PROBLEM According to proposers experience, many wind turbines because of fault s are operating in such a way that their lifetime consumption is higher than ne eded and the production is below the optimum. For example can anyone in a lands cape with many wind turbines observe, that wind turbines close to each other ve ry often don't have the same orientation towards the wind. That indicates yaw error on many turbines. Such a fault increases the fatigue loads and decreases the production. In other words, is a given turbine probably running in acc ordance with the design criteria and can the assumed lifetime for the turbine a nd its major components be expected? That is a question which cannot easily be answered, but nevertheless important por for obvious reasons. OBJECTIVE AND GOALS Consequently, the objective of the project is to develop methods for ana lysing faults and operation condition meeting these requirements for simple and cheap application. The idea is, that the information asked for shall be found by advanced analysis of few and easily measured data. Advanced spectral analysi s of a few measuring points is the basic method for that. The specific goals fo r the project is therefore to develop following methods: 1) spectral analysi s of the electrical power signal in order to identify yaw error and any other r otor fault such as unbalance, weakness in a blade, uneven pitch setting, fault on an airbrake etc. All these type of fault causes cyclic loads on the blades d etectable in the spectrum. Further, relative life time consumption of transmiss ion components bases on the of electric power as a measure of the torque distri bution. 2) Structural fatigue load distribution based on spectral analysis of measurements from a 3-D accelerometer placed in the nacelle. 3) Faults in rota ting components (bearings, gear wheels, couplings etc.) based on accelerometers placed on convenient components transmitting the vibrations. EQUIPMENT FOR CONDITION MONITORING The measuring equipment is expected to consist of a stand ard PC (built-in or mobile) with a convenient standard measuring card, external measuring devices comprising power converter, one or two 3-D accelerometers an d a reference anemometer. Further accelerometer for vibration measurements on m ajor components, first of all the gear. The equipment is expected to be install ed on wind turbine for a period which can vary from few hours to some weeks, or can be permanently installed. BASIC METHODS The basic method is in short: Oscillations and vibrations are measured directly or indirectly (in this case t he power signal as well as an accelerometer is used). A FFT is performed and th e frequency bands related to the exposure frequency considered are isolated. A PSD (power spectrum density) is calculated for the band as a measure of the amo unt of energy in that band. The analysis includes some techniques to separ ate the deterministic and the stochastic content in a frequency band. In genera l, the methods are developed using simulation in a aeroelastic code and verifie d by test on full scale turbines. With the scope is also vibration analysis for detecting faults in component before the final break- down.
Funding SchemeCRS - Cooperative research contracts
401 24 Göteborg