handed over individually or in smaller groups to start producing electricity as soon as possible.

Commissioning of a Wind Turbine

Once a wind turbine is assembled, teams of workers begin the steps necessary for making it operational. This is referred to as the commissioning phase and includes the inspection and testing of turbine functionality and electrical infrastructure, including substation. This phase can be work-intensive and may require a team of three to six people and more than 1,000 person-hours for each wind turbine.8 During commissioning, the work team performs quality control activities and tests the internal systems, including the turbine control systems, the remote monitoring and access systems, and all electrical systems. The rotor blades are set in slow rotation to test the drivetrain, along with the overspeed protection system. Once the turbine is connected to the grid, it is further tested in sequences and finally put into operation. This phase is of particular interest because the risk of electrical incidents is now present.9

Operations and Maintenance

Once they are operational, wind farms are essentially unmanned offshore facilities with personnel accessing them only to perform maintenance and repairs. Scheduled maintenance ensures ongoing functionality of the equipment and system, and scheduled inspections evaluate condition; maintain safety systems; and satisfy lease, permit, and regulatory requirements. Such routine access is often accomplished with smaller vessels that do not have cranes or large carrying capacity. Unscheduled maintenance, which can include major repairs such as replacing a major wind turbine component, may require the use of larger jack-up installation vessels that can carry replacement components and more personnel (Thomsen 2012). If the manufacturer supplies a warranty period for the wind turbines, the work crews supplied during the operations and maintenance period will consist of a team of two or more people for every 20 to 30 turbines. Routine or scheduled maintenance requires


8   J. Nielsen, Siemens, presentation to the committee, April 2012.

9   J. Nielsen, Siemens, presentation to the committee, April 2012.

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