SERVICE SPECIFICATION
DNVGL-SE-0190
Edition December 2015
Project certification of wind power plants
The electronic pdf version of this document found through http://www.dnvgl.com is the officially binding version.
The documents are available free of charge in PDF format.
DNV GL AS
FOREWORD
DNV GL service specifications contain procedural requirements for obtaining and retaining certificates and
other conformity statements to the objects, personnel, organisations and/or operations in question.
© DNV GL AS December 2015
Any comments may be sent by e-mail to [email protected]
This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document. The use of this
document by others than DNV GL is at the user's sole risk. DNV GL does not accept any liability or responsibility for loss or damages resulting from any use of
this document.
Changes – current
CHANGES – CURRENT
General
This is a new document.
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CHANGES – CURRENT .................................................................................................. 3
Sec.1
Sec.2
Sec.3
General ......................................................................................................... 7
1.1
Introduction ...........................................................................................7
1.2
Objective ..............................................................................................10
1.3
Scope ..................................................................................................10
1.4
Application ...........................................................................................11
1.4.1 General ...................................................................................... 11
1.4.2 Definitions .................................................................................. 15
1.5
References ...........................................................................................18
1.6
Procedure ............................................................................................19
1.6.1 Power plant life-cycle phases ......................................................... 19
1.6.2 Certification phases ...................................................................... 20
1.6.3 Applicant .................................................................................... 20
1.6.4 Certification body......................................................................... 21
1.6.5 Interfaces of certification phases ................................................... 23
1.6.6 Validity and maintenance ............................................................. 24
1.6.7 Customer - DNV GL interaction ...................................................... 25
1.6.8 Certification requirements, quality management............................... 26
1.6.9 Standards, codes and additional requirements ................................. 27
1.6.10 Combination of standards ............................................................. 27
1.6.11 Surveillance requirements ............................................................. 28
Development ............................................................................................... 29
2.1
General.................................................................................................29
2.2
Concept ...............................................................................................29
2.3
Design basis ........................................................................................30
2.3.1 General ...................................................................................... 30
2.3.2 Site assessment .......................................................................... 30
2.3.3 Wind turbines ............................................................................. 31
2.3.4 Substation ................................................................................. 35
2.3.5 Power cables .............................................................................. 36
2.3.6 Control station ............................................................................ 36
2.4
Design .................................................................................................37
2.4.1 General ...................................................................................... 37
2.4.2 Wind turbines ............................................................................. 37
2.4.3 Substation ................................................................................. 41
2.4.4 Power cables .............................................................................. 46
2.4.5 Control station ............................................................................ 46
Construction................................................................................................ 48
3.1
General.................................................................................................48
3.2
Manufacturing .....................................................................................48
3.2.1 General ...................................................................................... 48
3.2.2 Wind turbines ............................................................................. 51
3.2.3 Substation ................................................................................. 54
3.2.4 Power cables .............................................................................. 55
3.2.5 Control station ............................................................................ 55
3.3
Transport and installation ...................................................................56
3.3.1 General ...................................................................................... 56
3.3.2 Wind turbines .............................................................................57
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Contents
Contents
Sec.4
Sec.5
Substation ................................................................................. 57
Power cables .............................................................................. 58
Control station ............................................................................ 58
Commissioning, operation and maintenance .............................................. 59
4.1
General.................................................................................................59
4.2
Commissioning .....................................................................................59
4.2.1 General ...................................................................................... 59
4.2.2 Wind turbines .............................................................................. 60
4.2.3 Substation .................................................................................. 61
4.2.4 Power cables .............................................................................. 62
4.2.5 Control station ............................................................................ 62
4.3
Operation ............................................................................................62
4.3.1 General ...................................................................................... 62
4.3.2 Wind turbines .............................................................................. 62
4.3.3 Substation .................................................................................. 63
4.3.4 Power cables ............................................................................... 63
4.3.5 Control station ............................................................................ 63
4.4
Maintenance ........................................................................................64
4.4.1 General ...................................................................................... 64
4.4.2 Maintenance manual .................................................................... 64
4.4.3 Wind turbines .............................................................................. 64
4.4.4 Substation .................................................................................. 64
4.4.5 Power cables ............................................................................... 64
4.4.6 Control station ............................................................................ 64
4.5
In-service/periodic monitoring ...........................................................65
4.5.1 General ...................................................................................... 65
4.5.2 Wind turbines .............................................................................. 66
4.5.3 Substation .................................................................................. 66
4.5.4 Power cables ............................................................................... 66
4.5.5 Control station ............................................................................ 66
Lifetime extension ...................................................................................... 68
5.1
General.................................................................................................68
5.2
Wind turbines.......................................................................................68
5.3
Substation ............................................................................................68
5.4
Power cables ........................................................................................68
Sec.6
Decommissioning ....................................................................................... 69
Sec.7
Repowering ................................................................................................ 70
Sec.8
7.1
General................................................................................................70
7.2
Wind turbines.......................................................................................70
7.3
Substation ............................................................................................71
7.4
Power cables ........................................................................................71
Power plant related services/systems ........................................................ 72
8.1
General.................................................................................................72
8.2
Site-specific type certification ..............................................................72
8.3
Site suitability of onshore wind turbines .............................................73
8.3.1 General ...................................................................................... 73
8.3.2 Site design conditions................................................................... 73
8.3.3 Site-specific design assessment ..................................................... 73
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Contents
3.3.3
3.3.4
3.3.5
Meteorological masts ..........................................................................74
8.5
Navigation and aviation aids of offshore plants ...................................74
8.6
Power
8.6.1
8.6.2
8.6.3
8.7
Shop approval .....................................................................................76
8.8
Helicopter decks ..................................................................................77
8.9
Health, safety and environment ...........................................................78
plant performance .....................................................................75
General ...................................................................................... 75
Power performance ...................................................................... 76
Power plant grid code compliance................................................... 76
8.10 Integration of certificates ...................................................................78
8.10.1 General ...................................................................................... 78
8.10.2 Type certificate according to same edition of standard ...................... 78
8.10.3 Onshore type certificate in offshore project certification .................... 79
8.10.4 Offshore type certificate in onshore project certification .................... 79
8.10.5 Type certificates according to former editions of standards ................ 80
8.10.6 Type certificate or component certificate according to a standard
other than DNV GL ....................................................................... 80
8.10.7 Acceptance of certificates not issued by DNV GL .............................. 80
8.11 Escrow ................................................................................................81
App. A List of documents offshore substation ........................................................ 82
App. B Deliverables example .................................................................................. 84
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Contents
8.4
SECTION 1 GENERAL
1.1 Introduction
The reduction of the levelized cost of electricity is a key goal for the wind industry. The cost reduction may
come from many sources during the development, manufacturing, construction and operational lifetime of
the wind power plant. This implicitly includes increased focus on state-of-the-art technical requirements,
safety aspects and quality. DNV GL has been in the wind energy market for more than three decades. The
experiences gained and lessons learned from European offshore wind power projects in recent years were
taken into account during development of this new service specification (SE). The full life cycle of a wind
power plant is now considered and reference is made to all relevant standards in order to ensure that the
project certification scheme meets market needs and expectations.
DNV GL initiates and is involved in several joint industry projects. The work rendered in exploring new
methodologies, technologies and concepts has aided the industry in establishing relevant standards. The
technical standards provide for the user a basis to develop and execute their projects.
DNV GL also chairs the Committee of Experts (CoE). The CoE, which involves external members, ensure
that the DNV GL service documents benefit several stakeholders and most importantly, the market.
However, the combination with the experiences and know-how is essential to achieve an optimal power
plant performance. Further improvement of reliable quality, stable operation and proper risk management
will help to promote renewable power in a competitive energy sector even better.
In times of cost reduction the independent evaluation is of higher importance to monitor and prove the
state-of-the-art level of safety, quality and reliability. Focusing on reducing capital expenditure costs alone
may have critical quality impacts and may increase the overall lifetime risk and operational costs.
This service specification (SE) specifies DNV GL’s services for project certification of onshore and offshore
wind power plants. It serves as
— facilitator to identify and apply relevant technical standards in a holistic concept for the benefit of the
safety, quality and reliability of a wind power plant
— guidance for developers/owners during the whole life cycle from concept to decommissioning and
repowering of the wind power plant
— guidance for different subcontractors such as designer and manufacturer
— description to meet the state of the art for wind power plants, and to go beyond
— support in optimising the different life-cycle phases of the power plant
— common communication platform for describing the scope and extent of activities performed for
certification of a wind power plant and its assets
— contractual basis for certification of wind power plants or their individual assets.
The Table 1-1 provides an overview of the subjects covered by this services specification. The table serves
also as application oriented guidance. It eases the identification of the relevant sections of this document
with respect to the interests of the reader.
The service specification is divided into eight main sections.
Sec.1 gives an introduction and general guidance on procedure and requirements regarding certification of
wind power plants.
Sec.2 covers the development phase of a wind power plant with the respective certification phases concept,
design basis and design. The subsections by assets simplify the applicability.
Sec.3 covers the construction phase of a wind power plant with the respective certification phases
manufacturing, transport and installation. The subsections by assets simplify the applicability.
Sec.4 covers the operation and maintenance phase of a wind power plant with the respective certification
phases commissioning, operation and maintenance. The subsections by assets simplify the applicability.
Sec.5 covers the lifetime extension phase of a wind power plant with the respective certification phase.
Sec.6 introduces the decommissioning phase of a wind power plant with the respective certification phase.
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Sec.7 introduces the re-powering phase of a wind power plant with the respective certification phase.
Sec.8 contains further wind power plant related services, assets and systems, which can be certified on an
optional basis.
Within this service specification any reference to offshore requirements is meant for offshore projects only.
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Table 1-1 Project certification of wind power plants - document navigation table. numbers in brackets denote section numbers
Wind power plant
life-cycle phase
[1.6.1]
Cert. phase no.
Asset related
project certificate
0
I
II
III
IV
V
VI
VII
VIII
IX
[2.2]
[2.3]
[2.4]
[3.2]
[3.3]
Sec.4
[4.2] Commissioning,
[4.3] Operation
[4.4] Maintenance
[4.5]
Sec.5
Sec.6
Sec.7
Wind turbines
[1.4]
[2.2]
[2.3.3]
[2.4.2]
[3.2.2]
[3.3.2]
[4.2.2], [4.3.2], [4.4.3]
[4.5.2]
[5.2]
Sec.6
[7.1]
Project
certificate
wind turbines
Substation
[1.4]
[2.2]
[2.3.4]
[2.4.3]
[3.2.3]
[3.3.3]
[4.2.3], [4.3.3], [4.4.4]
[4.5.3]
[5.3]
Sec.6
[7.2]
Project
certificate
substation
Power cables
[1.4]
[2.2]
[2.3.5]
[2.4.4]
[3.2.4]
[3.3.4]
[4.2.4], [4.3.4], [4.4.5]
[4.5.4]
[5.4]
Sec.6
[7.3]
Project
certificate power
cables
Control station
[1.4]
[2.2]
[2.3.6]
[2.4.5]
[3.2.5]
[3.3.5]
[4.2.5], [4.3.5], [4.4.6]
[4.5.5]
Sec.5
Sec.6
Sec.7
Project
certificate control
station
Plausibility check
of the wind power
plant concept.
Design basis
covers the site
conditions and
the basis for
design and
subsequent
phases.
Design covers the
steps necessary to
achieve final design
approval. This
includes a sitespecific design
approval of the wind
power plant.
Manufacturing covers
the surveillance
during manufacturing
of the project related
assets.
Transport and
installation covers
the surveillance
during transport and
installation of the
project related
assets.
Commissioning involves all
follow-up evaluation and
on-site inspections during
the implementation of the
project.
Operation and maintenance
relates to the concepts and
manuals to be approved.
Lifetime extension
determines the
remaining lifetime
beyond the design
lifetime of the
plant.
Decommisioning
contains the
planning and
execution of the
decommissioning
and wind power
plant removal.
Repowering
covers the
renewal and
reinstallation of a
wind power plant
at a former power
plant site.
Demonstrating a
feasible concept
of the wind power
project.
Demonstrating
that a feasible
and compliant
catalogue of
applicable
standards and
methods is
prepared and site
conditions are
clarified.
Demonstrating that
Demonstrating that
the design is
the manufacturing of
compliant with the
key components is in
state of the art
compliance with the
defined in the design.
approved design.
Demonstrating that
the transport and
installation is not
interfering with
safety and integrity
of the assets.
Certification
report
Certification
report
Certification
report
Certification
report
Statement of
feasibility
Statement of
compliance
Statement of
compliance
Statement of
compliance
Certification phase
[1.6.2]
Wind power
plant assets
Power plant related
services/systems Sec.8
Site-specific TC [8.2]]
Site suitability [8.3]
Met mast [8.4]
Marking aids [8.5]
Performance [8.6]
Shop approval [8.7]
Helicopter decks [8.8]
HSE [8.9]
Integration [8.10]
Escrow [8.11]
Short description
Added value for
certification customer and
his stakeholders
Final
consistency
checks and
that all
outstanding
issues have
been solved.
Issuing of the
project
certificate.
In-service
involves follow-up
evaluation and
periodic on-site
inspections after
start of operation
and the power
plant lifetime.
Demonstrating that the
assets are ready for a safe
and reliable operation.
Demonstrating
consistency
from
development
to operation.
Independent
assurance of
the assets to
increase
reliability,
safety,
integrity and
value of the
power plant.
Demonstrating
reliable operation
over the lifetime
by independent
survey and
evaluation of the
asset conditions
on a regular basis.
Demonstrating
safe and reliable
extension of the
wind power plant
operation beyond
initial design
lifetime.
Performing a safe
and
environmentally
adequate
decommissioning
and dismantling.
Utilising the
existing site to
increase energy
yield according to
latest state of the
art.
Certification
report
Certification
report
Final
certification
report
Certification
report
Certification
report
Certification
report
Certification
report
Statement of
compliance
Statement of
compliance
Statement of
compliance
Statement of
compliance
Statement of
compliance
Statement of
compliance
Lifetime extension
certificate
Decommissioning
certificate
Repowering or
new project
certificate
Consideration of
conditions of the
project certificate,
operation and
maintenance.
Consideration of
conditions of the
project certificate
and operational
lifetime.
Consideration of
conditions of the
former project
certificate and
operation.
Certification body
deliverables of DNV GL
[1.6.4]
Statement
Certificate
Interfaces
[1.6.5]
Project
certificate
Site conditions
and design basis.
Compliance with
design basis.
Compliance with
design.
Compliance with
design and
manufacturing
observations.
Compliance with design,
manufacturing, transport
and installation
observations.
Compliance of
all previous
certification
phases.
Compliance of
the phases with
the certification
scheme.
Compliance with
design, operation
and maintenance.
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DNV GL AS
1.2 Objective
The objective of project certification is to ensure that the wind power plant will operate safely and cost
efficiently, risks are mitigated and all technical, design and construction requirements are met.
The aim of this document is to provide a flexible certification scheme to address individual needs, reduce
the costs over the lifetime while not compromising on quality. Additional certification phases [1.6.2] or
services Sec.8 can be chosen to enhance the power plant reliability and value. The service specification
serves also to detail and clarify the certification activities and facilitate achieving compliance.
The DNV GL scheme is also intended to cover the requirements implied when using IEC related certification
schemes. The main differentiators of the DNV GL scheme to other schemes such as BEK, BSH and IEC are:
— more guidance and descriptions to facilitate transparency, understanding and application
— most wind power plant relevant topics addressed in one service specification
— flexible concept to address and allow project specific needs
— more additional options for a more holistic concept containing additional phases
— shorter update cycles to facilitate implementation of the latest state-of-the-art technology and processes.
Depending on the specific individual interests and agreed scope the benefits by applying this service
specification can be among others:
— independent approval of the wind power plant to reduce risk in developing and designing
— building of trust in design and construction
— reducing costs by early detection of nonconformities
— confidence in technical integrity
— confirmation that requirements as stated by project developers, investors, operators, manufacturers
governmental and non-governmental organisations are fulfilled
— proof by an independent body to meet the national and internationally acknowledged state of the art
— utilise statements and certificates of authorisations by governmental institutions
— proof to investors or insurer that a third party approval has been successfully performed
— proof of sustainable energy production throughout life cycle
— secure investments and optimise return of investment
— secure better insurance/policy rates; decrease contingencies
— minimising financial project risks
— increasing reliability in the governmentals’ and consumers’ interests
— document stepwise the maturity of the wind power project
— mitigate risks to environment and people
— avoiding damages.
1.3 Scope
The certification scheme described in this service specification has been developed and is applicable for all
phases in the life cycle of onshore and offshore wind power plants. It constitutes a robust means to provide,
through independent certification, evidence to stakeholders that a set of requirements laid down in
standards are met during the development and construction, and is maintained during operation of the wind
power plant.
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1.4 Application
1.4.1 General
This service specification applies to wind power plants and their assets. It has been prepared for general
worldwide application. The following assets of a typical wind power plant are covered by the services
described herein (see Figure 1-1):
— wind turbines and their support structures
— substation(s) including topside(s) and support structure(s)
— power cables
— control station.
Figure 1-1 Offshore and onshore wind power plant assets
Each asset may be further subdivided into components of wind turbines and substations, sections for power
cables and systems for control stations, see Figure 1-2.
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Wind turbine components
Onshore:
Offshore:
• rotor-nacelle assembly
• support structure
• tower
• foundation
- rotor-nacelle assembly
- support structure
- tower
- sub-structure
- foundation
- installations / equipment
• installations / equipment
Substation components
Onshore:
• transformer station
• support structure
• foundation
• installations / equipment
Offshore:
- topside including installations
and equipment
- support structure
- substructure
- foundation
- installations / equipment
Power cables
Onshore:
Offshore:
• asset power cable
• array power cable
• installation, termination,
accessories and
supporting structures
-
asset power cable
array power cable
export power cable
installation, termination,
accessories and
supporting structures
Control station systems
•
•
•
•
•
condition monitoring systems
communication systems
operational systems (incl. SCADA)
protection systems
condition monitoring
Figure 1-2 Wind power plant assets and their components, sections and systems
The wind turbines of a wind power plant can be typically distinguished by the following components, see
Figure 1-3.
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Figure 1-3 Definition of offshore and onshore wind turbine components
The substation(s) of a wind power plant can be typically distinguished by the following components, Figure
1-4.
Figure 1-4 Definition of offshore and onshore substation components
The power cables of a wind power plant can be typically distinguished in the cable route sections illustrated
in Figure 1-1.
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The communication lines of the control station for the monitoring of a wind power plant can typically be
defined as in Figure 1-5. The certification of the control station can prove the capability of controlling wind
power plants of other operators as well.
Figure 1-5 Scheme of a power plant control
The subdivision of the different assets into components, cable route sections or control room systems is
done to enable optional services in certifying single components, cable sections or systems of an asset as
well. Alternatively a component certification according to DNVGL-SE-0441 can be conducted.
This service specification is generally applicable for fixed wind farm installations. In case of floating wind
turbine installations reference is made to DNVGL-SE-0422.
