The commissioning procedure shall be witnessed at one of the first wind turbines built in the version to be certified. The objective of this witnessing is the visual inspection of a plant by the certifier and the assessment of the safety-related tests in the commissioning manual. The witnessing of the commissioning shall be performed by GL Renewables Certification experts for the fields of electrical engineering and safety technology.

The plant is inspected and the technical execution is compared to the requirements of the design documents. Compliance with any restrictions expressed in the Certification Report is assessed as far as possible. Selected tests from the commissioning manual are carried out with a focus on the safety tests. In addition, the practicability of the tests is verified and the turbine behaviour is assessed for compliance with the design documents.

During surveillance of commissioning the following items are examined:

• General appearance
• Conformity of the main components with the certified design documentation and traceability / numeration of the same
• Operating tests and tests of the safety system
• Corrosion protection
• Damages

After witnessing of commissioning a Certification Report is issued.