Analysis of the quality of aluminum overhead conductors after 30 years of operation

Abstract

Overhead power conductors (OHL), which are installed in transmission and distribution lines, are designed for a service life of min. 30–50 years. During this time, the OHL conductors should work in a safe and fault-free state with the highest current capacity. This article refers to the testing of aluminum conductors after 30 years of operation. The mechanical properties and structural characteristics of the conductor were tested. The analysis of the quality of the supplied wire samples carried out with a scanning microscope allowed us to distinguish three types of wire damage, namely: corrosion on the surface of the outer layer, wires, local melting, and loss of cross section and wire breakage. On the basis of a detailed analysis of the areas of damage to wires from the tested OHL conductors, it can be stated that the main cause of their breakage is local smelting areas caused by an electric arc.High temperatures affect local material melting, leading to a large reduction and the consequence of strength decreasing. This situation leads to the loss of the conductor's carrying capacity and ultimately to its destruction. During 30 years, conductors had to be subjected to frequent short circuits caused by changing weather conditions, i.e., high wind or storms. The paper dealt with the results of the mechanical properties test, which showed that the aluminium wires are lower than those required by the standard. The greatest degradation of the strength properties occurs on the wires of the outer layer of conductor. The center wires show a negligible reduction in tensile strength.