IEC 61400-8:2024

Wind energy generation systems - Part 8: Design of wind turbine structural components

IEC 61400-8:2024 outlines the minimum requirements for the design of wind turbine nacelle-based structures and is not intended for use as a complete design specification or instruction manual. This document focuses on the structural integrity of the structural components constituted within and in the vicinity of the nacelle, including the hub, mainframe, main shaft, associated structures of direct-drives, gearbox structures, yaw structural connection, nacelle enclosure. It also addresses connections of the structural components to control and protection mechanisms, as well as structural connections of electrical units and other mechanical systems. This document focuses primarily on ferrous material-based nacelle structures but can apply to other materials also as appropriate

Systèmes de génération d'énergie éolienne - Partie 8: Conception des composants structurels des éoliennes

l'IEC 61400-8:2024 définit les exigences minimales de conception des structures d'éoliennes sur nacelles et n'est pas destinée à servir de spécification de conception complète ou de manuel d'instructions. Le présent document porte sur l'intégrité structurelle des composants structurels constitués à l'intérieur et à proximité de la nacelle, y compris le moyeu, le cadre principal, l'arbre principal, les structures associées d'entraînement direct, les structures des boîtes de vitesse, la connexion structurelle d'orientation, l'enveloppe de la nacelle. Il traite également des connexions des composants structurels aux mécanismes de commande et de protection, ainsi que les connexions structurelles aux unités électriques et aux autres systèmes mécaniques. Le présent document concerne principalement les structures de nacelle en matériaux ferreux, mais peut également s'appliquer à d'autres matériaux, le cas échéant. La conception des assemblages boulonnés et soudés dans les structures de nacelle est incluse, ainsi que les composants coulés et forgés.

General Information

• Status: Published
• Publication Date: 02-Jul-2024
• ICS: 27.180 - Wind turbine energy systems
• Technical Committee: TC 88 - Wind energy generation systems
• Drafting Committee: PT 61400-8 - TC 88/PT 61400-8
• Current Stage: PPUB - Publication issued
• Start Date: 03-Jul-2024
• Completion Date: 05-Jul-2024

Standards Content (Sample)

IEC 61400-8 ®
Edition 1.0 2024-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Wind energy generation systems –
Part 8: Design of wind turbine structural components

Systèmes de génération d'énergie éolienne –
Partie 8: Conception des composants structurels des éoliennes
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IEC 61400-8 ®
Edition 1.0 2024-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Wind energy generation systems –

Part 8: Design of wind turbine structural components

Systèmes de génération d'énergie éolienne –

Partie 8: Conception des composants structurels des éoliennes

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180  ISBN 978-2-8322-9063-7

– 2 – IEC 61400-8:2024  IEC 2024
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions, symbols and abbreviated terms . 10
3.1 Terms and definitions . 10
3.2 Symbols and abbreviated terms . 12
4 Reliability considerations . 14
4.1 Approaches to reliability based design . 14
4.2 Models and basic variables for structural verification . 16
4.2.1 Reliability assessment . 16
4.2.2 Material properties . 16
4.3 Partial safety factors and reliability targets . 16
5 Application of loads and analysis models . 17
5.1 Loads models . 17
5.2 Analysis model . 17
5.2.1 General . 17
5.2.2 Load path modelling . 17
5.2.3 Application of load components . 17
5.2.4 Boundary conditions . 18
5.3 Modelling of nonlinear mechanical behaviour . 18
5.3.1 General . 18
5.3.2 Nonlinear stress effects . 18
5.3.3 Application of ultimate loads . 18
5.3.4 Application of fatigue loads . 18
5.4 Partial safety factors . 19
5.5 Partial safety factor for resistance . 21
5.6 Nacelle and hub component considerations . 22
5.6.1 General . 22
5.6.2 Hub structure and bolts . 22
5.6.3 Nacelle front structure (alternatively: mechanical drive-train structure) . 23
5.6.4 Gearbox structure . 23
5.6.5 Yaw structure . 23
5.6.6 Nacelle rear structure . 24
5.6.7 Nacelle cover and spinner . 24
6 Deflection analysis . 24
7 Strength verification. 25
7.1 General . 25
7.2 Determination of stress and strain . 25
7.3 Material properties . 25
7.3.1 Material data . 25
7.3.2 Influence of size . 26
7.4 Static strength assessment . 26
7.4.1 Assessment process . 26
7.4.2 Cast, forged and steel components . 26
7.4.3 Welded structures . 28

