1 Scope
This document specifies additional requirements for the assessment of the external conditions of offshore wind turbine sites and basic design requirements to ensure the engineering integrity of stationary offshore wind turbines. The aim is to provide an appropriate level of protection against damage caused by various hazards during the expected lifetime of the wind turbine.
This document focuses on the engineering integrity of the structural components of an offshore wind turbine, but also addresses subsystems such as control and protection mechanisms, internal electrical systems and mechanical systems.
If the support structure of an offshore wind turbine is subject to hydrodynamic loads and is fixed to the seabed, then the turbine is a fixed offshore wind turbine. The design requirements in this document do not ensure the engineering integrity of floating offshore wind turbines. The design requirements for floating offshore wind turbines can be found in IEC 61400-3-2. The offshore wind turbines described in this document refer to fixed offshore wind turbines.
It is appropriate to use this document in conjunction with the applicable IEC and ISO standards referred to in Chapter 4. Particular attention is paid to the fact that this document is fully compliant with the requirements of IEC 61400-1. The safety class of offshore wind turbines designed by this document should be no less than IEC 61400-1. In some sections, IEC 614G01 has been reproduced in order to clearly describe the specified requirements.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of the normative G-pairs in the text. Where a reference is dated, only the version corresponding to that date applies to this document i Where a reference is not dated, the latest version (including all amendments) applies to this document.
ISO 2394 General principles on reliability for structures)
ISO 2533,1975 Standard atmosphere
ISO 19900 Petroleum and natural gas industries - General requirements for offshore structures
ISO 19901-1:2015 Petroleum and natural gas industries - Specific requirements for offshore structures - Part 1 : Meto-cean design and operating conditions
ISo 19901-4 Petroleum and natural gas industries - Specific requirements for offshore structures - Part 4: Geotechnical and foundation design considerations
ISo 19902 Petroleum and natural gas industries - Fixedsteel offshore structures
ISO 19903 Petroleum and natural gas industries - Fixed concrete offshore structures
IEC 61400-1:2019 Wind energy generation systems - Part 1: Designrequirements
IEC 60721 Classification of environmental condition
3 Terms and definitions
The terms defined in IEC 61400-1 and the following terms and definitions apply to this document.
4 Symbols and abbreviations
To facilitate understanding of the content of this document, the following symbols and abbreviations will be used in addition to those specified in IEC 61400-1.
5 Basic requirements
5.1 Overview
The engineering requirements given in the following clauses are intended to ensure the safety of the structure, mechanical systems, electrical systems and control systems of offshore wind turbines. These technical requirements apply to the design, manufacture, installation, operation and maintenance manuals and related quality management processes of wind turbines. In addition, the various safety procedures required for the installation, operation and maintenance of offshore wind turbines have been considered.
5.2 Design methods
This document requires the use of a structural dynamics model to predict design load effects. The model shall determine the load effects associated with all combinations of external conditions (specified in Chapter 6) and design states (specified in Chapter ?). This document defines the minimum relevant combinations as design load conditions.
The design of the support structure for an offshore wind turbine shall be based on site-specific external conditions and be consistent with the requirements specified in Chapter 6. These conditions should be summarised as design basics.
Where the initial design of the wind turbine - nacelle assembly of an offshore wind turbine is based on the standard class specified in IEC 61400-1:2019, 6.2, it shall be demonstrated that the site-specific external conditions at sea do not affect the structural integrity. This demonstration shall include a comparison between the results of the load and deformation calculations for the offshore wind turbine site and the initial design calculations, taking into account safety margins, environmental disturbances to the structure and the influence of the selected materials. In addition, the calculation of loads and deformations should consider the effect of site-specific soil properties on the dynamics of the offshore wind turbine and the potential long-term changes in dynamics due to seabed movement and scour.
6 Definition and assessment of external conditions
6.1 Overview
The external conditions specified in this chapter should be considered in the design of an offshore wind turbine.
The loads, service life and operation of offshore wind turbines are susceptible to environmental and electrical conditions as well as to the influence of nearby units. In order to ensure that appropriate safety and reliability requirements are met, environmental, grid and geological parameters should be considered in the design and should be detailed in the design documentation.
