Gefahren durch Freileitungen
1. Accidents through open-wire lines
Annually thousands of great birds have an accident in Germany. Many birds choose pylons as a place for resting. At the medium voltage pylons (1 to 30 kV) which are mainly made of concrete or steal the birds may touch the life components and cause accidental ground or short-circuit. That leads to a fatal electric shock.
The most dangerous ones are the supporting and the dead-end towers as well as pylons with dividers that are unsuitably constructed. Dead-end towers in this respect are twice as threatening, because of wires above the transverse beam and of the small distances to the parts under voltage in the horizontal line. Pylon dividers build their own catagory, even on the accident records.
The most frequent cause of death of the white stork are accidents at medium voltage pylons. The accidents are divided into 16% through the landing and 86% through electric shock. The dead birds hardly keep lying on the pylons. In most cases they fall off the pylon and are abducted by predators soon.
Protected birds species threatened by extinction:
- sea eagle, osprey
- peregrine falcon, kestrel
- common buzzard,
- kite
- hawk
- eagle owl, barn owl, screech owl
- white stork, black stork
- harrier
2. Protection measures against electric shock
2.1. Through bird-likely methods of construction (suspended constructional form) at new and re-constructions
When constructing or reconstructing medium voltage open-wire lines according to DIN VDE 0210 bird-likely constructions of pylons are to be made. It requires: "The transverse beams, insulator holders and additional components are to be formed, that there is no chance of landing and seating next to the electric parts for birds."
That is especially achieved by the suspended constructional form. At dead-end towers the distance from the edge of the transverse beam to components under voltage has to be 600mm at minimum.
2.2. By additional sharping through protective caps and seating bars as well as through chain lengthening at dead-end towers
Power supply companies already deactivated 16% of the particularly dangerous pylons. However, there is still a lot of work to do. At the moment, Baden-Württemberg is the only state in Germany that had stipulated a comprehensive changing of the pylons until 2002.
The technical solutions for the changing of pylons are in included in the VDEW-Proceeding directory "Bird protection at open-wire lines", 2nd edition 1991.
|