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1.4.2 Definitions
1.4.2.1 Terminology and definitions
Table 1-1 Definitions of verbal forms
Term
Definition
shall
verbal form used to indicate requirements strictly to be followed in order to conform to the document
should
verbal form used to indicate that among several possibilities one is recommended as particularly suitable,
without mentioning or excluding others, or that a certain course of action is preferred but not necessarily
required
may
verbal form used to indicate a course of action permissible within the limits of the document
Table 1-2 Definitions of terms
Term
Definition
accommodation platform
an accommodation platform is an installation which is used to accommodate a number of
people for a longer period of time
asset
term used in the context of wind power plant projects to describe the object to be
developed, manufactured and maintained
In this service specification the term refers either to “wind turbines”, the “substation”, the
“power cables” or “control station”.
cable section
this term is used to split the power cable into different lengths/routes, so called cable
sections
certification
refers to third-party issue of a statement or certificate, based on a decision following
review, that fulfilment of specified requirements has been demonstrated related to
products, processes or systems (ISO 17000)
component
a main part of an asset
In this service specification, the term refers to rotor–nacelle-assembly, part of the support
structure of the wind turbine (tower, sea ice substructure and foundation), topside
equipment, and parts of support structure for substation (topside structure, substructure
and foundation). The term main component is used for example to describe the main
transformer, converter, switchgear, cables, rotor blade, rotor hub, main bearing, gearbox
and generator of a wind turbine or substation.
control station
the control station is an onshore or offshore based facility to control the wind power plant
converter station
a converter station is an installation at which electricity is received from the offshore wind
turbines of a wind farm and/or one or more substations
It is used for the conversion from high voltage alternating current to high voltage direct
current for onward transmission of electrical energy to an onshore converter station.
customer
DNV GL’s contractual partner (applicant)
design brief
document for describing methodologies for design calculations
design lifetime
the time period that was consider during strength verification (e.g. of a wind turbine) when
the device was designed
Alternatively named as (original) design lifetime in the context of lifetime extension.
foundation
part of the support structure for a wind turbine or substation that transfers the loads acting
on the structure into the soil
J-tube
curved tubular conduit designed and installed on a structure to support and guide one or
more pipeline risers or cables (EN 12495)
lifetime extension
additional lifetime beyond the (original) design lifetime
offshore wind power plant
term referring to the assets of an offshore wind farm including total number of offshore
wind turbines, support structures, substations with topside and support structure and
power cables and control station
onshore wind power plant
term referring to the assets of an onshore wind farm including total number of onshore
wind turbines, support structures, and if relevant, substations, power cables and control
station
operating life / service life
lifetime from commissioning to decommissioning of a component or asset
total lifetime
lifetime after manufacturing of the component or asset until deconstruction
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Table 1-2 Definitions of terms (Continued)
Term
Definition
optional services
optional services are services which are not part of the scope which is required in order to
obtain statement of compliance and project certificates
outstanding issue
the term outstanding issue is used to denote a deviation from standards and technical
requirements specified in the certification agreement, and which needs to be completed for
full compliance
primary structure
the primary structure consists of the load-bearing structure that transfers permanent
loads, life loads and environmental loads, caused by gravity and environment and actions
on the support structure, to the soil
Structural parts the failure of which will have substantial consequences to the structural
integrity shall be classified as primary structure.
project certificate
a document signed by DNV GL and affirming that, at the time of assessment, the asset
referred to in the certificate met the requirements stated in the normative documents
recommendation
non-mandatory advice
secondary structure
secondary structures are e.g. boat landings, access ladders, access platforms, internal
platforms, internal ladders, landing points at transitions piece and hoisting point
special structure
same as primary structure
In addition the structural parts are subject to particularly arduous conditions (e.g. stress
condition that may increase the probability of brittle fracture, multi-axial stresses).
substation
term referring to transformer stations or converter stations or platforms, with or without
accommodations
An onshore or offshore substation may be defined as an integral asset of the wind farm
project or as a separate asset for DNV GL project certification. Whenever, in this service
specification the term is used in general, it describes the substation including the support
structure, as this is the power transferring unit.
substructure
term referring to the part of the support structure for a wind turbine which extends
upwards from the soil and connects the foundation and the tower
The term is also used to designate the part of the support structure for a substation which
extends upwards from the soil and connects the foundation and the topside or platform.
support structure
the support structure of a wind turbine is defined as the structure below the yaw system
of the rotor-nacelle assembly and includes tower structure, substructure and foundation
The term is also used to designate the structure below of the topside structure and includes
substructure and foundation of a substation.
transformer station
a transformer station is an installation at which electricity is received from the offshore
wind turbines of a wind farm and converted from medium voltage to high voltage in order
to facilitate transmission of electricity to an onshore transformer station or to an offshore
converter station using AC cables
verification
refers to the confirmation, through the provision of objective evidence, that specified
requirements have been fulfilled (ISO 9000)
wind power plant
energy producing facility, comprising all its main assets to produce power and transfer it
into the power grid
Typically also known as wind farm. In this service specification the term wind power plant
is associated with the main assets wind turbines and substation(s) including their support
structures, power cables and the control station.
wind turbine
system which converts kinetic wind energy into electrical energy
Whenever, in this service specification the term is used to describe the wind turbine in
general, it describes the rotor-nacelle assembly including the support structure, as this is
the power generating unit.
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1.4.2.2 Abbreviations and symbols
Abbreviations and symbols used in this service specification.
Table 1-3 Abbreviations
Abbreviation
In full
AC
alternating current
ALS
accidental limit state
BEK
Bekendtgørelse om teknisk certificeringsordning for vindmøller
BSH
Bundesamt für Seeschifffahrt und Hydrographie (Federal Maritime and Hydrographic Agency)
Cert.
certification
CMS
condition monitoring system
CoE
Committee of Experts
CIGRÉ
Conseil International des Grands Reseaux Électriques
EERA
escape, evacuation and rescue analysis
EMC
electromagnetic compatibility
FAT
factory acceptance test
FEM
finite element method
FLS
fatigue limit state (is one of the ultimate limit states)
FMEA
failure mode and effect analysis
GCC
grid code compliance
GWO
Global Wind Organisation
HAZID
hazard identification
HAZOP
hazard and operability study
HSE
health, safety and environment
IEC
International Electrotechnical Commission
ISO
International Organization for Standardization
ITP
inspection and test plan
LVRT
low voltage ride through
met
meteorological
NAI
normally attended installation
NDT
non-destructive testing
NUI
normally unattended installation
PM
periodic monitoring
QRA
quantitative risk analysis
RNA
rotor-nacelle assembly
RP
DNV GL recommended practice
SCADA
supervisory control and data acquisition
SDC
site design conditions
SE
DNV GL service specification
SLS
serviceability limit state
SSDA
site-specific design assessment
ST
DNV GL standard
TC
type certification
ULS
ultimate limit state
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1.5 References
This document makes reference to relevant international documents, DNV GL documents and other
documents. Unless otherwise specified in the certification agreement or in this service specification, the
latest valid revision of each referenced document applies.
Table 1-4 DNV GL service documents
Reference
Title
DNVGL-RP-0360
Subsea power cables in shallow water (planned published 2016)
DNVGL-RP-0416
Corrosion protection of offshore wind turbines (planned published 2016)
DNVGL-RP-0419
Analysis of grouted connections (planned published 2016)
DNVGL-RP-0440
Electromagnetic compatibility of wind turbines (planned published 2016)
DNVGL-SE-0073
Project certification of wind farms according to IEC 61400-22
DNVGL-SE-0074
Type and component certification of wind turbines according to IEC 61400-22
DNVGL-SE-0124
Certification of grid code compliance (planned published 2016)
DNVGL-SE-0263
Certification of lifetime extension of wind turbines (planned published 2016)
DNVGL-SE-0420
Certification of meteorological masts
DNVGL-SE-0422
Certification of floating wind turbines (planned published 2016)
DNVGL-SE-0436
Shop approval in renewable energy (planned published 2016)
DNVGL-SE-0439
Certification of condition monitoring (planned published 2016)
DNVGL-SE-0441
Type and component certification of wind turbines (planned published 2016)
DNVGL-ST-0076
Design of electrical installations for wind turbines
DNVGL-ST-0125
Grid code compliance (planned published 2016)
DNVGL-ST-0126
Support structures for wind turbines (planned published 2016)
DNVGL-ST-0145
Offshore substations (planned published 2016)
DNVGL-ST-0262
Lifetime extension of wind turbines (planned published 2016)
DNVGL-ST-0358
Certification of offshore gangways for personnel transfer
DNVGL-ST-0359
Subsea power cables (planned published 2016)
DNVGL-ST-0437
Loads and site conditions wind for turbines (planned published 2016)
DNV-OS-C401
Fabrication and testing of offshore structures
DNV-OSS-304
Risk based verification of offshore structures
DNV-RP-D201
Integrated software dependent systems
GL-IV-1
Rules and guidelines – IV Industrial services –Part 1: Guideline for the certification of wind
turbines
GL-IV-2
Rules and guidelines – IV Industrial services –Part 2: Guideline for the certification of offshore
wind turbines
Table 1-5
IEC documents
Reference
Title
IEC 61400-12-1
Wind Turbines – Part 12-1: Power performance measurements of electricity producing wind
turbines
IEC 61400-21
Wind turbines - Part 21: Measurement and assessment of power quality characteristics of grid
connected wind turbines
IEC 61400-22
Wind turbines – Part 22: Conformity testing and certification
IEC 82079-1: 2012
Preparation of instructions for use | Structuring, content and presentation | Part 1: General
principles and detailed requirements
IEC CS CBC 6A
IEC Clarification sheet, project certification, recognition arrangement, no. CBC 6A
IEC 61400-25 series
Communications for monitoring and control of wind power plants
IEC/TS 61400-26-1
Wind turbines - Part 26-1: Time-based availability for wind turbine generating systems
IEC/TS 61400-26-2
Wind turbines - Part 26-2: Production-based availability for wind turbines
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Table 1-6 ISO documents
Reference
Title
ISO 9000
Quality management systems - Fundamentals and vocabulary
ISO 9001
Quality management systems – Requirements
ISO/IEC 13273-1
Energy efficiency and renewable energy sources – common international terminology – Part 1:
Energy efficiency
ISO/IEC 13273-2
Energy efficiency and renewable energy sources – common international terminology – Part 2:
Renewable energy sources
ISO/IEC 17000
Conformity assessment – vocabulary and general principles
ISO/IEC 17065
Conformity assessment – requirements for bodies certifying products, processes and services
ISO/IEC 17025
General requirements for the competence of calibration and testing laboratories
ISO 55000
Asset management – overview, principles and terminology
ISO 55001
Asset management – management systems – requirements
ISO 55002
Management systems – guidelines for the application of ISO 55001
Table 1-7 Other documents
Reference
Title
BSH no. 7005
Standard design of offshore wind turbines, federal maritime and hydrographic agency
CIGRÉ TB 279
Maintenance for HV cables and accessories
EN 1090-2
Execution of steel structures and aluminium structures - Part 2: Technical requirements for steel
structures
EN 12495
Cathodic protection for fixed steel offshore structures
EN 50308
Wind turbines – protective measures – requirements for design, operation and maintenance
GWO BST
Global wind organisation standard basic safety training, version 5, 2013-11-21
IEEE 762
IEEE Standard - Definitions for use in reporting electric generating unit reliability, availability, and
productivity
1.6 Procedure
1.6.1 Power plant life-cycle phases
The main power plant life-cycle phases are typically as shown in Figure 1-6.
Development
Construction
Operation and
Maintenance
Decommissioning
Figure 1-6 Main power plant life-cycle phases
The power plant life-cycle phases can be supported during the project execution by respective certification
phases to prove their feasibility and reliability. The overview Figure 1-1 provides guidance in selecting the
relevant certification phases (and sections of this service specification) meeting the power plant life cycle.
Complementary phases are listed as well, which can be seen as proposal to complete the life cycle of a
power plant. The related certification phases are described in the following section [1.6.2].
The wind power plant design lifetime is typically 20 years. The cost reduction pressure in the power sector
makes it necessary to consider also to increase the design lifetime for example to 25 or 30 years. The wind
power plant design lifetime shall be chosen by the developer and shall be taken into consideration from the
project beginning through all relevant phases.
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1.6.2 Certification phases
The five certification phases within the project certification extend from design basis to commissioning,
operation and maintenance, see Figure 1-7 (darker arrows). The certification scheme proposed in this
service specification expands these certification phases by further optional certification phases such as
concept and decommissioning, see Figure 1-7 (brighter arrows).
Figure 1-7 Certification phases for wind power plants
Each phase will be completed by a statement of compliance.
The following certification phases are shown in Figure 1-7:
— Concept: covers the concept development at the beginning of the wind power project.
— Design basis: covers the site conditions and the basis for design.
— Design: covers the steps necessary to achieve final design approval. This includes the site-specific
design approval of the integrated structural system of the project related assets.
— Manufacturing: covers the surveillance during manufacturing of the project related assets.
— Transport and installation: covers the surveillance during transport and installation of the project related
assets.
— Commissioning: involves all follow-up evaluation and on-site inspections during the implementation and
start of operation of the power plant.
— In-service: involves follow-up evaluation and periodic on-site inspections after start of operation and
during the subsequent in-service period.
— Lifetime extension: covers the subject to continue to operate a wind power plant over its initial design
lifetime.
— Decommissioning: contains the planning and execution of a wind power plant decommissioning and
removal.
— Repowering: covers the renewal and reinstallation (typically upgrading) of a wind power plant at a
former power plant site.
1.6.3 Applicant
1.6.3.1 General
The typical project certification applicant is the wind farm developer, owner or operator. The applicant or
customer is the direct contractual partner for whom DNV GL is performing the verification and certification
services.
Guidance note:
Typically, but not necessarily, DNV GL carries out the verification and certification work related to the
—
—
—
site conditions and overall wind power plant for the project developer
wind turbine type for the wind turbine supplier
support structures, substation and power cable for the selected contractor.
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1.6.3.2 Deliverables
The documentation submitted for the certification process shall be complete and self-explanatory. The
content shall meet the requirements of the agreed and applied standards. All relevant documentation shall
be subject oriented and in a logical sequence to facilitate cross checking between documents (e.g. design
basis, design, manufacturing, transport, installation, commissioning etc.). Each document shall be named
explicitly by e.g. title, report no., page no., date and a revision description table. Furthermore the
documents should be signed officially at least by the author and/or the approver to identify responsibilities.
Alternatively the documentation submitted shall bear unambiguous evidence of having been subject to
designer’s and/or owner’s quality management system.
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The documentation, including standards and codes as well as other requirements and specifications, shall
be prepared in the English language, unless otherwise agreed in writing between DNV GL and the customer.
All documentation for evaluation shall be forwarded to DNV GL in electronic form, preferably as pdf-files.
Other forms of documentation such as print-outs can be an alternative, if agreed.
Guidance note:
The documents submitted should be in a logical work package basis per certification phase (see Figure 1-7) and cover the
requirements as stipulated in the respective section of this service specification to facilitate the process.
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1.6.4 Certification body
1.6.4.1 General
DNV GL has been audited on a regular basis to prove its competence and independency. This is processed
and documented by the accreditation according to ISO/IEC 17065. Among others DNV GL is accredited and
internationally acknowledged according to the following project certification schemes:
— BSH no. 7005 Standard Design of Offshore Wind Turbines
— DNVGL-SE-0073 Project certification of wind farms according to IEC 61400-22
— DNVGL-SE-0190 Project certification of wind power plants
— GL-IV-1 Guideline for the Certification of Wind Turbines
— GL-IV-2 Guideline for the Certification of Offshore Wind Turbines
— IEC 61400-22 Conformity Testing and Certification
— BEK 73 Executive order on the technical certification scheme for wind turbines.
The current accreditation certificate of DNV GL shall be provided on request.
Guidance note:
Reference lists and list of certifications are published on www.dnvgl.com/renewables-certification.
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1.6.4.2 Deliverables
Certification deliverables in the context of this service specification are documented by certification reports,
statements of compliance, final certification report and the project certificate, see Figure 1-8.
Certification Report
Design Basis
Certification Report
Certification Report
Design
Manufacturing
Certification Report
Certification Report
Transport and
Installation
Commissioning,
Operation, Maintenance
Final Certification Report
Project Certificate
[Asset X]
Project Certificates of
other assets
Final Certification Report
Project Certificate
Wind Power Plant
Legend:
Certification Report
Certification Report
Statement of
Compliance
In-Service
Project Certificate
Figure 1-8 Overview on certification deliverables
DNV GL project certificates can be issued for onshore or offshore wind power plants or its individual assets
as defined in this service specification. The project certificate for a wind power plant includes all four assets
ensuring the evaluation of the interfaces considering the wind power plant with its four assets as a whole.
A project certificate for a wind power plant contains the assets:
— wind turbines
— substation(s)
— power cables
— control station.
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A project certificate is supported by at least the following certification deliverables:
— statement of compliance design basis
— statement of compliance design
— statement of compliance manufacturing
— statement of compliance transport and installation
— statement of compliance commissioning, operation and maintenance
— final certification report.
A statement of compliance will be issued after successful completion of a certification phase. Each statement
of compliance is supported by (a) phase related certification report(s).
After completion of the certification phases a final certification will be performed. During the final
certification DNV GL shall check that all outstanding issues have been solved. All parts of the certification
(reports, statements and type certificate) shall be consistent and complete with regard to the assets subject
to certification. A DNV GL project certificate will be issued after successful completion of the final
certification.
The project certificate(s) may be maintained throughout the in-service phase. For in-service a certification
report and statement of compliance is issued for maintenance of project certificate, see [1.6.6].
Certification reports and statements of compliance can also be issued for subdivisions of the different assets
into components, cable route sections or control room systems as described in [1.4.1].
App.B illustrates an example of a DNV GL project certificate and statement of compliance.
In the event that full compliance is not obtained during the wind power plant certification, the deliverables
will depend on the nature of the lack of compliance. Three deliverable outcomes are available depending on
the lack of compliance and described in the following:
— No outstanding issue. Statement(s) of compliance with the accompanying DNV GL certification reports
will be issued. A DNV GL project certificate will be issued based on the statements of compliance for the
asset verified.
— Non-safety critical outstanding issues. One or more provisional statement(s) of compliance will be
issued with the outstanding issue(s) listed in the statement(s) of compliance. A provisional project
certificate can be issued on request, which points out the outstanding issue(s). The outstanding issues
listed on the statements of compliance will be repeated in the project certificate. Specific description of
the outstanding issues will be given in the accompanying DNV GL certification reports. As outstanding
issues become closed, an updated statement of compliance and finally a project certificate with no
outstanding issues can be issued.
— Safety critical outstanding issues. Statement(s) of compliance and the project certificate will not be
issued. DNV GL will deliver the DNV GL certification report(s) that will list the outstanding issues whose
rectification is required before the statement of compliance can be issued.
On request intermediate certification reports can be issued to document the certification status [1.6.7].
1.6.5 Interfaces of certification phases
The wind power plant life-cycle phases as displayed in Figure 1-6 are building on each other and are
interconnected by various relationships.
During project development, the design basis lays out requirements for subsequent phases. Further
examples are aspects of transport and installation to be considered already during the design phase as well
as manufacturing processes that have to fulfil certain criteria that have been underlying the assessment of
the design.
The certification interfaces shall be considered during the execution of the certification process. Figure 1-9
provides an overview of the interfaces and inputs to be considered implementing the type certificate and
during project certification.
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Type Certificate
Technical specifications, drawings, manuals
II
Design
III
Manufacturing
Report on observations
IV
Transport and
Installation
Certification phase
Applicable for type certified assets
Transfer of certified documentation
from one phase to another
Documentation proving that assets are applicable
V, Commissioning,
Operation,
Maintenance
Manuals and plan for
Periodic monitoring inspections
Report on ovservations
Techn. specifications, drawings, input to manuals
List of applicable standards, guidelines, requirements
I
Design Basis
VI
In-Service
Figure 1-9 Interfaces of the certification phases
The purpose of the final certification report as described in [1.6.4.2] is to assess the interfaces and check
for consistency and completeness with regard to the phases and assets (certification reports and statements
of compliance, type certificate) described in this service specification.
1.6.6 Validity and maintenance
The validity of the wind power plant project certificate is limited to the design lifetime of the installation
stated in the project certificate.
Maintenance of the project certificate is conditional on periodic in-service evaluation by DNV GL and
requires the following:
— maintenance and repair is carried out according to the approved maintenance manuals
— periodic inspections by DNV GL or other acknowledged in-service inspectors during the validity period
of the certificate to check that the wind power plant corresponds with the certified design, see [4.5]
— annual reporting by the customer covering the certified wind power plant (or assets) including
information about:
— the operation statistics of the on the site installed certified assets; e.g. annual yield, availability
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— abnormal or deviant operating experience or operating failures as well as their repair and minor
modifications
— reporting by the customer of planned major repairs and modifications without delay and in sufficient
time to allow for evaluation by DNV GL before implementation and to enable updating of the design
assessment and others, if relevant
— major modifications and repairs shall be performed with DNV GL approval.
Following a successful completion of an in-service evaluation, a certification report and the statement of
compliance in-service that validates the project certificate will be issued, see [4.5].
The project certificate shall be confirmed one year after the date of first issuance by a statement of
compliance in-service.
Guidance note:
It is not expected that all assets are inspected by an independent inspector within the first year of operation, see [4.5.1]. The
independent review is based on provided documentation as described in this section above.
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In case an in-service agreement for the power plant is in place between DNV GL and the customer, the
interval of confirmation of the project certificate is set to the duration of the service agreement plus one
year; however, five years is the maximum period of confirmation. The certification report in-service will be
issued yearly, the related statement of compliance at the end of the validity of the agreement or every five
years, whatever applies earlier.
Guidance note:
The in-service certification phase is optional. However, it becomes mandatory, if maintenance of the project certificate is chosen. It
is strongly recommended to perform the maintenance of the project certificate for the complete lifetime. The resuming of certificate
maintenance of a suspended or invalid project certificate can be difficult or even impossible. Maintaining the validity by in-service
increases the value of the power plant and documents the increase for a possible sale.
