Trains are such a common sight in many societies that very few people stop to think of the sophisticated infrastructure essential to the smooth running of the service. Even fewer realize how reliant the service is on electrical power. Apart from the obvious ones like the overhead gantries feeding power to electric trains, there is an entire world of other applications on the railway for which electrical power is critical: traffic management systems like control rooms, data centers, computer rooms; automatic train protection systems, such as European Train Control System (ETCS); traffic lights; level crossings; railroad points; video surveillance and communication.
Even a minor disturbance in the power supply can have a knock-on effect and result in major disruption to the rail network. More importantly, the reliable functioning of the railway infrastructure is not just a matter of convenience – it is also a serious health and safety issue.
The rail network poses a particular challenge in that, often, two separate power schemes have to be catered for, eg, 16.67 Hz single-phase and 50 Hz three-phase. ABB dual-frequency UPS systems are designed for this task and they benefit from a simple design derived from standard parts, eliminating the need for expensive customization.
Typically, ETCS power supplies, for instance, are fed from a 400 Vrms, 50 Hz generator functioning as a backup supply. three phase network with a diesel electric The diesel electric generator has a significant impact on the entire system installation cost and, because it takes up considerable space, on the system power density. ABB’s solution not only aims to remove the backup diesel electric generator (and associated greenhouse emissions and noise), but also to increase the level of redundancy by adding a battery pack.
Where an independent second mains network, for example, 230 Vrms/16.67 Hz single-phase, is available, it can also be used in the backup power scheme. An ABB dual-frequency UPS converter makes it possible to harness both networks, so the load can utilize either, or both, as appropriate. For example, if the 50 Hz three-phase line were to develop a fault, the dual-frequency UPS would feed the critical load via the single-phase 16.67 Hz line, and vice versa. In the event of a fault on both independent networks, the third energy storage option, the UPS battery pack, would provide the energy requested by, say, a control system like ETCS, thus guaranteeing zero downtime for the entire system.
Doing something special with standard products
Many customers have adopted ABB’s UPS solutions. In a recent typical implementation, for the Swiss state railway, ABB used a standard modular product equipped with two module slots, one compatible with a 16.67 Hz infeed and one with a 50 Hz infeed. The batteries, able to operate autonomously for more than 30 minutes, and the isolating transformer were integrated into the UPS cabinets, thus saving cost and valuable space. The batteries can be configured as one contiguous unit or as two separate units, one for each module. During normal operation, the load is split evenly between the two supply networks. Should the power supply of one of the modules move out of the tolerance zone, the battery will for the appropriate module will activate. If one module is defective, the other module will take on 100 percent of the load. If the power to both infeeds should fail, the modules switch to battery operation. This particular project was delivered as an integrated total solution. It included all aspects of consulting and planning, construction and comprehensive testing of prototypes, logistics, service, installation at over 300 locations and supervision of commissioning.
For further details, please download the new railway application brochure here: