The Structure of the Near-Surface Layer of the AAAC Overhead Power Line Wires after Operation and Its Effect on Their Elastic, Microplastic, and Electroresistance Properties

Maria V Narykova,Boris K Kardashev,Roman V Sokolov,Vasily N Kuryanov,Alexey I Lihachev,Andrej G Kadomtsev,Andrei G Panfilov,Pavel N Brunkov,Aleksandr A Levin,Nikita D Prasolov,Vladimir N Tyshkevich,Makhsud M Sultanov

doi:10.3390/cryst12020166

Maria V Narykova, Boris K Kardashev + Show 10 more

Open Access

https://doi.org/10.3390/cryst12020166

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Journal: Crystals	Publication Date: Jan 24, 2022
Citations: 4	License type: CC BY 4.0

Affiliation: Ioffe Institute

Abstract

Overhead power-transmission lines are one of the most important components of modern infrastructure. Their service life is determined by the state of the near-surface defect layers (NSDLs) of wires constituting these lines. Both the structure and microstructure of the NSDLs of wires of the AAAC type (All Aluminum Alloy Conductor), which were in operation during 0 (new) to 62 years, were investigated by methods of the X-ray (XRD) and electron back-scattering diffraction, optical microscopy, and resistivity measurements, as well as by means of densitometric and acoustic measurements with layer-by-layer removal of the near-surface material by etching. Two characteristic thicknesses of the NSDLs were obtained, different methods providing close results, namely, ~30–50 μm and ~56–140 μm. According to the mass-density distribution (XRD), these characteristic thicknesses correspond to the depths from the surface where they occur, respectively, ~70% and ~99% of the density drop in comparison with the bulk density value. The rate of increase in NSDL thickness is ~4 μm/year in the interval from 0 to 18 years. Results of investigation of elastic and microplastic properties of wires after removal of ~35 μm of the upper layer are also presented.

Highlights

Overhead power lines have been in use for over 125 years as the backbone of electricity systems that transport electricity from power plants to places of consumption [1]
We study the profile of the near-surface defect layers (NSDLs) of Al wires depending on the depth from the surface using X-ray diffraction (XRD), densitometry, and resonant acoustic methods
The change in the intensity of X-ray reflections observed in Figure 11a,b with a change in the operating time from 0 to 62 years is discussed in detail in [9] and is associated with the development of a preferential orientation along the crystallographic direction [011] in the crystal lattice of Al wires due to the growth of crystallites and grains after the operation of the wires

Summary

Introduction

Overhead power lines have been in use for over 125 years as the backbone of electricity systems that transport electricity from power plants to places of consumption [1]. Conductive cables are the main part of these lines, consisting of one or more stranded conductors, twisted from several wires of highly conductive metals. The conductive wires are usually made of aluminum [2,3,4,5,6,7,8,9]. Aluminum has good conductivity (about 60% of the conductivity of copper), but is about three times less dense than copper and, three times lighter than wire segments of the same size. Aluminum wires are quite resistant to atmospheric corrosion due to the formation of an amorphous oxide layer (Al2 O3 , γ-AlOOH, Al(OH)3 ) on their surface with a thickness of about 4–10 nm [4,10]. Aluminum is a much cheaper metal than copper

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