Development of
Wind Industry Consensus Standards

Darrell M. Dodge
National Renewable Energy Laboratory

February 27, 1996

CONTENTS

Objectives and Scope of Work
Standards Development Process
Status of IEC Standards
NREL's Technical Role
Certification
Obtaining Standards Documents

1.0 Objectives and Scope of Standards Development Activities

Since 1978, DOE has provided technical and financial support to American Wind Energy Association (AWEA) efforts to develop wind industry consensus standards. This support also helps ensure that the U.S. wind industry can actively participate in the development of standards by international organizations. Since 1984, the DOE support has been conducted by NREL.

Specific standards development activities conducted by AWEA involve the development, review, adoption and publication of standards documents by experts in wind technology and related topics from industry, utilities, and the research community. AWEA's Standards Coordinating Committee (SCC) coordinates and ensures the review of all standards documents and participates in international wind energy standards development. AWEA has been designated as a standards-making organization by the American National Standards Institute (ANSI) and is recognized as the lead wind energy standards organization in the United States.

NREL also provides technical support through direct participation on domestic and international standards-making subcommittees and targeted analytical efforts.

2.0 Standards Development Process

AWEA serves as the lead organization for the development of U.S. industry consensus standards in liaison with a variety of professional organizations, including the American Society of Mechanical Engineers (ASME), the American Society for Testing of Materials (ASTM), ANSI, the National Fire Protection Association (NFPA), the American Gear Manufacturer's Association (AGMA), and the Institute of Electrical and Electronics Engineers (IEEE). In addition, AWEA participates in the development of international wind energy standards in conjunction with the International Energy Agency (IEA), the International Standards Organization (ISO), the International Electrotechnical Committee (IEC) and other appropriate international organizations.

Domestic standards development activities are performed under established AWEA standards subcommittees which are guided by the Standards Coordinating Committee (SCC). The subcommittees create standards documents which are then approved under a consensus process that involves soliciting comments from the industry at large and the eventual acceptance of the documents by the SCC for publication as AWEA standards.

Since 1988, it has been recognized that domestic U.S. standards must be compatible with IEC standards to ensure that U.S. wind businesses have full access to foreign markets. Therefore, the primary role of the domestic standards subcommittees has been threefold: 1) to develop guidelines and recommendations that have an impact on international standards, 2) to assess and vote on the adoption of international standards as U.S. domestic standards, 3) to develop standards for aspects of wind technology development and use that are not yet covered by international standards.

International standards are developed by the working groups of Technical Committee-88 (TC-88) of the International Electrotechnical Commission (IEC), the recognized international body for standards development activities.

2.1 Domestic Standards Development

Task 1 - Acoustics

Chair: T.James DuBois, DuBois and Associates

The Acoustics subcommittee is finalizing the Tier III standard (emissions from multiple arrays) and reviewing the approved IEC acoustics standard for adoption by AWEA as a U.S. national standard.

Task 2 - Design Criteria

Chair: John Westergaard, Boreal Enterprises

Gearbox Working Group Chair: Brent Reardon,

The Design Criteria subcommittee shall meet to review progress on the IEC Working Group 7 standard and shall submit the final version of the standard practice developed by the Gear Box working group to the SCC for adoption.

Task 3 - Siting

Chair: Bruce Bailey, AWS Scientific, Inc.

The Siting subcommittee is revising the 1986 Measurement Standard to incorporate the effects of recent changes and improvements in measurement technology. A workshop on site assessment technology will be held at Windpower '96 in Denver, CO, June 23-27, 1996.

Task 4 - WECS/Diesel

Chair: Robert Sherwin, Atlantic Orient Corporation

The Wind/Diesel subcommittee will hold a workshop in June 1996 in Halifax, Nova Scotia to continue the exchange of technical and market data and the promotion of ties between the wind industry and the diesel power industry.

Task 5 - Certification

Chair: Thomas Gray, American Wind Energy Association

The Certification subcommittee is continuing the process of harmonizing AWEA plans for certification in the United States with European countries. AWEA provides NREL and DOE with up-to-date information on the status of certification programs in other countries.

2.2 International Standards Activities

AWEA maintains liaison with the International Electrotechnical Commission (IEC) standards activities through involvement of an AWEA representative as the U.S. technical coordinator for TC-88 and the support of other U.S. industry members who serve as delegates to the Working Groups. The status of the IEC standards is provided in Table I.