Environmental conditions are classified as wind conditions, marine conditions (waves, currents, water levels, sea ice/lake ice, sea life, seabed movement and scouring) and other environmental conditions. Electrical conditions refer to grid conditions. The design of offshore wind turbine foundations is related to soil characteristics, taking into account changes in soil properties over time due to seabed movement, scouring and other seabed instabilities.
Wind conditions are fundamental external conditions for determining the structural integrity of the wind turbine - nacelle assembly, although ocean conditions can have an impact on certain load conditions that relate to the dynamic characteristics of the supporting structure. In all cases (including those where ocean conditions are negligible in the design of the wind turbine-nacelle assembly), due consideration should be given to the ocean conditions at each particular site (i.e. the proposed location of the offshore wind turbine) when demonstrating structural integrity.
The design process for an offshore wind turbine is illustrated in Figure Peal. The assessment of the external conditions at a particular site is the first step in the design process and is the basis for the design. The definition and assessment of external conditions is provided in this chapter.
Other environmental conditions can also affect design characteristics such as control system function, durability, corrosion, etc.
External conditions can be divided into normal and extreme external conditions. Normal external conditions usually relate to recurring structural load conditions, while extreme external conditions represent rare external design conditions. The design load conditions should include possible critical combinations of these external conditions with different operating modes of the wind turbine and other design conditions.
7 Structural design
7.1 Overview
The structural integrity of the load-bearing components of the offshore wind turbine shall be verified and ensured to have an acceptable safety rating. The ultimate strength and fatigue strength of the structural components shall be verified by calculation, test or a combination of both to demonstrate that the structural integrity of the offshore wind turbine has an appropriate safety rating.
Structural analysis shall be carried out in accordance with ISO 2394.
Calculations shall be carried out using appropriate methods and a description of the calculation methods shall be provided in the design documentation. These descriptions should include evidence of the validity of the calculation method or references to the appropriate validation studies. The load levels in all strength verification tests should correspond to the safety factors applicable to the characteristic loads in 7.6.
Resonance characterisation of the support structure, wind turbine and drive chain shall be analysed to a minimum of 2 times the excitation range of the blade through the tonnage. For DLC 1.2, the possibility of resonance at 30% turbulence level for the NTM wind condition Class C design Ziz flow shall be analysed. If high resonance loads are found at low turbulence levels, measures should be taken to avoid resonance or to take it into account in the design loads.
7.2 Design methods
Model tests and prototype tests to verify that the limit states of the wind turbine are within the design limits specified in So 2394 can also be used instead of calculations to verify the soundness of the structural design.
Design calculations shall be based on validated methods and approved rules.
In accordance with IEC 61400-1, the model used for the design calculations shall be verified by means of load tests. The tests shall be carried out on onshore or offshore wind turbines that are similar in dynamic response and structure to the designed wind turbine, but where the details (e.g. interchangeable support structures) may differ. The load test requirements can be found in ISO 2394.
8 Control systems
The control system for the operation and safety of the offshore wind turbine shall comply with the requirements of IEC 61400-1.
To avoid exposure to the marine environment, all components of the control system and protection system should be adequately protected from the effects of the marine environment. See Appendix G for relevant corrosion protection guidelines.
In addition, the following provisions shall apply.
For reasons of personal safety, wind turbine rotation should be stopped, if necessary, by remote control prior to the arrival of personnel.
To ensure personal safety (during helicopter lifting operations or when avoiding collision between the blade tip and the vessel), the yaw system should be remotely operated and braked by the operator, if necessary, before the helicopter or vessel approaches the offshore wind turbine.
If braking by a system other than a locking device is used (e.g. yaw brake or mechanical disc brake>, measures should be taken to avoid any slippage. Appropriate indicators should be installed on the offshore wind turbine to inform approaching personnel that the wind turbine and yaw system are in braking mode.
If the wind turbine and yaw systems are automatically or remotely braked, measures should be taken to prevent these systems from being automatically or remotely restarted without the request of the operator in the wind turbine, in the helicopter or on board the vessel. Personnel in the wind turbine should be able to disable the automatic or remote restart function of the wind turbine and yaw system before entering the risk area. Appropriate annotations should be given in the relevant documentation.
9 Mechanical systems
For the purposes of this document, mechanical systems are systems that combine shafts, connecting rods, bearings, sliding parts, wheels and other equipment for use or transfer of relative motion, and do not include separate static structural or electrical components. The auxiliary components can be electrically, hydraulically or pneumatically operated. Good.
