North Hoyle Windfarm Report

6 MCA Radar trials

6.3 Results of the trials

6.3.1 Shadow and blind areas

As has been noted previously, the WTGs produced blind and shadow sectors behind them in which other turbines and vessels could not be detected and displayed. An example of this is illustrated in Figure 6-6. Additionally, the strong response of the WTGs when nearby, and with their close spacing, appears to produce saturation areas in which targets are not detected, particularly if receiver gain is reduced to reduce side lobe and other spurious echoes. However, in general, this would only be a significant problem if:

• the search vessel or target were not able to move to different locations from where the target was not in these sectors;
• the target lay within the poor cross and down range discrimination areas of the WTG responses, as illustrated in the following trials.

Figure 6-6: Shadow and blind arcs with side lobe echoes

6.4 Principles of range and bearing discrimination testing

The effect of turbine blades on turbine echo size is illustrated in Figure 6-7, where the plane of the rotor blades is approximately at right angles to the direction of the radar scanner. Here the angular width of the turbine is 1.6 times that of the anemometer mast. Corresponding sizes of the echoes displayed at the relevant ranges are about 610 metres and 300 metres respectively. The displayed size of turbine and anemometer mast is 2 tan(µ=2)£R, whereRis the range in metres and µ is the angle subtended by the displayed echo. The displayed range discrimination is approximately 200 metres.

Figure 6-7: Range and bearing discrimination