Table I - Status of IEC Wind Turbine Standards

Group	Title	Convener	Start	Finish (Plan or Actual)	Status	Document #
WG-1 WG-2 WG-3	Safety Requirements for Large Wind Turbines	R. Sherwin, AWEA, USA	09/1989	12/1993	International Standard	IEC 1400-1
WG-4	Small Wind Turbine Systems	F.Van Hulle, ECN, NL	02/1992	Mid 1996	DIS*	IEC 1400-2
WG-5	Acoustic Measurement Techniques for Wind Turbine Noise Emissions	T.J. DuBois	11/1992	Mid 1996	DIS* in Preparation
WG-6	Performance Measurement Techniques	T. Pedersen, Riso NL, DK	11/1992	Mid 1996	Vote on DIS*
WG-7	Revision of IEC 1400-1	P.H. Madsen, Riso NL, DK	Spring 1994	Spring 1996	Approval Draft in Preparation
WG-8	Fatigue Testing Techniques of Wind Turbine Rotor Blades	D.van Delft, TU Delft, NL	Spring 1994	Spring 1996	Meeting in Denver, CO USA 03/1996
WG-9	Wind Turbine Certification	J.McGuire, Lloyds Register, UK	10/1995	1997	Underway
WG-10	Power Quality Requirements	J.O.Tande, Riso NL, DK	02/1996	1997	Underway
WG-11	Load Measurements	F.Van Hulle, ECN, NL	02/1996	1997	Underway

*Approved "Draft International Standard"

Description of TC-88 Standards and Working Groups

This section provides brief summaries of IEC activities. Standards are not available for use or application until they exist as approved "Draft International Standards" or "International Standards." These documents should be ordered from the IEC, citing the document number in Table I and specifying whether the standard is draft or final.

WG1, 2, 3 - Safety of Wind Turbine Generating Systems

Background - The first three TC-88 working groups (Safety Philosophy, Design, and Installation and Operation) were originally chartered separately, but were combined when it became evident that their objectives and roles were interdependent.

Scope of Work - This international standard deals with safety philosophy, quality assurance and engineering integrity, and specifies requirements for the safety of Wind Turbine Generator Systems (WTGS), including design, installation, maintenance, and operation under specified environmental conditions. Its purpose is to provide the appropriate level of protection against damage from all hazards from these systems during their planned lifetime. This standard is concerned with all subsystems of WTGS such as control and protection mechanisms, internal electrical systems, mechanical systems, support structures, foundations and the electrical interconnection equipment. The standard applies to 1) all sizes of WTGS connected to electrical power networks and 2) WTGS with swept area equal to or larger than 40 m2.

Contact - Robert Sherwin, Atlatnic Orient Corporation, USA

WG4 - Safety Requirements for Small Wind Turbines

Background - Standards for wind turbines with swept areas under 40 square meters (m²) were developed separately because of the unique control methods and features used by designers of these systems (such as foldable tails.) The separate standard was developed to avoid imposing costly requirements that would not result in improved safety of the smaller systems, which have different inherent risk factors than larger systems.

Scope of Work - Deals with safety philosophy, quality assurance, engineering integrity and specifies requirements for the safety of small wind turbine generators (SWTGS), including design, installation, maintenance and operation under specified external conditions. This standard is concerned with all subsystems of SWTGS such as protection mechanisms, internal electrical systems, mechanical systems, support structures, foundations and the electrical interconnection with the load. The standard applies to WTGS with swept area less than 40 m².

Contact - F.Van Hulle, ECN, The Netherlands

WG5 - Acoustical Measurement Techniques

Background - This standard was developed to provide a uniform methodology that will ensure consistency and accurcy in the measurement and analysis of acoustic emissions by Wind Turbine Generator Systems (WTGS). The standard was prepared with the anticipation that it would be applied by:

- The WTGS manufacturer striving to meet well defined acoustic emission performance requirements and/or a possible declaration system;

- The WTGS purchaser in specifying such performance requirements;

- The WTGS operator who may be required to verify that stated, or required, acoustic performance specifications are met for new or refurbished units;

- The WTGS planner or regulator who must be able to accurately and fairly define acoustical emission characteristics of WTGS in response to environmental regulations or permit requirements for new or modified installations.

Scope of Work - Presents sound measurement procedures that enable noise emissions of a wind turbine to be characterized. This involves using measurement methods appropriate to noice emission assessment at locations close to the machine, in order to avoid errors due to sound propagation, but far enough away to allow for the finite source size. The procedures described are different in some respects from those that would be adopted for noise assessment in community noise studies. The are intended to facilitate characterization of wind turbine noise with respect to a range of wind speeds and directions and comparisons between different wind turbines.

Contact - T.J. DuBois, DuBois and Associates, USA

WG6 - Power Performance Measurement Techniques

Scope of Work - Specifies a procedure for measuring the power performance characteristics of wind turbine generator systems of all types and sizes connected to the electric power network. It is applicable for both the determination of the absolute power performance characteristics of a WTGS and relative differences among the power performance characteristics of various WTGS configurations.

The WTGS power performance characteristics are defined by the measured power curve and the estimated annual energy production (AEP). The measured power curve is determined by collecting simultaneous measurements of wind speed and power output at the test site for a period long enough to establish a statistically significant database over a range of wind speeds and under varying wind conditions. The AEP is estimated by applying the measured power curve to reference wind speed frequency distributions, assuming 100% availability.