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Re-certification may be necessary, if additional requirements for maintenance of the project certificate are
set by national authorities or by the applicable design code or standard during the validity period of the
certificate.
Safety relevant incidents shall be reported to DNV GL without delay. DNV GL shall evaluate the incidents.
In case of a serious defect of the asset in question, DNV GL shall suspend the certificate until elimination of
the cause. The certificate shall be reaffirmed after successful evaluation of the rectifying measure.
Provisional statements or provisional certificates have a maximum validity of one year. During this period
the customer shall document the closing of the outstanding issues (see [1.6.4.2]) and these shall be
evaluated by DNV GL.
1.6.7 Customer - DNV GL interaction
The project certification provides the customer an independent evaluation and an independent proof of
compliance of the wind power plant considering specific standards and needs.
This service specification should be referred to as a contractual document in the project certification
agreement between the customer and DNV GL. This document specifies the obligations of the customer
when his wind power plant or its assets are to become certified, as well as DNV GL’s service obligations to
the customer.
The deliverables by DNV GL shall be agreed in detail between the customer and DNV GL as part of the
contract. The DNV GL project certificate is issued when all of the required statements of compliance
according to the project certification scheme have been issued and the final evaluation is done successfully.
The deliverables and further details are listed in [1.6.4.2].
Each certification phase for an asset, component, system or power cable section can be verified separately
according to the DNV GL project certification scheme. Timeframes of the verification and certification
activities shall be discussed and agreed between the customer, DNV GL, and suppliers before
commencement of the work.
The certification scheme described here contains issuing one project certificate per asset. This allows the
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involvement of asset related contractors in the project certification, which eases the involvement of
additional resources from the applicant’s perspective.
For a new project under development, uncertainties should be reduced early in the development and
changes should be managed in an effective way. Early involvement of DNV GL having an in-depth
understanding of the activities required may lead to better decisions with an appropriate risk profile.
Guidance note:
Cost, influence
Identification of risks and their mitigation will be less costly at an early design stage compared to a later stage (Figure 1-10). A
reduction of interfaces can help reducing project risks. This service specification provides the respective information to influence all
project phases from the beginning.
Ability to
influence
Cost of change
Concept
Commissioning
Time
Figure 1-10 Effects of early identification and mitigation of risk
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In the course of the certification project DNV GL will issue intermediate status reports on request or at
agreed intervals. Provisional statements of compliance and project certificates may be issued, depending
on the grade of outstanding issues with a limited validity, see [1.6.4.2] and [1.6.6].
The evaluation of single assets’ components, systems or power cable sections can be offered optionally to
enable issuing statements of compliance after successful completion of the respective activities.
On request, optional services to DNV GL project certification may be performed and will be documented
separately see [1.6.2] and Sec.8.
1.6.8 Certification requirements, quality management
In general subsequent certification phases should not be initiated before previous or dependent phases are
completed and approved. For example, prior to evaluation of the manufacturing phase, the design basis
phase and the design phase should both be completed and approved. Alternative ways are possible and can
be agreed with DNV GL.
The customer shall provide evidence of a consistent quality management system covering all aspects of the
development and operation of the wind power plant or its assets. In particular the customer shall show
quality relevant procedures to DNV GL for his procedures and his suppliers, covering design, manufacturing,
transportation, installation, inspection, operation and documentation processes. When a valid certificate for
ISO 9001 of an accredited certification body is in place, DNV GL will reduce this assessment to a plausibility
check.
The quality management system certificate according to ISO 9001 attests quality capability for example of
a manufacturing facility. This will not necessarily imply that the purchasers’ specification and often
ambitious component requirements and quality expectations are met. Measures to cover these expectations
and prove them independently are listed in this service specification, e.g. see [3.2].
Test reports delivered shall be prepared by accredited testing laboratories and meet the requirements of
ISO/IEC 17025 and relevant standards for the specific testing. For non-accredited testing laboratories,
DNV GL shall verify that the laboratories carry out their work according IEC/ISO 17025, as applicable.
For the use of information from a component or type certification of a rotor-nacelle assembly or wind turbine
type for the purpose of the project certification DNV GL shall be given written permission by the component
or type certificate owner, see also [2.4.2] and [8.10].
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1.6.9 Standards, codes and additional requirements
This service specification provides the key references to the technical requirements to be fulfilled for the
assets subject to project certification.
The standards, codes and requirements which form the basis for the wind power project shall be listed and
agreed in the design basis document during the certification phase design basis. For the site in question,
relevant statutory requirements shall also be listed. Such requirements could be decommissioning and
safety related issues such as requirements for embarkation and rescue.
Other requirements relevant for the project certification such as requirements for the grid connection and
specific requirements of the owner and the grid operator shall be listed as well.
The standards, codes and additional requirements which are applicable for the project and site in question,
will be verified for compliance with the design prerequisites of the project and for completeness and
adequate suitability and applicability.
This service specification and referenced DNV GL standards present the state of the art in wind power plant
technology mainly with respect to the strength, quality and safety of the plants.
Additional requirements for the wind power plant resulting from, e.g.
— local regulations
— manned / unmanned operation
— shipping and navigational requirements
— lighting and marking aids
— boat / helicopter services
— personnel health and safety
shall be taken into account besides the requirements defined in this service specification. This service
specification provides additional guidance with respect to some of the listed topics.
For dated standards and codes, only the edition cited applies. For undated references, the latest edition of
the referenced document including any amendments applies. In case of deviations from this rule, it shall be
agreed on an individual basis and in advance with DNV GL.
1.6.10 Combination of standards
DNV GL certification according to internationally recognized standards shall follow the principles described
in this service specification. Wherever combinations of such standards are used, the exact terms of
reference and documents to be issued shall be agreed and specified in detail in the design basis.
The application of standards other than those referenced in this document does not allow for a reduction of
the targeted safety as described in this services specification and related technical standards. DNV GL
reserves the right to ask for additional requirements to cover issues essential to the certification process if
they are not covered by the standards in question.
It is not allowed to combine safety measures of different standard systems due to the possible differences
in the underlying safety philosophies of the different standard systems.
In case standards are combined, caution shall be exercised and the choice of standards is subject to
acceptance by DNV GL.
Guidance note:
Within a particular standard, aspects such as requirements for partial safety factors for calculations of design loads and design
resistance are generally mutually balanced to give an overall acceptable safety level. In another standard with the same overall
acceptable safety level, the requirements for the safety factors may have been balanced differently. Picking requirements for load
factors from one standard and material factors from another can therefore easily result in unpredictable, and possibly too low or
unnecessary high, safety levels.
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1.6.11 Surveillance requirements
The customer, or other entity having legal responsibility for the premises where DNV GL personnel will
work, shall inform DNV GL of any safety and health hazards related to the work and/or any safety measures
required for the work, prior to starting the work, or if such information is not available at that time, during
the performance of the work.
Whenever DNV GL undertakes to work on site, the customer shall provide all adequate safety measures to
ensure a working environment that is safe and in accordance with all relevant legislation.
If at any time during the execution of work on site a DNV GL employee judges that the work situation is
unsafe then work shall be suspended until such situation has been made safe.
DNV GL will report critical findings to the customer immediately after any surveillance. DNV GL shall issue
surveillance reports to the customer and the frequency of these shall be agreed with the customer. The
report shall describe the extent of the surveillance including findings, nonconformities and possible
recommendations.
In offshore projects the transport surveillance can be combined with the marine warranty survey, if both
are carried out by DNV GL or other acknowledged marine warranty surveyor and agreed at the beginning
of the project. Caution should be taken as the scope of the transport surveyor and marine warranty surveyor
differ significantly with respect to the project certification purpose. Briefings and written approvals for
consent between the parties with respect to availability and instructions of the marine warranty surveyor
for the success of the transport surveillance are required.
With reference to installation surveillance it shall be considered that the DNV GL surveyor for project
certification shall be present during the installation to verify compliance with previous certification phases.
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SECTION 2 DEVELOPMENT
2.1 General
This section provides guidance which should be considered from the early beginning of the project during
the conceptual phase to the final design of the wind power plant. The aim is to make use of the most
influencing phase of the whole project (see Figure 1-10) to keep as low as possible the cost of change and
as high as possible the ability to adapt to the most convenient life-cycle costs.
2.2 Concept
The design of a wind power plant is a major task, influenced by many aspects. It is useful to have a look at
the whole arrangement of the plant in the very early planning stages by a third party. By this, the risks of
the design approaches shall be identified and evaluated to enable a possible trade-off between risks,
timeline, costs and gains.
The concept of a new wind power plant is checked for plausibility by DNV GL. The following topics are looked
at regarding their technical impact and feasibility:
1) site wind conditions, mean / extreme wind speed
2) water depth, currents and mean / extreme sea state, if applicable
3) reliability of the sources of item 1. and 2.
4) grid connection possibilities resp. distance to main consumers, local rules of authorities
5) logistic accessibility for large components and human resources
6) general soil conditions, depth of effective foundation level below (soil or water) surface
7) general foundation type (on- or offshore, if offshore: fixed or floating)
8) general plant layout
9) size, type and number of wind turbines and their distances to each other
10) control of wind power plant
11) homogeneity of life-cycle concept of wind power plant, i.e. trade-off between dimensioning of
components and maintenance / repair frequency, if applicable
12) standards to be applied for design and their interfaces. Advantages and disadvantages of different
standard series and their holistic concept (i.e. fit of the design standard to the planned manufacturing
standard).
13) risk analyses for different possible design approaches for the components of the wind power plant.
Trade-off between high risk approach and its possible gains/losses as compared to conventional design.
14) reviewing extent, contents and time horizon of test series required for newly innovated design parts or
components.
The review of the concept is an optional certification phase. It is a technical plausibility check during the
genesis of the preliminary conceptional work for the wind power plant. DNV GL’s review accompanies the
actual concept work, checking each major step regarding its implications for a later certification process.
If applied, the concept phase considerably eases the later certification process, as the critical questions are
known and have been duly handled long time before the actual manufacturing begins. Changes in this early
design phase are easily accomplished, while later, during the certification process with a less mature
concept, any design change is very costly, both in time and money.
As new promising innovations often fail due to small and easily avoidable issues, the plausibility check may
in these cases, at least partially, go into the detail design process to assure a feasible concept which can be
developed further.
Once the evaluation of the concept has been successfully completed, DNV GL will issue a certification report
and on request a statement of feasibility, listing the assets subject to evaluation.
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2.3 Design basis
2.3.1 General
The design basis shall include all parameters relevant for the wind power plant design, stating the methods
to be used. If values are taken from background documents, those shall be referenced and handed in. The
design basis will be assessed for plausibility, quality issues and completeness.
In particular, choices, supplementary information and deviations relating to the design issues shall be
clearly stated in the design basis.
Developing the design basis is a combined effort by several parties (contributors) including reports on
specialized topics supplied by expert consultants. The coordination of the interfaces between the
contributor’s documents is facilitated if this responsibility is clearly anchored in the customer’s project
organization.
With information from several contributors information on the same topic may be provided in more than
one document. In case of multiple data or documentation on the same topic the customer is requested to
clearly inform DNV GL, which data/documentation is part of the design basis and subject to evaluation and
what to disregard.
A way to address the above is in a document that describes the data sources to be applied in the design
basis and which project partner is responsible for supplying which information.
Once the evaluation of the design basis has been successfully completed, DNV GL will issue a certification
report and a statement of compliance for design basis, listing the assets subject to evaluation.
A certification report and a statement of compliance for site assessment only can be issued on request.
2.3.2 Site assessment
2.3.2.1 General
One integral part of the design basis are the site design conditions which denote all external influences
acting on the wind turbine and auxiliary structures of the wind power plant from outside.
The following site design conditions shall be documented:
— site and wind power plant configuration incl. cable route
— wind conditions
— marine conditions (bathymetry, waves, tides, correlation of wind, waves and current, coastal zone
dynamics (for the cable landfall), sea ice, scour, marine growth etc.)
— soil and geotechnical conditions
— other environmental conditions, such as: salt content of the air, temperature, ice and snow, humidity,
lightning strike, solar radiation etc.
— electrical grid conditions
— influence of nearby wind power plants
— terrain roughness and terrain complexity
— seismic influence, if present
— other site conditions, such as traffic, disposed matters, pipelines and existing cables.
These site design conditions including reports on measurement results and further analyses will be assessed
for plausibility, quality and completeness.
2.3.2.2 Geotechnical site conditions
Geotechnical site assessment means getting information about the soil or rock conditions in the place of the
planned wind power plant. The target is to design the substations’ and turbines’ foundations as cost and
time effective as possible within the limitations of the state of the art.
The soil investigations shall provide all necessary geotechnical design data for the foundation. They may be
divided into geological studies, geophysical surveys and geotechnical ground investigations. Further details
can be found in the DNVGL-ST-0126.
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Soil investigations should normally comprise the following types of investigation:
— site geological survey to find out, whether the subsoil conditions are homogeneous or not.
— in-situ testing on each position of platform and turbine
— soil and rock sampling with subsequent static laboratory testing
— topography survey of the seafloor, if applicable.
They may also comprise, if useful in special circumstances or required by local authorities:
— geophysical investigations for correlation with borings and in-situ testing
— shear wave velocity measurements for assessment of maximum shear modulus
— cyclic laboratory testing.
The extent and contents of a ground investigation programme is not a straight-forward issue and will
depend on the foundation type. The local conditions strongly determine the type and extent of the site
assessment.
It should be emphasised, that for the most commonly used foundation types such as monopiles and jackets,
very detailed and distinct information for the individual location of each single platform and turbine is
required, while the vast space between the various sites is of little interest.
If little or no information is available, conservative assumptions for the geotechnical parameters shall be
taken by the geotechnical expert. Conservative parameters tend to increase the size and the cost of the
foundation. As the foundation’s share of the total wind power plant cost is substantial, this may have serious
consequences for the financial balance of the whole project. The more detailed the investigations are, the
more cost-effective the later foundations will be.
To reduce the cost of the geotechnical site assessment itself, the most favourable procedure is therefore
— first to plan the plant layout,
— then perform the site assessments at the turbine and platform locations only.
In this case a geophysical investigation can be omitted.
Guidance note:
Last minute changes typically spoil the above sequence. The turbine size may be changed and therefore also the power plant layout.
Often, the turbine sites are pushed to locations where no soil investigations had been executed. To minimize the later cost of the
whole plant is advantageous to repeat the whole soil investigation campaign for all new locations, although initially this means losing
time and investing money. The money invested will pay off later, but the additional time is often lost.
An alternative may be to do an intensive geophysical investigation from the start and to try to correlate its findings with the results
of the geotechnical campaign (which may comprise more locations than shown by the first plant layout). If successful, this may give
geotechnical design values also at locations where no detailed geotechnical soil investigations took place.
The degree of accuracy for this procedure and thus its eventual cost-effectiveness for the whole project depends significantly on the
soil situation and the density of the geophysical and geotechnical investigations. For some site conditions, it is very successful, for
some not. Thus, the site assessment may develop into a trade-off between minimum costs and plant layout flexibility in a limited
project time frame.
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The decision, which course shall be followed, should be taken as early as possible. The importance of the
site assessment for the overall cost effectiveness of all plant substructures is usually underestimated,
leading to higher total plant cost than necessary.
2.3.3 Wind turbines
2.3.3.1 General
During the certification phase design basis documents that cover the requirements defined in this section
shall be submitted.
The objective of the design basis is to compile the information required for design, manufacturing,
transport, installation and operation of the support structure and the site-specific approval of the wind
turbine. The design basis should therefore present factual information in a logical and unambiguous way to
support the planning and execution of the wind power plant assets and their life cycle.
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The design basis shall describe the main data of the wind turbines in the wind power plant. The following
items are typically included in the design basis document:
— geographical locations of the wind turbines
— general description of wind turbine type and wind power plant layout
— project co-ordinate system and well-defined vertical reference including project datum
— water depth ranges
— allowable frequency range
— type of substructure and foundation
— design lifetime
— applicable standards, codes and additional requirements
— site conditions, see [2.3.2]
— technical interface, e.g. to adjacent components
— materials and welding
— coating and corrosion protection system
— manufacturing and storage methods and requirements
— transportation and installation methods and requirements
— operation and maintenance methods and requirements
— decommissioning methods and requirements.
Guidance note:
The elevations of the interface at tower bottom and tower top, hub height and lowest and heights blade tip, main access platform
should be stated. Figures depicting the layout and elevations with the design values facilitate the understanding.
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2.3.3.2 Standards
The referenced standards, methods and procedures shall be defined in hierarchical order for the various
fields of applicability.
At least the following standards shall be applied for the asset wind turbine:
— loads and site conditions wind for turbines (DNVGL-ST-0437)
— support structures for wind turbines (DNVGL-ST-0126)
— corrosion protection of offshore wind turbines (DNVGL-RP-0416).
2.3.3.3 Developer’s requirements
The developer may have requirements in addition to the standards and codes that are listed in the design
basis. Such requirement shall be clearly described and forwarded to DNV GL with the design basis
documents.
2.3.3.4 Load and response
The relevant input parameters for the load and response analysis shall be documented in the design basis.
These include the site conditions, wind power plant layout, RNA, type of support structure, design life time,
structural, hydrodynamic and soil damping, aero-elastic code applied in the load analysis as well as other
codes used in this regard (e.g. for considering of hydrodynamic loading) and a validated simulation model
(e.g. from an existing type certificate), see DNVGL-ST-0437 for detailed information on the required data.
Guidance note:
Specifying different lifetimes for components or structures such as the substructure may be reasonable and should be considered.
For instance the impact of installation situations and periods (e.g. substructure without tower) have to be considered in the design
load cases, see DNVGL-ST-0437.
When specifying damping values, the individual sources of damping should be considered separately. The aerodynamic damping and
in case of a co-simulation the hydrodynamic damping are accounted for automatically by means of aero-elastic simulations. Other
sources of damping include structural damping in the support structure, soil damping and if not already included due to co-simulation
hydrodynamic damping. Possible contributions from active or passive damping devices may be added but are subject to
documentation and evaluation at latest as a part of the design phase.
A lower and upper bound of the vertical seabed elevation should be defined that accounts for the overall seabed variation over the
design lifetime, together with local scour (around elements) and global scour (overall structure). It is recommended to define this as
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detailed as possible in the design basis. However, pending issues may be postponed to the design phase if explicitly mentioned in the
design basis.
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The site-specific load case definitions for the wind turbines shall be derived and documented in the design
bases, based on the approved load case definitions from the existing wind turbine type certificate, the
applied standards, the site conditions and possible site-specific modifications of the control and protection
system. The load case definition shall clearly demonstrate how the operational conditions such as
misalignment of wind and waves and the extreme conditions are considered and how wind, waves, currents
and water depth are correlated.
Within an offshore wind power plant the substructures may:
— be exposed to different design wave loads
— be placed in different water depths
— have different soil stiffness
— have different damping
— have different structural stiffnesses etc.
In order to determine the design loading based on only a few representative design positions, it shall be
documented that the loading will be conservative for those positions, where no integrated load analysis will
be performed. If this proof is not possible during the design basis certification phase it shall be documented
as part of the design certification phase.
An overview of the link between the various kinds of information required is shown in Figure 2-1.
Figure 2-1 Development of load and responses (offshore)
The environmental conditions are verified as part of the site assessment [2.3.2]. However the (design)
metocean conditions are influenced by wind farm layout and sub-structure design (e.g. due to scour and
wake effects). The method of deriving the design metocean conditions as well as the resulting design
metocean conditions shall be documented as part of the design basis.
Guidance note:
The simulation model of the RNA including the control and safety system may be available at DNV GL due to component or type
certification of the machine and hence it would not be necessary to generate the model. The use of a possible model is subject to
written authorization by the turbine manufacturer who commissioned the model development.
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2.3.3.5 Design methodologies
Part of the design basis is a description of the main design methodology, including the method of load
calculation, and structural and geotechnical design methodologies.
DNV GL will evaluate the principles used to establish load combinations for the SLS, the ULS, the FLS and
if relevant the ALS for compliance with DNVGL-ST-0437.
The impact of the secondary structure on the primary structure is considered part of the primary steel
evaluation. This impact also includes ship impact, see DNVGL-ST-0126.
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2.3.3.6 Wind turbine type
The wind turbine type to be integrated in the project certificate shall bear a type certificate. Interfaces
between type and project certification are shown in [1.6.5], Figure 1-9. The certification scheme applied for
the type certification shall be stated in the design basis.