7.4.4 Bolted joints. 28
7.4.5 Fibre reinforced material . 29
7.5 Fatigue strength assessment . 29
7.5.1 Fatigue strength methods . 29
7.5.2 Determination of local stresses . 29
7.5.3 Stress hypothesis for fatigue . 29
7.5.4 S/N curves . 30
7.5.5 Influence on fatigue strength . 30
7.5.6 Partial safety factors for fatigue . 31
7.5.7 Damage accumulation . 32
7.5.8 Bolted joints. 33
7.5.9 Fibre reinforced material . 33
7.6 Fracture mechanics assessment . 33
7.6.1 General . 33
7.6.2 Define objective . 34
7.6.3 Material parameter . 34
7.6.4 Defect model . 35
7.6.5 Structural model . 36
7.6.6 Loading . 36
7.6.7 Strength assessment . 37
7.7 Fracture mechanics-based design . 40
8 Material data for design from testing . 41
8.1 Qualification of material . 41
8.2 Derivation of static strength and impact energy properties (base material) . 41
8.3 Derivation of fatigue strength properties (base material) . 41
8.4 Welded joints . 42
8.5 Cast, forged and steel . 42
8.5.1 Derivation of static strength properties. 42
8.5.2 Fracture toughness . 42
8.5.3 Derivation of fatigue strength properties . 43
8.6 Bolts . 44
8.7 Nacelle cover . 44
9 Model verification and validation . 44
Annex A (informative) Model verification and validation methods . 46
A.1 General . 46
A.2 Verification. 46
A.3 Validation (laboratory testing) . 46
A.4 Validation (field testing) . 46
Annex B (informative) Welded joint stresses . 47
Annex C (informative) S-N curve determination by test, statistical evaluation and
influencing factors . 48
C.1 General . 48
C.2 S-N curve. 48
C.3 Specimens . 48
C.4 Test procedure . 48
C.4.1 General . 48
C.4.2 Finite lifetime . 49
C.4.3 Long life fatigue regime . 49

– 4 – IEC 61400-8:2024  IEC 2024
C.5 Influencing factors of S-N curve . 49
Annex D (informative) Limit state equations . 50
D.1 General . 50
D.2 Yielding failure . 50
D.3 Fatigue limit state equation . 51
D.4 Fatigue assessment based on fracture mechanics . 55
Annex E (informative) Load effect uncertainty computation . 58
Annex F (informative) Considerations for structural elements . 60
F.1 General . 60
F.2 Global and local failures . 60
F.3 Mean stress influence . 61
Bibliography . 63

Figure 1 – Illustration of a nacelle structure, where for example a direct drive generator
is mounted behind the hub . 22
Figure 2 – Idealized elastic plastic stress-strain curve . 27
Figure 3 – Representative S /N curve . 30
Figure 4 – Fracture mechanics calculation – process flow chart . 34
Figure 5 – Idealized crack types . 35
Figure 6 – Failure assessment diagram (FAD) . 37
Figure 7 – Crack growth under cyclic loading by Paris/Erdogan . 39
Figure 8 – Crack propagation and critical crack length in failure assessment diagram . 40
Figure B.1 – Fatigue analysis procedure for the weld toe . 47
Figure D.1 – Haigh diagram with R as the yield stress and R as the tensile limit . 53
e m
Figure E.1 – Model example . 58
Figure F.1 – Locations of failure for local (A) and global (B) failure . 60
Figure F.2 – Local and global failure for two different notch radii . 61
Figure F.3 – Haigh-diagram for evaluation of mean stress influence . 61

