IEC TS 61400-50-4:2025

IEC TS 61400-50-4 ®
Edition 1.0 2025-05
TECHNICAL
SPECIFICATION
Wind energy generation systems –
Part 50-4: Use of floating lidar systems for wind measurements
ICS 27.180  ISBN 978-2-8327-0342-7

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– 2 – IEC TS 61400-50-4:2025 © IEC 2025
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions, symbols and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Symbols and abbreviated terms . 16
3.2.1 Symbols . 16
3.2.2 Abbreviated terms . 17
4 Overview . 18
4.1 General . 18
4.2 Measurement methodology overview . 19
4.3 Document overview. 19
5 System requirements . 20
5.1 General . 20
5.2 Floating lidar system (without mooring system) . 20
5.2.1 Functional requirements . 20
5.2.2 Documentary requirements . 24
5.3 Mooring system (below the water line) . 24
5.3.1 Functional requirements . 24
5.3.2 Documentary requirements . 25
6 Unit qualification (calibration of FLS wind measurements) . 25
6.1 Calibration method overview . 25
6.2 Component verification . 26
6.2.1 General. 26
6.2.2 Lidar onshore calibration . 26
6.2.3 Auxiliary systems . 26
6.3 Setup of offshore calibration test . 26
6.3.1 Site requirements . 26
6.3.2 Setup requirements . 27
6.4 Full calibration test methodology . 28
6.4.1 General. 28
6.4.2 Identification of a trusted reference system . 28
6.4.3 Data completion criteria . 29
6.4.4 Wind speed uncertainty . 29
6.5 Simplified calibration protocol . 31
6.5.1 General. 31
6.5.2 Campaign duration . 31
6.5.3 Analysis . 31
6.6 System and data availability . 32
6.7 Offshore calibration intervals . 33
6.8 Reporting requirements . 34
7 Type qualification (classification) . 35
7.1 General . 35
7.2 Treatment of intermediate variables . 36
7.3 Long-term tests . 36
7.3.1 Data acquisition . 36

7.3.2 Data completion criteria . 37
7.3.3 List of environmental variables to be considered . 37
7.4 Sensitivity study . 38
7.5 Evidence base supporting the evaluation of FLS performance . 39
7.6 Reporting requirements . 39
7.6.1 General. 39
7.6.2 Reporting requirements for type qualification tests . 40
7.6.3 Reporting requirements for evidence base . 40
8 Quantification of final (measurement) uncertainty budget . 41
8.2 Calculation of classification uncertainty . 42
8.2.1 General. 42
8.2.2 Sensitivity uncertainty scenarios . 43
8.3 Calculation of calibration uncertainty . 46
8.4 Calculation of configuration uncertainty . 46
8.4.1 General. 46
8.4.2 Drift tolerances . 47
8.4.3 In situ data quality assurance . 47
8.4.4 Change in buoy configuration . 47
8.4.5 Change in buoy stability. 47
9 Measurement procedure . 47
9.1 General . 47
9.2 Pre-deployment checks and requirements . 48
9.2.1 Health, safety, and environment . 48
9.2.2 Measurement setup . 48
9.2.3 Mooring . 49
9.3 Installation/deployment and documentation requirements . 50
9.3.1 General. 50
9.3.2 Checklist . 50
9.3.3 Meta data format. 51
9.4 Campaign . 51
9.4.1 Campaign checks and notifications . 51
9.4.2 In situ data quality assurance . 52
9.4.3 In the event of a change in buoy configuration . 53
9.4.4 Data availability . 54
10 Reporting . 55
Annex A (normative) The instrument qualification cycle . 57
A.1 General . 57
A.1.1 Overview . 57
A.1.2 Instrument qualification. 57
A.1.3 Measurement uncertainty . 57
A.1.4 The qualification cycle . 58
A.2 Type qualification . 59
A.2.1 General. 59
A.2.2 Lidar measurement procedure . 59
A.2.3 Intermediate value uncertainty due to changes in environmental

conditions . 60
A.2.4 List of environmental variables to be considered . 60
A.2.5 Significance of uncertainty contribution . 60
A.2.6 Evidence base supporting the adequacy of the WFR . 60

– 4 – IEC TS 61400-50-4:2025 © IEC 2025
A.2.7 Envelope of operational conditions . 61
A.2.8 Uncertainty scenarios . 62
A.2.9 Extension of evidence base . 62
A.2.10 Test results comprising the evidence base. 62
A.3 Unit qualification . 63
A.3.1 General. 63
A.3.2 Reference instrumentation . 63
A.3.3 Measurement procedure . 63
A.3.4 Filtering . 63
A.4 Reporting requirements . 63
A.4.1 Type qualification . 63
A.4.2 Unit qualification .
...