Rotor Condition Monitoring for Improved Operational Safety of Offshore Wind Energy Converters

2005 ◽  
Vol 127 (2) ◽  
pp. 253-261 ◽  
Author(s):  
Peter Caselitz ◽  
Jochen Giebhardt
Keyword(s):  
Wind Energy ◽  
Condition Monitoring ◽  
Research Work ◽  
Field Tests ◽  
Rotor Blades ◽  
Fault Prediction ◽  
Offshore Wind ◽  
Offshore Wind Energy ◽  
Operational Safety ◽  
Energy Converters

Background: Due to cost effectiveness and operational safety online monitoring of rotor blades is recommended, especially for offshore wind energy converters. Method of Approach: Statistic evaluation of wind speed and power output of a wind energy converter is used to monitor the overall rotor performance including increased blade surface roughness. Nacelle oscillation spectral analysis methods are applied to monitor the rotor faults mass imbalance and aerodynamic asymmetry. Results: Results of ISET’s research work related to online rotor condition monitoring are presented. A description of the fault effects on the rotor, the sensor and data acquisition equipment and a description of the developed signal processing and fault prediction algorithms are given. The paper also presents results from experiments and field tests. Conclusions: The developed algorithms have been verified due to their monitoring capabilities and suitability in commercial online condition monitoring systems.

Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
S. Thöns ◽  
M. H. Faber ◽  
W. Rücker
Keyword(s):  
Wind Energy ◽  
Limit State ◽  
Sensitivity Study ◽  
Offshore Wind ◽  
Ultimate Limit State ◽  
Offshore Wind Energy ◽  
Limit States ◽  
Serviceability Limit State ◽  
State Models ◽  
Energy Converters

This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for establishing the “as designed and constructed” reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thöns et al. (“Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters,” ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data.

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