A review of electrical winding failures in wind turbine generators

A quantitative review of the failure modes of over 1200 wind turbine generators repaired or replaced since 2005 has uncovered that fewer that half of the failures were electrical in nature and most of those were due to mechanical failures of the insulation support structure. In this paper, we will discuss briefly the overall failures and, in more depth, the nature of the electrical failures. Many of the failures appear to be of a serial nature due to inadequate original design of the machine and/or the insulation system. Some possible suggestions will be offered regarding repairs after catastrophic failure to help insure that the same type of failure will be less likely to repeat during the projected life of the turbine. These generators are exposed, at least in some part, to the typical voltage irregularities and mechanical stresses of any machine that operates 100 meters in the atmosphere in a wide variety of weathers. However, they are also sometimes affected by poor power quality from the IGBT based convertors used in most turbines. These failures could result from voltage stresses created by the convertor in the turbine or from neighboring turbines or, as has been suggested, even from neighboring wind parks. Defining actual root causes is therefore very difficult, but the immediate causes within the generator will be reviewed. Statistical information from other industries will also be used as a comparison to the relatively short experience of wind energy equipment. Where proper maintenance and mechanical analytical predictive techniques can drive major improvements in the mechanical life of the generators, the electrical failures are more difficult to identify before failure.