Table 1 – Component classes as in IEC 61400-1:2019 . 17
Table 2 – List of potential sources for modelling deviations . 20
Table 3 – Modelling partial safety factor γ : yielding where coefficient of variation
modelling
of yield strength is less than 15 % . 20
Table 4 – Modelling partial safety factor, γ : fatigue of welded details and cast iron . 21
modelling
Table 5 – Minimum resistance partial safety factors, γ , for welded steel for different
M
survival probabilities of the characteristic S-N curve . 21
Table 6 – Minimum resistance partial safety factors γ , for cast iron, forged and steel
M
components (if not utilizing relevant design standards such as EN 1993-1-9) for
different survival probabilities of the characteristic S-N curve. 21
Table 7 – Partial safety factors γ for S/N-curves of cast iron materials . 32
M
Table D.1 – Representative stochastic model for fatigue analysis of cast iron . 55
Table E.1 – Test cases combination. 58
Table E.2 – Result comparison validation vs simplified models and ratio δ
mf
calculation . 59

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
WIND ENERGY GENERATION SYSTEMS –

Part 8: Design of wind turbine structural components

FOREWORD
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IEC 61400-8 has been prepared by IEC technical committee 88: Wind energy generation
systems. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
88/1010/FDIS 88/1023/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

– 6 – IEC 61400-8:2024  IEC 2024
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
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.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document 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.

INTRODUCTION
This part of the IEC 61400 series outlines the minimum requirements for the design of wind
turbine nacelle-based structures and is not intended for use as a complete design specification
or instruction manual.
Several different groups can be responsible for undertaking the various elements of the design,
manufacture, assembly, installation and maintenance of a wind turbine nacelle and for ensuring
that the requirements of this document are met. The division of responsibilities between these
parties is a contractual matter and is outside the scope of this document.
The requirements stated in this document may be altered if it can be sufficiently demonstrated
that the structural integrity of the system is not compromised.
The specific scope of the document is provided in Clause 1. For cases out of the scope of this
document, reference should be made to relevant IEC/ISO standards.

– 8 – IEC 61400-8:2024  IEC 2024
WIND ENERGY GENERATION SYSTEMS –

Part 8: Design of wind turbine structural components

1 Scope
This part of IEC 61400 outlines the minimum requirements for the design of wind turbine
nacelle-based structures and is not intended for use as a complete design specification or
instruction manual. This document focuses on the structural integrity of the structural
components constituted within and in the vicinity of the nacelle, including the hub, mainframe,
main shaft, associated structures of direct-drives, gearbox structures, yaw structural connection,
nacelle enclosure. It also addresses connections of the structural components to control and
protection mechanisms, as well as structural connections of electrical units and other
mechanical systems. This document focuses primarily on ferrous material-based nacelle
structures but can apply to other materials also as appropriate. The design of bolted and welded
joints in the nacelle structures is included, as well as cast and forged components. Material
testing requirements to use in the design process for nacelle structures are specified. While the
structural connections of the gearbox and the main shaft are in the scope, the design of the
gears and bearings are not included.
The safety level of the wind turbine designed according to this document shall be at or exceed
the level inherent in IEC 61400-1:2019. Probabilistic methods to calibrate partial safety factors
and for use in the design process are provided.
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 61400-1:2019, Wind energy generation systems – Part 1: Design requirements
IEC 61400-3-1:2019, Wind energy generation systems – Part 3: Design requirements for fixed
offshore wind turbines
IEC TS 61400-3-2:2019, Wind energy generation systems – Part 3-2: Design requirements for
floating offshore wind turbines
IEC 61400-5:2020, Wind energy generation systems – Part 5: Wind turbine blades
IEC 61400-6:2020, Wind energy generation systems − Part 6: Tower and foundation design
requirements
IEC 61400-13:2015, Wind turbines – Part 13: Measurement of mechanical loads
ISO/IEC 17025:2017, General requirements for the competence of testing and calibration
laboratories
ISO 148-1:2016, Metallic materials – Charpy pendulum impact test – Part 1: Test method
ISO 945-1:2019, Microstructure of cast irons – Part 1: Graphite classification by visual analysis

