Konstanz Z-Bridge provides fast connection, CITEL ensures safety and economy

The requirements for LED street lighting are often clearly described. Optimal illumination for the most economical operation, but whenever special solutions are required, e.g. lightning and surge protection in the luminaire, it becomes more difficult. This was the experience of the team of the Konstanz public utility authority, which found the ideal solution. But let’s start from the very beginning.

Lake Constance is one of the most scenic regions in Germany. No surprise then that the development of new living space plays an important role here. The district town of Constance has done a particularly exemplary job in the suburb of Petershausen in expanding the city. This was achieved, among other things, by incorporating the former warehouse and railroad premises.

For some time now, a forward-looking traffic policy has provided a generous inner-city network of pedestrian and bicycle paths, which, however, ended at a gated level crossing.

The solution was a bridge over the railroad tracks, which allows a smooth and safe transition. The planning and execution of this challenging construction project was entrusted to the Constance municipal utilities, among others. The department of planning, installations and networks for street lighting had to take various requirements into account:

1. The railroad company requires the grounding of street lighting masts.
2. The ecological concept and sustainability must be guaranteed.
3. The lighting should be durable and economical.

The planning and execution of the Z-bridge had to be based on DIN EN 50122-1, which regulates the area of electrically operated railroads.

Railroad earthing is used especially for bridges, tunnels and other structures. Electrically conductive metal parts and all other buildings in the area of the railroad line are connected to each other.

This creates a metallically separated system. A clear dividing line must be established between railroad ground and building grounding. If the system is routed separately, personal protection must be achieved by various measures. The planner decides whether the particular earthing system is laid separately or interconnected.

The special feature of railroad earthing is the widely spread rail system. This can lead to operational disturbances in the form of track return current. The traction current has a lower frequency of 16⅔ Hz.

CITEL‘s solutions for lightning and surge protection ensure that lighting is safe and economical.

The railroad earth as the main component of railroad earthing consists of rails that serve as traction current conductors. A good connection of longitudinal and transverse direction provides an increased conductivity. On a railroad earthing system, potential displacement can occur. This can lead to backflow currents into the grid of the public utilities and have effects on the electrical installations in the DNO grid.

After appropriate market analysis, CITEL was found as a partner for lightning and surge protection that could meet all requirements. Especially the requirement for short-circuit protection in the luminaire head was a special challenge, but it was solved professionally and quickly.

After intensive discussions between the municipal utilities and us, the project was completed after one year and the following products were used:

3 pcs DS254VG-300 in the distribution cabinet
30 pcs MLPX1-230L-W in the cable junction boxes
30 pcs MLPC2-230L-V/ESP2 in the lighting heads

In detail the products have the following functions:

The CITEL DS254VG-300 is a multi-pole combined arrester type 1+2+3 based on gas-filled spark gaps. It complies with the IEC 61643-11 and EN 616431 standards. The devices are particularly economical for the operator, since no line follow current is generated and these devices are free of leakage and operating currents. Remote signalling is standard on all devices and the disconnecting device is particularly safe.

The CITEL MLPX1VG-230L-W is a compact type 2+3 surge protective device designed and manufactured on the basis of CITEL VG technology. It is particularly ideal for use in end circuits such as LED lighting and meets the relevant standards. The double-insulated housing and cables have IP67 protection and are easy to install. In addition, the devices have status signalling and ensure that the mains and power circuits are separated in the event of defects.

The CITEL MLPC2-230L-V/ESP2 has integrated protection against electrostatic charge and is a type 2+3 surge arrester. It is easy to install. The connection is made via screw contacts. A signalization shows the current status. For the municipal utilities, the decision for CITEL meant that all products are optimally matched, from planning to execution. The cooperation with the local technical consultant, Andreas Kaifer, ensured fast communication and processing.

The Z-Bridge in Constance-Petershausen provides a secure connection between the old and new districts with commercial, residential and office buildings by day and night. To reach the school for example, 3,000 students use the new crossing every day.

Further information can be found at: