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 realise 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.