The grasslands of the western slopes and plains of New South Wales contain large flocks of native galahs and sulphur-crested cockatoos.These birds typically feed on seeds and are consequently common in rural areas where grain crops ate grown.
Investigations along the route of the Inverell-Moree Line and the Queensland-NSW Line have indicated that bird damage to insulators was most prevalent in areas close to grain farmlands and where sources of water were available at creeks or dams. Nesting trees close to a transmission line were also found to be a factor in increasing the local bird population.In any case,the potential for damage to insulators is not necessarily due solely to large flocks as even a single bird can inflict severe pecking damage.
The most common damage to composite insulators arises from birds`chewing` the insulators rather than eating them.Both of the species responsible for the damaging insulators have parrot-like beaks which grow continuously throughout their lives.Chewing is apparently a natural practice necessary to wear down the beaks and galahs and cockatoos have been known to chew timber and even softer metals.
The novelty of any new structure in the area(such as new transmission line structures) is also considered a factor behind the chewing of insulators.Often,these birds will ignore a line after it has been present for some time.
On both lines mentioned above,no insulator damage has been record once the lines were made operational,which suggests that energizing a line to service voltage may well be a deterrent for bird pecking of insulators.
In order to eat seeds,cockatoos and galahs have immense closing pressure on their beaks(estimated to be between 1.0-1.7Mpa).Therefore,it is considered impractical to develop a composite insulator with sufficient tear strength to withstand such pressure.Rather,to protect insulators during construction,it has been considered necessary to equip composite insulators with special plastic protective covers until the line is energized.
These protective covers have been manufactured from 1 mm thick polypropylene sheet pre-formed into a roll and held in place with self-adhesive strips.Birds will only chew a material if they can access it and, in this respect,they rely on claws which can easily grip around most transmission line conductor,fittings,hardware and insulator sheds,The protective shroud acts as a barrier to the sheds and its rigid slippery surface prevents bird claws from taking a hold.
The shrouds are removed immediately prior to the line being energized and may subsequently be re-used.
From 《Insulator News & Market Report INMR》
