IEC TS 61400-31:2023

Wind energy generation systems - Part 31: Siting risk assessment

IEC TS 61400-31:2023 establishes a guideline for the assessment of the risks which a wind turbine may pose to the general public.
This document aims to facilitate a uniform scope and a uniform use of methods in wind turbine risk assessments. This document covers risk due to internal or external causes, such as technical failures, human errors, extreme wind conditions, turbine icing, lightning strikes, earthquakes, flooding, landslides or fire.This document covers only onshore wind turbines with a horizontal axis and a swept area greater than 200 m2. Substations and other external structures are excluded.
This document describes risks during operation of the wind turbine including maintenance, idling and standstill. It does not describe risks during construction, civil works, crane operations, assembly or decommissioning.
Risks according to this document are assessed by prescriptive and/or risk-based methods.
This document covers risk reduction measures that might be necessary to reduce risk to a tolerable level.

General Information

• Status: Published
• Publication Date: 14-Nov-2023
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: PT 61400-31 - TC 88/PT 61400-31
• Current Stage: PPUB - Publication issued
• Start Date: 09-Aug-2023
• Completion Date: 15-Nov-2023

Standards Content (Sample)

IEC TS 61400-31 ®
Edition 1.0 2023-11
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –
Part 31: Siting risk assessment

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IEC TS 61400-31 ®
Edition 1.0 2023-11
TECHNICAL
SPECIFICATION
colour
inside
Wind energy generation systems –

Part 31: Siting risk assessment

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS  27.180 ISBN 978-2-8322-7744-7

– 2 – IEC TS 61400-31:2023 © IEC 2023
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 8
3 Terms, definitions and symbols. 8
3.1 Terms and definitions . 8
3.2 Symbols used in this document . 12
3.3 Abbreviated terms . 13
4 Risk assessment process . 13
4.1 Overview. 13
4.2 Documentation requirements in the risk assessment process . 14
4.3 Involvement of stakeholders. 14
5 Risk management throughout service life . 15
5.1 Overview. 15
5.2 Reviewing, documenting and reporting of the risk management process . 15
6 Harm to people . 16
6.1 Overview. 16
6.2 Direct harm . 16
6.3 Indirect harm. 16
6.4 Domino effect . 17
6.5 Consequences of impacts of objects . 17
7 Risk assessment approaches and associated acceptance criteria . 17
7.1 Risk assessment approaches . 17
7.2 Risk acceptance criteria . 19
7.3 Risk regions . 20
7.4 Types of risk criteria . 21
7.5 Prescriptive risk acceptance criteria . 21
7.6 Qualitative risk acceptance criteria . 22
7.7 Semi-quantitative risk acceptance criteria . 22
7.8 Quantitative risk acceptance criteria . 23
7.8.1 General . 23
7.8.2 Quantitative risk criteria for individuals . 24
7.8.3 Quantitative societal risk criteria . 26
8 Hazard identification . 30
8.1 General . 30
8.2 General principles of hazard identification . 30
8.3 Wind turbine failure modes . 30
8.3.1 General . 30
8.3.2 Tower collapse . 30
8.3.3 Shedding of hub or nacelle . 30
8.3.4 Rotor blade failure . 31
8.4 Ice fall and ice throw . 31
8.5 Fire . 32
8.6 Occupancy . 32
8.7 Project relevant hazards . 33
9 Estimation of the risk . 33
9.1 General . 33

9.2 Wind turbine failures – tower collapse, shedding of hub or nacelle and rotor
blade failure . 33
9.2.1 General . 33
9.2.2 Input information . 34
9.2.3 Additional assumptions/models . 34
9.2.4 Tower collapse . 35
9.2.5 Shedding of hub or nacelle . 35
9.2.6 Blade breakage . 35
9.2.7 Summation of impact probabilities and risks . 36
9.3 Ice fall and ice throw . 36
9.3.1 Input information . 36
9.3.2 Additional assumptions/models . 37
9.3.3 Calculation of trajectories of ice pieces . 37
9.4 Wind turbine fire . 38
9.5 Calculation of the risk . 38
9.5.1 General . 38
9.5.2 Effective cross-section for people and cars . 39
9.6 Analysis of domino effects . 39
10 Risk evaluation . 40
11 Risk treatment . 40
11.1 General . 40
11.2 Selection of risk reduction measures . 40
11.3 Examples of risk reduction measures . 40
11.4 Ice detection systems and rotor blade heating systems . 41
12 Uncertainties in risk assessments . 42
Annex A (informative) Summary of failure frequencies published by the Dutch RIVM . 44
Annex B (informative) Overview of used risk criteria in different countries . 45
Annex C (informative) Introduction to trajectory models for blades and blade
fragments . 49
Bibliography . 54

Figure 1 – Flow chart of the risk assessment process (Modified from
ISO/IEC Guide 51 [3]) . 13
Figure 2 – The risk assessment process . 14
Figure 3 – Flow chart of the selection of risk assessment methods with different levels
of fidelity . 19
Figure 4 – Risk regions . 20
Figure 5 – Example tables for a semi-quantitative risk assessment . 23
Figure 6 – Combination of hazards and impacted persons. . 27
Figure 7 – Example of an f-N plot . 28
Figure 8 – Example of societal risk criteria . 29
Figure C.1 – Blade-fixed and inertial reference frames. . 50

– 4 – IEC TS 61400-31:2023 © IEC 2023
Table 1 – Examples of risk acceptance criteria for different risk assessment
approaches . 21
Table 2 – Policy factor according to [11] . 26
Table 3 – Examples for hazardous installations that could be affected by domino
effects triggered by wind turbine failures . 39
Table A.1 – Failure frequencies from [13] in units of failures per turbine and year. . 44
Table B.1 – Overview of used risk criteria in different countries . 45

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 31: Siting risk assessment

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide
...