The mechanical system of an offshore wind turbine should be designed to meet the requirements of IEC 61400-1.
To prevent the mechanical system from being affected by the marine environment, provisions should be made for its proper protection. See Appendix G for relevant corrosion protection.
10 Electrical system
11 Foundation and substructure design
12 Assembly, installation and lifting
13 Commissioning operation and maintenance
Appendix A (informative) Key design parameters for offshore wind turbines -
Appendix B (Informative) Shallow water hydrodynamics and breaking waves
Appendix C (Informative) Guidelines for the calculation of hydrodynamic loads
Appendix D (Informative) Design recommendations for offshore wind turbine support nets under ice loads
Appendix E (Informative) Design of foundations and substructures for offshore wind turbines
Appendix F (Informative) Statistical extrapolation of marine meteorological operating parameters for ultimate strength analysis
Appendix G (informative) Corrosion protection
Appendix H (Informative) Prediction of extreme wave heights due to tropical cyclones
Appendix I (Informative) Recommendations for regional safety level adjustments for tropical cyclones...
Bibliography
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Basic requirements
6 Definition and assessment of external conditions
7 Structural design
8 Control systems
9 Mechanical systems
10 Electrical system
11 Foundation and substructure design
12 Assembly, installation and lifting
13 Commissioning operation and maintenance
Appendix A (informative) Key design parameters for offshore wind turbines -
Appendix B (Informative) Shallow water hydrodynamics and breaking waves
Appendix C (Informative) Guidelines for the calculation of hydrodynamic loads
Appendix D (Informative) Design recommendations for offshore wind turbine support nets under ice loads
Appendix E (Informative) Design of foundations and substructures for offshore wind turbines
Appendix F (Informative) Statistical extrapolation of marine meteorological operating parameters for ultimate strength analysis
Appendix G (informative) Corrosion protection
Appendix H (Informative) Prediction of extreme wave heights due to tropical cyclones
Appendix I (Informative) Recommendations for regional safety level adjustments for tropical cyclones...
Bibliography
1 Scope
This document specifies additional requirements for the assessment of the external conditions of offshore wind turbine sites and basic design requirements to ensure the engineering integrity of stationary offshore wind turbines. The aim is to provide an appropriate level of protection against damage caused by various hazards during the expected lifetime of the wind turbine.
This document focuses on the engineering integrity of the structural components of an offshore wind turbine, but also addresses subsystems such as control and protection mechanisms, internal electrical systems and mechanical systems.
If the support structure of an offshore wind turbine is subject to hydrodynamic loads and is fixed to the seabed, then the turbine is a fixed offshore wind turbine. The design requirements in this document do not ensure the engineering integrity of floating offshore wind turbines. The design requirements for floating offshore wind turbines can be found in IEC 61400-3-2. The offshore wind turbines described in this document refer to fixed offshore wind turbines.
It is appropriate to use this document in conjunction with the applicable IEC and ISO standards referred to in Chapter 4. Particular attention is paid to the fact that this document is fully compliant with the requirements of IEC 61400-1. The safety class of offshore wind turbines designed by this document should be no less than IEC 61400-1. In some sections, IEC 614G01 has been reproduced in order to clearly describe the specified requirements.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of the normative G-pairs in the text. Where a reference is dated, only the version corresponding to that date applies to this document i Where a reference is not dated, the latest version (including all amendments) applies to this document.
ISO 2394 General principles on reliability for structures)
ISO 2533,1975 Standard atmosphere
ISO 19900 Petroleum and natural gas industries - General requirements for offshore structures
ISO 19901-1:2015 Petroleum and natural gas industries - Specific requirements for offshore structures - Part 1 : Meto-cean design and operating conditions
ISo 19901-4 Petroleum and natural gas industries - Specific requirements for offshore structures - Part 4: Geotechnical and foundation design considerations
ISo 19902 Petroleum and natural gas industries - Fixedsteel offshore structures
ISO 19903 Petroleum and natural gas industries - Fixed concrete offshore structures
IEC 61400-1:2019 Wind energy generation systems - Part 1: Designrequirements
IEC 60721 Classification of environmental condition
3 Terms and definitions
The terms defined in IEC 61400-1 and the following terms and definitions apply to this document.
