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Wind farm meeting 27 April 2010, Goteborg (SE) Measurements of primary radiation at a wind farm close to the Sardinia Radio Telescope R. Ambrosini (IRA), P. Bolli (OAC), C. Bortolotti (IRA), F. Gaudiomonte (OAC), F. Messina (OAC), M. Roma (IRA). Agenda.
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Wind farm meeting 27 April 2010, Goteborg (SE) Measurements of primary radiation at a wind farm close to the Sardinia Radio Telescope R. Ambrosini (IRA), P. Bolli (OAC), C. Bortolotti (IRA), F. Gaudiomonte (OAC), F. Messina (OAC), M. Roma (IRA)
Agenda • The Sardinia Radio Telescope; • The RFI mobile station at SRT; • Characteristics of the wind farm under test; • Measurements: • Spectrum in P, L and S bands from power station and from each single turbine; • Wide and narrow band emission; • Dependence of the RFI intensity vs the distance.
SRT TechnicalSpecifications • Fully steerable radio telescope for: Radio astronomy , Geodynamical studies, Deep Space Network, Single dish and VLBI • 0.3-100 GHz continuous frequency coverage • 64 m diameter primary mirror; 7.9 m diameter secondary mirror • Gregorian configuration with Shaped Surfaces • Active Surface: Primary mirror with 1116 actuators • a) Compensate gravitational and thermal deformations • b) Convert Shaped surface of the primary to a Parabolic • surface for primary focus operation • Six focal positions (up to 20 receivers): • Primary, Gregorian, Four Beam Wave Guide • Primary surface accuracy: 150 um RMS • Pointing accuracy (RMS): 2 ÷ 5arcsec
Featuresof SRT site The SRT site is located 35 Km North of Cagliari (700 m asl). Latitude: 39d 29m 50s N Longitude: 9d 14m 40s E The site is well shielded by mountains around the radio telescope. The area is far away from populated centers (small villages at > than 5 Km).
Effectsproducedbywind farm • Microwave link for telemetry and remote control; • Emissions from generators and transformers; • Sparks and corona from power lines and insulators; Primary radiation Secondary radiation Reflection of radio links; Instability of background Modulation of the near field background signal of the antenna by its periodically varying electrical characteristic
Survey at the wind farm AZC 40° Distance @ 3.5 Km; session #3
Pointing measurement Pol. V Pol. H -62.6 dBm AZC 40° yellow AZC 40°+90° blue AZC 40°-90° purple
Wide-bandmeasurement Max hold Single view Blue : Pol. V Yellow: Pol. H Distance @ 500 m; session #3
Zero-spanmeasurement Distance @ 1 Km; session #3
Emission in P-band 20 Jan. (rainy) 19 Jan. (sunny) Distance @ 3.5 Km; session #1,2
Emission at largedistance n. 9 @ 7 Km
RFI campaign at a wind farm Powerintensitydrops in line-of-sight at -100 dBm at 85 Km!
Monitoring in L and S bands 21 cm line S band Below the sensitivity? Distance @ 1 Km; session #3
Other notes • Narrow band analysis in P and L-band (to monitor intentional control signal) did not show any signals coming from the wind park…. • We didn’t measure wide-band emission from the single turbine….. • …..with the sensitivity of • our RF equipment!
Conclusions • Very high power wide band RFIs coming from power station have been received (especially in P-band, but also in L-band). • Those effects are probably due to sparks phenomena which are worst in dry condition. • The spectral distribution and the polarization of the RFI emission are variable (depending on the position); • More accurate measurements of emission from single turbine and investigations of secondary effects are planned.