Laboratory Assessment of ARC Damage in Railway Overhead Contact Lines With a Case Study on Copper-Silver and Low Oxygen Content Copper
Özgün Sunar, David Fletcher, A. Beagles
Abstract
New laboratory-based test equipment is described for controlled arc exposure of short lengths of railway electrification contact wire (100 mm) enabling a rapid and low-cost experimental investigation of electric arc damage due to loss of contact between the pantograph and overhead line. The extreme local heating typical of arc sites is found to locally reduce wire hardness, seeding sites for wear and fatigue crack initiation. Contact loss may be produced by poor dynamic behaviour at the pantograph to overhead line interface, often caused by changes in system stiffness or local misalignment of the overhead line. In this study, arcs were generated with computer control of pull away and approach to the wire to carbon strip contact, with peak currents in the range 100 to 200 A for direct current and ± 200 A for alternating current. Metallurgical and mechanical damage identified is correlated against energy input quantified through voltage and current measurements. Interior void formation within the contact wire and modification of grain size are revealed with optical microscopy, metallography, surface mapping and microhardness tests. Initial tests using the new equipment with two materials show the potential for investigating mitigation of arc damage by changing contact wire composition.