SOME CONSIDERATIONS ON THE MECHANICAL TESTING OF ALUMINUM-STEEL CONDUCTORS AND THEIR CORES
Keywords:aluminum-steel conductor, conductor core, horizontal tensile testing machine, stress-strain curve, elastic compliance
Safe electrical energy transport on high-voltage overhead lines requires the physical-mechanical characteristics of aluminum-steel conductors and steel cores to be experimentally determined and compared to standard values. The basic characteristics of aluminum-steel conductors can be obtained by tensile testing to failure. Such tensile tests are regulated by the standards: CEI-IEC 1089, CEI-IEC 61089, SR-CEI 1089 and BS EN 50182.
Because of a wide rigidity range, aluminum-steel conductors require adapted testing conditions and experimental data analysis, ensuring that by tensile testing the most important mechanical characteristics can be put into perspective, for the whole conductor and for its core.
Therefore, a complete conductor testing procedure has been developed in this paper, according to the European standards in effect and applied for two conductors with a rigidity ratio of 4.42.
The experimental tests were carried out on a horizontal tensile machine, designed and built in the Laboratory for Conductors and Cables of the “Politehnica” University of Timisoara, Romania, having a length of 13 m and developing a force up to 2500 kN.The tensile tests have firstly shown that a (sometimes significant) difference can be observed between the stress-strain curves obtained according to the standards in effect and the ones based on the strains measured at the beginning of each hold period. This shows the creep tendency of conductors over a short period of time, when exposed to overloads. Secondly, it has been found that in case of high rigidity conductor steel cores, current standard testing is limited only to the elastic region.