UHF sensor for PD detection on wind turbines

The environmental matters fostered the power generation using renewable energies. This led, among the different possible solutions, to the diffusion of wind farms for wind power generation. The wind farms could be constituted by different kind of wind turbines with different kind of generators. Considering the nature of this generation systems, remote controlled diagnostic solutions should be implemented. A predictive maintenance program based on partial discharges (PD) measurements on the power generator and electrical apparatuses installed in the nacelle could be useful. In fact partial discharge measurements permit to obtain information on the insulation systems conditions. Preferably, not invasive PD sensors should be installed for continuous on line PD activity monitoring. In this view, radiated PD signals could be detected by means of UHF antennas. The measurement could be affected by the noise coming from electronic devices and sources transmitting in the same frequency band useful for PD signals detection. Therefore, a noise map has to be well defined to evaluate the best PD signal receiver bandwidth. Preliminary in site test campaigns have been performed in order to characterize an ad hoc UHF antenna designed for PD detection. The noise in the bandwidth of the considered antenna has been measured locating the sensor in different positions inside the nacelle. The acquired signals during the measurement campaigns have been post processed and analyzed. The preliminary acquisitions permitted to determine the amplitude and the frequency range of the noise in the different sites. The frequency ranges with low level noise have been identified and the preamplifier bandwidth was set coherently. This allowed to achieve a high signal-noise ratio.