Ensuring the safety of drivers in the longest road tunnel in Poland

The over 2-kilometer-long tunnel under the Ursynów district is a critical point in Warsaw's southern ring road. It connects sections of the A2 highway from west to east forming a part of the Trans-European Transport Network. Since its opening in late 2021, all critical tunnel installations have been operating without any unplanned interruptions, reacting reliably in case of, for example, vehicle collisions.

The tunnel made in the slurry wall technology was a huge engineering challenge. This refers not only to digging the tunnel itself or avoiding collision with the 1st line of the Warsaw Metro that crossed the southern ring route. Another challenge was the technology that was supposed to ensure reliable operation of critical systems in the tunnel and thus - the safety of drivers. The most modern solutions available on the market were applied: drives, UPS systems, switchgears, and circuit breakers. Moreover, some systems can be connected to the cloud, further enhancing safety and monitoring functions.

_{Packed with technologies}

‘In the tunnel, we used various advanced technical solutions from leading manufacturers. As a result, it is one of the most modern installations of its kind in Europe. The tunnel is equipped with the latest technologies, for example, sensors measuring the concentration of toxic substances. If standards are exceeded, proper fans are switched on. Systems of monitoring, traffic control, communications, lighting, and power supply work together to ensure the safety of tunnel users. The whole system is supervised 24 hours a day by specialists from the Tunnel Management Centre’, says Maciej Wronowski from ELIN company, which was the general contractor for electrical installations.

A situation that occurred in February this year proves the effectiveness of the installed systems. There was a collision on one of the tunnel lanes. Video surveillance quickly showed that a dangerous event had occurred, and variable message signs for road traffic management were activated. Securing the lane by the appropriate services went very smoothly.

The power supply is obviously crucial in such cases. In the Warsaw tunnel, ABB's system pro E power and UniSec switchgear provide power distribution to all vital systems – including lighting, ventilation, smoke exhaust, and sound systems. They allow the tunnel to operate efficiently during rush hours and in harsh environmental conditions, constantly affected by temperature, pollution, and water. For safety reasons, the tunnel uses two independent power supplies. However, if both are to fail, ABB PowerWave UPS will maintain the full functionality of the critical infrastructure.

‘Regarding the electrical installation in such a complex project, all systems had to be designed for the specific requirements of the tunnel. This requires specialized knowledge and, above all, close cooperation with suppliers at every stage, from concept to implementation. We are glad that from the beginning we could count on the support of ABB, which has experience in this type of projects, including the construction of the Gotthard Tunnel’, says Dariusz Galas, chairman of ELTAR ENERGY, which was responsible for the delivery of power supply equipment for the tunnel infrastructure.

Plant circuit breakers provide an additional safety function in the tunnel. ABB Emax 2 analyzes the network in real-time and provides detailed information about short circuits or overloads. This allows the operator to continuously monitor and even predict failures. The functionality of the circuit breakers can be extended at any time by connecting the device to the cloud.

_{Control algorithms and drives}

One of the most important components of tunnel infrastructure is ventilation. It is also one of the key safety systems. ‘Developing a control system for such a long tunnel was an ambitious engineering project’, admits Wojciech Płaczek from Mercor, which provided the solutions needed to build, among other things, the tunnel's ventilation system. – ‘A complex control algorithm adjusts ventilation levels to time of day and traffic intensity. At the same time, such an algorithm must predict many options for smoke removal, depending on the place where exceedances occur and their intensity’.

Ventilation systems controlled by ABB drives for HVAC applications help to efficiently remove vehicle exhaust fumes from the tunnel. It obviously improves air quality and visibility. The drives also increase the energy efficiency of the ventilation by adjusting the fan speed to the tunnel needs. Additionally, in the case of a fire, the drives allow fans to start up quickly and change the airflow direction to stop smoke and toxic gases from spreading. ‘Our equipment must often respond to algorithm changes, so we chose ABB drives, which guarantee the appropriate level of performance, reliability, and flexibility for this type of critical application’, adds Wojciech Płaczek.

Importantly, the installed ventilation systems, including motors, drives, and fans are compliant with the standard EN 12101-3: 2015 "Smoke and heat control systems. Specification of powered fans for smoke and heat control ventilators (fans)”.

Mercor delivered fire switchgear for the ventilation system, which powers and controls fans and fire dampers. The designers used, among other things, 250kW drives for 6 exhaust fans, 75kW drives for 6 cooling fans, and soft starters responsible for controlling the jet fans.

This is another piece of equipment that has helped meet key safety targets. The minimum safety requirements for tunnels in the Trans-European Road Network are defined by directive 2004/54/EC on road tunnel safety. It covers such areas as ventilation and lighting systems, emergency power supply, fire protection, traffic management, providing communication and information to users as well as monitoring systems. The Ursynów Tunnel satisfied these requirements more than adequately.