Failure analysis on over-temperature combustion of transformers in 4 MW offshore wind turbines

Wind power is one of the prevailing types of renewable energy, but the reliability of its components is always challenged by the severe service environment, especially on the offshore. Hence, case studies on failed components deserve to be publicly reported for experience sharing and failure prevention. In this event, severe degradations like combustion and abnormal electrical resistance rise were frequently detected on a large number of windings and lead bars within the transformers in 4 MW offshore wind turbines. To solve this problem, a series of characterization methods were utilized to investigate the assembly structure, matrix materials and macro/microscopic morphologies of the failed transformers. Temperature simulation experiment was also carried out to evaluate the normal operating conditions. The analysis results showed that risky factors induced from inappropriate installation, unreasonable design, unqualified fabrication and improper maintenance were the root causes for the failure. Finally, relevant mechanisms were discussed in detail and specific countermeasures were put forward.