With an approximate length of 57 km, the Gotthard Base Tunnel will be the longest tunnel in the world for decades to come. The client, AlpTransit Gotthard AG, has awarded the contract for the implementation of the railway infrastructure systems to Transtec Gotthard,
the general contractor. As subcontractor, ABB was allocated the task of putting into place a medium-voltage supply system for the tunnel’s infrastructure. Numerous ABB transformers will also ensure that the 50 Hz grid is supplied the power it needs.
For the operation of the ventilation system, one of the most important sub lots of the tunnel project, the client has appointed a consortium consisting of ABB and the German TLT Turbo GmbH, the company behind the largest tunnel ventilation system ever built.
The challenge for the customer
The difficult ambient conditions and harsh environment are major challenges for Gotthard. The 50 Hz power supply grid in the tunnel is exposed, for example, to salt deposits, brake dust, soot particles, and abraded material from the rails and contact wires, but has to be maintained at minimum cost at the same time. In addition, there are strong pressure fluctuations of ±10 kPa, because the trains pass the connecting galleries at a speed of up to 155 mph.
The power supply system must also operate safely and reliably, otherwise rail traffic might be interrupted. In the event of a fire, the ventilation system must guarantee enough fresh air in the emergency stop stations and targeted smoke extraction for maximum personal safety.
For the 50 Hz tunnel infrastructure, ABB will use type ZX0 gas-insulated medium-voltage switchgear bays. The 16 kV switchgears are extremely compact. Linking up to six bays to a fully functional switchgear block makes it possible to replace the switchgears completely
within a short time frame, in case of malfunction. In addition to the standard gas-tight welded high-voltage section, the local control cubicle has been designed according to Protection Class IP65 in order to prevent any ingress of dust or water jets.
More than 500 REF542plus Feeder Protection and Control devices with multi-stage remote protection ensure optimal security over the entire length of the tunnel. In order to ensure optimum selectivity and stable security of supply in a grid at the same time, fault types and locations must be quickly detected and transmitted to the tunnel control system. Stored programs and protective data can be accessed remotely via an Ethernet LAN thanks to a remote service.
Several hundred ABB vacuum pressure-impregnated dry-type transformers ensure 50 Hz power supply in the tunnel on top of that in the emergency grid. The transformers are characterized by low rate of loss and high efficiency, have a high overload protection, short-circuit strength and require no maintenance for years. ABB is also supplying all of the dry-type and oil transformers that are needed at tunnel entrances in the buildings and to serve the 50 Hz power supply grid.
The ventilation system has a redundant design and therefore meets the exacting safety requirements for tunnels, ensuring energy-efficient operation. ABB is supplying medium and low-voltage distribution, including traction transformers and converters (ACS1000) to operate the ventilation system, as well as low-voltage components (switching devices and soft starter) for the 24 jet fans at the tunnel portals. Also included in the delivery are the AC800M control system, programming and communication, and the instruments and sensors of the entire ventilation system.
Contribution to a project of the century
ABB has previously supplied the drive system with an ACS 6000 and a synchronous motor for the intermediate heading at Sedrun, and has transported the excavation equipment, building materials, personnel and machinery. Also in Sedrun, ABB has
installed a pump system, including electrical installations and automation technology, which pumps out accumulating water 2,788 feet upward.
The tunnel will enter into operation sometime around 2017. When it opens, as a part of this historic project, ABB’s components will assist in the safe conveying of millions of passengers for decades to come.