Study on order analysis for condition monitoring wind turbine gearbox

A complex 3-stage gearbox design, in which one planetary gear set at first stage and two sets of parallel gears at second and third stage, is conventionally applied on the large wind turbine configuration with Doubly Fed Induction Generator. In this variable-speed wind turbine, it is hard to directly apply conventional frequency analysis on condition monitoring of the gearbox planetary stage. Proper signal processing and analysis become crucial here for interpreting the conditions of gears and bearings. In this paper, order analysis is studied for condition monitoring the planetary stage of wind turbine gearbox. The approach takes advantage of angular resampling to achieve cyclo-stationary vibration signals and lessen the effects due to speed changes. One key element in the scheme is taking angular information to enable resampling the time-domain signals into angular-domain signals. A vibration signal model for gearbox planetary stage is firstly described, and the scheme is then tested on simulated signals to achieve fine frequency resolution. Time synchronous averaging is applied as a pre-processing technique to enhance the Signal to Noise Ratio (SNR) in order spectrum.