Simplified dynamic model of a wind turbine shaft line operating in non-stationary conditions applied to the analysis of IAS as a machinery surveillance tool

Abstract

Instantaneous Angular Speed (IAS) has been shown to be an alternative signal to detect bearing faults in geared systems. Detection of the presence of bearing faults in rotating systems requires understanding of the transfer way between the defect and its manifestation in the measured signal. This step is mainly performed by the development of numerical models describing the couplings between the defects and the rest of the device. To the authors’ knowledge, the majority of the models in the literature are lump parameter models, with no regard between the dynamic of the bearing and the rotational degree of freedom of the shaft. The influence that the dynamics of a faulted bearing has over the rotating shaft leading to IAS variations has been presented in a previous work. This influence has been introduced by means of a roller bearing model which dynamics, modified by the defect, introduces torque perturbations to the shaft. The aim of this paper is to couple the faulted bearing model to a multiple gear stage simplified wind turbine transmission. The model is built with a classic finite element approach and is suitable for the test of non-stationary simulations. First results show bearing faults are detectable in different locations of the geared system by the measurement of IAS. Even if experimental validation have not been yet performed, numerical results appear very promising to deepen the understanding of the IAS variation phenomena.