ISO 1083:2018, Spheroidal graphite cast irons – Classification
ISO 1099:2017, Metallic materials – Fatigue testing – Axial force-controlled method
ISO 1143:2021, Metallic materials – Rotating bar bending fatigue testing
ISO 2394:2015, General principles on reliability for structures
ISO 3800:1993, Threaded fasteners – Axial load fatigue testing – Test methods and evaluation
of results
ISO 6892-1:2019, Metallic materials – Tensile testing – Part 1: Method of test at room
temperature
ISO 7500-1:2018, Metallic materials – Calibration and verification of static uniaxial testing
machines – Part 1: Tension/compression testing machines – Calibration and verification of the
force-measuring system
ISO 12107:2012, Metallic materials – Fatigue testing – Statistical planning and analysis of data
ISO 12108:2018, Metallic materials – Fatigue testing – Fatigue crack growth method
ISO 12135:2021, Metallic materials – Unified method of test for the determination of quasistatic
fracture toughness
ISO/TR 14345:2012, Fatigue − Fatigue testing of welded components − Guidance
ISO 16269-6:2014, Statistical interpretation of data − Part 6: Determination of statistical
tolerance intervals
ASTM-E466-21:2021, Standard Practice for Conducting Force Controlled Constant Amplitude
Axial Fatigue Tests of Metallic Materials
BS 7910:2013, Guide to methods for assessing the acceptability of flaws in metallic structures
CEN/TS 16415:2013, Personal fall protection equipment – Anchor devices – Recommendations
for anchor devices for use by more than one person simultaneously
EN 1090-2:2018, Execution of steel structures and aluminium structures – Part 2: Technical
requirements for steel structures
EN 1090-3:2019, Execution of steel structures and aluminium structures – Part 3: Technical
requirements for aluminium structures
EN 1369:2012, Founding – Magnetic particle testing
EN 1369:1996, Founding – Magnetic particle inspection
EN 1371-1:2011, Founding – Liquid penetrant testing – Part 1: Sand, gravity die and low
pressure die castings
EN 1371-1:1997, Founding – Liquid penetrant inspection – Part 1: Sand, gravity die and low
pressure die castings
EN 1993-1-8:2007, Eurocode 3: Design of steel structures – Part 1-8: Design of joints

– 10 – IEC 61400-8:2024  IEC 2024
EN 1993-1-9:2007, Eurocode 3: Design of steel structures – Part 1-9: Fatigue
EN 1993-1-10:2007, Eurocode 3: Design of steel structures – Part 1-10: Material toughness
and through-thickness properties
EN 1999-1-1:2008, Eurocode 9: Design of aluminium structures – Part 1-1: General structural
rule
EN 1999-1-3:2007, Eurocode 9: Design of aluminium structures – Part 1-3: Structures
susceptible to fatigue
EN 12680-3:2011, Ultrasonic examination – Part 3: Spheroidal graphite cast iron castings
EN 50308:2004, Wind turbines − Protective measures − Requirements for design, operation
and maintenance
DIN 50100:2016, Load controlled fatigue testing – Execution and evaluation of cyclic tests at
constant load amplitudes on metallic specimens and components
FKM Guideline, Fracture Mechanics Proof of Strength for Engineering Components, 2018 (FKM
– RBM-04-18)
IIW-Doc. 2259-152259-15, Hobbacher A., Recommendations for fatigue design of welded joints
and components, International Institute of Welding, 2014
IIW-Doc. XIII-2240r2-08/XV-1289r2-08, Fricke W., Guideline for the Fatigue Assessment by
Notch Stress Analysis for Welded Structures, 2010
VDI 2230-1:2015, Systematic calculation of highly stressed bolted joints – Joints with one
cylindrical bolt
VDI 2230-2:2014, Systematic calculation of high duty bolted joints – Joints with several
cylindrical bolts
VDMA 23902:2014, Guideline for fracture mechanical strength assessment of planet carriers
made of nodular cast iron EN-GJS-700-2 for wind turbine gear boxes, Verband Deutscher
Maschinen- und Anlagenbau e.V.
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Terms and definitions
3.1.1
basquin equation
power law representation of S-N curves

