . 52
Annex A (informative) Health and safety – inspection and performance criteria . 54
A.1 General . 54
A.2 Content and format of any reports issued . 56
A.3 Operation and maintenance data . 57
Annex B (informative) Data requirements for primary load path . 58
B.1 Input data requirements . 58
B.2 Condition monitoring data requirements . 65
Annex C (informative) Physical inspections – best practice for documentation of
results, findings and insights . 72
C.1 Physical inspections . 72
C.2 Inspection scope . 74
C.3 Highly recommended inspections . 74
C.3.1 Tower . 74
C.3.2 Blades . 75
C.3.3 Pitch bearings. 75
C.3.4 Yaw ring and bearing . 75
C.3.5 Foundation . 76
C.3.6 Transition piece (offshore) . 76
C.3.7 Nacelle frame / bedplate . 77
C.3.8 Hub . 77
C.3.9 Bolted connections . 78
C.3.10 Safety systems . 78
C.3.11 Main bearing . 79
C.3.12 Main shaft . 79
C.4 Recommended inspections . 79
C.4.1 Gearbox inspections . 79
C.4.2 Generator inspection . 79
C.4.3 Yaw drives . 80

– 4 – IEC TS 61400-28:2025 © IEC 2025
C.4.4 Nacelle condition . 80
C.5 Scheduled service (change or prolong existing schedule service) . 80
C.6 Additional inspections and testing .
...