Reliability and O&M key performance indicators of onshore and offshore wind turbines based on field-data analysis

Based on maintenance data from over 1000 onshore and offshore wind turbines covering more than 4200 operating years, this study presents an analysis of failure rates, repair times, and maintenance resource requirements, focusing on subsystem-level reliability. Failure rates per turbine and megawatt are compared, and failure behaviour over time is examined. Next to failure events, further corrective and preventive maintenance interventions are analysed. To provide more detailed insights for operation and maintenance simulations, a distinction is made between total major component replacements and those specifically requiring a jack-up vessel. Results show that onshore wind turbines have higher failure rates per megawatt than offshore wind turbines. Key subsystems including the pitch system, the control system, and power converter system are identified as critical to overall wind turbine reliability for both onshore and offshore wind turbines. For the overall wind turbine system, a failure behaviour over time following a bathtub curve is identified, with distinct trends for individual subsystems.