04-02-2013, 11:47 AM
Mitigation of Transmission Lines against Bird Hazards - the Israeli
Experience
1Mitigation of Transmission.pdf (Size: 216.82 KB / Downloads: 59)
ABSTRACT
The extensive use of transmission lines by different bird species in Israel for
perching and roosting causes severe damage to the transmission network,
mainly to 110 and 161 KV lines but also rarely to a 400 KV line. Birds are seldom
electrocuted when perching on lower arms of transmission poles, while in close
proximity to the above wires. However, a much more common phenomenon
occurs when birds' streamers produce flashovers that result in outages. These
may account for more than 90% of the overall damage to transmission lines in
Israel, including several dozens of events of severe outages every year. Most of
them are caused by wintering birds in specific locations. Costs of such events
vary and may reach several hundred-thousands $ US each or even more. The
Israel Electric Corporation uses several mitigation devices to prevent outages.
These include spikes, wires, additional perches, "umbrellas" and insulating
sleeves. These devices considerably improved the situation in some areas, but
on the long-run proved to be insufficient and the damage remains severe. The
current paper describes the causes of the outages, and the various measures
that were implemented to reduce the damage.
Introduction
Since the mid 1990’s, systematic bird damage to transmission lines has been
observed in certain areas of Israel. This damage involved perching and roosting
birds of several species, including mainly migrating White Storks (Ciconia ciconia)
and wintering Black Storks (Ciconia nigra). In addition, wintering raptors,
including Long-legged Buzzards (Buteo rufinus), Common Buzzards (Buteo
buteo), Imperial Eagles (Aquila heliaca), Black Kites (Milvus migrans), Saker
Falcons (Falco cherugg) and European Kestrels (Falco tinnunculus) are
observed regularly perching on transmission lines while foraging during daytime.
Most of the raptors tend to perch on the upper arms as single individuals.
However, Black Kites which are highly gregarious, usually perch in groups on a
single pole (O. Bahat – pers. obs.) (see Fig. 1).
Materials and methods
Observations were contacted all year round since early January 2009 until the
end of February 2010, documenting birds' activity on transmission lines (161 and
400 KV) in three areas: Carmel coast area, south of the city of Haifa (161 KV
line), Akko Valley, north of the city of Haifa, (161 KV line) and an area north-east
of the town of Hadera (400 KV line), all in the north-west of Israel. Night
observations were usually made from a 4x4 car, in order to prevent disturbance
to the birds, at specific locations not closer than 150 meters from the
transmission poles, to prevent disturbances to the birds' activity. Daytime
observations were also conducted from a car for the same reason. Night
observations started 2 hours before sunset (at approximately 15:00) and ended
in the morning after the last bird left the poles (at approximately 07:00). These
were conducted twice every week during the 2009 and 2010 winters, when birds'
activity was at its peak, and once a week in other seasons in the three study
areas. Daytime activity observations covered the perching and foraging
behaviour of birds around and on transmission line poles. They were conducted
after the roosting birds left the transmission line (at approximately 06:00) until
first arrivals of roosting birds (at approximately 15:00).
Results
Most bird activity in the three study areas was performed by a very limited
number of species: Nocturnal activity was solely conducted by the Black Stork
(Ciconia nigra), the only species in the study area that regularly uses
transmission lines for roosting. This species usually starts to appear at the study
areas during September on its early migration from its nesting habitats in
northern Europe to its wintering grounds in Israel and further south into Africa (8).
However, significant roosting on transmission lines in the study area started only
on late October. The wintering of the Black Storks in the study area, including the
use of transmission line poles for roosting, continued until mid March, when the
birds migrated north. A peak of use of the poles for roosting took place on the
autumn migration from late October until late November with regular roosting on
the poles in all the study area. Maximum number of birds on a single pole was 21
for a 161 KV pole and 25 for a larger 400 KV pole. However, the number of birds
on a single pole usually did not exceed 15 and 20 for the 161 and 400 KV poles
respectively.