Bird-flight diverters increase the visibility of the electricity transmission facilities and therefore prevent birds from accidentally colliding with them.
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Electricity transmission facilities (lines and substations) interact with environmental elements, including wildlife, and especially birds.
The risk of electrocution is impossible in overhead transmission lines, with a voltage of 220 kilovolts or above, as the distances that separate the conductors of the different phases from each other, or the metal parts of the towers is too large for simultaneous contact to take place.
However, birds usually collide with the grounding cables of transmission lines (cables that protect the lines against electrical discharges during storms), which, being smaller in diameter than the conductors, are less visible. Therefore, actions geared towards reducing the risk of collision are based on marking these cables with devices known as bird-flight diverters that increase their visibility.
To prevent birds from colliding with lines, Red Eléctrica increases the visibility of their line infrastructure with two models of bird-flight diverters that have been field tested to check their effectiveness:
- Spiral bird-flight diverters. This is a spiral of white and yellow, or orange polypropylene one metre in length and 35 centimetres in diameter. One spiral is placed every 5 metres when there is only one cable, whereas when there are two grounding cables they are installed and located keeping a distance of 10 metres between the devices.
- Blade or rotating sphere bird-flight diverters. The design consists of a body with flat plates or polyamide blades, each one with one face that has reflective sheets of different colours and shades. It is suspended, using links, to a freewheeling element so that the plates reflect the smallest amount of light. In the case where there is only one cable, a device is placed every 7 metres; where two grounding wires are present they are placed keeping a distance of 14 metres between each device.
Both the spiral bird-flight diverters and the blade may be used for any bird species and facility, but blade devices increase their efficiency in birds with crepuscular habits and those located in foggy areas.
In late 2014, the Spanish transmission grid had 2,776 kilometres of line marked with bird-flight diverters, of which 578 kilometres cross Special Protection Areas for Birds (SPAs).