Reliability of wind turbine subassemblies

TLDR

The study examined reliability of over 6000 onshore wind turbines and subassemblies in Denmark and Germany over 11 years, analyzing average failure rates and time‑varying failure intensity using a Power Law Process for generators, gearboxes, and converters, and also compared different turbine concepts. The analysis revealed that generators and converters are the least reliable subassemblies, with reliabilities below other industries but improving over time, while gearboxes match external industry levels; the study recommends prioritizing converters and generators in offshore turbine reliability testing.

Abstract

We have investigated the reliability of more than 6000 modern onshore wind turbines and their subassemblies in Denmark and Germany over 11 years and particularly changes in reliability of generators, gearboxes and converters in a subset of 650 turbines in Schleswig Holstein, Germany. We first start by considering the average failure rate of turbine populations and then the average failure rates of wind turbine subassemblies. This analysis yields some surprising results about which subassemblies are the most unreliable. Then we proceed to consider the failure intensity function variation with time for wind turbines in one of these populations, using the Power Law Process, of three subassemblies; generator, gearbox and converter. This analysis shows that wind turbine gearboxes seem to be achieving reliabilities similar to gearboxes outside the wind industry. However, wind turbine generators and converters are both achieving reliabilities considerably below that of other industries but the reliability of these subassemblies improves with time. The paper also considers different wind turbine concepts. Then we conclude by proposing that offshore wind turbines should be subject to more rigorous reliability improvement measures, such as more thorough subassembly testing, to eliminate early failures. The early focus should be on converters and generators.