The final delivery for the completion of Gotthard Base Tunnel, consisting of 899 medium-voltage systems, has arrived

A view of the Gotthard Base Tunnel. ABB has provided the medium-voltage switchgears that supply power to the infrastructure.

The Gotthard Base Tunnel, a landmark project, is approaching completion. ABB has contributed to the project, supplying the very last medium-voltage switchgear in mid-August this year on time, in good time to power the breakthrough of this momentous Alpine tunnel.

On the first weekend in June 2016, all eyes will be on Switzerland or, more precisely, on the world’s longest railroad tunnel.  According to current plans, that’s when the Gotthard Base Tunnel will be unveiled in a grand opening ceremony. The plan is to start regular passenger and freight services after a period of trial runs and to launch a new train schedule in December 2016 – one year earlier than originally planned in 2008.

Back then, ABB received an order from Balfour Beatty Rail to supply all of the medium-voltage switchgears required to power the infrastructure of the Gotthard Base Tunnel: 50 Hz technology that supplies power for the lighting, signaling and safety systems, the communications, ventilation, and air conditioning systems, and the safety doors. Balfour Beatty Rail is part of the Transtec consortium, that was awarded the construction lot to install the railroad infrastructure by the building owner, AlpTransit Gotthard AG.

Just six years later, the project teams of Balfour Beatty Rail and ABB met at the installation site in Schattdorf (Uri Canton) on August 20, 2014 to celebrate the delivery of the very last two medium-voltage switchgears in the lot, numbers 898 and 899.

Fine particulates and pressure fluctuations

“The continuity over the years as regards the project teams at both ends has been a tremendous help in the successful implementation of the project”, points out Eberhard Hunger, Balfour Beatty Rail’s Project Manager. The final delivery saw the involvement of the very same team that had launched the project.

Each of the tunnel’s two parallel tubes measures 35 miles in length.  By way of comparison, that is equal to a stretch from the City of Zurich, across the whole of the Aargau Canton, through to Egerkingen. The two tubes are connected by 44-yard cross-cuts, at a distance of 355 yards apart. In every second tunnel of these connecting tunnels, which primarily function as escape routes, electrical supply systems are installed. For these, ABB has supplied type ZX0 gas-insulated medium-voltage switchgears, which have been adapted to the difficult conditions in the railroad tunnel. “We had to pay attention, above all, to fine dust from the abraded materials from rails and contact wires and to the enormous pressure fluctuations in the cross-cuts created by express trains passing at 155 mph,” explains Guido Huser, ABB’s Project Manager. “It creates over- and underpressure, each of up to 10 kPa.”

Intensive testing

ABB produces the type ZX0 switchgear in Ratingen, Germany. In order to withstand the environmental conditions in this record-making tunnel, in addition to the standard gas-tight welded high-voltage part of the switchgear, the accompanying local control cubicle has been designed according to the IP65 Protection Rating: the cubicle is therefore dust-tight and provides protection against water jets. This was successfully tested using prototypes in the Hagerbach Test Gallery, situated in the east of Switzerland.

For the purposes of pressure strength testing, the Swiss Federal Laboratories for Materials Science and Technology (Empa) subjected the ZX0 switchgear, including the control cubicle, to 200,000 load cycles of increasing and decreasing pressure over 47 days.  These continuous load tests have demonstrated that the system is optimally suited for unusual environmental conditions such as these.

Since the cross-cuts double up as escape routes, there were considerably stricter requirements for arc fault protection and arc resistance as for example in a restricted-access substation. Although an arc fault is highly unlikely to occur in a gas-insulated switchgear, the safety of passengers must be ensured even in unlikely events. The special ZX0 pressure relief system eliminates all risk to human safety in cross-cuts in the event of hot gases caused by an electrical arc.

Suitable protection

For suitable protective equipment, ABB has delivered more than 400 REF542plus feeder terminals – a single device for all applications. ABB has developed the REF542, a protection device that has been successfully tested tens of thousands of times, in partnership with our customers. The multi-stage remote protection enables rapid detection of fault types and locations, which makes it possible for any faulty parts of the network to be selectively switched off. And the remote service function that comes with the REF542plus allows stored programs and protection data, not only to be queried remotely, but also to be corrected and completed.

“Only one of the 42 meetings we’ve had over the years as part of this major project could be called a crisis meeting”, Hunger and his team say looking back. The open, honest communication between the suppliers and customers has greatly contributed to the success of implementation. “The project will only be complete when the first trains start thundering through the tunnel on a regular basis. Nevertheless, the verdict on record so far is that I’d do business with ABB again anytime”, Hunger concludes on a positive note.

Balfour Beatty Rail’s and ABB’s project teams, with the last medium-voltage switchgear delivered, in front of the north portal of the Gotthard Base Tunnel.

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