Surge protection in the Saaser Tunnel

National highway 28 is the main link to and from Davos and is heavily used in the winter months. The Saaser Tunnel is part of the “Bypass Saas” project and diverts the national highway under the municipality of Saas im Prättigau in Switzerland.

Prior to the construction of the tunnel, traffic was directed to the Saas through road. The tunnel has now drastically reduced the traffic through the town.

Data on the Saaser Tunnel:

• Location: Canton of Grisons, Switzerland
• Length: 2.58 km
• Design: 10.0 T (one main tube with two-way traffic, with one lane in each direction, one safety tunnel in parallel to the main tube)
• Opened: October 2011
• Constructor: Civil Engineering Department of Grisons/Federal Roads Office, Switzerland
• Volume of traffic: approximately 15,400 vehicles/day

The main distribution's energy is supplied via a transformer. As this cable is outside the protection zone of the tunnel, and therefore comes from lightning protection zone 0_A, the tunnel supply must be protected.

Additional systems, which also need to work properly in the event of a power failure, are supplied by means of uninterruptible power supplies. This also includes the controller which regulates traffic in the event of an emergency and informs road users accordingly.

Technical equipment in the tunnel:

• Video cameras
• GSM antennas, radiating cable for radio and wireless
• FL/Natt lighting, fire emergency lighting
• Smoke detection, fire detection
• CO and visibility measuring devices, wind measurement
• Light signals, fire doors

The Civil Engineering Department of Grisons uses the FLASHTRAB compact PLUS (FLT-CP-PLUS) type 1 lightning current arrester from Phoenix Contact to protect the main distribution in the Saaser Tunnel. It is installed directly in the main distribution and, in the event of damage, the lightning currents that occur are discharged directly to ground.

The uninterruptible power supplies are protected with VALVETRAB compact (VAL-CP) type 2 surge protective devices. They are located directly at the cable entry from the tunnel to the distribution. As every system is connected to the UPS via its own supply line, all the supply lines are also connected via type 2 surge protective devices.