Hugo André

Instantaneous Angular Speed Monitoring of a 2MW Wind Turbine Using a Parametrization Process

One cannot but notice that a variable speed wind turbine utilizes the available wind resource more efficiently than a fixed speed wind turbine, especially during light wind conditions. Most wind turbines are equipped with doubly fed induction generator, thereby allowing them to keep on producing while the speed varies over a wide range. This enhancement forces the monitoring methods to deal with these large variations in speed and torque, since the conditions are seldom if ever stationary. In an original and inexpensive attempt to tackle this issue through angular sampling, this paper proposes to base the surveillance of the line shafting on the instantaneous angular speed variations experienced by the high speed shaft. The unsteady behaviour of these wind turbines is also a difficulty in term of long term diagnostic, since the comparison of successive measurements is usually performed under the same operating conditions. Parametrization of the indicators according to well chosen variables might bring a valuable tool regarding several aspects. A long term experimental study carried over a 2MW wind turbine will be presented as a first application, and will be used to dress an interesting diagnosis on another wind turbine.

Reconstruction of the Instantaneous Angular Speed Variations Caused by a Spall Defect on a Rolling Bearing Outer Ring Correlated with the Length of the Defect

In the framework of monitoring of rotating machinery, this paper proposes a simple signal processing tool to reconstruct the Instantaneous Angular Speed (IAS) variations caused by the presence of spalled bearing. This tool is applied to signals obtained on a specific test bench. Associated with an angular sampling, the analysis of these variations can identify the length of the defect whatever the mode of operation, particularly in non-stationary operating conditions in rotation speed.

Modelling Roller Bearing Dynamics Inducing Instantaneous Angular Speed Variations

Modelling the dynamics of roller element bearings has been used to explain the interactions between localized faults and their impact on the measurable quantities representing the dynamic behavior of the system e.g. acceleration. Most part of the models describes the non-linear contact of roller bearing normal forces by means of Hertz Theory. Recently, analysis of the Instantaneous Angular Speed (IAS) has been proven to effectively detect bearing mechanical faults and it has shown to be an advantageous tool for non-stationary machinery surveillance. Mechanical analysis implies that rotating speed variations are due to torque variations. However, the phenomena describing how dynamic interaction of bearing components induces tangential forces generating angular periodic disturbances to the shaft speed, have not been discussed at all. In this work an original formulation to induce tangential forces to the shaft due to the bearing components dynamics is presented. The roller bearing model is based on Hertzian contact, localized faults can be added and the analysis is suitable for simulation of non-stationary conditions.

Hybrid Scheme for Wind Turbine Condition Monitoring Based on Instantaneous Angular Speed and Pattern Recognition

Wind turbines are designed to operate under varying conditions of speed and load. These rough operational conditions undermine conventional monitoring techniques and lead to unexpected failures of mechanical components. This work comes within the framework of wind turbine on-line condition monitoring. For this purpose, a particular attention was given to Instantaneous Angular Speed (IAS) emerging as a viable alternative to vibration analysis, especially in non stationary conditions. In this work, IAS signals were recorded from extensive measurement campaigns on different operating wind turbines. Suitable processing techniques have been specifically developed and allowed to analyze signals in healthy condition and in the presence of different bearing faults. Based on the latter, a huge number of expected relevant indicators was extracted. Different configurations of features transformation, selection and classification tools were tested. An optimized hybrid scheme has been designed. This approach allowed an optimal exploitation of IAS information and the construction of an effective tool for wind turbine condition monitoring.

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

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.

Detection of Bearing Spalling Faults Using IAS Monitoring System - Experimental Studies on the Influence of Operating and Environmental Parameters

Experimental works carried out in recent years have demonstrated the feasibility of detecting a bearing fault through the spectral analysis of the Instantaneous Angular Speed (IAS) in the angular domain. Since these works have been carried out on complex mechanical systems (automotive gearboxes, vehicle wheels, wind turbines), neither the influence of operating parameters, nor the influence of structural parameters over the observed angular speed variations have been clearly identified. However, the implementation of effective tools for condition monitoring prospects requires a deep understanding of these interactions. In this regard, a test bench has been designed to allow defective bearing monitoring through IAS observation of a simple shaft running under varying loads and speeds, the system being simple enough to be easily described in various kind of mechanical or phenomenological models. The aim of this paper is to present a better understanding of the relationships between the speed variation induced by the monitored fault, the structural response and the observed phenomena. In the first part results obtained for a healthy bearing will be analyzed. These initial results serve as a reference for analysis of the results obtained with bearing defects. Coupled with dynamic modeling, they will also highlight the existence of a low frequency torsion mode. The results of this first part also highlight the wider interest of the IAS analysis for the study of rotating systems. In a second part, the measurements are performed with bearings having spalling type defects on their outer ring. The aim of this section is to estimate the influence of operating conditions on IAS monitored indicators. All these results will provide further phenomenological explanations of coupling between bearing fault and rotating speed.