Simplified overhead line equipment for railway mainline applications: system design, materials, and fault prediction

Overhead Line Equipment (OLE) is widely used to electrify railways due to low
environmental impacts and higher operational speeds, compared to diesel-powered trains. Electrifying railway mainlines can pose financial challenges - many local, regional and diversionary lines remain unelectrified or partly electrified such as Sheffield-Manchester.

This research explores feasibility of the Simplified Catenary, i.e. a trolley wire modified with additional support structures near masts for low-speed, low-usage, branch, local and
diversionary lines with up to 150 kph speed. This work is the first in-depth analysis of such
simple OLE on dynamic performance since 1990.

An overhead line dynamic model was created through the Finite Element Method, and
validated against test track data from which the validated model exhibited versatility
adequate for exploring various designs of the Simplified Catenary numerically.

Parametric studies were performed considering the contact wire stiffness variation, contact force, and axial loads in contact wires. Results revealed potential benefits of using physical springs at registration arms as suspension, and of using stitch wires placed towards midspan.

This work invented a new assessment metric named ‘Design Score’ considering the current collection quality, and mechanical failures including wear, arcing, tensile failure, and fatigue. Geometric optimisation was performed using the Design Score as an objective function and Surrogate Optimisation algorithm from which some optimised Simplified Catenary was found to be operational at higher than 150 kph in compliance with EN50367.

Despite being optimised, the Simplified Catenary exhibited weaknesses in the contact force spikes – peaks (mechanical wear) and drop-offs (arcing) – near masts when pantographs experienced steep gradients. SOLARC2 (Sheffield Overhead Line Arcing 2) was designed and built in this work to assess such localised damage which helped understand their importance and suggest means of mitigation through the Oxygen Free Copper.

This research has explored the feasibility of the Simplified Catenary in mainlines through a
combination of numerical and experimental works as an exploratory step paving the way for further investigations on its potential in practice. The next step might involve incorporating more realistic operational scenarios in the model such as with gradient, or scaled tests.