The New Rail Link through the Alps (NRLA) is the centrepiece of Swiss transport policy. With three base tunnels and further extensions, Switzerland has thus created an efficient railway infrastructure through the Alps. It enables shorter journey times and higher quality in passenger and freight transport.
The Lötschberg Base Tunnel has been in operation since 2007, the Gotthard Base Tunnel since 2016. With a length of 15.4 km, the Ceneri Base Tunnel is the third major structure of the NRLA. Like the Gotthard Base Tunnel, the Ceneri Base Tunnel consists of two single-track tubes with a regular centre distance of around 40 m, which are connected every 325 m by cross-passages.
Power Supply System Secured by Multiple Backups
The safety infrastructure in the tunnel includes lighting, ventilation and escape routes. These operations are powered by a multi-security power supply system, which was realised in a successful collaboration between Avesco and its partner HITEC Power Protection, the Dutch manufacturer of the dynamic rotary UPS systems
Even the failure of one of these systems is secured: The west and east backup grids are coupled through a so-called „master-slave circuit“. This means that if one DRUPS system fails, the remaining system can supply both backup grids with emergency power without interruption. The backup grids run empty and can be used immediately at full capacity if necessary.
The “mean time between failure” (MTBF) as a measure of the safety level, i.e. the number of operating hours during which statistically a single total failure may occur, is an extremely high 4 million operating hours for the power supply of the Ceneri Base Tunnel.
This backup system, in particular the master-slave circuit, was developed for the construction of the Gotthard Base Tunnel. For the Ceneri tunnel, the plant engineers were able to benefit from this experience and use the system again with minor adjustments.
A special challenge in this project were the exceptionally long power lines; in some cases, lines up to around 6 km long were used. Due to the extremely long and unloaded lines, there is a very high capacitive reactive power proportion, which results in additional power for the generators. Also due to the cable length, the short-circuit power of the DRUPS systems must be very high; it is 17 times the nominal power. For comparison: classic emergency power systems, as they are normally installed, have a threefold short-circuit current.
Support and Maintenance of the System
Even after the official opening of the Ceneri Base Tunnel in September 2020 and its commissioning the following December, work on the emergency power supply will not be completed. A framework contract has been concluded with the owner SBB for support and maintenance, which regulates the services to be provided by Avesco on all DRUPS systems in the Gotthard and Ceneri base tunnels. This ensures maximum system reliability for continuous and uninterrupted power supply.