Testing |
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 Wind Turbine Type Testing Type testing of wind turbines is carried out by an accredited test laboratory, such as the NWTC. The testing and the test results are documented in a test report which is then evaluated by the Certification Organization. The Certification Organization assesses that the tests have been carried out in accordance with the appropriate test procedures and that they properly document the aspects required for the certification. For small WTGS (according to IEC 1400-2), the Safety and Function Tests and the Load Measurements may be replaced by a Duration Test for Small Wind Turbines. Scroll through this section to discover the various aspects of type testing or click on the hyperlinks at the left to go to specific topics. |
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| Safety And Function Tests | The purpose of the safety
and function tests is to verify that the turbine under test displays the behavior
predicted in the design. Since the performance of the control and protection system is
critical the safety and loads tests must demonstrate at least the following ;
The duration of these tests need to be sufficient to give statistically significant results documenting the turbine behavior at rated wind speed and above. || Contents || |
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| Dynamic Behavior Tests | The purpose of this
testing is to confirm the basic dynamic behavior of the wind turbine under critical
operational modes and failure conditions. The behavior of the WT is measured in order to
verify that the behavior is in conformance with the design documentation. Particular emphasis is given to confirming major structural component predicted eigenfrequencies and extreme dynamic response during various operational modes. Assessment shall be based on measured acceleration spectral frequencies and magnitudes. Eigenfrequencies shall be as predicted and shall not result in excessive vibrations consistently exceeding 0.5 Gs during of the following operating conditions:
For small wind turbines the dynamic behavior of the turbine is assessed experimentally in order to verify that system natural frequencies do not interfere with operational frequencies. The dynamic behavior of the turbine shall be observed at least at wind velocities of 10, 15, and 20 m/s. A short report, including a checklist of tests completed and summary results, is prepared by the NWTC. || Contents || |
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| Duration Tests For Small Wind Turbines | Due to the fact that only
a few simplified calculations are required for design approval of small turbines, a
duration test can be used to demonstrate the safety, the reliability, the structural
integrity and the functioning of the turbine. The aspects to be investigated in the duration test are:
These aspects will be checked at start and end of the test period and compared where relevant.. The tests and report format need to meet the specifications defined in IEC 1400-2 (Safety of Small Wind Turbines). In cases where applicable IEC standards are not available, the test procedure is agreed between the wind turbine manufacturer and the Certification organization. In the duration test period, the wind turbine shall be subjected to a minimum wind spectrum. This is defined as a minimum number of hours of normal operation (power production) at given wind speeds:
Moreover, in the test period the wind turbine should achieve at least 5000 h of energy production. These criteria normally can be met at sites with an annual average wind speed of 6.5 m/s at hub height in a time span of 1 year. Depending on the wind regime at the test site of the wind turbine the test period has to be determined such that the minimum wind spectrum and production hours can be expected to occur. The wind turbine has to show an availability of at least 90 % within the test period. If the availability of 90% is not achieved within the preset test period, the test is continued until 90% is reached. For stand-alone systems the wind turbine is operated for full, half and near zero load capacity of the battery pack. Therefore the battery pack and the power dump load belonging to or prescribed for the system have to be used in combination with an additional dump load to simulate the energy consumption from the system. The additional dump load is selected to keep the battery pack in conditions between full and empty for time periods proportional with the duration of the test. || Contents || |
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| Load Measurements | Mechanical load
measurements - referred to here as Type Load Testing - are required for type
certification. The tests are conducted according to the minimum requirements given below.
The purpose of Type Load Testing is to provide data to enable the certification body to
confirm safe operational loads and to verify safe operational dynamic behavior. For Type Load Testing, the fundamental loads in the wind turbine construction have to be measured as well as meteorological quantities and indicative operational parameters defining the turbine operating conditions. As a minimum, the specific load and other quantities listed in IEC 1400-13 have to be measured. The load measurement campaigns shall be based on and consist of measurement load cases (MLC) that are as close as practically possible to the design load cases (IEC 1400-1). The principles and requirements of the measurement load cases are described in IEC 1400-13. For the measurement of the fatigue loading, measured load data shall be collected in a capture matrix, in order to collect a statistically significant amount of load data for relevant wind speeds and turbulence intensities. The evaluation of the load measurements for design verification shall be conducted according to methods described in IEC 1400-13. The tests and reporting format need to address the requirements described in the IEC 1400-13 (Mechanical Load Measurements) standard. If this standard is not available, minimum requirements defined in Annex D of the standard need to be met. In cases where applicable IEC standards are not available, the test procedure shall be agreed between the turbine manufacturer and the Certification organization. || Contents || |
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| Blade Tests | Component test of a blade
is required for every new type of blade. A new type of blade is described not only by its
size and shape but also by its internal build-up and structure. Component tests of blades
need to be carried out in accordance with methods in IEC code 1400-23. A type certificate of a blade can include the following items:
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| Other Component Tests | Where the documentation of a part of
the wind turbine is subject to uncertainty, the certification organization may require
additional component tests to be carried out. Main components for a wind turbine can have a Type Certificate. This certificate describes the limits for the use of the component. This document must include the extreme and fatigue strength and the environmental, site and operational conditions. In order to get a certificate of a component the specified component must be documented theoretically. || Contents || |
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| Test Results Attestation | The Certification organization attests
that the necessary type tests have been carried out by NREL in accordance with relevant
international standards. In many cases type testing will be conducted by the staff of NREL at a the NWTC testing facility. In other cases the turbine may be installed at a site or facility that is operated by the manufacturer or another third party. In this later case, the Test Engineer prepares a test plan which is reviewed by the staff of the Certification Body and is additionally agreed to by both the turbine manufacturer and the site facility owners. This test plan conforms to the requirements described under "Type Testing" including the plan for quality assurance of the testing process. The tests are conducted according to the test plan as attested to by the staff of the Certification organization. This attestation is, at a minimum, based on the following:
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| Test Reports | Type test reports prepared by the NWTC
conform to the relevant standard used to define the test requirements. Each test report
includes, at a minimum:
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| Type Test Conformity Statement | The certification organization also
issues a conformity statement based on an assessment of the test report. The conformity
statement specifies:
The signatories of the conformity statement need to be different from the persons responsible for the test reports, attestation of the tests or accreditation of the test laboratories. || Contents || |
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Prepared by Updated: November 21, 2002 |
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