Enhancement on Al–Mg–Si alloys against failure due to lightning arc occurred in energy transmission lines Sedat Karabay, Ersin Asım Güven ⇑ , Alpay Tamer Ertürk Mechanical Engineering Department, Engineering Faculty, Kocaeli University, Turkey article info Article history: Received 18 November 2011 Received in revised form 1 February 2013 Accepted 1 February 2013 Available online 19 February 2013 Keywords: Al–Mg–Si alloy OPGW Lightning Inoculation AlB 2 abstract This article has been prepared to share some experience and technical investigation related to lightning and short circuit strength of the OPGW type conductor used in transmission lines. It is well known that overhead ground wires are vulnerable to strand breakage due to lightning strikes. Recently applications of composite fiber optic ground wire have become more important to protect them from such damage. In this paper, we present test results before and after application of modification to the main conductive part of the con- ductor, which is composed of AA-6101 alloy, galvanized steel and SS-steel tube with fibers. Modification of AA-6101 aluminum alloy was performed by adding 3% AlB 2 into molten metal. After having completed manufacturing of the improved feedstock at CCL, we per- formed the drawing and stranding of wires. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Overhead ground wires (OPGWs), installed on the upper portions of overhead transmission lines to protect conductors from lightning, may have their strands broken when struck by lightning with extremely powerful energy [1]. Particularly, those lines passing through areas where winter lightning with big energy frequently occurs or areas total days on which lightning occurs, is comparatively high require upgraded lightning resistance overhead ground wires to increase reliability of the power transmission systems [2–6]. Two types of OPGW are available at present [7]. One is a tight buffer type, where the optical fibers are housed with tension members. The other is a ‘‘loose buffer type’’, where the optical fibers are loosely housed inside the tube. The representative tight buffer type called ‘‘spacer type’’ has an aluminum spacer inserted in the alu- minum tube to suppress fiber movement. It is mainly used by Japan domestic power companies and has proved extremely reliable in actual installations. The representative looses buffer type, predominantly produced in Europe and called the ‘‘stainless steel tube type’’ has fibers having surplus length and a jelly compound inserted into the stainless steel tube. Grease is used to fill up spaces between the tube and aluminum clad-steel or galvanized steel and aluminum alloy wires AA-6101 or AA-6201 to avoid galvanic corrosion due to different metal contacts with each other. However, if the stranding of the wires is not formed perfectly, the gaps between wires cause the grease to leak during heavy rain. The other issue is that grease can become hardened by sunlight or a dry atmosphere; prolonged exposure to these environmental conditions causes the grease’s anti-corrosion effect to weaken. This phenomenon is exacerbated in particularly harsh environments. These events 1350-6307/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engfailanal.2013.02.005 Abbreviations: GW, ground wire (ffiground conductor); OPGW, Optical ground wire; AA, aluminum alloy (AA-6101 or AA-6201); AAI, aluminum alloy inoculated with AlB 2 ; ACS, Aluminum-clad steel wire; CST, Aluminum-clad steel tube; GSW, galvanized steel wire; SST, stainless steel tube; CCL, continuous casting line; RTS, rated tensile strength; UTS, Ultimate tensile strength. ⇑ Corresponding author. Tel.: +90 2623033441. E-mail addresses: sedat.karabay@kocaeli.edu.tr, sedatkarabay58@gmail.com (S. Karabay), asimguven@kocaeli.edu.tr, asimgven@gmail.com (E.A. Güven), tamer.erturk@kocaeli.edu.tr, tamererturk@gmail.com (A.T. Ertürk). Engineering Failure Analysis 31 (2013) 153–160 Contents lists available at SciVerse ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal