800xA control system for Norra Länken road tunnel in Sweden

More than 14,000 objects controlled or monitored, including doors, mobile phones, cameras, fire alarms, traffic signs and ventilation

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In this massive project, ABB has delivered the tunnel's heart and brain - 36 kV switchgear to power the entire underground system, and a unique 800xA control system tailored for large tunnels

Reducing traffic in central Stockholm

The basic idea of building Norra Länken (the Northern Link) is to reduce traffic and thereby get better environment in central Stockholm. Norra Länken tunnel is also a prerequisite for the construction of the new districts Hagastaden and Stockholm Royal Seaport.

But this road, which shortens both the queue and driving time, benefits not only Stockholm inhabitants. It also has a connection to Värtahamnen and Frihamnen, the country's main ports for goods and passengers travelling to the Baltic states, Finland and Russia.

The 13 km tunnel between Karlberg and Värtan was blasted, dug and cut with diamond wire and all soil and rock transported away would fill the Stokholm Globe arenas three times. It has cut its way as a scalpel over and above existing tunnels.

Main facts

Industry	Roads and tunnels infrastructure
Customer	Tunnelentreprenad
Country	Sweden
Solution	System 800xA control system with 38 AC 800M controllers 6,280 S800I/O channels 6 operator work stations 2 engineering stations

Redundancy built into a road tunnel

On a typical weekday, 100,000 cars are expected to pass Norra Länken, which of course makes tremendous demands on safety and technical solutions.

"The redundancy built into a road tunnel has the task of ensuring that there is always access to information about what is happening there. If something turns wrong, there should be a back up. You should be able to view the situation through the cameras, shut off the tunnel, change the signs, send messages and so on", says Urban Wiklund, Goodtech in charge of systems installations for the construction company Tunnelentreprenad.

300 automatic activities in case of an accident

When a truck caught fire in Södra Länken (the South Link) in June 2008, the following happened:

The tunnel was closed off , as all the bars dropped down. Road signs in that part of the road got changed to lead the traffic out. The opposite direction lane was closed off to make way for the emergency services.

Tunnel ventilation was shut down and minimal smoke ventilation got started instead. The lighting got increased and guidance lighting lit. Information sign with "Evacuate the tunnel" was lit, a pre-recorded message was broadcast on the FM band, and a pre-recorded evacuation instructions were played through the speakers of the relevant parts of the tunnel.

The accident started a total of about 300 automatic activities. In Norra Länken's new tunnels, the ABB 36 kV switchgear secures the availability of power supply and 800xA control system ensures that all these activities are carried out.

A total of more than 14,000 objects are to be controlled or monitored, including doors, mobile phones, cameras, fire alarms, traffic signs and ventilation. And all of this is fully automated. For example, if a car stands still somewhere, the system will detect this, it send an alarm and everything can be supervised via the cameras.

15 independent operation areas

The tunnel section of Norra Länken is divided into 15 different areas of operation, to be able to function independently of each other. They are all controlled by the respective local 36kV substations with built-in redundancy. The gas-insulated switchgear has two incoming lines and is approved for installation in areas without pressure relief, which in this case means rooms interspersed in the mountains.

Let's say that a fire manages to beat out the redundancy of an operations area. Then we can still send out messages, shut down and control the the affected area traffic through the neighboring areas - or through the central process control unit. "It's like 15 small self-functioning pieces of a cake. If a fire starts in a tunnel, it can burn substantially. It gets hot very quickly in a tunnel and it is important to still have control over it in case of fire."

In case of an accident, ABB 36 kV switchgear secures the availability of power supply and 800xA control system ensures that all automatic activities are carried out

One integrated system, easy to handle and engineer

Norra Länken has a fiber optic cable in the ceiling, measuring the temperature at every meter. The cable is connected to System 800xA that controls the fire suppression system with around 200 valves that can be opened, spray water and reduce a fire to facilitate for the fire department.

“The main difference, compared to Södra Länken, is the fact that we have installed a DCS system (Distributed Control System). With help of ABB’s substations and the control system we have created an integrated system, which is easy to handle and engineer. Södra Länken has a solution that really consists of a number of smaller systems. If you need to make changes, you’ll have to make them in many different places instead of a single one as we have it now“, says Urban Wiklund, Goodtech.

Urban Wiklund, Goodtech in charge of systems installations for the construction company Tunnelentreprenad.

Project execution details

Product solutions

Via the company Tunnelentreprenad, ABB has leveraged 17 substations – 36 kV for a safe power supply – and a uniquely adjusted 800xA system for control of the tunnel’s different safety functions.

System integrator

Tunnelentreprenad has been the system integrator and been in charge of the technical system installations in the tunnels.

Value provider

Goodtech, Authorized Value Provider for ABB, has on behalf of Tunnelentreprenad and in cooperation with ABB adjusted the 800xA control system for tunnels.