Network Rail completes overhead line system upgrade in Severn Tunnel, replacing 838 support arms

en.Wedoany.com Reported - Network Rail, in partnership with contractor ARQ (AmcoGiffen, REL, and QTS), has completed the upgrade of overhead line equipment and power supply systems in the Severn Tunnel, marking the first large-scale engineering solution to address corrosion issues since the tunnel's electrification.

The 7-kilometer tunnel, located beneath the Severn Estuary, has been continuously affected by seawater and moisture since its electrification. Bimetallic corrosion, occurring between different metals in damp, saline conditions, has accelerated the wear of overhead line equipment. In response to this environmental challenge, Network Rail developed a specialized overhead line system featuring modified bridge arms and continuous copper contact wires to enhance system resilience and reliability while reducing future maintenance needs.

In 2025, the solution was successfully trialed on the line to Cardiff. Subsequently, Network Rail and ARQ completed the installation on the line to Bristol, achieving the system's first large-scale deployment. The project involved replacing 838 overhead line support arms, installing 14 kilometers of new wiring, laying over 7 kilometers of single copper contact wire supported by modified bridge arms, and removing and replacing 7.2 kilometers of aging equipment within the tunnel. Approximately 250 engineers worked around the clock to complete the project within 16 days.

Nick Millington, Network Rail's Route Director for Wales and Borders, stated that the solution is the result of years of innovation and collaboration between the team and industry partners, specifically designed to withstand the harsh conditions within the tunnel. Vinny O'Holloran, Operations Director at ARQ, noted that the team demonstrated resilience, skill, and professionalism under extreme heat and the unique challenges of the tunnel, successfully delivering the system.

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