Guidance note:
For offshore wind turbines a rotor-nacelle assembly (RNA) component or type certificate may be available instead of a wind turbine
type certificate. This certificate can be integrated in a project certificate, too. The tower is usually project specifically designed.
For onshore wind turbines a type certificate may be available including the tower, however the above mentioned case with an RNA
and a site-specific tower is applicable for onshore projects as well.
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For the purpose of simplification, the term wind turbine is used in the following also as synonym for the
RNA, in case of general descriptions. Thus the term type certificate will be used also with reference to the
component certificate of an RNA. The distinction will be made where relevant.
The type certificate shall preferably be issued by DNV GL. However, type certificates issued by other
accredited certification bodies may be accepted by DNV GL, see [8.10.7]. The type certificate shall be
submitted during the design basis phase.
Guidance note:
Major deviations from the RNA design covered by the type certificate may require an update of the type certificate; see DNVGL-SE0441.
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The wind turbine specification in the design basis shall uniquely define the type. If the wind turbine has been
type certified by DNV GL, the specification may be limited to a reference to the type certificate. The
specifications of possible deviations from the wind turbine type defined in the type certificate, such as
additional corrosion protection, shall be submitted for design basis certification. For the use of information
from the type certification [1.6.8] shall be considered.
Specifications and turbine models from the DNV GL type certification shall be made available to DNV GL for
the independent load analysis of the integrated RNA and support structure, see [1.6.8]. The control system
applied shall be the same as for the type certified wind turbine.
If the wind turbine has been type certified by another certification body recognized by DNV GL, DNV GL will
require documentation of the wind turbine type (see also [8.10]), necessary for evaluation and independent
calculation of the loads and response of the integrated RNA and support structure, and DNV GL will review
this documentation.
Guidance note:
The design basis information regarding the wind turbine requires contributions from the turbine manufacturer. There is a significant
interaction in the design process of the support structure between the substructure and foundation designer and the wind turbine and
tower supplier, see [1.6.5]. The resulting requirements and deliverables should be contractually agreed at project start.
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2.3.3.7 Manufacturing, transport, installation and commissioning
The design basis shall state assumptions, specifications and requirements for structural design for loads
occurring during manufacturing, transportation, installation and commissioning, such as environmental
loads, lifting loads, and local loads from temporary supports. The design basis shall also state assumptions,
specifications and requirements for the manufacturing, transportation, installation and commissioning
programs themselves. Manufacturing and commissioning of the wind turbine is usually properly
documented through the type certification, see [1.6.5] and Figure 1-9. Commissioning requirements for the
substructure and the foundation are usually very limited.
Assumptions, specifications and requirements may include, but are not necessarily limited to:
— standards, codes and additional requirements, see [1.6.9]
— specifications and tolerances
— limiting environmental conditions
— manufacturing requirements and quality management systems
— methods and loads of relevance for transportation and installation
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— requirements for transportation, installation (incl. loading) and commissioning manuals
— quality management systems for the installation contractors.
The assumptions, specifications and requirements are expected to depend on owner’s requirements as well
as on the actual contractual arrangements for the wind power plant project.
When the wind turbine has been type certified by DNV GL, only those assumptions, specifications and
requirements not verified as part of the type certification may be stated.
DNV GL shall evaluate assumptions, specification and requirements stated in the design basis.
2.3.3.8 Operation and maintenance
The design basis shall state assumptions, specifications and requirements for structural design against loads
occurring during operation and maintenance. The design basis shall also state assumptions, specifications
and requirements for the operation and maintenance programs.
Assumptions, specifications and requirements to be stated include, but are not necessarily limited to:
— inspection scope and frequency
— target lifetime of components, systems and structures
— requirements for service and maintenance manuals
— requirements for condition monitoring systems.
For the type certified wind turbine, most of these assumptions, specifications and requirements are covered
by manuals approved in the type certification process, see [1.6.5] and Figure 1-9.
When the wind turbine has been type certified by DNV GL, only assumptions, specifications and
requirements not verified as part of the type certification may be stated.
DNV GL shall evaluate assumptions, specification and requirements stated in the design basis.
An approved design basis might need to be modified due to requirements or conditions which become
available during the project development in particular in the design phase. The design basis is then subject
to evaluation and if completed a new revision of the statement of compliance and accompanying
certification report will be issued.
2.3.4 Substation
A design basis document shall be created in the development phase to document the basic criteria to be
applied in the general design (structural, machinery, electrical, safety etc.) of the installation.
Following items are normally to be included in the design basis document:
— platform/unit geographical location and main functionalities
— general description of wind turbine type and wind power plant layout
— project co-ordinate system and well-defined vertical reference including project datum
— general description, main dimensions and water depth ranges
— type of substructure and foundation
— service life of platform
— applicable standards, codes and additional requirements
— site conditions, see [2.3.2]
— topside interface requirements with details of leg spacing, topside weight and centre of gravity
— materials and welding
— coating and corrosion protection system
— manufacturing and storage methods and requirements
— transportation and installation methods and requirements
— operation and maintenance methods and requirements
— decommissioning methods and requirements.
Further details on required content and scope of the design basis can be found in the relevant sections of
DNVGL-ST-0145.
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DNV GL shall evaluate the design basis for compliance with DNVGL-ST-0145 and other standards and codes
identified in the design basis.
2.3.5 Power cables
Design and assessment require early definition of applied standards or calculation techniques for the
planned cable system. Functional requirements (e.g. specified design loads, environmental aspects, etc.)
have to be defined by the applicant detailing the performance expectations and desired characteristics.
A design basis document shall be established specifying all boundary conditions of the cable project, which,
together with the functional specifications, enable a designer to pursue the design activities. Subjects
covered in a design basis shall include the following:
— general description of power cable types and wind power plant layout
— geographical locations and system overview
— applicable standards, codes and additional requirements
— site conditions, see [2.3.2]
— technical interfaces
— manufacturing and storage methods and requirements
— transportation and installation methods and requirements
— operation and maintenance methods and requirements
— decommissioning methods and requirements.
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
2.3.6 Control station
Design basis for the control station means a first definition of the functionalities of the control station.
Therefore a design basis document shall be established specifying all functions of the control room. Subjects
covered in this document shall include the following:
Hardware:
— wind turbines, substation and cabling to be controlled
— communication system of the wind power plant
— condition monitoring system for assets.
Software:
— operating systems, safety systems and SCADA of the wind power plant.
Tasks:
— control and monitoring of wind turbines
— control and monitoring of substation
— control and monitoring of power cables
— control and monitoring of grid connection
— condition monitoring of wind turbines (optional for onshore, mandatory for offshore wind power plants)
— condition monitoring of substation (optional).
Guidance note:
The communication system of the wind power plant should be based on IEC 61400-25 series.
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The design basis document shall be submitted for assessment.
For the certification of condition monitoring systems and condition monitoring bodies DNVGL-SE-0439 shall
be applied.
DNV GL recommended practice DNV-RP-D201 (see A. Concept, Section 6) for integrated software
dependent systems may be applied.
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For asset management the ISO 55000 series may be applied. With respect to asset management in general
ISO 55000 specifies the overview, concept and terminology in asset management. The requirements for the
establishment, implementation and improvement of a management system for asset management are
given in ISO 55001. Further interpretation and implementation guidance is given by ISO 55002.
2.4 Design
2.4.1 General
DNV GL shall evaluate the final design for compliance with design criteria and design basis selected
according to [2.3].
The final design basis document shall be submitted at the beginning of the design phase, at latest. As an
optional intermediate step the design principles given in design briefs may be verified before the final design
documentation is delivered to DNV GL. Details of the evaluation activities in this phase are given in the
following sections.
It is strongly recommended that the designer during his design work prepares a report that states all
assumptions made in design and that this report is used as input for the development of the subsequent
phases such as manufacturing and maintenance, see Figure 9 in [1.6.5]. The documentation for these
phases may not be finalised during the design phase and the evaluation of this documentation will therefore
be covered in the respective relevant phase. However, at the design phase the design influencing
assumptions shall be documented, at least.
Once the evaluation of the design has been successfully completed, DNV GL will issue a certification report
and a statement of compliance for design, listing the assets subject to evaluation.
For onshore sites and optional services, reference is made to [8.2].
For the purpose of simplification in description, the term type certificate will be used also in reference to a
component certificate of an RNA. The distinction will be made where relevant, see [2.3.3.6].
2.4.2 Wind turbines
2.4.2.1 General
Typically a type certified RNA and a site-specific support structure are used for offshore projects. For
onshore projects, the tower and foundation may be site-specific or may be covered by the existing type
certificate.
A site-specific load analysis based on the design basis according to [2.3.3.4] shall be performed using an
integrated simulation model, which includes aero-elastic and hydrodynamic effects. If for wind turbines
being installed offshore aero-elastic and hydrodynamic loads are not determined by co-simulation, the
method used is subject to approval by DNV GL. For onshore sites, it may be possible to avoid site-specific
load analysis, if it can be shown, that the site conditions are more benign than the design conditions, see
DNVGL-ST-0437.
In cases where all wind turbines including support structure are identical and where it is possible to
determine the highest-loaded turbine, a single load analysis may be sufficient. However if there are
differences in the turbine or support structure design (e.g. due to different water depths) or if a highestloaded turbine cannot be determined, several load simulations are required. In such case turbines can be
combined into clusters, where each cluster is represented by one position for which load simulations are
performed.
The models used for load analysis as well as the results of the load analysis shall be documented and are
subject to evaluation. Unless the load simulation model has been verified as part of the type certification
and DNV GL has been granted permission by the wind turbine manufacturer to utilise the evaluation results,
the evaluation shall include an independent analysis to verify the model used for load analysis.
2.4.2.2 Rotor-nacelle assembly
The rotor-nacelle assembly (RNA) shall be evaluated for project certification. This shall be documented by
a type certificate or the mandatory phases of the type certification according to DNVGL-SE-0441 shall be
fulfilled, see [8.2] and [8.10]. This will be evaluated with respect to the specific project and site-specific
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conditions in project certification. In the following reference is made to the term type certification only, even
when the fulfilment of the mandatory phases of type certification is possible, too, for the purpose of project
certification.
DNV GL shall verify that a valid type certificate is in place. The certificate shall be valid at the date of issue
of the statement of compliance for the design phase and of the project certificate. The certification scheme
applied for the RNA type certificate shall be stated in the design basis. In addition, the following conditions,
requirements and specifications shall be presented to DNV GL and shall be certified by DNV GL:
— external conditions assumed for the RNA design including the grid conditions
— requirements for transportation and installation
— requirements for operation and maintenance
— specification for the interfaces between wind turbine and support structure, e.g. tower–substructure
geometry, stiffness of support structure, and stiffness of soil support
— adaptions or extensions to the type certified electrical system (e.g. grid connection equipment).
Guidance note:
Adequate implementation and site-specific adaptations of the type certified RNA for the project is part of the project certification
process. Potential synergies from type certification may be used where identified and possible. Alternatively the site-specific type
certificate (see [8.2]) may be implemented into the project, see [8.10.6]. Regarding permissions required by suppliers see [1.6.8].
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A methodology for how to handle deviations from the conditions of the type certificate, such as
reinforcements of the blades, reinforcements of the tower top and yaw system, and modification of the
electrical systems, shall be outlined.
Guidance note:
Major deviations from the wind turbine design including the controller, covered by the component or type certificate may require an
update of the component or type certificate; see [8.10.3].
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The RNA specification shall uniquely define the type. If the RNA has been type certified by DNV GL, the
specification may be limited to a reference to the type certificate and specifications of possible deviations
from the certified RNA type, such as additional corrosion protection or other site-specific configurations, see
[8.3.3]. Permissions required by suppliers to use specifications and wind turbine models from the DNV GL
type certification shall be provided to DNV GL by the developer or contractor, see [1.6.8]. The use of
information from the type certification, such as the independent load analysis of the integrated RNA and
support structure will be required to implement the RNA into the project.
The control system applied in the project shall be the same as for the type certified RNA. If this is not the
case the new control system release (hardware and software) shall be included in the type certification or
a site-specific design evaluation shall be performed as part of the project certification.
If the RNA has been type certified by a certification body other than DNV GL and this body is recognized by
DNV GL, DNV GL shall require documentation of the wind turbine type and will evaluate this documentation,
see [8.10].
Guidance note:
Documentation of the RNA type for evaluation and independent calculation of the loads and response of the integrated wind turbine
and support structure may include turbine specifications and a software model of the wind turbine and the load conditions and loads,
which form the basis for the type certificate. In that way DNV GL should assess the adequacy of the model before performing an
independent load analysis of the RNA and the site-specific support structure.
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DNV GL shall certify that the RNA design basis is in compliance with the certified design basis of the wind
power plant. The type certificate for the RNA will be evaluated with respect to the site-specific loads and
responses.
DNV GL shall review the RNA type certificate conditions and limitations as compared to the actual site
conditions. The action taken by designers with respect to these conditions shall be stated in the design
documentation. In addition this comparison will cover metocean conditions, if applicable, including other
relevant conditions such as:
— temperature
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— humidity
— solar radiation
— rain, hail, snow and ice
— chemically active substances
— mechanically active particles
— salinity
— electrical conditions
— vibration
— lightning
— earthquake.
Due account shall be taken of the generally more aggressive offshore environment. Environmental
conditions other than wind and marine conditions can affect the integrity and safety of the offshore wind
turbine by thermal, photochemical, corrosive, mechanical, electrical and other physical actions.
Moreover, combinations of the environmental parameters given may increase their effects. Hence, the
documentation for utilization ratios used will be subject to special considerations.
In particular, electrical components like generator, converter, transformer, switch gear and enclosures shall
be designed for the appropriate site conditions, reference is made to DNVGL-ST-0076.
The corrosion protection systems shall be able to withstand the site-specific marine environment, reference
is made to DNVGL-ST-0126 and DNVGL-RP-0416.
DNV GL shall review the submitted design report of the site-specific loads with respect to the loads assumed
for the type certificate. The objective is to evaluate that the loads do not exceed the verified capacity. Any
increases in load level as well as any changes in modes shapes and natural frequencies shall be stated in
the design report and will be evaluated.
Design documentation shall be provided for new, modified or reinforced components and systems, such as
corrosion protection systems, which are not fully covered by the type certificate for the wind turbine. The
documentation shall be prepared according to the design basis and, if relevant, according to the
requirements for the type certification scheme applied.
DNV GL shall evaluate that the RNA electrical system including the RNA or wind turbine terminals meets the
requirements in the approved design basis with respect to the following:
— the design of the electrical system shall ensure minimal hazards to people as well as minimal potential
damage to the wind turbine and external electrical system during operation and maintenance of the
wind turbine under all normal and extreme conditions
— the electrical system, including all electrical equipment and components, shall comply with the relevant
standards
— the design of the electrical system shall take into account the fluctuating nature of the power generation
of RNA or wind turbines
— provisions shall be made to ensure adequate protection of all electrical components and systems against
the effects of corrosion and humidity.
2.4.2.3 Support structure
The support structure comprises the tower, the substructure connecting the tower to the foundation, Jtubes
and the foundation, which transfers the loads into the soil. Distinction is made between primary and
secondary structures for the support structure (see [1.4.2.1]). Primary structures transfer permanent loads
and environmental loads, acting on the support structure, to the soil. Secondary structures covered by the
DNV GL scope comprise access ladders, main structural elements in external access platforms or boat
landings.
Guidance note:
Certain elements of the primary structure such as cans of tubular nodes, ring flanges of tubular towers, thick-walled deck-to-leg and
column connections may be classified as special structures. Special structures are part of the primary structures. The reasoning for
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introducing this terminology is to distinguish these structures for their special loading and stress conditions, and the necessity for
additional quality demands. The same terminology is used in DNVGL-ST-0126.
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DNV GL shall evaluate that the design of the support structure is in compliance with the design basis. The
evaluation of the structural design will include design review and independent design analyses, if deemed
necessary.
The design evaluation shall be carried out to an extent sufficient to enable DNV GL to state that the support
structure complies with the approved design basis and DNVGL-ST-0126.The customer shall document that
the resulting safety level complies with the level intended in DNVGL-ST-0126. Fatigue design documents
should be based on DNVGL-ST-0126.
The following evaluation activities are conducted:
— review of detailed design calculation reports, design drawings and manufacturing specifications for
detailed structural design of the support structure
— relevant independent analyses of loads and structural strength.
The evaluation may include independent analyses of the support structure using appropriate methods, such
as FEM analyses, and covers:
— structural strength (stress levels, buckling and joint check) in both in-situ scenarios and transitional
stages
— soil stiffness and soil capacity
— fatigue life (incl. consideration of fatigue accumulated during phases of installation and commissioning)
— dynamic behaviour/natural frequency checks
— vibrations induced by vortex shedding
— serviceability (if applicable).
If the design includes highly utilized structural connections, such as grouted connections of steel structures
and tubular joints, detailed independent FEM calculations of the connections may have to be carried out by
DNV GL.
For grouted connections DNVGL-ST-0126 and DNVGL-RP-0419 shall be applied.
Environmental loads from wind, if relevant, waves and current, acting on the support structure, shall be
based on a load analysis of the integrated system of RNA and support structure, and documentation in a
form suitable for evaluation shall be submitted to DNV GL. The evaluation may include an independent
analysis according to DNVGL-ST-0126.
The evaluation of the structural design shall focus on:
— review of design calculations for ULS, SLS, FLS and ALS
— review of design implementation of manufacturing and installation requirements, however only with
respect to the structural integrity of the final installed (permanent) support structure
— evaluation of proposed corrosion protection system(s) against design requirements with a view to
required design life, standards and codes, operation and maintenance
— review of design drawings and manufacturing specifications with respect to requirements in standards,
codes and with respect to assumptions in calculations regarding dimensions, materials, tolerances and
testing.
For geotechnical design of foundations reference is made to DNVGL-ST-0126. The purpose of a soil
investigation is to provide a range of strength and deformation parameters with sufficient accuracy.
Additionally the investigations shall supply information to evaluate deterioration from dynamic loads in
sufficient detail. The investigations should be targeted on the actual phase of the project with respect to
extent, details and accuracy.
The evaluation of the geotechnical design shall focus on:
— evaluation of calculation methods, stability and failure modes
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— review of geotechnical design calculations for ULS, FLS, SLS and, if relevant, ALS
— review of design documentation regarding soil preparation, tolerances and scour protection
— the expected stiffness and damping of the support structure will be checked against assumptions made
in calculations of wind turbine loads.
The following design documentation shall be submitted for evaluation of the final structural and geotechnical
design:
— design documentation for the structural and geotechnical design calculations, for ULS, SLS, FLS and
ALS. The documentation should include descriptions of the assumptions made for the calculations, for
example regarding manufacturing and installation methods.
— design report containing design calculations for the corrosion protection system(s)
— design report of the driveability study, if applicable
— design drawings including general note drawing(s)
— design documentation regarding scour and scour protection design, if relevant
— installations / equipment.
2.4.3 Substation
2.4.3.1 General
DNV GL shall evaluate that the design of the substation is in compliance with the design basis, DNVGL-ST0145 and other standards and codes defined in the design basis as well as national regulations.
2.4.3.2 Installation categories
The installations to which this service specification and DNVGL-ST-0145 applies may be categorized in the
following way:
I.
Purpose of the installation
a) Transformer Station
b) Converter Station
c) Accommodation Platform
d) Combined Purpose
From case to case a combination of above mentioned items a. to c. on a single unit or installation
(combined purpose) may be feasible.
II.
Method of connection to the sea bed
The following types of construction may be distinguished:
— installation permanently fixed by piling or suction caissons/anchors
— installation or units resting on the sea bed by action of gravity (gravity foundation)
— installation or unit with excess of buoyancy, connected to a base by tensioned anchoring elements
(tension leg foundation).
III.
Manning
a) Normally manned installation
Installation on which persons are routinely accommodated. Also referred to as normally attended
installation (NAI).
b) Normally unmanned installation
Installation on which persons are not routinely accommodated and which is only visited for
inspection and maintenance tasks. Also referred to as normally unattended installation (NUI).
2.4.3.3 Structural design and geotechnical design
The evaluation of the design of the substation topside and the support structure shall be based on loads,
capacities, design methods and principles specified in the approved design basis and in relevant DNV GL
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standards, e.g. DNVGL-ST-0145 and DNVGL-ST-0126. For areas where the approved design basis or the
DNV GL standards do not apply, reference to a recognized standard or design method may be accepted by
DNV GL.
