A progressive study into offshore wind farm maintenance optimisation using risk based failure analysis

Offshore Wind Farm consists of an array of Wind Turbines electrical, communication, command and control systems. At present the cost of maintaining Wind Turbines in the offshore locations is very high (about 35% of lifetime costs). This work puts emphasis on using failure analysis as a basis for designing a condition based prognostic maintenance plan in order to control cost of power and make maintenance more efficient. An essential aspect of such failure analysis is to identify wind turbine components, ascertain their failures and find root causes of the failures. However as a first step, identification of prominent failures in the critical assemblies of a wind turbine using available inspection methods and making provisions to control their occurrence would make significant contribution in improving wind turbine reliability. This work introduces Failure Modes Effects and Criticality Analysis (FMECA) as an important failure analysis tool that has in the past successfully benefitted the airlines, marine, nuclear and spacecraft industries. FMECA is a structured failure analysis technique that can also evaluate the risk and priority number of a failure and hence assist in prioritising maintenance works. The work shows, how with a slight modification of the existing FMECA method, a very useful failure analysis method can be developed for offshore wind turbines including its operational uniqueness. This work further proposes modifying the format for calculating the Risk Priority Number (RPN) for wind turbine failure. By using wind turbine gearbox as a case study, this work illustrates the usefulness of RPN number in identifying failures which can assist in designing cost effective maintenance plan. Some preliminary results of a FMECA tool that has been developed to automatically evaluate the effects and criticality of a failure in a wind turbine at the component level is included.