4 Symbols and abbreviations
To facilitate understanding of the content of this document, the following symbols and abbreviations will be used in addition to those specified in IEC 61400-1.
5 Basic requirements
5.1 Overview
The engineering requirements given in the following clauses are intended to ensure the safety of the structure, mechanical systems, electrical systems and control systems of offshore wind turbines. These technical requirements apply to the design, manufacture, installation, operation and maintenance manuals and related quality management processes of wind turbines. In addition, the various safety procedures required for the installation, operation and maintenance of offshore wind turbines have been considered.
5.2 Design methods
This document requires the use of a structural dynamics model to predict design load effects. The model shall determine the load effects associated with all combinations of external conditions (specified in Chapter 6) and design states (specified in Chapter ?). This document defines the minimum relevant combinations as design load conditions.
The design of the support structure for an offshore wind turbine shall be based on site-specific external conditions and be consistent with the requirements specified in Chapter 6. These conditions should be summarised as design basics.
Where the initial design of the wind turbine - nacelle assembly of an offshore wind turbine is based on the standard class specified in IEC 61400-1:2019, 6.2, it shall be demonstrated that the site-specific external conditions at sea do not affect the structural integrity. This demonstration shall include a comparison between the results of the load and deformation calculations for the offshore wind turbine site and the initial design calculations, taking into account safety margins, environmental disturbances to the structure and the influence of the selected materials. In addition, the calculation of loads and deformations should consider the effect of site-specific soil properties on the dynamics of the offshore wind turbine and the potential long-term changes in dynamics due to seabed movement and scour.
6 Definition and assessment of external conditions
6.1 Overview
The external conditions specified in this chapter should be considered in the design of an offshore wind turbine.
The loads, service life and operation of offshore wind turbines are susceptible to environmental and electrical conditions as well as to the influence of nearby units. In order to ensure that appropriate safety and reliability requirements are met, environmental, grid and geological parameters should be considered in the design and should be detailed in the design documentation.
Environmental conditions are classified as wind conditions, marine conditions (waves, currents, water levels, sea ice/lake ice, sea life, seabed movement and scouring) and other environmental conditions. Electrical conditions refer to grid conditions. The design of offshore wind turbine foundations is related to soil characteristics, taking into account changes in soil properties over time due to seabed movement, scouring and other seabed instabilities.
Wind conditions are fundamental external conditions for determining the structural integrity of the wind turbine - nacelle assembly, although ocean conditions can have an impact on certain load conditions that relate to the dynamic characteristics of the supporting structure. In all cases (including those where ocean conditions are negligible in the design of the wind turbine-nacelle assembly), due consideration should be given to the ocean conditions at each particular site (i.e. the proposed location of the offshore wind turbine) when demonstrating structural integrity.
The design process for an offshore wind turbine is illustrated in Figure Peal. The assessment of the external conditions at a particular site is the first step in the design process and is the basis for the design. The definition and assessment of external conditions is provided in this chapter.
Other environmental conditions can also affect design characteristics such as control system function, durability, corrosion, etc.
External conditions can be divided into normal and extreme external conditions. Normal external conditions usually relate to recurring structural load conditions, while extreme external conditions represent rare external design conditions. The design load conditions should include possible critical combinations of these external conditions with different operating modes of the wind turbine and other design conditions.
7 Structural design
7.1 Overview
The structural integrity of the load-bearing components of the offshore wind turbine shall be verified and ensured to have an acceptable safety rating. The ultimate strength and fatigue strength of the structural components shall be verified by calculation, test or a combination of both to demonstrate that the structural integrity of the offshore wind turbine has an appropriate safety rating.
Structural analysis shall be carried out in accordance with ISO 2394.
Calculations shall be carried out using appropriate methods and a description of the calculation methods shall be provided in the design documentation. These descriptions should include evidence of the validity of the calculation method or references to the appropriate validation studies. The load levels in all strength verification tests should correspond to the safety factors applicable to the characteristic loads in 7.6.
Resonance characterisation of the support structure, wind turbine and drive chain shall be analysed to a minimum of 2 times the excitation range of the blade through the tonnage. For DLC 1.2, the possibility of resonance at 30% turbulence level for the NTM wind condition Class C design Ziz flow shall be analysed. If high resonance loads are found at low turbulence levels, measures should be taken to avoid resonance or to take it into account in the design loads.