In 1995, participants in WG6 agreed to approve the draft standard with the understanding that extensions would be added to the scope of work. These extensions will handle the special requirements of power performance testing of small turbines, as well as testing of all turbines in complex terrain and in wind farm environments.

Contact: Troels Pedersen, Riso National Laboratory, Roskilde, Denmark

WG7 - Safety of Wind Turbine Generator Systems (Revision of IEC 1440-1)

Background - Changes in the technology, increasing proliferation of wind turbine installations, and an increased understanding of environmental load cases for wind turbines have necessitated a revision of the safety requirements standards set forth by combined working groups 1, 2, and 3.

Scope of Work - Deals with safety philosophy, quality assurance and engineering integrity, and specifies requirements for the safety of Wind Turbine Generator Systems (WTGS), including design, installation, maintenance, and operation under specified environmental conditions. Its purpose is to provide the appropriate level of protection against damage from all hazards from these systems during their planned lifetime. This standard is concerned with all subsystems of WTGS such as control and protection mechanisms, internal electrical systems, mechanical systems, support structures, foundations and the electrical interconnection equipment. The standard applies to WTGS with swept area equal to or larger than 40 m2.

Contact - Peter H. Madsen, Riso National Laboratory, Denmark

WG8 - Full Scale Structural Testing of Rotor Blades for WTGS

Background - NREL and many other wind energy laboratories throughout the world are conducting static, dynamic fatigue, and modal tests of full-scale wind turbine blades using various test methods and configurations. This standard will help establish commonality among these methods and will provide guidelines to help ensure that results are comparable.

Scope of Work - This standard is intended to be used as a guideline for full scale testing of rotor blades of a WTGS as a possible part of a final design verification of the structural integrity of the blade. The tests included are fatigue tests, static tests, and modal tests. The standard describes recommended practices to perform varous tests on full scale blades and gives guidance on interpretation or evaluation of results. It describes the blade and load data with the appropriate format necessary to evaluate the test results. Guidance is given on which (partial) safety factors should be incorporated during testing and evaluation.

Contact - Don van Delft, Delft University, The Netherlands

WG9 - Certification Standard

Scope of Work - Develop guidelines for certification and type approval of wind turbines using test data and analyses (scope of work under development).

Contact - John McGuire, Lloyds Register, UK

WG10 - Power Quality Requirements for Grid Connected Wind Turbines

Background - Existing certification procedures and other standards for wind turbines for grid copnnection do not deal with the requirements of the design of the turbine to minimize its effects on the power quality of the electrical network. As the power capacity/penetration increases, an evident need arises for a standardized specification of the power quality characteristics of the turbine output. and for defining requirements to the wind turbine design

Scope of Work - To prepare a standard for determining the characteristics of wind turbine output, with respect to the impact on the power quality in the public supply system, while securing proper operation of the wind turbine

Contact - J.O. Tande, Riso National Laboratory, Roskilde, Denmark

WG11 - Load Measurements for WTGS

Scope of Work - Develop guidelines for measuring loads on wind turbine structures (scope of work under development).

Contact - F. Van Hulle, ECN, The Netherlands

3.0 NREL's Technical Role in Standards Development

NREL has one technical representative (employee or consultant) on most of the IEC Working Groups. NREL personnel have had a major impact on the standards development process, ensuring that standards do not impede international industry development and trade opportunities, while ensuring that environmental, safety, and health interests of industry employees, utility personnel, and the general public are maintained.

NREL also provides analytical support to standards development. For example, NREL employs its design codes and test data to validate the load cases used for wind turbine design standards developed under Working Group 7 (Safety of WTGS.) This is required to ensure that the cases accurately represent the full range of load environments that will be encountered by wind turbines. As a world leader in structural blade testing technology, NREL provides significant technical support to the development of the blade testing standard under Working Group 8. NREL personnel also participate in the periodic Technical Experts Meetings sponsored by the International Energy Agency. These meetings result in the development of recommended practices that are used in guiding the formation of standards under the IEC working groups.

3.1 NREL Certification Capability Development

The AWEA Board of Directors has recently made a formal request to the U.S. Department of Energy to support the development of certification test capability at NREL. It is envisioned that NREL will begin by offering power performance and acoustics testing in 1996. This will be expanded to loads testing and operational testing in future years. Blade tests will also be offered as a test service. Power performance, acoustics, and loads testing will be performed either at NREL or at a site designated by the company. Blade tests and other component tests (such as dynamometer tests of drive trains) will be conducted at the National Wind Technology Center.

4.0 Obtaining Wind Energy Standards Documents

Order AWEA Standards Documents

Order IEC Standards Documents dn@iec.cn

Go to IEC Home Page

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