Depending on the agreed scope the structural design evaluation shall include:
— loads and load combinations
— geotechnical design
— design of primary structure
— design of secondary structures
— topside arrangement
— transportation, installation, operation and maintenance
— grout design, if applicable
— connections.
For the geotechnical design of foundations reference is made to DNVGL-ST-0126. Guidance for prediction
of scour and for means to prevent scour is also given in DNVGL-ST-0126. The purpose of a soil investigation
is to provide a range of strength and deformation parameters with sufficient accuracy. Additionally the
investigations shall supply information to evaluate deterioration from dynamic loads in sufficient detail. The
investigations should be focused on the actual phase of the project with respect to extent, details and
accuracy.
The design documentation shall include reports, calculations, plans, specifications, procedures and other
documentation, where applicable. An exemplary list can be found in App.A.
The evaluation of the structural design of the topside and support structure shall in general focus on design
methodology and safety levels as well as the aspects defined in Table 2-1.
Table 2-1 Focus of verification for substation
Subject of verification
Topside structure
Support structure
Primary
Secondary
Primary
Secondary
X
X
X
X
ULS
X
X
X
X
SLS
X
X
X
X
ALS
X
X
X
X
Eigen frequency and vortex shedding
analyses
X
X
X
X
Design drawings
X
X
X
X
Installation methods and occurring loads
X
X
X
X
Manufacturing specifications
X
X
X
X
Material
X
X
X
X
Corrosion protection systems
Design calculation
FLS
X
Fatigue design documents shall be based on DNVGL-ST-0145. A combination of standards with regard to
design fatigue factors and S/N-curves is not acceptable.
The following evaluation activities are conducted:
— review of detailed design calculation reports, design drawings and manufacturing specifications for
detailed structural design of the support structure
— relevant independent analyses of loads and structural strength.
The verification may include independent analyses of the structure using appropriate methods, such as FEM
analyses, and covers:
— structural strength (stress levels, buckling and joint check)
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— soil stiffness and soil capacity
— fatigue life.
If the design includes highly utilized structural connections (e.g. grouted connections of steel structures and
tubular joints), detailed independent finite element calculations of the connections have to be carried out
by DNV GL. Such analysis will be described in an independent scope of work.
2.4.3.4
Electrical design
The electrical design shall be assessed for compliance with DNVGL-ST-0145 and further standards, codes
and requirements specified in the design basis. The focus of the evaluation shall be on the safety of the
installation as defined in the approved design basis. The evaluation will be carried out by spot checks of the
diagrams, specifications and calculations of the transmission and distribution system.
The electrical design review shall include:
— main components design (main transformer, switchgear, cables and, if applicable, semiconductor
converter)
— arrangement of components, with regard to safety
— electrical protection
— lightning protection
— earthing and equipotential bonding
— cabling and termination
— station and emergency power supply.
An exemplarily list of documentation which shall be submitted for the evaluation of the electrical system
and cabling can be found in App.A.
Specific studies for which documentation shall be made available may include:
— short-circuit studies
— discrimination study
— load schedule on emergency power systems
— protection coordination and setting.
The evaluation activities shall include review of the following:
— high-voltage / power equipment safety
— control and protection system design
— main components (main transformer, converter, switchgear) utilization and protection
— emergency generation capabilities
— platform marking, identification, lighting and instrumentation
— heating/ventilation/air conditioning, as well as corrosion protection measures.
Optionally the electrical performance of the substation connected to wind power plant and grid can be
reviewed by analysis, see [8.6].
2.4.3.5
Fire and explosion protection design
Evaluation of the fire and explosion protection design shall be based on applicable standards, i.e. DNVGLST-0145 and national regulations.
The documentation listed in App.A shall be submitted to DNV GL for evaluation as applicable.
The documentation submitted to DNV GL for evaluation shall in addition address the following topics:
— nature and risks of potential fires and explosions
— quantities of fluids, flammable and combustible materials handled, processed and stored on the
substation
— manning philosophy and human factors.
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In the context of fires and explosions, the results of the evaluation process and the decisions taken with
respect to the need for, and role of, any risk reduction measures (the “fire and explosion strategy”) shall
be reviewed during the evaluation.
Guidance note:
Complex substations are likely to require detailed studies to address hazardous fire and explosion events. Simple substations may
rely on the application of recognized codes and standards. The fire and explosion strategy should describe the role and functional
requirements for each of the systems used to manage possible hazardous events on the substation.
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As for functional requirements, the following shall be reviewed during the evaluation:
— purpose and duty of a particular system
— integrity, reliability and availability of the system
— survivability of the system and dependency on other systems.
Deck layout and firefighting measures shall be checked for compliance with applicable standards and
regulations.
For substations featuring an accommodation module, specific evaluations to assure compliance with
applicable standards and regulations shall be carried out.
2.4.3.6 Access and transfer design
Evaluation of the access and transfer design shall be based on applicable standards such as DNVGL-ST-0145
and national regulations.
The following documentation shall be submitted for evaluation:
— boat landing documentation
— helicopter deck documentation (if applicable)
— helicopter winching area documentation (if applicable)
— details of area and deck-to-deck access.
The design of the boat fender system shall be verified as part of the structural design review.
Evaluation of the design of the helicopter deck is optional. A specific scope shall be agreed, see [8.8].
Layout of stairs and ladders shall be verified as part of the emergency response design.
2.4.3.7 Emergency response design
Evaluation of the emergency response design shall be based on applicable standards as specified in the
design basis, e.g. DNVGL-ST-0145 and national regulations.
The following documentation shall be submitted for evaluation:
— safety philosophy and design principles
— platform arrangement
— orientation, fire and safety plans.
The documentation submitted to DNV GL for evaluation shall in addition address the following topics:
— environmental conditions
— distance to the nearest installation, to shore and to coastal facilities
— number and distribution of personnel
— effect of time of day on emergency response
— immediate effects of an incident on the installation and people
— development of heat and smoke in the event of fire
— capacity for treatment at available medical facilities.
The evaluation of the emergency response design shall include an assessment of the proposed emergency
response measures, comprising an analysis of performance of the measures and a judgement of their
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adequacy. Platform layout and safety systems shall be evaluated with regard to hazard identification and
safety for humans, the environment and the asset considering:
— alarms and communications
— shutdown
— escape routes and muster areas
— evacuation, rescue and recovery.
For the assessment of the selection of emergency response equipment, the following issues shall be
considered:
— location
— type
— number
— capacity
— accessibility and survivability under emergency conditions
— reliability and/or availability
— maintenance, usability and training requirements.
Changes on the installation or changes of the external situation that may affect the emergency response
procedures shall also be part of the assessment. Such changes in particular include:
— potential emergency scenarios
— emergency response equipment
— emergency response organization
— emergency response procedures
— staff experience
— research results and new knowledge
— changes in statutory legislation.
2.4.3.8 Manufacturing, transport, installation and commissioning plan
Evaluation of the manufacturing, transportation, installation (incl. loading and unloading, such as lifting
loads) and commissioning processes shall be based on applicable standards, e.g. DNVGL-ST-0145.
2.4.3.9 In-service plan
DNV GL shall require that relevant input to the inspection and maintenance plans shall be prepared. The
input to the inspection plan and the maintenance manual shall be seen as a help to the operations and
maintenance organization that normally will be established later. Examples of issues to be covered are
inspections and checks of the scour protection system and the corrosion protection system, assumed
service vessel(s), and inspections for fatigue cracks if relevant.
Evaluation of the operation and maintenance programme shall be based on applicable standards such as
DNVGL-ST-0145 and industry best practice.
The following documentation shall be submitted for evaluation:
— description of risk based inspection and maintenance programmes, covering inspection, scheduled
maintenance and unscheduled maintenance
— service and maintenance manual for key components.
The documentation shall be evaluated and verified for compliance with the approved design basis regarding
scope and intervals of the following:
— operational monitoring and condition monitoring
— safety related inspection and maintenance
— scheduled maintenance
— unscheduled maintenance provisions
— record keeping and quality control.
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2.4.4 Power cables
Cable design is highly dependent on the conditions of the power plant project being developed. Important
assumptions and applicable parameters shall be clearly described in the design brief, including at least:
— site conditions
— overall number of turbines
— type and rating of turbine
— location of the individual turbines
— location of offshore substation or onshore grid connection
— voltage level(s)
— choice of the cable type(s)
— choice of cable route(s)
— feasibility of cable installation and burial
— condition monitoring of power cable(s), if applicable.
Electrical system studies should establish basic electrical design parameters. Normal, emergency operation
or other interconnection schemes specified for the wind power plant shall be studied in:
— power flow simulations (static, transient, harmonics)
— short-circuit calculations.
Ground investigations shall be conducted in order to investigate site geological, geophysical and soil
conditions.
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
2.4.5 Control station
Design of the control station means that all tasks the control station is dealing with shall be described in
detail. These tasks are:
— operation management of the wind power plant (technical / commercial)
— control and monitoring of wind turbines
— control and monitoring of substation
— control and monitoring of power cables
— control and monitoring of grid connection
— condition monitoring of wind turbines (optional for onshore, mandatory for offshore wind power plants)
— condition monitoring of substation (optional)
— maintenance management of wind turbines
— maintenance management of substation
— maintenance management of power cables.
Guidance note:
The maintenance management includes scheduling of measures, scheduling of maintenance personnel, organisation of spare parts
and organisation of tools.
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Condition monitoring can be performed by the control station itself or by a separate independent monitoring
body. If the condition monitoring is performed by a separate monitoring body, the communication with this
separate monitoring body shall be described in detail.
A condition monitoring within the control station shall be carried out by experts, who are not in charge of
the controlling of the wind power plant.
The descriptions listed above shall be submitted for assessment.
For the certification of condition monitoring systems and condition monitoring bodies the DNVGL-SE-0439
shall be applied.
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DNV GL recommended practice DNV-RP-D201 (see B. Engineering, Section 7) for integrated software
dependent systems may be applied.
For asset management the ISO 55000 series may be applied, see [2.3.6].
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SECTION 3 CONSTRUCTION
3.1 General
This section contains requirements for state-of-the-art quality management measures, which shall be
applied to achieve desired lifetimes and availability rates of the wind power plant.
Safe and failure-free operation requires different operational measures, selection of adequate material and
reliable designing. In addition to this the importance of diligent and careful material processing should not
be underestimated to ensure the power plant safety and availability.
In this certification phase DNV GL provides surveillance during manufacturing, transport and installation in
order to evaluate compliance between the approved design and the wind power plant built. This may
support the applicant to determine and eliminate at an early stage possible defects during engineering,
manufacturing and installation, which may impact the later availability of the plant or parts of it.
For the applicant it may be of additional value, to involve an independent expert for surveillances in addition
to his own controls to detect and avoid remaining quality deviations at an early stage.
For surveillances [?1.6.11] shall be considered.
3.2 Manufacturing
3.2.1 General
DNV GL shall conduct manufacturing surveillance in order to evaluate compliance between the approved
design and the product in the workshop. The surveillance shall be conducted at the manufacturer’s premises
for production of main components and structures as well as in the rotor-nacelle assembly shop and
manufacturing of offshore substations. It shall involve:
— survey of manufacturing
— evaluation of quality management system, if ISO 9001 certificate is not available
— product related quality audits
— survey of contractor’s quality management activities.
Manufacturing surveillance consists of (initial) audits and inspections of project related components. The
surveillance activities comprise both on-site inspections and document review. This means that the
manufacturing surveillance consists of three main activities, document review, initial audit and inspection,
see Figure 3-1.
Manufacturing Surveillance
Document Review
Initial Audit
Inspection
Figure 3-1 Activities of manufacturing surveillance
The purpose of the (initial) audit is to check the qualification (ability to perform the production of relevant
components according to the expected quality and to document this ability) of the manufacturing company
prior to commencement of production and to check the documentation forming the basis for the production.
The detailed scope of the inspections will be developed based on the results of the audits, which may result
in an adjustment of inspections to be performed in the ongoing process. Complementary to the inspection
the manufacturing records are reviewed.
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Guidance note:
The general document review (documents not unique to the particular project) and initial audit may be omitted during project
certification, if a shop approval for the production purpose is available, see [8.7].
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The customer shall assure that DNV GL gets access to the relevant manufacturing and assembly sites.
Permissions required by suppliers shall be provided to DNV GL by the developer or contractor.
The extent of the inspections and the number of occasions when surveillance has to be carried out for
project certification shall be evaluated by DNV GL for each specific project.
For component manufacturers producing on a large scale (no pre-series production) with a good track
record, the number of inspections may be reduced to a minimum but generally some inspection will be
performed. In other cases more detailed inspections shall be performed.
In general manufacturing surveillance starts with a higher extent at the beginning and depending on the
inspection results the extent and quantity of inspections will be adapted during the process after evaluation
of each inspection performed using a risk based approach. For planning purpose initially three inspections
will be assumed as a minimum, at start, mid, and end of production at each manufacturer. Alternatively a
time-based approach should be elaborated. The following sections [3.2.2] to [3.2.5] provide further
guidance with reference to the component and asset related inspections.
Guidance note:
In contrast to defining a sample size (i.e. number of components to be inspected), the time-based approach may be more appropriate
to achieve the aim of a representative and value adding independent inspection. This applies in particular for offshore substations
where usually only one unit per project is being manufactured. Instead of a fixed quantity of components to be inspected an
agreement on time-based inspections over the whole production period can be found. Purpose is to cover the most critical
manufacturing processes of a project specific asset (e.g. substation) by an independent inspection.
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The risk based approach defines three different verification levels, which depend on the estimated risk for
failure, the willingness to take a risk and the involved consequences. The risk level is higher for a component
or an assembly the failure of which will lead to severe consequences. On the other hand a higher verification
level will help to reduce the risk level. Verification levels and surveillance frequency are described in DNVOSS-304, Sec. 2, Pt. D400.
High
Supplier qualification
Low
No or reduced
inspection scope
Reduced extent
of surveillance
(verification level: low)
(verification level: medium)
Higher scope in the beginning,
option to reduce if results are
positive
Need for surveillance,
particular high scope in the
beginning
(verification level: medium)
(verification level: high)
LOW
Relevance of component for structural integrity
HIGH
LOW
Complexity of component
HIGH
Figure 3-2 Risk dependence of manufacturing abilities and complexity/importance of a component
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The verification level shall be specified by the customer and confirmed by DNV GL dependent on suppliers’
qualification, relevance of components’ integrity and complexity and the consequences of a potential failure,
see Figure 3-2.
Following criteria shall be considered for taking the decision on the verification level.
Suppliers’ qualification:
— certificates of the supplier (e.g. Shop Approval [8.7], ISO 3834-2, EN 1090-2)
— qualification of the supplier by a 2nd party in place (e.g. by the purchaser)
— suppliers track record (e.g. same parts produced for type certification)
— experience with the supplier from previous surveillances (e.g. track record)
— experience of the supplier with the component in question (e.g. new or known type of component, track
records)
— experience of the supplier and purchaser (e.g. similar components for the same purchaser produced
before).
Relevance of component for structural integrity:
— location of the component (e.g. in the load path)
— special, primary, secondary member (e.g. type of stressing, risk for brittle fracture)
— redundant / non-redundant component.
Complexity of component:
— innovative or complex design
— easy / difficult to manufacture
— new or innovative material.
For wind turbines it is assumed that a serial production is running in all manufacturing workshops subject
to inspection such that all important processes according to inspection and test plan (ITP) for one
component can be seen in one visit.
The surveillance shall be based on relevant standards together with design documentation previously
submitted to DNV GL as input for the design assessment, such as documentation of:
— critical items
— test programs
— inspection and test plan
— approved design drawings and specifications
— qualification of personnel.
Each survey shall be completed at the manufacturing premises and the following documentation shall be
made available to DNV GL for the surveillance to be conducted:
— workshop qualification (e.g. workshop approval)
— manufacturing process mapping
— general arrangement drawings and specifications
— manufacturing drawings, specifications and instructions
— inspection and test plan (ITP)
— welding procedure specifications and related welding procedure qualification records
— work procedures for NDT and corrosion protection
— inspection check sheets, NDT reports, and measurements reports
— certificates of personnel qualifications (e.g. for NDT testing).
Each survey shall be documented in a detailed surveillance report including photo documentation whenever
deemed necessary. Permissions required by suppliers shall be provided to DNV GL.
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Depending on the scope and extent of the manufacturing certification conducted during the type
certification, synergies can be determined and used for the manufacturing surveillance for the project
certification. In case a site-specific type certification [8.2] is available the manufacturing surveillance can
be adapted to minimum.
Guidance note:
The manufacturing evaluation during the type certification is a random inspection. The manufacturing surveillance for project
certification is a project specific inspection of a representative quantity of the project ordered components. This surveillance is ordered
by the developer (project certification applicant) and performed in the developers’ interest.
The purpose of referring to the site-specific type certification [8.2] is to reduce efforts and costs for the project developer during
project certification. At the same time the turbine manufacturer may prepare a site suitable product to reduce avoidable adaptation
during a project certification.
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Once the surveillance of the manufacturing has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for manufacturing, listing the assets subject to
evaluation. The verification level and surveillance frequency applied for manufacturing surveillance shall be
stated as well in the certification deliverables.
3.2.2 Wind turbines
3.2.2.1 Surveillance of wind turbine components
The type certification of the wind turbine is based on design assessment, manufacturing certification,
evaluation of quality management, testing and measurements, see DNVGL-SE-0441 and [1.6.5]. As
suppliers of the wind power plant the wind turbine manufacturer and the suppliers of the main components
shall operate a quality management system.
If a quality management system in conformity with ISO 9001 is not available, DNV GL shall evaluate the
system. The DNV GL project certification will in addition to this perform inspection and audit activities in
order to evaluate that the manufacturing of the wind turbines for the specific project are carried out
according to the approved design and with the intended quality.
The surveillance of the assembly of hub and nacelle shall be completed in the wind turbine assembly
workshop. The manufacturing surveillance at the assembly workshop will be carried out at start of the
project specific assembly of these components and depending on the results in the course of production as
stated in section [3.2.1]. The manufacturing surveillance shall focus on:
— compliance with quality plan requirements
— visual inspection of units under assembly
— visual inspection of electrical installation
— documentation review (components certificates, production worksheets and final documentation).
The components of a standard wind turbine listed in the following and the described processes shall in
general be subject to manufacturing surveillance in connection with project certification. The list of
components and processes to be inspected shall be evaluated for each project under consideration of the
wind turbine specific design, e.g. direct drive or gearbox design. If the results of a manufacturing process
can be inspected sufficiently in a subsequent process, inspection at the manufacturer for this process is not
necessary, e.g. inspection of machined areas for a cast or welded component may be inspected during
incoming goods inspection at the assembly workshop. Therefore the list below should be reduced or
extended. This shall be agreed at the beginning of the project.
— rotor blades
— rotor hub
— rotor shaft or axle journal
— main bearing(s)
— main bearing housing(s)
— gearbox
— generator
— transformer
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— frequency converter
— high-voltage switchgear
— generator structures (direct drive only)
— main and generator frame
— hub assembly
— nacelle assembly.
The manufacturing surveillance for these components will be carried out at the start of the project specific
manufacturing of these components and depending on the inspection results in the course of production as
stated in section [3.2.1]. The extent of surveillance shall be based on a documentation review at the
manufacturers’ premises, covering the following items:
— compliance with quality plan requirements
— visual inspection of on-going jobs in order to check compliance with documented manufacturing
procedures
— test documentation review
— final documentation review.
Guidance note:
Focuses for manufacturing surveillance are the project specific adaptations of a type certified turbine and its components. The
manufacturing surveillance is a project specific inspection of a representative quantity of the project ordered components. The
availability of a quality management system at the workshop is a prerequisite. Quantities of inspection are adjustable, if reasonable
and still representative. The manufacturing sites in projects are often neither limited to, nor the same as, in the type certification. If
synergies are identified (e.g. by same manufacturing site as inspected during type certification), these can be used to reduce efforts,
upon agreement and permissions, see [3.2.1].
In general the sub-sub-suppliers of the wind power plant developer may not be inspected, if the documentation is complete and
processes at the sub-supplier compliant. However, in practice it may be helpful to decide for inspection at the sub-sub-supplier to
avoid observations of discrepancies at a later stage during the sub-supplier inspection.
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Secondary steel (ladders, boat landings, etc.) is not a mandatory part of the manufacturing surveillance
and needs to be agreed in advance.
Guidance note:
In certain cases, depending on whether the parts are critical or not with respect to design, component strength, and manufacturing
process or innovative material. Furthermore certain components are catalogue parts and may not be subject to inspection (e.g.
certain types of bearings). The same applies for standard designs of generators (not direct drive).
