Amir Rasekhi Nejad

Frequency based Wind Turbine Gearbox Fault Detection applied to a 750 kW Wind Turbine

Reliability and availability of modern wind turbines are of increasing importance, for two reasons. The first is due to the fact that power grids around in the world depends at a higher and higher degree on wind energy, and the second is the importance of lowering Cost of Energy of the wind turbines. One of the critical components in modern wind turbines is the gearbox. Failures in the gearbox are costly both due to the cost of the gearbox itself, but also due to lost power generation during repair of it. Wind turbine gearboxes are consequently monitored by condition monitoring systems operating in parallel with the control system, and also uses additional sensors measuring different accelerations and noises, etc. In this paper gearbox data from high fidelity gearbox model of a 750 kW wind turbine gearbox, simulated with and without faults are used to shown the potential of frequency based detection schemes applied on measurements normally available in a wind controller system. This paper shows that two given faults in the gearbox can be detected using a frequency based detection approach applied to sensor signals normally available in the wind turbine control system. This means that gearbox condition monitoring/ fault detection could be included in the standard control system, which potentially can remove the cost of the additional condition monitoring system and the additional sensors used in it.

Statistical fault diagnosis of wind turbine drivetrain applied to a 5MW floating wind turbine

Deployment of large scale wind turbine parks, in particular offshore, requires well organized operation and maintenance strategies to make it as competitive as the classical electric power stations. It is important to ensure systems are safe, profitable, and cost-effective. In this regards, the ability to detect, isolate, estimate, and prognose faults plays an important role. One of the critical wind turbine components is the gearbox. Failures in the gearbox are costly both due to the cost of the gearbox itself and also due to high repair downtime. In order to detect faults as fast as possible to prevent them to develop into failure, statistical change detection is used in this paper. The Cumulative Sum Method (CUSUM) is employed to detect possible defects in the downwind main bearing. A high fidelity gearbox model on a 5-MW spar-type wind turbine is used to generate data for fault-free and faulty conditions of the bearing at the rated wind speed and the associated wave condition. Acceleration measurements are utilized to find residuals used to indirectly detect damages in the bearing. Residuals are found to be nonGaussian, following a t-distribution with multivariable characteristic parameters. The results in this paper show how the diagnostic scheme can detect change with desired false alarm and detection probabilities.

Gear Train Internal Dynamics in Large Offshore Wind Turbines

Today in the wind turbine global analysis codes such as Hawc2 [1] or FAST [2], the entire gear train is modelled by one degree of freedom constant stiffness torsional spring. This is because the focus in the global analysis programs lies mainly on the aerodynamic loads and the dynamic behaviour of structural members. For the small size gear trains, since the internal natural frequencies are expected in a frequency range above the overall wind turbine harmonics, this approach can be justified. However, as the industry trend is toward the larger drivetrains in offshore developments, the internal dynamic of gear trains are required to be modelled more accurately. Moreover, the development in generator technology with low, medium and high speed options has brought a variety of gear train design options with specific dynamic behaviour.In this paper the natural modes and internal dynamic excitations of high ratio wind turbine gear trains is investigated. Case study gear trains of 0.6, 2, 5 and 10 MW are modelled by pure torsional elements in a Multi Body Simulation (MBS) program; Simpack [3], where the natural modes are obtained and possible excitation are evaluated. The results show the resonance trend in various size wind turbine gear trains.Copyright

Drivetrain load effects in a 5-MW bottom-fixed wind turbine under blade-pitch fault condition and emergency shutdown

In this paper, the effect of the blade-pitch fault and emergency shutdown on drivetrain responses in a 5-MW bottom-fixed wind turbine are investigated. A 5-MW reference gearbox with 4-point support is employed and the decoupled analysis approach is used for the load effect analysis. The effect of this fault event is then investigated for all bearings and gears inside the gearbox as well as main bearings. The results show that the blade-pitch fault creates significant axial forces on main bearings which increases the nontorque force entering the gearbox. Due to the emergency shutdown, the rotor torque reversal occurs which causes force reversals in gears. The main bearings are more affected than gears and bearings inside the gearbox in this fault condition and emergency shutdown, but first-stage bearings may also be considerably affected. It is therefore recommended to conduct a thorough inspection of main bearings and first stage bearings in case of such blade-pitch fault condition and emergency shutdown.

Main bearings in large offshore wind turbines: development trends, design and analysis requirements

This paper discusses analysis requirements for design and operation of main bearings in modern multi-megawatt offshore wind turbines, motivated by the industrys search for reliable and cost effective main bearing solutions that limit the effects of non-torque loads, and the need for effective bearing health monitoring. Gearboxes historically received attention on the grounds of reliability, sparking significant interest in drivetrain dynamics. However, design trends in modern, large turbines, influencing choices for a future 10+ MW generation, indicate that more attention to main bearings or rotor support bearings is needed as part of a more holistic approach to flexural dynamics. Through a survey of existing research, offshore wind turbine design trends, design codes, industry practices and standards, we look at how main bearings are treated in a life cycle perspective, considered design features, modeling and simulation approaches, interaction and interfaces between industry stakeholders, as well as reuse of simulation models for predictive analytics in operation. We conclude that flexible main bearing representation is important in dynamic analyses and that industry practices are needed that enable sufficient model exchange or interfaces and thus effective exploitation of the benefits of a simulation model throughout the turbine life cycle.