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),

Wind farm meeting27 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)

Osservatorio Astronomico di Cagliari

Istituto di RadioastronomiaSezione di Medicina

2/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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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.

3/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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• 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 ÷ 5 arcsec

SRT Technical Specifications

4/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Features of SRT siteThe SRT site is located 35 Km North of Cagliari (700 m asl).

Latitude: 39d 29m 50s NLongitude: 9d 14m 40s E

1. The site is well shielded by mountains around the radio telescope.

2. The area is far away from populated centers (small villages at > than 5 Km).

5/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Wind farm close to SRT

6/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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SRT Mobile RFI station

7/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Features Mobile station of SRT

Van Mercedes Sprinter 315 CDI

Maximum seats 2

Max frequency 18 GHz (Normal operation); 40 GHz

Antennas 1 LPDA (0.3 – 0.6 GHz); 1 LPDA (0.1 – 1.3 GHz); 1 dual ridge horn (1 – 18 GHz); 1 dual ridge horn (18 – 40 GHz)

Telescope pole height

11 m

Telescope movement

Up/down servo; Azimuth servo or manual; Polarization servo

Spectrum analyzer PSA 4446 E (up to 44 GHz)

Characteristics

Band Frequency band Antenna gain

Chain gain Noise figure

P 290 – 428 MHz 9 dBi 36.2 dB 3.8 dB

L 1.17 – 1.84 GHz 7 dBi 29.8 dB 4 dB

S 1.99 – 3.37 GHz 7.8 dBi 25 dB 5.3 dB

S / C 2.98 – 5.81 GHz 12 dBi 25 dB 5.5 dB

C / X 5.22 – 9.25 GHz 11.5 dBi TBD TBD

X / Ku 7.76 – 18 GHz 12.5 dBi TBD TBD

K / Ka 18 – 40 GHz TBD TBD TBD

8/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Effects produced by wind farm

Primary radiation

Secondary radiation

Instability of background

•Microwave link for telemetry and remote control;• Emissions from generators and transformers;• Sparks and corona from power lines and insulators;

Reflection of radio links;

Modulation of the near field background signal of the antenna by its periodically varying electrical characteristic

9/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Characteristics of the wind farmModell of turbine VESTAS V-52

Number of turbins 26

Electrical power (maximum) 22 Mwatt (850 Kwatt each)

Operational data 50 Hz/60 Hz - 690 V

Dimension of each turbine Height of the metallic mast 55 m, 3 resin blades with radius 26 m

Blade rotation velocity 14 - 31.4 rpm (average 26 rpm)

10/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Electrical scheme

11/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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RFI campaignsSession Date Weather Monitored

bandsTarget

1 19 Jan 2010

Sunny day P and L General overview

2 20 Jan 2010

Rainy day P and L Power station

3 11 Feb 2010

Sunny day P, L, and S Power stationand single turbine

12/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Survey at the wind farm

AZC 40°

Distance @ 3.5 Km; session #3

13/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Pointing measurementPol. V Pol. H

AZC 40° yellow AZC 40°+90° blueAZC 40°-90° purple

-62.6 dBm

14/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Wide-band measurementMax hold Single view

Blue : Pol. VYellow: Pol. H

Distance @ 500 m; session #3

15/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Zero-span measurement

Distance @ 1 Km; session #3

16/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Emission in P-band 20 Jan. (rainy)

19 Jan. (sunny)

Distance @ 3.5 Km; session #1,2

17/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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n. 9 @ 7 Km

Emission at large distance

18/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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RFI campaign at a wind farm

Power intensity drops in line-of-sight at -100 dBm at 85 Km!

19/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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Monitoring in L and S bands

Below the sensitivity?

21 cm line S band

Distance @ 1 Km; session #3

20/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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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!

21/21

P. Bolli, Measurements of primary radiation at a wind farm close to SRTW

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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.