On the railway line between Stabio in Switzerland and Bevera in Italy, lighting-induced damage was caused in the signalling systems in both countries. This occurred despite the galvanic isolation of the return current systems. Overvoltages were transmitted via the trunk cable connecting the two signalling installations. Enotrac carried out a root cause analysis and developed measures to ensure lightning protection and equipotential bonding of the signalling systems in the future.
About the project
The Mendrisio–Varese railway line connects two railway power supply systems: the 16.7 Hz system of Swiss Federal Railways (SBB) and the 3 kV DC system of Rete Ferroviaria Italiana (RFI). These two systems are electrically decoupled at the neutral section. However, a trunk cable connects the signalling installations in Stabio on the Swiss side and Bevera on the Italian side.
A lighting strike in Bevera caused overvoltages which were transmitted to Stabio via this trunk cable. Due to insufficient lighting protection, damage occurred not only in Bevera but also in Stabio.
The main challenge was the combination of different earthing and return current systems, cross-border infrastructure and an unusual situation regarding lightning protection. In collaboration with SBB and industrial partners, various approaches were analysed and evaluated from a technical perspective. The aim was to manage the complex earthing situation safely and sustainably and to prevent future failures.
Our contribution
Enotrac analysed the incident, conducted a root cause analysis, developed various technical approaches and derived the necessary measures for a final concept. Focus was the superordinated concept regarding earthing and return currents as well as improved lightning and surge protection.
Our services at a glance: Analysis of the root cause
- Assessment of the existing earthing and equipotential bonding, return current and lightning protection systems
- Development and comparison of several technical approaches
- Definition of an optimised earthing and equipotential bonding system
- Design of a multi-stage lightning and surge protection system
The solution is essentially based on a specific equipotential bonding system combined with the use of staged surge protection devices in order to safely limit critical voltage differences and reduce the stress on the trunk cable.
Facts ans Figures
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Client
Schweizerische Bundesbahnen SBB
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Period
July 2025 – Mach 2026
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Location
Stabio, Switzerland and Bevera, Italy