3.1.2
component capacity
maximum static stress the component can withstand
3.1.3
damage equivalent load
equivalent constant range load
load which when repeated a certain number of cycles, causes the same amount of damage as
the original combination of several loads and cycles
3.1.4
defect model
model which is used to substitute the geometrical dimensions of an idealized defect type
3.1.5
design life
minimum intended life of the structure, as used in the design process that the structure shall
survive under fatigue
3.1.6
design load
mechanical loads whether dynamic or static that the structure shall withstand in its design life
3.1.7
failure assessment diagram
FAD
diagram which is used to check if there is any risk of brittle failure of plastic collapse while
performing a fracture mechanic strength assessment
3.1.8
fail-safe
design property of a structure or system which prevents its failure
3.1.9
global stresses
stresses in terms of nominal stresses which are applicable for simple continuous structures
(e.g. beams, shells, plates), where the stress can be derived out of sectional forces by analytical
methods
Note 1 to entry: Notch factors may need to be considered.
3.1.10
impact energy
energy absorbed/required to break a V-notched test sample on pendulum impact testing
machine
3.1.11
limit state
state of a structure beyond which it no longer satisfies the design requirements
3.1.12
local stresses
local stress analysis points at specific regions of a global structure (e.g. at radii, notches) with
consideration of the notch shape

– 12 – IEC 61400-8:2024  IEC 2024
3.1.13
mode I
failure mode I
crack opening mode (in tensile direction) in accordance with FKM Guideline of fracture
mechanics or BS 7910
3.1.14
Paris-Erdogan equation
equation used to compute the cyclic crack growth behaviour
3.1.15
primary structures
structures which are in the main force flow of the nacelle structure (e.g. the planet carrier of the
gearbox)
3.1.16
S-N curve
relation between the number of stress cycles a material can undergo before failure
3.1.17
safe-life
design life period of a system after which it should be removed from service
3.1.18
secondary structures
structures which are not in the main force flow of the nacelle structure (e.g. the housing of the
gearbox)
3.1.19
structural model
model oriented to the shape and dimensions of the defect surrounding structure
3.2 Symbols and abbreviated terms
COV coefficient of variation
EPFM elastic plastic fracture mechanics
FAD failure assessment diagram
FE finite element
FEA finite element analysis
LEFM linear elastic fracture mechanics
LRF load reserve factor against fatigue load
f
LRF load reserve factor against ultimate load
u
LRF load reserve factor with the full detailed model
full
LRF load reserve factor with the simplified model
simplified
LSE limit state equation
PSF partial safety factor
M mean value of δmf
δmf
RNA rotor nacelle assembly (herein used without inclusion of blades)
S/N stress cycle curve for fatigue of materials

