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Letter 15091
Selection and evaluation of aluminum
alloys for transmission lines
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Dear Sirs,
I'm studying the application of aluminum alloys in fittings
commonly used in overhead transmission lines by the company in which
I work.
Initially, I studied and applied a conductor cable that works in a
range of maximum temperatures oscillating between 150イ (without
aging) and 180イ(with aging).
On that occasion, I followed the material employee's evaluation in
their fittings, even so now in a second work, I intend to go more
thoroughly in the subject.
For not disposing of bibliographical references on this subject, I
am counting with your collaboration so that I can solve and elucidate
with this some doubts.
I have the following comments / doubts to do:
1 - the commonly used alloy in the conductor cables of our
overhead transmission lines is 1350 EC (hard temper / duty ?).
2 - the manufacturers of fittings with aluminum alloys for the
overhead transmission lines, uses here in Brazil the aluminum alloy
1050 (rich in aluminum, low quantities of silicon and magnesium) and
6101-T4 (less aluminum in its chemical composition, even so more
silicon and magnesium that the previous, and the magnesium increases
the mechanical resistance of this aluminum alloy in relationship to
the previous one).
3 - Other concept also obtained with the manufacturers is that the
aluminum alloy 6101-T4, after its solution, and with the temperature
increase and aging, changes from T4 to T6.
4 - it is also used in Brazil, even so in small scale, the league
6201 as conductor cable. It has the characteristic of presenting
smaller expansion linear coefficient, consequently smaller sag in the
conductor cables.
5 - the Japanese conductor cables that I studied, is of the series
of aluminum alloys 8000, and above the Japanese aluminum alloy that
is already nationalized, there are other two alloys . The aluminum
alloy ztal and xztal, whose conductor cables operate with the range
of temperatures around 240イ and 330イ.
6 - the national conductor cable manufacturers , that the
annealing occurs in a temperature around 93イ, while this fact
doesn't occur with the aluminum alloys such as tal, ztal and xztal,
in function of the presence of the zirconium and lant地io in the
alloy. The overhead transmission line fittings manufacturers already
inform that the annealing occurs in temperatures greater than 93イ.
This is my doubt, that will be explained better with the explanation
of the experience that is in process.
7 - In the experience that I meet accomplishing in laboratory of
fitting manufacturers, we are beginning, with the temperature of the
control conductor cable around 180イ, two anchorage compression
fittings , with different dimensions.
One of them, for having larger dimensions and more mass, for a
same value of current, presents inferior temperatures to 90イ. In my
opinion on the subject, this fitting won't present annealing problem
with respect to the aluminum, therefore it won't present reduction in
supporting efforts mechanics, when compared to the other fitting.
The other sample, presents smaller dimensions, and for the same
value of current mentioned above, presents superior temperatures to
90イ. Such fact would occur in the annealing of the aluminum, with
reduction of yours mechanical characteristics.
Is my way correct of analyzing the situation with regard to the
annealing of the aluminum alloy?
Face to the facts exposed above, I'm needing a help to my
technicians questions, as well as bibliographical references to
clarify them.
Expecting your answer, as sooner as possible, I'm grateful in
advance,
Best Regards,
Paulo Americo de Mattos
Cardoso
Enersul- Empresa EnergÈtica de Mato Grosso do Sul S.A> -
Campo Grande, Mato Grosso do Sul, Brazil
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