NG Global

Remote control of heated switch points for SBB

Technically, the national Swiss railway SBB is one of the most advanced in Europe.

During winter, the extreme Swiss weather conditions mean that in over 700 railway stations, workers are on call around the clock for clearing snow or ice from the switch points to prevent them blocking.

For the SBB, the main purpose of installing automatically controlled heating systems at all strategic locations was to avoid the enormous costs for manpower. Meanwhile, hundreds of switch points have been fitted with small heaters that are powered by gas or electricity. Thanks to a complex algorithm based on data from temperature and humidity sensors, the possibility of ice of snow on the rails is detected automatically. A complex PID control system switches the heaters on, and the rapid temperature increase prevents the build-up of snow or ice on the switch points.

In each railway station, automation is performed by a TBox remote terminal unit (RTU) located in a control cabinet. Depending on the complexity and size of the station, one or more remote RM21 modules are provided as sub-stations in the field to operate and monitor a group of switch point heaters. Via a local RS 485 network that can be up to several kilometers in length,) the sub-stations handle the measurement and control tasks of the individual heating systems. Despite the severe electrical interference that occurs each time a train passes, both automation and communication remain perfectly stable. Each sub-station has its own operating console for possible maintenance purposes and manual control.

All the data (correct sensor operation, set-points, outside temperature, gas pressure, present consumption, etc.) from the TBox-RTUs are transmitted to a central station using WIZCON SCADA software and an Ethernet with TCP/IP protocol. This WAN (wide-area network) of the SBB uses fiber optics and 10Base-T communication. For redundant safety, each TBox-RTU has its own PCMCIA modem that can be directly addressed for maintenance or control purposes, but also in order to send e-mails or alarms to GSM systems.

For the SBB, the main advantages of the TBox solution are:

• An extremely fast return on investment thanks to high savings in electricity and gas consumption by the fully controlled heating system;

• Complete remote control of each railway station, eliminating the need for local personnel to clear the switch points;

• Only one device for communication and remote control of the heating systems;

• Utmost reliability of the hardware and software components in an extremely harsh environment (high electrical interference, low temperatures);

• Local data logging of events and for recording energy consumption, temperatures, and operating time of the equipment

• Automatic alarm signaling to specialized maintenance personnel in charge of the switch points;

• Just-in-time filling of the gas tanks;

In the railway station of Zürich, more than 8000 I/O's are remote controlled by TBOX ! This concentration cabinet has 8 TBOX in Ethernet network, each TBOX has his own RS485 sub-network to up to 47 remote I/O modules RM21.