a depth of surface cracks, half depth of embedded cracks/ mm
continuous embedded cracks
a initial crack length mm
a critical crack length/limiting crack depth mm
crit
a calculated crack length after calculated lifetime mm
end
A elongation at fracture %
c half crack length of surface and embedded cracks mm
C constant value in crack growth law, e.g. Paris-Erdogan equation
da/dN crack growth rate per load cycle mm/load cycle
D accumulated damage -
E modulus of elasticity (Young’s modulus) MPa
h location of the crack in the depth direction mm
L FAD parameter, ratio of applied load to plastic limit load -
r
J-Integral
J kJ/m , N/mm
0,5
K stress intensity factor
Mpa·m
0,5
K fracture toughness
Mpa·m
C
0,5
K stress intensity factor for crack opening mode I (tensile mode)
Mpa·m
I
0,5
K fracture toughness for crack opening mode I (tensile mode)
Mpa·m
IC
0,5
K FAD parameter, ratio of applied SIF to fracture toughness K
Mpa·m
r mat
0,5
K characteristic value of fracture toughness
Mpa·m
mat
Kv impact energy Joule, Nm
m slope of S/N curve -
M mean stress sensitivity -
n exponent in crack growth law according to Paris-Erdogan -
equation
n counted number of fatigue cycles in load bin i -
i
N number of cycles at knee in characteristic stress-life curve for -
D
test specimens, from constant amplitude tests
th
N -
endurable number of cycles at the i load level, derived from
i
the S/N curve
R stress ratio -
R yield strength MPa
p0,2
V coefficient of variation of δ
δmf mf
t thickness of defect model mm
Z reduction of area at fracture
mm
γ partial safety factor for loads -
f
γ consequence of failure factor -
n
γ partial safety factor accounting for uncertainties in the material -
M
parameters and resistance models
partial safety factor accounting for simplifications in the load
γ
modelling
effect model
– 14 – IEC 61400-8:2024  IEC 2024
γ
mt product of partial safety factors of γ and γ
modelling M
ratio of load reserve factor with full model to load reserve factor
δ
mf
with simple model
0,5
cyclic stress intensity factor
∆K MPa·m
t
annual reliability index
β
0,5
threshold value under cyclic loading
∆K
MPa·m
th
ε total strain limit %
lim
ρ plasticity interaction factor -
σ amplitude of occurring stress cycle MPa
a
σ design fatigue strength of component at N cycles MPa
A D
σ value of σ relevant to loading cycles with minimum/maximum MPa
A,R A
ratio R
σ relevant stress for crack opening mode I (tensile mode) MPa
I
σ endurance limit at knee point of the constant amplitude S/N MPa
D
curve
σ component capacity (e.g. yield strength, tensile strength) in MPa
lim
terms of limiting stress level
σ mean stress MPa
m
σ component stress (e.g. von Mises equivalent stress, first MPa
L
principal stress)
σ net section stress MPa
ref
σ yield strength of the material MPa
Y
4 Reliability considerations
4.1 Approaches to reliability based design
Structures comprising the nacelle and hub components shall fulfil a set of requirements related
to functionality, sustainability and integrity under normal and abnormal events. In addition, the
RNA structure should fulfil a certain level of reliability balancing cost (amount of structure) and
the risk of failure (likelihood of a critical failure). This is conducted through structural reliability
assessments of models established for different limit state functions.
The RNA structure shall be evaluated for the limit states given in IEC 61400-1:2019 (7.6.1.1)
and the structural analysis and reliability assessment shall be based on ISO 2394 and
IEC 61400-1:2019, 7.1. For completeness, the limit states as described in IEC 61400-1:2019
are given below:
• analysis for ultimate strength,
• analysis for fatigue failure,
• stability analysis (e.g. buckling),
• critical deflection analysis.
Further elaboration of these limit states can be found in ISO 2394.
Three approaches for structural design assessment may be implemented as stated in ISO 2394:
• the risk informed approach,
• the reliability-based approach (probabilistic design),
• the semi-probabilistic approach (deterministic design).
Although all three approaches may be applied, wind turbine design including RNA design either
follows the reliability-based -or semi-probabilistic approach. For semi-probabilistic approach,
structural design standards shall be used i.e. IEC 61400-1:2019 or Eurocodes.
Reliability based assessment shall use uncertainty models which shall describe the structure
and its behaviour, through which the design requirements of the structure are quantified,
considering external relevant conditions. Those uncertainty models can be represented by
stochastic variables or processes and a limit state approach to model the relevant failure
scenarios.
Models may be simplified considering decisive factors and neglecting those factors with low
impact, based on proper studies. Uncertainties quantification should follow the guidance given
in ISO 2394 and IEC 61400-1:2019, Annex K.
The requirements for each LSE shall be consistent with the design equations following
deterministic codes of practice as IEC 61400-1 or equations resulting from specific studies
where response function of such component
...