Sweden has many catenary systems designed to be used for 40–60 years. Normally they can meet basic operational requirement within this period, but after a long time in service the catenary structures get weakened. Today there are about 40 incidents on catenary breaking each year, which leads to disastrous consequences to the railway network. The significant dynamic interaction of the pantograph-catenary system, together with mechanical wear, chemical corrosion, thermal softening, environmental disturbances, multiple-pantograph operation and increased traffic volume, can significantly weaken the physical strength of the catenaries and result in fatigue and structural damage. To reflect the catenary degradation, a study on the catenary dynamic-fatigue is performed with some factors considered, e.g. material softening due to high temperature and annealing, and cross-section losses due to wear, structural defects and small damages. This study finds that among all Swedish catenary systems the soft catenary system SYT 7.0/9.8 is relatively weak and its messenger wire is the most vulnerable component. The results show that the dynamic tensile load is dependent on position and operational speed. The weakened material strength due to high temperature and annealing have the main responsibility for the system failures. In the end, this paper suggests that, besides the regular visual inspections to the catenary structure, it is necessary to measure and control the degradation of physical strength of the key components to ensure safety and reliability in operation and also to extend the catenary service life.
- Catenary breaking
- Physical strength degradation
- Copper annealing