Abstract
The health of the components that make up the cables of power lines, and hence their service life, is governed at the micro level by changes in their structure and microstructure. In this paper, the structure and microstructure of aluminum wires of overhead power transmission lines (without a steel core) of different service life from 0 to 62 years have been investigated by quantitative techniques of X-ray diffraction, diffraction of back-scattered electrons, and the densitometric method. Elastoplastic properties of the wires have been tested by the acoustic-resonance method. A decrease in the Al material density Δρ/ρ∼−0.165% was found in the near-surface layer of ∼36 μm depth and in the bulk of the wires with an increase in the service life from 0 to 18 years. The density decrease is associated with the accumulation of microcracks. The following density increase (Δρ/ρ∼−0.06%) in wires with a service life of 62 years is attributed to the formation of ∼0.7 vol.% of crystalline Al oxides in the near-surface layers of the wires. The nature of the change in the elastic modulus, microplastic flow stress, and decrement indicates complex structural changes correlating with the results obtained by diffraction methods.
Highlights
Power cables are the most important items of the distribution and transmission infrastructure of electrical networks, being laid in different environments such as air [1,2,3], underwater [4], or underground [5,6]
In contrast to the investigations discussed above, the present study examines a set of AAAC wires of the existing overhead power-transmission lines with a different service life from 0 to 62 years
As was expected according to the wire-maker’s data sheet, the results of the EDX analysis proved the main element of the wires to be Al (∼99 wt.%) with small admixtures of Fe (0.26 to 0.6 wt.%), Si (0.06 to 0.16 wt.%), and O, whose content in samples notably rises after their long service life
Summary
Power cables are the most important items of the distribution and transmission infrastructure of electrical networks, being laid in different environments such as air [1,2,3], underwater [4], or underground [5,6]. Cables can contain one or more multi-wire strands of highly conductive materials, usually aluminum in the case of air cables [1,2,3] or copper [4,6,7] in the case of either submarine or underground cables or cables at nuclear power plants. Can be clad in insulating plastic protective coat to increase their service life by minimizing the possibility of short circuits due to contact either between cables of different phases, or with trees in the forest, or atmospheric icing, and so on (see [1,8,9] and references therein).
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