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3.2.2.2 Surveillance of support structure
The support structure for the wind turbine consists of the following components:
— tower
— substructure, if applicable
— foundation.
Separate surveillances of these components will be carried out as outlined in the following.
A tower section manufacturing surveillance shall be carried out for conical or tubular steel towers. The
surveillance shall be completed at the manufacturer’s shop and will be focused, on a random basis, on:
— compliance with quality plan requirements
— incoming goods inspection
— welding procedures specification and welding procedures qualification
— welders qualification
— construction drawings (shop drawings) versus reviewed drawings (design drawings)
— visual inspection of on-going jobs
— repair work
— witnessing of non-destructive testing and review of its documentation
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— painting
— visual inspection of finished sections before shipping
— documentation review.
Surveillance of monopiles and jacket structures shall be completed at the manufacturers’ shops or in the
fabrication yard and will be focused, on a random basis, on:
— compliance with quality plan requirements
— incoming goods inspection
— welding procedures specification and welding procedures qualification
— welder qualifications
— construction drawings versus reviewed drawings
— visual inspection of on-going jobs
— repair work
— corrosion protection systems
— witnessing of non-destructive testing and review of its documentation
— visual inspection of finished monopiles before shipping
— documentation review.
Surveillance of concrete structures and foundations shall be completed at the fabrication shop or
construction site and will be focused, on a random basis, on:
— construction and shop drawings for compliance with design drawings and specifications
— surveillance of measuring and testing equipment
— compliance with the specifications, standards and procedures
— formwork, reinforcing steel, embedment prior to concrete casting
— preparations for casting, use of correct materials, construction joints, grouting of ducts, curing
conditions etc.
— material tests
— corrosion protection systems
— repair work
— documentation review.
For other types of support structures, such as suction buckets or lattice towers, a detailed manufacturing
surveillance programme will be tailor made for each specific project.
Agreed surveillance of secondary structures shall be completed at the fabrication shop or at the
manufacturers’ premises. The surveillance will be carried out on a random basis and shall be focused on:
— compliance with quality plan requirements
— welding procedures specification
— welder qualifications
— construction drawings versus reviewed drawings
— visual inspection of on-going jobs
— witnessing of non-destructive testing and review of its documentation
— visual inspection of finished structures before shipment
— documentation review.
Alternatively the scope and type of components to be inspected can be determined by the risk based
approach described in [3.2.1] and in more detail in DNV-OSS-304.
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3.2.3 Substation
3.2.3.1 Surveillance of topside structure
The manufacturing surveillance of the topside structure will be carried out at the start of the project specific
manufacturing and depends on the inspection results in the course of production as stated in section
[3.2.1]. Depending on the number of manufacturing sites five to ten surveillance visits to the
manufacturer’s workshop or shipyard are considered as the minimum number of surveillances to be
completed by DNV GL.
The surveillance activities shall prioritize components and processes with highest risk and failure with most
severe consequences as described in [3.2.1]. The surveillance shall be focused on:
— compliance with quality plan requirements
— welding procedures specification and welding procedures qualification
— welders’ and NDT operators’ qualifications
— construction drawings versus reviewed drawings
— visual inspection of on-going jobs
— witnessing of non-destructive testing and review of its documentation
— visual inspection of finished sections before shipping
— documentation review
— review of as-built documentation, including nonconformities and technical queries which are relevant
for the design.
3.2.3.2 Surveillance of topside equipment
Electrical equipment is part of the project certification of the substation and therefore manufacturing
surveillance of such topside equipment is necessary for certification of the substation.
For topside equipment, the following documentation shall be submitted to DNV GL for the evaluation of the
manufacturing activities:
— general arrangement drawings and specifications
— manufacturing drawings, specifications and instructions.
For other topside equipment, the following documentation, in addition to the above mentioned shall be
submitted to DNV GL for the evaluation of the manufacturing activities:
— fire-fighting, life-saving and escape-route general drawings
— layout and arrangement of the topside equipment and systems.
The manufacturing surveillance of the topside equipment will be carried out at the start of the project
specific manufacturing and depends on the inspection results in the course of production as stated in section
[3.2.1]. Three surveillance visits to the topside assembly workshop or shipyard are considered as the
minimum number of surveillances to be completed by DNV GL. Two additional surveillance visits may be
necessary for testing purposes.
Surveillance shall be focused on:
— fire insulation
— fire-fighting appliances
— fire detection
— escape routes
— life-saving equipment and its arrangement
— electrical systems and installations.
3.2.3.3 Surveillance of support structure
The surveillance shall be completed in accordance with specifications given in relevant parts of [3.2.3.1].
The manufacturing surveillance of the support structure will be carried out at start of the project specific
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manufacturing and depends on the inspection results in the course of production as stated in section
[3.2.1]. Depending on the number of manufacturing sites five to ten surveillance visits are considered as
the minimum number to be completed by DNV GL, a specific agreement shall be established in each case.
For support structure concepts known to and for manufacturers DNV GL worked with, the minimum number
of surveillance visits may apply. For other types of support structures, such as concrete structures, new
concepts, and for manufacturers DNV GL starts to work with, the number of surveillance visits shall be
agreed for each project on a case-by-case basis, see [3.2.1].
If not agreed otherwise, the manufacturing and surveillance shall be based on DNVGL-ST-0145 and DNVOS-C401.
Guidance note:
A hierarchy of standards for the manufacturing requirements should be agreed at the beginning of the project. Usually the substation
is not subject to classification but certification according to this service specification. In case the substation is manufactured in
accordance with DNV-OS-C401 but in the context of this service specification the requirements listed in DNV-OS-C401 Ch.3, with
respect to qualification of companies may be excluded.
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3.2.4 Power cables
Power cables or its components shall be subject to manufacturing inspection and a comprehensive test
programme before, during and after the manufacturing process. This includes:
— type tests, demonstrating satisfactory performance through mechanical testing followed by electrical
and material testing
— routine tests, verifying that the product meets specifications, including tests on manufactured cable
lengths, tests on factory joints and factory acceptance tests of delivery cable lengths.
For the testing and test reports requirements listed in [1.6.8] shall be considered. Witnessing of tests may
be required and shall be agreed with DNV GL in advanced.
The manufacturing surveillance will be carried out at the start of the project specific production of the power
cables and depends on the results in the course of production as stated in section [3.2.1].
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
3.2.5 Control station
Construction for the control station besides installing the hardware and software means that all necessary
manuals (if not already available) and instructions shall be written in detail. They shall be available at the
control station during operation. Further on the reporting procedures have to be prepared.
The necessary manuals are:
— detailed technical description(s) of the wind turbine(s)
— detailed technical description of the substation
— operating manual for the wind turbines
— operating manual for the sub station
— maintenance manual for the wind turbines
— maintenance manual for the substation.
The necessary instructions are:
— process instructions for operation of the wind power plant
— process instructions for the monitoring of the wind power plant
— process instructions for the condition monitoring of the wind power plant (optional for onshore,
mandatory for offshore wind turbines of the power plant)
— list of availabilities of personnel for twenty-four-seven operation
— list of responsibilities of personnel
— process instructions for emergency cases.
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The necessary reporting procedures are:
— log book for each wind turbine (incl. commissioning report)
— log book for the sub station
— log book for the power cables
— event tracking for the whole wind power plant
— reporting to investors, insurance and authorities (i.e. DNV GL, BSH).
Manuals, instructions and reporting procedures listed above shall be submitted for assessment.
Manufacturing surveillance is not intended for the control station in the sense of this service specification.
In case of individual customer requests the scope shall be agreed with DNV GL.
For the certification of condition monitoring systems and condition monitoring bodies DNVGL-SE-0439 shall
be applied.
DNV GL recommended practice DNV-RP-D201 (see C. Construction, Section 8) for integrated software
dependent systems may be applied.
For asset management the ISO 55000 series may be applied, see [2.3.6].
3.3 Transport and installation
3.3.1 General
Transportation and installation is a crucial temporary life-cycle phase in a wind power project. DNV GL shall
perform transportation and installation surveillance as part of the project certification process.
For wind power projects the transport and installation surveillance starts with loading at the manufacturers’
production sites and ends at the wind power plant site.
The transportation and installation surveillance shall be followed up by a detailed surveillance report. This
surveillance report will include photo documentation whenever deemed necessary. Permissions required by
suppliers shall be provided to DNV GL by the developer or contractor.
Prior to the transportation of the component or assets, method statements for transportation and
installation manuals including loading and unloading shall be issued for DNV GL review.
As part of the project certification process DNV GL shall perform
— review of the transport and installation documentation (e.g. installation manuals, method statements,
drawings)
— surveillance of transport and installation.
The target of these certification activities is to assure that
— the loads on components and subsystems of the asset are not exceeding the design limits during
transport and installation
— the execution of transport and installation procedures are in conformity with the requirements stated in
the approved design documentation
— possible transport and/or handling damages or deviations from the approved procedures are being
detected and evaluated in terms of impact to the integrity of the asset.
The documentation for the transport and installation shall include at least the following information:
— wind power plant overview
— wind power plant site plan
— technical specifications applicable for transport and installation (among others these comprise
dimensions, weights of components and centres of gravity, dimensions of the barges and installation
vessels, offshore cable mechanical properties)
— limiting environmental conditions for transport and installation (e.g. wind speed, wave height,
temperature, timeframe)
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— technical data of transport and installation arrangement including required fixtures (sea fastening),
tooling and equipment (e.g. upending tools, lifting arrangements)
— proofs and respective certificates/ evaluation reports of structural integrity of the components during
transport and installation (including intermediate construction and transportation states or deviating
scenarios)
— relevant component/ type certificates (e.g. type certificate of the offshore wind turbine)
— detailed description of working steps having influence on the asset integrity over the lifetime of the wind
power plant (among others load-out, transport, lifting, set-down, piling, suction, levelling, grouting,
pre-assembly of rotor star, installation of tower segments, nacelle, rotor star / rotor blades, installation
of substation topside, welding, cable laying, cable trenching, cable pull-in, scour protection, corrosion
protection)
— description of required protection measures (e.g. protecting caps, vortex ropes, active corrosion
protection, environmental protective coverage)
— limiting values (among other cable trenching depth, cable pull-in strengths, pile driving number/energy,
jacket levelling angle, tightening moments for bolt connections)
— description of quality control check points, measurements and inspections (including non-destructive
tests), required by the design.
Transport and installation surveillance includes the following activities:
— identification and allocation of relevant components of the assets
— inspection of components / prefabricated subassemblies to be transported and installed for adequate
quality of manufacture (in case this has not been carried out at the manufacturers’ workshops)
— monitoring of environmental conditions for conformity with the approved documentation
— design-actual comparison installation location coordinates (for foundations)
— monitoring of methodology, sequences, limiting values and timing of important working steps (load-out,
transport, lifting, set-down, pile driving, grouting, welding, bolting, installation of scour protection,
activation of corrosion protection system, etc.)
— checking the components for damage during transport and installation.
Once the surveillance of the transport and installation has been successfully completed, DNV GL will issue
a certification report and a statement of compliance for transport and installation, listing the assets subject
to evaluation.
3.3.2 Wind turbines
The transport and installation surveillance of the wind turbines shall cover at least 10% of the wind turbines
of the wind power plant where the first installation site is part of this scope.
The surveillance comprises the support structure (e.g. monopile, transition piece, jacket, suction bucket,
tower) and the RNA itself (e.g. nacelle, hub, blades).
The amount of surveillance will be increased to avoid higher cost implications during later phases such as
operation, in the case of appearance of
— transport and/or handling damages or deviations from the approved procedures,
— coordination, management or quality issues.
The general section above applies, see [3.3.1].
3.3.3 Substation
The transport and installation surveillance of the offshore substation and/or accommodation platform shall
cover all components including support structure and topside.
The general section above applies, see [3.3.1].
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3.3.4 Power cables
The transport and installation surveillance of the inner park cabling system shall cover at least 10% of the
system length where the first installation site is part of this scope. The export cable route shall be
accompanied to full extent, if applicable.
The amount of surveillance will be increased in the case of appearance of
— transport and/or handling damages
— coordination, management or quality issues.
The installation certification phase includes onshore (landfall) and offshore construction activities as well as
load-out and transport. Processes and limiting conditions shall be well analysed and documented in socalled method statements (procedures) for the installation and testing execution of the complete subsea
cable system. Risk assessments, including hazard identification (HAZID), hazard and operability study
(HAZOP) and/or failure mode and effect analysis (FMEA) shall be carried out for each step of the installation
procedures. An overall installation manual shall be developed. The installation manual shall include the
installation sequence and methodologies for the individual installation steps.
The applicable operational limiting conditions shall be defined based on the intended vessel’s capabilities,
the planned installation techniques, the applicable weather windows and suitable contingencies. The
operational limiting conditions shall be based on detailed load effect analyses, vessel station keeping
capability and FMEA / HAZOP data. Continuous monitoring and recording of the measuring devices required
for control of the operational limiting conditions shall be performed during all phases of installation activities
in order to assure the power cable integrity.
The operational criteria shall account for uncertainties both in weather forecasts and monitoring of
environmental conditions. Regular weather forecasts of a recognised meteorological centre shall be
available on-board of the cable installation vessel, supplemented by historical environmental data.
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
3.3.5 Control station
The transport and installation topic is not applicable for the control station in the sense of this service
specification. In case of individual customer needs the scope should be agreed with DNV GL.
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SECTION 4 COMMISSIONING, OPERATION AND MAINTENANCE
4.1 General
An as-built survey covering the complete power plant shall be performed to evaluate that the completed
installation meets the specified requirements, and to document any deviations from the original design.
DNV GL shall evaluate the commissioning, operation and maintenance manuals and shall witness the
commissioning to evaluate compliance between the approved design basis, design and the as built wind
power plant.
The commissioning, operation and maintenance manual submitted for certification should be those intended
for the end-user (developer, operator etc.). The manuals shall cover all assets of the wind power plant under
certification. The manuals may also be in digital format. IEC 82079-1:2012, especially Chapter 5.9, shall
be considered for preparation of manuals.
The manuals shall be compliant with the requirements of the type certification and the design basis of the
wind power plant. Provision for documenting operational and maintenance records shall be included in the
manuals.
The detailed scope of work shall be agreed upon and stated in the certification contract between customer
and DNV GL.
For surveillances [1.6.11] shall be considered.
4.2 Commissioning
4.2.1 General
For commissioning of the assets the following activities will be performed for certification:
1) assessment of the commissioning manual
2) commissioning surveillance
3) inspection of installations and review of commissioning records.
The requirements for the commissioning manual are described below.
The requirements for certification of the different assets are described below.
For each asset the commissioning manual shall be submitted to DNV GL for certification.
The commissioning manual shall describe all working steps that shall be performed during commissioning.
The format and level of detail shall be such that the qualified technical personnel can comprehend the
instructions.
The commissioning manual shall contain the following information as a minimum:
— type identification of the respective assets
— checks required before the start of commissioning
— working steps of the commissioning process
— checks required to conclude the commissioning
— warnings for hazardous situations
— blank form sheets for the commissioning report.
IEC 82079-1:2012, especially Chapter 5.8.3, shall be considered for the preparation of the manuals.
Once the surveillance of the commissioning has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for commissioning, listing the assets subject to
evaluation.
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4.2.2 Wind turbines
4.2.2.1 Assessment of the commissioning manual
The commissioning manual shall be submitted for assessment.
4.2.2.2 Commissioning surveillance
Before commissioning surveillance starts, the customer shall provide a written statement that the wind
turbine has been erected properly and completely. The commissioning shall be performed under
surveillance of DNV GL.
This surveillance covers witnessing by the inspector during the actual commissioning, whereas DNV GL is
obligated to follow up quality-relevant nonconformities found during the surveillance. Quality-relevant
nonconformities and their consequences shall be communicated immediately.
In the course of commissioning surveillance the commissioning manual shall be followed and functions of
the wind turbine shall be tested. This includes the following tests and activities:
— test of the emergency stop buttons
— triggering of the brakes and witnessing of turbine’s behaviour
— test of the yaw system
— behaviour at grid loss
— behaviour at over speed
— test of automatic operation
— visual inspection of the entire installation
— test operation of ballast system and bilge pumps, if applicable
— test on draught and stability for floating structures.
In addition to the tests, the following items shall be examined during commissioning surveillance by visual
inspection of the entire wind turbine:
— general appearance
— corrosion protection
— damages
— conformity of the main components with the certified types / versions
— control software version
— design and traceability / numeration of the same.
The number of wind turbines for commissioning surveillance shall be agreed between the customer and
DNV GL.
In case the surveillance reveals serious nonconformities, the number of wind turbines for surveillance shall
be increased. A respective agreement between DNV GL and the customer shall be reached.
4.2.2.3 Inspection of installations and review of commissioning records
The wind turbines shall undergo an inspection of the entire wind turbine. This inspection shall be performed
after the commissioning has been carried out. DNV GL does not require witnessing of the actual
commissioning process at the turbines chosen for inspection.
The following items shall be inspected:
— general appearance
— corrosion protection
— damages
— conformity of the main components with the certified types and versions
— design and traceability including numeration of the same.
Additionally the commissioning records shall be submitted to DNV GL for assessment.
The number of inspections and review of commissioning records of wind turbines shall cover at least 10%
or two turbines (the larger of the two numbers shall be chosen) of the wind power plant.
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In case the inspection reveals serious nonconformities, the number of wind turbines for inspection shall be
increased. A respective agreement between DNV GL and the customer shall be reached.
4.2.3 Substation
4.2.3.1 Assessment of the Commissioning manual
The commissioning manual is to be submitted for assessment.
4.2.3.2 Commissioning Surveillance
Before commissioning surveillance starts, the customer shall provide a written statement that the
substation has been erected properly and completely. The commissioning shall be performed under
surveillance of DNV GL.
This surveillance covers (inside the scope agreed) witnessing by the inspector during the actual
commissioning, whereas DNV GL is obligated to follow up quality-relevant nonconformities found during the
surveillance. Quality-relevant nonconformities and their consequences shall be communicated immediately.
The commissioning procedure may be divided in different parts like e.g. onshore commissioning, offshore
commissioning without grid connection, offshore commissioning with grid connection. In the course of
commissioning surveillance the commissioning manual shall be followed and functions of the substation
shall be tested. This includes the following tests and activities:
— test of the emergency lighting
— test of emergency power supply
— behaviour at grid loss
— test of fire fighting systems
— visual inspection of the entire installation
— test operation of ballast system and bilge pumps, if applicable
— test on draught and stability for floating structures.
In addition to the tests, the following items shall be examined during commissioning surveillance by visual
inspection of the entire substation:
— general appearance
— corrosion protection
— damages
— conformity of the main components with the certified types / versions
— design and traceability of the same.
The scope of commissioning surveillance shall be agreed between the customer and DNV GL. It shall be
stated in the contract.
In case the surveillance reveals serious nonconformities, the scope of the surveillance shall be increased. A
respective agreement between DNV GL and the customer shall be reached.
4.2.3.3 Inspection of installations and review of commissioning records
The substation shall undergo an inspection of the parts which were not in the scope of the commissioning
surveillance. This inspection shall be performed after the commissioning has been carried out. DNV GL does
not require witnessing of the actual commissioning process at the components and systems chosen for
inspection.
The following items shall be inspected:
— general appearance
— corrosion protection
— damages
— conformity of the main components with the certified types/versions
— design and traceability of the same.
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Additionally the commissioning records shall be submitted to DNV GL for assessment.
The scope of the inspection shall be agreed between the customer and DNV GL.
4.2.4 Power cables
Subsea cables and fibre optic elements shall subsequently be commissioned after successful laying and
installation. Fixation, testing and termination works shall be carried before the cables will be put into
operation.
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
4.2.5 Control station
4.2.5.1 General
Commissioning of the control station is performed in conjunction with the commissioning of the wind
turbines and the substation. The tests described in [4.2.2] (wind turbine) and [4.2.3] (substation) shall be
preferably executed at a practicable place and monitored by the control station. Before execution of these
tests the communication system within the wind power plant shall be tested for functionality.
DNV GL recommended practice DNV-RP-D201 (see D. Acceptance, Section 9) for integrated software
dependent systems may be applied.
For asset management the ISO 55000 series may be applied, see [2.3.6].
4.2.5.2 Assessment of the Commissioning manual
The commissioning manual shall be submitted for assessment.
The control station’s commissioning manual shall describe how the communication tests are to be
performed and how the control station’s/SCADA quality criteria shall be validated in enabling the tasks of
the power plant operating phase.
