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Experience at Venezuelan Utility with Ceramic and Non-Ceramic
Insulators
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| The following article has been prepared by Messrs.
Joaquín Oliveira Da Silva and José Antonio Pardiñas of
C.V.G. EDELCA and is based on an edited version of the presentation given by
Mr. Pardiñas at INSULATOR 2000 in Barcelona during November
1999. |
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INTRODUCTION
C.V.G. Electrificación del Caroní (EDELCA)
is an electric power generation and transmission company created by the
Venezuelan Government in 1963. Its transmission system comprises 2100 km of 765
kV lines, 2400 km of 400 kV lines and 500 km of 115 kV to 230 kV lines. This
system is connected to the Guri Dam (10,000 MW) as well as to the Macagua
Complex (2950 MW), which in 1998 together generated 56,190 GWh - equivalent to
approximately 70% of the country’s total electricity consumption.
765 kV TRANSMISSION
SYSTEM
EDELCA first began construction of its 765 kV transmission
system in the early 1980’s and, by 1986, the first two lines began
operating covering a length of 1250 km. During 1991, a third transmission line
was completed adding 850 km to this system. Together, these 2100 km of 765 kV
lines have now been in service for more than 10 years.
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The
performance of insulators affected by pollution is not only a result of
creepage distance but is also related to the shape of the insulators.
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In terms of insulators, almost 700,000 ceramic insulator
units have been utilized on this system, of which approximately 60 per cent are
porcelain and 40 per cent glass. These lines are 4-bundle ACAR 1300 MCM per
phase with two overhead ground wires of alumoweld 7#8 AWG. The configuration of
the insulator string is I V I (i.e. I string at both outside phases and V
string in the center).
The 765 kV lines from the hydro-electric stations in the
southern Guayana Region to the urban centers of the northern and western parts
of Venezuela, pass through a region known as Mesa de Guanipa which is noted for
its high levels of agricultural pollution and adverse climatic conditions.
Weather studies indicate that the dry season in this area lasts from 4 to 6
months beginning in November. This results in an accumulation of pollution and
during the evenings the relative humidity levels approach 100%. These heavy
contamination conditions have affected the design of the insulation level of
the lines more than any considerations related to switching surges.
At first, EDELCA analyzed the performance of two 400 kV
lines as well as a 230 kV line located in this area and which had been in
service since 1971 and 1968 respectively. During a period of eight years from
1971-1978 there were 17 faults on the 400 kV lines during the January-March
period - all attributed to insulator contamination. Although there were no
outages due to contamination on the 230 kV line, a high level of corrosion was
observed on the pins of insulators. |
Volume 8 Number 3
