Fault frequency tracking during transient operation of wind turbine generators

As remote and offshore wind turbines increase their contribution to renewable energy generation, effective and reliable condition monitoring techniques will be required to reduce failure downtime. This paper examines the possibilities for analysing electrical signals from the stator of wound rotor induction generators, commonly used in wind turbines. Previous work derived analytical expressions for the frequency content of line current and total instantaneous power for healthy and faulty wound rotor induction generators under steady state conditions. This paper builds upon those results to examine fault detection under transient, variable speed conditions, such as encountered in a wind turbine. Through comparison between a time-stepped analytical model and a physical test rig it is concluded that the tracking of speed dependent fault frequencies is possible and could be an effective and reliable way to monitor the health of a wind turbine wound rotor induction generator.