4.3 Operation
4.3.1 General
The operation manual shall include at least the following information:
— site-specific requirements
— general description of all wind power plant components that are covered by the manual
— the adherence to grid code compliance should be documented
— description of general operation of the wind power plant
— description of SCADA (supervisory control and data acquisition)
— description and specification of all operation activities to be carried out during the operational life of the
wind power plant
— description of emergency cases (including personnel safety) and actions
— description of power back-up installations
— telecommunication procedures
— details about access possibilities (helicopter, ship, …) and the conditions associated with it
— fault handling and resetting
— personnel safety requirements.
Once the evaluation of the operation manuals has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for operation, listing the assets subject to evaluation.
4.3.2 Wind turbines
The operation manual for the wind turbines, certified as part of the type certification, shall be included, see
[1.6.5] and Figure 1-9. Modifications to the manual, due to the prevailing site conditions, shall be explicitly
mentioned.
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4.3.3 Substation
The operation manual for the substation shall be in compliance with DNVGL-ST-0145.
4.3.4 Power cables
This section refers to requirements for a safe and reliable operation of a subsea power cable system during
its service life with the main focus on management of cable integrity. The cable owner / operator shall
establish and maintain an asset management system for the subsea cable installation which complies with
regulatory requirements, when not included in the overall offshore wind power plant management system.
The cable shall be operated and maintained to ensure adequate performance with regard to safety and
required system availability considering, e.g., environmental conditions and consequences of failures.
Detailed procedures for all required in-service activities shall be established including specification of
monitoring, inspection and repair activities.
The requirements of DNVGL-ST-0359 shall be applied in general.
4.3.5 Control station
The main objective of the control station is to operate the wind power plant. The necessary personnel to
operate the power plant consist of:
— wind power plant operator
— plant manager
— maintenance manager
— control personnel
— monitoring personnel
— condition monitoring personnel (optional for onshore, mandatory for offshore wind power plants).
Task of the wind power plant operator:
— operation of the wind power plant (based on weather forecast, trace of vessel traffic within wind power
plant borders etc.).
Tasks of the plant manager:
— analysis of the operating data, availability of each wind turbine
— cost effectiveness study
— revenue prognosis
— optimisation possibilities.
Tasks of the maintenance manager:
— coordination of maintenance and periodic monitoring of wind turbines
— scheduling of maintenance
— scheduling of maintenance personnel and necessary equipment
— scheduling of periodic monitoring (ideally performed by DNV GL).
The task descriptions shall be submitted for assessment.
DNV GL recommended practice DNV-RP-D201 (see E. Operation, Section 8) for integrated software
dependent systems may be applied.
For asset management the ISO 55000 series may be applied, see [2.3.6].
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4.4 Maintenance
4.4.1 General
For the maintenance of the assets the following activities will be performed for certification:
1) assessment of the maintenance manual
2) assessment of the inspection plan for the periodic monitoring inspections.
The requirements for the maintenance manual are described below.
The requirements for certification of the different assets are described below.
Once the evaluation of the maintenance manuals has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for maintenance, listing the assets subject to evaluation.
4.4.2 Maintenance manual
For each asset the maintenance manual is to be submitted to DNV GL for certification.
The maintenance manual shall describe all working steps that shall be performed during maintenance. The
format and level of detail shall be such that the qualified technical personnel can comprehend the
instructions.
The maintenance manual shall include at least the following information:
— prerequisites for maintenance
— working steps tests and inspections to be performed at the maintenance
— warnings against hazardous situations
— maintenance record templates
— maintenance plan.
IEC 82079-1:2012, especially Chapter 5.10, shall be considered for the preparation of the manuals.
4.4.3 Wind turbines
The maintenance manual shall be submitted for assessment.
The inspection plan for the periodic monitoring inspections (see [4.5.2]) shall be submitted for assessment.
4.4.4 Substation
The maintenance manual shall be submitted for assessment.
The inspection plan for the periodic monitoring inspections (see [4.5.3]) shall be submitted for assessment.
4.4.5 Power cables
The maintenance manual shall be submitted for assessment. The DNVGL-ST-0359 shall be considered.
The inspection plan for the periodic monitoring inspections (see [4.5.4]) shall be submitted for assessment.
Objectives for (continuous) monitoring are to record the status of the cable system, to detect changes in
operating conditions and to take mitigation actions such as restricting operational parameters (e.g.
electrical current, temperature).
4.4.6 Control station
For the maintenance of the control station reference is made to [4.3.5].
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4.5 In-service/periodic monitoring
4.5.1 General
The objective of in-service or periodic monitoring (PM) is the inspection of the entire assets and components
of the wind power plant under consideration of the site-specific conditions by DNV GL. The certification
documents of the different certification phases of the project certification shall be available as they contain
relevant information and conditions.
Within the scope of in-service or periodic monitoring are the topside of the substation (if applicable), rotor
and nacelle of the wind turbine, support structures and seabed level or scour protection.
Structural integrity including electrical systems, machinery, functioning of safety and braking systems shall
be examined as well.
In-service or periodic monitoring shall be carried out on the basis of this service specification. Additional
standards and regulations valid at the site shall be observed and applied.
The in-service or periodic monitoring concept is based on different sources of information and shall be
submitted to DNV GL, see Figure 4-1.
The wind power plant operator is responsible to prepare the in-service or periodic monitoring concept. All
relevant information such as conditions from certification (see Figure 1-9), reports on repairs and building
permit should be part of the concept.
At least the following documentation shall be reviewed and considered for periodic monitoring:
— certifications, approval and certification reports, including all annexes and supplements
— building and operation permit
— operating manual
— filled-out commissioning record
— filled-out maintenance checklist (maintenance records) of at least the last maintenance
— reports of previous in-service or periodic monitoring or condition surveys, e.g. condition-based
monitoring measurements (if available)
— documentation of modifications / repairs and necessary approvals, if relevant
— reports of inspection of scour protection or seabed level
— reports of inspection of the underwater structures and splash zone
— annual report (e.g. trend analysis by CMS) of the monitored wind turbine components.
For preparation of inspection an individual inspection check list, based on the concept and documentation
review, shall be prepared by the independent DNV GL inspector for each wind turbine, substation and power
cable to be inspected.
All assets of the entire wind power plant should be inspected at least once during a five-year period.
Inspection intervals for subsequent inspections should be modified based on findings. The determination of
the quantity of wind turbines subject to inspection for in-service/periodic monitoring shall be agreed before
inspection on a project specific situation.
The result of the inspection shall be stated in the inspection report to be submitted to the certification body
of DNV GL for the assessment.
Annually the compliance will be attested by DNV GL, see also [1.6.6].
Once the evaluation of the in-service or periodic monitoring has been successfully completed, DNV GL will
issue a certification report and a statement of compliance for in-service, listing the assets subject to
evaluation. Regarding validity of the project certificate reference is made to [1.6.6].
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Checklist of
maintenance
manual
(filled)
Requirements of
type certificate and
site specific design
assessment
Modification and
repair reports
Reports /
requirements of
former PM‘s
Periodic monitoring
concept
Operating
instructions
Records of
commissioning,
transportation,
installation and
operation
Building permission
(incl. annexes)
Individual
inspection
checklists
Inspection
New requirements
for PM
Requirements for
maintenance
manual
Inspection report
Statement of compliance
(one year extension of
project certificate &
operating license)
Figure 4-1 Overview periodic monitoring (PM) concept
4.5.2 Wind turbines
The wind turbine manuals, certified as part of the Type certification, shall be included, see [1.6.5] and
Figure 9. Modifications to the manuals, due to the prevailing site conditions, shall be explicitly mentioned.
The general section above applies, see [4.5.1]. In addition reference is made to DNVGL-ST-0126.
4.5.3 Substation
The general section above applies, see [4.5.1]. In addition reference is made to DNVGL-ST-0145.
4.5.4 Power cables
DNVGL-ST-0359 shall be applied and requirements stipulated therein shall be fulfilled for certification.
4.5.5 Control station
The in-service or periodic monitoring as described in [4.5.1] to [4.5.4] shall be preferably coordinated by
the maintenance manager, see [4.3.5] considering following items for the wind power plant.
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— coordination of periodic monitoring of wind turbines
— coordination of periodic monitoring of substation
— coordination of periodic monitoring of power cables
— scheduling of periodic monitoring.
— For asset management the ISO 55000 series may be applied, see [2.3.6].
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SECTION 5 LIFETIME EXTENSION
5.1 General
Wind turbines (incl. support structure) are designed for a finite lifetime. Usually a design lifetime of 20 years
is taken as the basis for the design.
If a wind turbine or wind power plant shall be operated beyond its design lifetime (see Figure 5-1), the
turbine/wind power plant is to be assessed with regard to its potential for lifetime extension.
Different approaches can be taken to provide the necessary evaluation.
Figure 5-1 Definition of lifetimes
Once the evaluation of the lifetime extension has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for lifetime extension, listing the assets subject to
evaluation.
5.2 Wind turbines
Certification requirements regarding lifetime extension of wind turbines can be found in DNVGL-SE-0263.
Technical requirements on extending the lifetime of wind turbines are defined in DNVGL-ST-0262.
5.3 Substation
For substations the principals stipulated in the documents listed under [5.2] can be taken as a basis for the
evaluation of the extension of the original design lifetime.
5.4 Power cables
For power cables the subject of lifetime extension is addressed in CIGRÉ TB 279, chapter 8.
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SECTION 6 DECOMMISSIONING
The certification of decommissioning and subsequent deconstruction and transport of the wind power plant
is an optional module. The removal of the wind power plants hardware including all assets and equipment
from site (i.e. deconstruction and transport) may be enforced by law or may be carried out for economic or
reputation reasons.
The degree of deconstruction shall be defined in the beginning. It may vary from partial to complete removal
of power plant components or even to an extensive restoration of the original site state (including sub soil).
Local laws may prescribe this very stringently.
The decommissioning manual shall document at least the following:
— methodology and description of all working steps of the decommissioning of all the wind power plant
assets
— estimation of the duration of the decommissioning including possible waiting time
— requirements for transportation.
The concept of the decommission and deconstruction should be developed before construction of the wind
power plant.
The detailed decommission and deconstruction manuals shall be developed at latest during operation and
adapted continuously where necessary to meet the real conditions and circumstances of the power plant
and its environment.
The following steps shall be certified:
1) decommission and deconstruction concept
2) decommissioning
3) deconstruction
4) transport.
For all steps, the general concept as well as the manual shall be reviewed. Additionally, there is an
exemplary witnessing on site for the steps two to four.
Concepts and manuals shall describe the methodology of the work to be performed in a traceable and
plausible way. A time schedule for each major step, with a view to the seasonal weather conditions, shall
be included. The steps may be similar to the ones of the construction phases transport, installation and
commissioning, just in a reverted order.
All works shall be planned with a view on minimizing risks for personnel and the environment. The concepts
shall contain the relevant risk scenario analyses. A possible loss of certain components and their eventual
recovery shall be treated in a conceptual way.
In case of deviations of the real actions on site from the manual, DNV GL shall be contacted immediately;
the deviations shall be documented and submitted for assessment.
For decommissioning of power cables DNVGL-RP-0360 shall be applied.
The results of the decommissioning concept evaluation (see above step 1) will be documented by a
certification report and a statement of compliance. The certification can be continued on this basis until final
decommissioning (see above steps 2 to 4).
Once the evaluation of the decommissioning has been successfully completed, DNV GL will issue a
certification report and a statement of compliance for decommissioning, listing the assets subject to
evaluation.
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SECTION 7 REPOWERING
7.1
General
Repowering means the substitution of existing wind turbines or assets with new ones at the same site. The
substitution of major components may also be meant as repowering. Usually, the reason for repowering is
to increase the energy output on a given area. Compared to a completely new site, an existing one has
generally lower barriers for obtaining a (re-)building permission, may have higher mean wind speeds, better
logistics and grid availability.
More modern and bigger wind turbines usually have a larger hub height, earning energy in a larger air
volume with higher wind speeds on the same area. Due to more advanced turbines, transformers and
control technology, the new power plant has a higher mean power, can be better integrated into the grid
and has lower life-cycle costs, benefitting from the wind turbine operating experiences in the past.
After at least 10 years of continuous operation, there may be much more precise environmental data
available for the site than in the original design phase. These can be used to design the wind power plant
in a way that it fits exactly to this special site.
The certification process is similar to that for new wind power plants.
For some certification phases, there are differences to the handling of a power plant on a new site. For
example:
— design basis
all environmental data (i.e. soil, wind, wave, currents, scour) shall be completely updated and diligently
compared to formerly available data.
— design
environmental conditions may have had an impact on the operation and/or maintenance of the old
turbines, e.g. dust, sun radiation, salt, local grid characteristics. This shall be taken into account for the
components of the new wind power plant to achieve lower life-cycle costs.
For gravity based foundations, the soil may be consolidated for the loads of the old wind power plant,
giving better parameters for a new gravity based foundation newly erected at the same location.
The re-powering certification can be even more cost efficient, if the repowering is carried out based on a
former DNV GL certified project. In this case information and documents from the previous certification can
be used to increase synergies. Permissions required shall be provided to DNV GL.
Once the evaluation of the repowering has been successfully completed, DNV GL will issue a certification
report and a statement of compliance for repowering, listing the assets subject to evaluation. Depending
on the scope of the repowering a certification of the new power plant as described in [2.3] to [4.4] may be
necessary.
7.2 Wind turbines
Repowering may show the following options:
1) Exchange of turbines on each single site, using the old substructures for the new wind turbines.
New, larger turbines have higher rated powers, but the substructure may be designed for ultimate loads
of equal size due to updated environmental data and better turbine control systems.
The fatigue damage for a given wind scenario is much less influenced by new controllers, but an analysis
of the damage accumulated so far may show enough reserve for a second life of the substructure.
If the confidence in the analysis of past damages is not high enough, the substructure may still be used
for new turbines on basis of the observational method. An already existing substructure may profit from
10 years or 20 years of periodic monitoring. All structural faults due to low quality and low cycle fatigue
have by than shown up, leaving only the pure fatigue damages as unknown factor. The required
monitoring (and repair) concept has to take a lower number of probable failure modes into account than
required for a fully new design at an unknown site. Reference is made to Sec.5.
2) Exchange of turbines on the same single sites, using new substructure.
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The original geotechnical data may be used (and re-interpreted, e.g. by large scale tests), saving a new
geotechnical campaign.
3) New wind power plant layout, i.e. new turbines on new individual sites.
For turbine and sub-structure detailed design, this can be treated as a new power plant. The old
components may have to be removed, please refer to Sec.6.
As the cost for the substructure comprises a substantial part of the total building investment, option 1 is
financially most attractive, but also the most demanding one from an engineering point of view. Its key
aspect is the environmental and structural damage data acquisition over the operational life of the old wind
power plant on which the evaluation of the fatigue damages is based. A relevant instrumentation of new
wind power plants with a view to a later repowering may be worthwhile.
7.3 Substation
If the power output of the wind power plant increases, the required transforming power of the substation
increases. Two main options are seen:
1) The support structure of the substation remains unchanged, while the transformers and others systems
are partially or completely exchanged. Minor changes to the support structure are possible, as long as
no main load carrying members are affected.
2) The substation is designed and erected completely new. The old components may have to be removed,
please refer to chapter Sec.6.
Option 1 requires a re-calculation of the substructure, based on updated loads. As the fatigue action on
substructures is relatively low and as the new extreme and fatigue design loads may be lower than the old
ones, this may be successful. The whole procedure can be based on that for the wind turbines (see Sec.5),
but under less stringent boundary conditions.
Further options such as an additional substation to an existing one can be possible.
7.4 Power cables
A higher power output also means a higher cable load. In most cases, the existing cables may be completely
exchanged. As for the other components, the design of the new components may benefit by the
environmental data accumulated during the operation of the existing power plant.
Further options such as an additional power cable to an existing one can be possible.
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SECTION 8 POWER PLANT RELATED SERVICES/SYSTEMS
8.1 General
This section provides a description of typical wind power plant related services and systems. These can be
certified on an optional basis as part of the above described asset related project certification or be provided
as stand-alone. These optional services are available on request, based on the individual needs. In case of
a certification of the wind power plant as a whole these systems should be part of the wind power plant
project certification as long as the topic is applicable to the site and configuration of the power plant.
Further topics not specifically addressed in this service specification or only partly by the referenced
standards are:
— submarine warning devices
— SCADA systems
— wind power plant access (procedures, instructions)
— ice warning and protection systems
— air and ship traffic.
These items would not exclusively relate to one of the assets, but can be relevant for the power plant
operation and maintenance. Thus these items can be part of the above described certification process, if
contractually agreed. The subjects require an early consideration in the wind power plant planning.
Therefore, they should be taken into account within the work for the above mentioned design basis of the
wind power plant and all subsequent certification phases, see [2.3].
In case the SCADA system will not be considered as part of the certification of the wind power plant, the
relevant chapters of the manuals will not be verified by DNV GL. A later certification may be only partly or
not possible at all.
In case the SCADA system is part of the certification, it shall be considered throughout the different
certification phases from design basis certification phase to in-service for the assets wind turbines,
substation, power cables and control station.
8.2 Site-specific type certification
The project certification or parts of it are always project related, thus for a specific project intention and
therefore linked to a defined site.
In general the adaptation and implementation of an existing type of turbine into a project is part of the
project certification and described in this service specification above. The existing type certificate is taken
as the basis.
Guidance note:
This work is typically done in collaboration between the project developer and the wind turbine manufacturer.
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Alternatively it is possible to perform a site level certification according DNVGL-SE-0441, see [8.2].
The site level certification is introduced to be prepared for project certification of offshore and onshore
projects. The site level certification aims at minimising the efforts in project certification for the turbine
manufacturer. In this case the implementation of an existing type of turbine into the project is facilitated.
The site-specific type should already consider the project specific needs the wind turbine shall comply with.
In the project certification the implementation of such a site-specific type certification will then be limited
to checking that all current requirements of the project are being met.
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Table 8-1 Site-specific type certification according to DNVGL-SE-0441
Module:
Design
Test
Manufacturing
Final Deliverable
Level
Site
Statement of
Compliance
Site-Design
Statement of
Compliance
Site-Test
Statement of
Compliance
Site-Manufacturing
Site-specific loads
A-Test +
A-Manufacturing +
Options:
Tower design
Foundation design
Options:
Noise emission
Power performance
Electrical characteristics
Inspection/audits
according to inspection
program.
Type Certificate
Site-Specific
8.3 Site suitability of onshore wind turbines
8.3.1 General
In particular for smaller onshore wind power plants, the objective to ensure a safe and cost efficient
operation may in many cases not be achieved by performing a full project certification according to Sec.2
to Sec.4 of this service specification. Instead for such projects the assets substation, power cables and
control station may not be subject to certification and the focus may be put on an independent verification
of the site suitability of the wind turbine including the site-specific support structures and other site-specific
design modifications.
The site suitability is determined within the certification modules design basis [2.3] and design [2.4], whereas
the certification modules manufacturing, transportation and installation as well as commissioning, operation,
maintenance are outside the scope of site suitability. Within the verification of site suitability for a wind turbine,
it may not be required to cover all aspects of the design basis and the design. Therefore the certification
modules site design conditions (SDC) and site-specific design assessment (SSDA) which can be tailored to the
requirements of a specific project have been defined for the site suitability of onshore wind turbines.
8.3.2 Site design conditions
The verification of the site design conditions covers relevant aspects of the design basis and results in a
certification report and a statement of compliance for the site design conditions. All or a sub-set of the
following items are subject to verification within the site design conditions module:
— site wind conditions
— site complexity analysis
— wind farm influence / wake analysis
— geotechnical conditions
— seismic site conditions
— other environmental conditions.
Since the scope covered by the site design conditions is not fixed, the statement of compliance for the site
design conditions will clearly indicate the validity for each of the items listed above, if they have been
subject to evaluation or not.
8.3.3 Site-specific design assessment
Basis for the site-specific design assessment is typically a statement of compliance for the A-design
assessment or a type certificate according to DNVGL-SE-0441 or other certification schemes. The sitespecific design assessment covers relevant aspects of the design and results in a certification report and a
statement of compliance for the site-specific design assessment. All or a sub-set of the following items are
subject to verification within the site-specific design assessment module:
— site-specific controller modifications
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— wind farm influence / wake analysis (if both SDC and SSDA are performed, this item is part of SDC)
— site-specific fatigue loads and seismic loading if applicable
— site-specific extreme loads and seismic loading if applicable
— geotechnical design
— foundation design
— tower design
— design modifications of the RNA
— grid code compliance.
