Letter 15091

Selection and evaluation of aluminum alloys for transmission lines [Brazil]

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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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