7.2 Design methods
Model tests and prototype tests to verify that the limit states of the wind turbine are within the design limits specified in So 2394 can also be used instead of calculations to verify the soundness of the structural design.
Design calculations shall be based on validated methods and approved rules.
In accordance with IEC 61400-1, the model used for the design calculations shall be verified by means of load tests. The tests shall be carried out on onshore or offshore wind turbines that are similar in dynamic response and structure to the designed wind turbine, but where the details (e.g. interchangeable support structures) may differ. The load test requirements can be found in ISO 2394.
8 Control systems
The control system for the operation and safety of the offshore wind turbine shall comply with the requirements of IEC 61400-1.
To avoid exposure to the marine environment, all components of the control system and protection system should be adequately protected from the effects of the marine environment. See Appendix G for relevant corrosion protection guidelines.
In addition, the following provisions shall apply.
For reasons of personal safety, wind turbine rotation should be stopped, if necessary, by remote control prior to the arrival of personnel.
To ensure personal safety (during helicopter lifting operations or when avoiding collision between the blade tip and the vessel), the yaw system should be remotely operated and braked by the operator, if necessary, before the helicopter or vessel approaches the offshore wind turbine.
If braking by a system other than a locking device is used (e.g. yaw brake or mechanical disc brake>, measures should be taken to avoid any slippage. Appropriate indicators should be installed on the offshore wind turbine to inform approaching personnel that the wind turbine and yaw system are in braking mode.
If the wind turbine and yaw systems are automatically or remotely braked, measures should be taken to prevent these systems from being automatically or remotely restarted without the request of the operator in the wind turbine, in the helicopter or on board the vessel. Personnel in the wind turbine should be able to disable the automatic or remote restart function of the wind turbine and yaw system before entering the risk area. Appropriate annotations should be given in the relevant documentation.
9 Mechanical systems
For the purposes of this document, mechanical systems are systems that combine shafts, connecting rods, bearings, sliding parts, wheels and other equipment for use or transfer of relative motion, and do not include separate static structural or electrical components. The auxiliary components can be electrically, hydraulically or pneumatically operated. Good.
The mechanical system of an offshore wind turbine should be designed to meet the requirements of IEC 61400-1.
To prevent the mechanical system from being affected by the marine environment, provisions should be made for its proper protection. See Appendix G for relevant corrosion protection.
10 Electrical system
11 Foundation and substructure design
12 Assembly, installation and lifting
13 Commissioning operation and maintenance
Appendix A (informative) Key design parameters for offshore wind turbines -
Appendix B (Informative) Shallow water hydrodynamics and breaking waves
Appendix C (Informative) Guidelines for the calculation of hydrodynamic loads
Appendix D (Informative) Design recommendations for offshore wind turbine support nets under ice loads
Appendix E (Informative) Design of foundations and substructures for offshore wind turbines
Appendix F (Informative) Statistical extrapolation of marine meteorological operating parameters for ultimate strength analysis
Appendix G (informative) Corrosion protection
Appendix H (Informative) Prediction of extreme wave heights due to tropical cyclones
Appendix I (Informative) Recommendations for regional safety level adjustments for tropical cyclones...
Bibliography
Contents of GB/T 31517.1-2022
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviations
5 Basic requirements
6 Definition and assessment of external conditions
7 Structural design
8 Control systems
9 Mechanical systems
10 Electrical system
11 Foundation and substructure design
12 Assembly, installation and lifting
13 Commissioning operation and maintenance
Appendix A (informative) Key design parameters for offshore wind turbines -
Appendix B (Informative) Shallow water hydrodynamics and breaking waves
Appendix C (Informative) Guidelines for the calculation of hydrodynamic loads
Appendix D (Informative) Design recommendations for offshore wind turbine support nets under ice loads
Appendix E (Informative) Design of foundations and substructures for offshore wind turbines
Appendix F (Informative) Statistical extrapolation of marine meteorological operating parameters for ultimate strength analysis
Appendix G (informative) Corrosion protection
Appendix H (Informative) Prediction of extreme wave heights due to tropical cyclones
Appendix I (Informative) Recommendations for regional safety level adjustments for tropical cyclones...
Bibliography