Since the scope covered by the site-specific design assessment is not fixed, the statement of compliance
for the site-specific design assessment will clearly indicate the validity for each of the items listed above, if
they have been subject to evaluation or not. In the event that the site-specific wind turbine design deviates
from the statement of compliance for the A-design assessment or from its type certificate, or where e.g.
the foundation design was not part of the type certificate but shall be included in the site-specific design
assessment, the scope of verification for these elements will be outlined in the statement of compliance.
Guidance note:
The SDC and SSDA assessment may be performed independently from each other, neither one of them requires the other to be
performed first or in parallel.
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8.4 Meteorological masts
The meteorological (met) mast located close to the wind power plant can be certified. The met mast
structure will be certified against DNVGL-ST-0126 and equipment and instrumentation against IEC-6140012-1. This will ensure that the set of requirements laid down in the standards are met during design and
construction, and maintained during operation of the met mast. In addition this will ensure that the
stakeholders will get a reliable structural design and reliable wind (and wave) measurement for the wind
power plant throughout the service life of the met mast.
For the project certification the met mast is divided in two parts comprising:
— met mast structure and
— equipment and instrumentation.
More information can be found in DNVGL-SE-0420, where all relevant information can be found for off- and
onshore met mast certification as well as how to maintain the certificate by periodic maintenance during
the service life of the met mast.
8.5 Navigation and aviation aids of offshore plants
The assessment of the navigation and aviation aids (see Figure 8-1) of offshore plants is an optional service
recommended by DNV GL and even mandatory in some countries (e.g. Germany) in addition to the regular
project certification. This service aims at increasing the safety of sea and air traffic within and close by the
offshore plants and is divided into three steps:
1) assessment of navigation and aviation aids concept
2) commissioning
3) periodic inspections.
In a first step, DNV GL assesses the navigation and aviation aids concept, which describes the planned
actions with regards to the four most important aspects of a marking concept:
— day marker or aids
— night aids
— radio
— infrastructure.
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The second step is the commissioning of the four aspects listed above, which shall assure that all aspects
are realised as planned in the concept and that the operation of the system is verified by DNV GL. The
periodic inspections are the third step and shall assure the functionality and the proper conditions of all
installations with regard to the navigation and aviation aids. When project certification and the navigation
and aviation aids are both performed by DNV GL, synergies during manufacturing, commissioning and
operation and maintenance can be used.
The scope of work for the navigation and aviation aids of offshore plants can be agreed with DNV GL.
Figure 8-1 Overview of the navigation and aviation aids
8.6 Power plant performance
8.6.1 General
Optionally the project characteristics measurements may be performed for the specific wind power plant.
The measurements comprise one or more of the following items:
— grid connection compatibility according to grid codes (see Section [8.6.3])
— evaluation of power performance
— evaluation of acoustic noise emission.
The electrical performance of the substation connected to wind power plant and grid may be reviewed by
analysing the:
— wind power plant electrical layout
— active and reactive power flows
— influence on the existing electrical power grid (harmonics, flickers, lines overload, compensation)
— critical details.
The applicant may select the assessment of power quality measurements. In this case the measurements
shall be compliant to IEC 61400-21 and corresponding grid codes.
DNV GL shall evaluate the test reports. Section [8.6.3] provides further guidance with respect to the
application of grid codes and fulfilment of compliance.
Furthermore the electromagnetic compatibility (EMC) of the wind turbines can be evaluated according to
DNVGL-RP-0440.
In general reference is made to [1.6.8] regarding the reporting of measurements and the testing
laboratories.
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Once the evaluation of the power plant performance has been successfully completed, DNV GL will issue a
certification report and statement of compliance for wind power plant performance.
8.6.2 Power performance
The wind turbine power curve is typically determined for commercial turbines. The planning of the wind
power plant and the estimation of the total wind power production are based on such single turbine power
performance curves. The wind power plant consists of many wind turbines with a certain positioning. Thus
a power plant performance curve would be useful to predict the power plant output more adequately for a
given wind forecast.
The definitions in IEC/TS 61400-26-1 and IEC/TS 61400-26-2 can be considered to report availability and
other performance indicators of wind power plants. ISO/IEC 13273-1, ISO/IEC 13273-2 and IEEE 762 may
be considered in addition.
The power performance of the plant can be determined by load flow calculations considering for example
the electrical losses due to the power plant layout.
The evaluation of a wind power plant performance and availability can be offered on an individual basis.
8.6.3 Power plant grid code compliance
DNV GL recommends to perform this optional GCC (grid code compliance) service. This service can be a
part of the project certificate but also an independent service. This service deals with the certification of the
grid code compliance of the power plant and possible ancillary services to be offered to the transmission or
distribution system operator by the plant (e.g. reactive power capability or voltage control). It is a twostage certification procedure, see Figure 8-2. The first stage is the assessment of corresponding capability
of a wind turbine type which will be installed in the power plant under certification. In the second stage the
grid code compliance assessment of the power plant under consideration of the site-specific information and
requirements shall be performed.
The DNV GL standard (DNVGL-ST-0125) and service specification (DNVGL-SE-0124) offer different
assessment levels (GCC-class) for the above mentioned stages resulting in different kinds of certificates.
For project level the minimum GCC-Class is II. DNVGL recommends GCC-Class I. Applying DNVGL-SE-0124
only, alternative ways to certify parts are possible.
Stage 2: Project Certificate
GCC-Class I or II
Stage 1:
Type
Certificate
GCC-Class
I or II
Site Specific
information
(Cable,
Substation ...)
System
Operator
requirements
(reactive
power, LVRT ...)
Figure 8-2 Project certification of GCC (for more details see DNVGL-SE-0124)
8.7 Shop approval
DNV GL recommends performing shop approvals at wind turbine component or other asset component
suppliers. This includes for example various workshops for rotor blades, rotor blade repairs, steel support
structures, foundations, grouting material as well as mechanical components.
DNV GL certifies by this service that a workshop operates with approved production facilities, working
procedures and qualified staff. DNV GL assesses the ability to manufacture wind turbine components in
compliance with international standards and guidelines or acknowledged methods.
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The DNV GL Shop Approval is independent of component, type- or project certification and always specific
for the respective workshop. It consists of the two elements “general document review” and “on-site
inspection”, see Figure 8-3. The general document review includes evaluation of the general quality
documentation, e.g. specification for manufacturing purposes. Furthermore, a validity check of equipment
being used, abilities as well as skills of staff, is covered by this service. Within the on-site inspection the
evaluation of workshop with related manufacturing and quality processes is included.
During component and type certification the general document review as part of the manufacturing
certification may be omitted if a workshop holds a shop approval, see Figure 8-3. However, the scope of
specific document review shall be agreed with DNV GL. For type certification a design specific audit as part
of the manufacturing certification shall be carried out. If a workshop holds a shop approval the scope of the
audit may be reduced in agreement with DNV GL.
During project certification the general document review as part of manufacturing surveillance and the
initial audit may be omitted (see [3.2.1]) if a workshop holds a shop approval, see Figure 8-3. However,
the scope of the specific document review shall be agreed with DNV GL. The scope of regular inspection may
be reduced in agreement with DNV GL.
There is already a risk reduction through the on-site inspection before or at an early stage of project start.
The DNV GL service specification for shop approval services (see DNVGL-SE-0436) offers guidance for wind
turbine component suppliers.
Figure 8-3 Benefit and interaction concept of DNV GL shop approval for different certification services
8.8 Helicopter decks
Requirements of DNVGL-ST-0145 regarding helicopter landing platforms shall be observed. Special
attention shall be paid to
— helicopter deck structure and arrangement
— equipage including lighting equipment, fueling facility, fire protection, rescue equipment, escape routes
— helicopter deck marking.
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National requirements for helicopter decks shall always be followed. Required approvals by national
legislation shall be available.
Once the evaluation of the helicopter deck has been successfully completed, DNV GL will issue a certification
report and a statement of compliance for helicopter deck.
8.9 Health, safety and environment
For personnel health and safety related to the wind power plant and its operation, compliance with local
health and safety legislation shall be considered.
In the design of the wind turbine, investigations concerning aspects of occupational health and safety can
be taken into account through compliance with the standard EN 50308 in addition to offshore related
standards and guidelines. Compliance checks with national requirements regarding HSE may be performed.
The assessment according to this section can optionally be extended by the conformity assessment of
occupational health and safety of personnel aspects according to European or local laws and / or EN 50308.
Compliance should also be checked with respect to standards such as the series of the Global Wind
Organisation (GWO) Standard Basic Safety Training.
For the certification of offshore gangways for transfer of personnel DNVGL-ST-0358 should be applied.
Once the evaluation of the personnel health and safety has been successfully completed, DNV GL will issue
a certification report and a statement of compliance for personnel health and safety.
8.10 Integration of certificates
8.10.1 General
Within the project certification of onshore or offshore wind power plants according to this service
specification, there may be occasions when it is intended to integrate an existing wind turbine type
certificate or a component certificate of the rotor nacelle assembly. Possibilities for this are described in this
section.
It shall be considered that the integration of any type certificate shall be agreed with DNV GL in advance
for each individual project as not all possible options can be foreseen nor are shown within this service
specification.
As a project certificate attests compliance to a certain standard, it has to be ensured that the type and other
certificates to be used support this. Ideally, the type or component certificate is in compliance with the same
standard applied for project certification. If this is not the case, additional items shall be assessed within
the project certification procedure. In general it is possible to integrate a type certificate or component
certificate issued in accordance with DNVGL-SE-0441.
The integration of the type certificates or statements of compliance in the project certification shall be
reported in the final certification report of the respective certification phase and accordingly in the project
certificate.
In general for the integration of an existing type certificate or rotor-nacelle assembly component certificate,
the following documents shall be provided to DNV GL:
— type certificate or component certificate and all corresponding statements of compliance.
— certification reports related to the statements of compliance for the type or component certificate.
— further documentation needed e.g. for manufacturing or transport and installation surveillance,
manuals, grid connection parameters relevant for project certification.
Depending on the standard applied, additional requirements as listed in the following sections may apply.
8.10.2 Type certificate according to same edition of standard
The site-specific adaptations of the wind turbine type are considered within project certification as follows:
— evaluation of the site-specific loads shall be performed
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— a comparison of the site-specific loads with those analysed for the design assessment for the type
certificate shall be provided by the manufacturer
— the evaluation of the site-specific turbine adaptations in comparison with the formerly certified turbine
shall be performed, if necessary
— the evaluation of the site-specific foundation or support structure shall be performed by DNV GL
separately
— further documentation needed is e.g. for manufacturing, transportation and installation surveillance,
manuals, grid connection parameters relevant for project certification.
8.10.3 Onshore type certificate in offshore project certification
An onshore type certificate in an offshore project certification or vice versa requires additional actions.
In the event that a DNV GL type certificate based on the DNV GL service specification DNVGL-SE-0074 for
the onshore version of the turbine is available this can be used for offshore project certification. The
adaptation shall be agreed in advance for every project individually.
For fixed offshore wind turbines the steps listed below have to be considered.
1) The turbine (rotor-nacelle assembly) in question may need to be modified to comply with the offshore
environment and the changes operation and maintenance requirements. All modifications made shall
be reported by the manufacturer in a separate, consistent report. Special attention shall be paid e.g. to
the following issues:
— atmospheric control and corrosion protection of the machinery
— if the type certified tower shall be included a corrosion protection according to offshore requirements
shall be applied
— for structures in the splash zone material shall be selected according to offshore guidelines
— safety system remote control options
— requirements regarding offshore grid connection and electrical equipment
— adaptation of machinery materials (e.g. elastomers) and auxiliary materials (e.g. lubricants) to the
offshore conditions
— adaptation of fastenings, pad eyes etc. to the requirements of marine operations
— adaptation of manuals for transport, installation, operation and maintenance to the offshore
environment and the requirements of the offshore guidelines
— document explaining why onshore type testing is acceptable for the offshore version of the turbine.
2) DNV GL verifies whether the type certificate fulfils the requirements of the offshore application.
Outstanding issues and questions arising during this evaluation shall be resolved. After evaluation
DNV GL issues Certification reports for the above mentioned topics.
3) Site-specific adaptations of the wind turbine are considered within the site-specific design evaluation
and subsequent manufacturing, transportation and installation surveillance performed during project
certification:
— within the project certification a evaluation of the site-specific loads shall be performed
— a comparison of the site-specific loads with those used in the design assessment for the type
certification shall be provided by the manufacturer
— the evaluation of the site-specific support structure is performed by DNV GL separately. The support
structure includes the substructure, the foundation and, if not considered within the type
certification, the tower as shown in Figure 1-3.
8.10.4 Offshore type certificate in onshore project certification
In general the items listed in [8.10.3] shall be considered accordingly for the inclusion of an offshore type
certified wind turbine in an onshore wind power plant. The adaptation shall be agreed in advance for every
project individually.
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8.10.5 Type certificates according to former editions of standards
In case the type certificate is based on standards earlier than the valid editions, an upgrade of the type
certificate is required. In general the type certificate shall be valid on the date of issue of the statement of
compliance for the design phase and project certificate.
8.10.6 Type certificate or component certificate according to a standard
other than DNV GL
If the type certification or component certification is performed in accordance with standards other than
DNV GL, additional actions have to be taken to achieve acceptance.
If the wind turbine manufacturer holds a type certificate or component certificate according to a standard
other than DNV GL the documents listed in [8.10.1] and [8.10.2] of this service specification shall be
supplied. In addition the documents of the certification phase design basis shall be submitted. They shall
give a clear understanding of the design basis and show which standards and codes were used during the
type or component certification process and under which conditions they were applied. These documents
shall list all standards and codes applied and shall be given for all main components.
It should be noted that for integration of type or component certificates in offshore project certification the
same requirements as mentioned in [8.10.1] to [8.10.3] are to be considered.
DNV GL shall analyse these documents and decide which parts of the type or component certificate will be
acceptable and which parts shall be amended. This evaluation is done with a view on fulfilment in principle
of the governing standard in question and a special view on the project certification process according to
this service specification, and does not include any evaluation of strength calculation.
Further documentation, if found necessary for the project certification (e.g. manuals, grid connection
parameters) may be requested.
After assessment of the relevant documentation (including possible strength calculations) and under
consideration of the information provided by the type or component certificate issuing certification body,
DNV GL shall inform the project certification applicant regarding the acceptance of the type or component
certificate and of any conditions or additional evaluations which may be needed to integrate the type or
component certificate in the project certificate.
8.10.7 Acceptance of certificates not issued by DNV GL
The acceptance of wind turbine type certificates and rotor-nacelle assembly component certificates
originating from certification bodies other than DNV GL shall be agreed in advance for every project
individually. Following minimum requirements apply:
— the type or component certificate shall be issued by a certification body holding an accreditation
according to ISO 17065 for the relevant standards. Copies of the accreditation document including
amendments listing the scope and standards shall be provided
— escrow agreement for the type or component certificate design documentation or written confirmation
by the certification body that all type or component certificate related documentation will be kept for
the intended life duration of the project
— permission by the manufacturer to contact the type or component certificate issuing certification body
and exchange information regarding the type or component certificate of the turbine or component in
question
— clarification meeting with the type or component certificate issuing certification body and type or
component certificate accepting certification body for the project certification, if necessary
— documentation as required for the integration of type or component certificate in project certification.
DNV GL shall review the documentation provided. The review shall cover as a minimum the following
aspects:
— if the scope of work is within the accredited scope
— the scope of work and certification work process
— the quality of the technical reporting
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— if the defined scope of work is completed and concluded
— if interfaces to other certification modules are clearly described and the relevant documentation needed
is provided
— if the conditions for validity are understood such that they can be considered in the final project
certificate
— if the status of outstanding items and provisions - if any - is clearly described such that these can be
accounted for in the finalization of the project certification.
In general the documentation provided shall not lead to lack of knowledge of overall integration of systems,
increase the risk of the certification or fragment the certification process outside of natural interfaces.
After assessment of the relevant documentation and under consideration of the information provided by the
type certificate issuing certification body DNV GL will inform the project certification applicant regarding the
acceptance of the type or component certificate and of any conditions or additional assessments that may
be needed to integrate the type certificate in the project certificate.
DNV GL shall not take responsibility for other certification bodies’ work, which shall be stated in the project
certificate.
The quantity of certificates and statements to be integrated shall be limited to a feasible number to ensure
the quality of the project certificate to be delivered. DNV GL shall evaluate the possibilities on an individual
basis for each project.
8.11 Escrow
Wind power plants can only be realised with a large volume of information and a lot of know-how. Escrow
agreements offer a secure and sustainable deposit of sensible data for all stakeholders. DNV GL acts as an
independent escrow agent. DNV GL supports developers, manufacturers and its customers regarding the
secure handling and keeping of documentation for renewable energy projects and assets. Regardless of
whether a supplier or end user of products, it is important to protect the know-how and to have reliable
access to business-critical documents in case one or more business partners fail. As an internationally
recognized and independent certification body, we are able to act as an escrow agent on behalf and in the
interest of all contractual parties in order to minimise risks and safeguard knowledge.
The benefits are as follows.
— reliable deposit of important and confidential information
— safeguarding of expertise against plagiarism
— access to business-relevant data in the case of failure of one or more business partner(s).
DNV GL offers following escrow services.
— escrow agent engagement agreements and product escrow agreements
— closing of product escrow agreements for fixed contract durations
— safekeeping of the complete documentation including regular updates.
The more critical the role of external expertise for companies is, the greater is the importance of security
by escrow.
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APPENDIX A LIST OF DOCUMENTS OFFSHORE SUBSTATION
The below list of required documents should serve as example and provide exemplarily guidance. The extent
of required documentation will depend on the agreed scope and the individual design of the substation.
Summary of required reports, specifications, etc.
1
design basis / design brief (incl. site assessment, geotechnical site report, concept grouted connection, draft
for foundation)
2
material specification
3
design calculation for corrosion protection
4
coating specification
5
fabrication / manufacturing specification
6
fire / explosion protection design documentation
7
access and transfer concept
8
evacuation concept
9
operation & maintenance concept
10
load out, transportation, installation and commissioning plan
11
operation and maintenance plan / manual
12
scour assessment or protection design report
13
site survey report and soil foundation expertise
14
primary structure design report (topside, support structure, grouted connection)
15
secondary structure design report (topside, support structure)
16
geotechnical / foundation design report
17
load out, transportation and installation analysis report
18
weight control report
19
driveability analysis study
Summary of required drawings, plans etc.
I
Structural
1
general arrangement plans
2
loading / weight plans
3
general note drawing (topside, substructure, foundation)
4
all structural drawing in order to trace the structural design documentation including dimensions, tolerances
and testing. E.g.:
4.1
substructure & foundation
4.1.1
plan views
4.1.2
elevation views
4.1.3
joint details
4.1.4
welding details
4.1.5
cathodic protection plans
4.1.6
intersection/connection at interfaces
4.1.7
boat landing
4.1.8
access platforms
4.1.9
stairs and ladders
4.1.10
lifting, transport and installation details
4.2
topside
4.2.1
plan views
4.2.2
elevation views
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4.2.3
joint details
4.2.4
welding details
4.2.5
deck plates
4.2.6
wall plates
4.2.7
helicopter deck structure
4.2.8
intersection/connection at interfaces
4.2.9
stairs and ladders
4.2.10
lifting, transport and installation details
4.2.11
access platforms
4.2.12
handrails and gratings
II
Electrical
1
general arrangement plans, operational philosophy
2
electrical network studies
3
data and test records of electrical equipment
4
ventilation and arrangement of electrical installations
5
system protection, earthing and bonding principles
6
single line diagrams including identification of components
7
cable rating and selection
8
cable lists, routing and dimensioning
9
cable data sheets or type lists, including information on fire protection properties and certificate references
10
cable schedules
III
Safety systems
1
quantitative risk analysis (QRA)
2
areas classification / categorization
3
passive fire protection rating of walls and floors
4
fire and safety equipment location plans
5
fire and gas detection systems plans
6
causes and effects charts
7
escape, evacuation and rescue analysis (EERA)
8
life-saving appliances plans
IV
Safety arrangement
1
general arrangement showing fire zones and passive fire protection
2
arrangement of safety devices and equipment
3
arrangement of fire detection and fire alarm systems
4
escape routes
V
Mechanical System
1
diesel generator / emergency diesel generator
2
mechanical system
3
heating, ventilating, and air conditioning
4
drain system
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APPENDIX B DELIVERABLES EXAMPLE
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DNV GL
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