Description

TVM system: Two voltage monitors in a safety enclosure

The TVM System voltage monitors simply have to work. Space is limited in the tunnel, installation effort must be kept to a minimum, and the system must operate reliably even under adverse external conditions. The WITT TVM system has been developed precisely for this application: instead of installing two separate voltage monitoring devices for both directions of travel, you install a single, highly compact housing that monitors and reports on both directions simultaneously. The robust V2A stainless steel housing is designed to remain operational even when subjected to severe external impacts – such as rockfall or vandalism. Like the TVM component, the TVM system is also delivered pre-configured and tested at the factory: you receive a ready-to-use system for easy installation, not a kit requiring on-site commissioning.

In a tunnel, every minute counts in an emergency: maintenance staff or emergency services must be able to determine beyond doubt whether either of the two directions of travel is still live – and they must be able to do so at a single, easily accessible point rather than at two separate devices, which would be more difficult to access in the narrow tunnel cross-section. Because the TVM system combines both directions of travel in a single housing, the safety-critical check in an emergency is reduced to a single test point rather than two – a significant advantage when time and accessibility are limited. We have summarised the fundamental regulatory background to this – established safety principles for maintenance and emergency response in the rail sector – in detail on the TVM component page; it applies equally to the TVM system, but takes on added significance here due to the restricted access conditions in the tunnel.

Benefits for the business

• Easy installation: A ready-to-use, factory-preconfigured system – no on-site assembly or parameterisation required.
• Designed for use in tunnels: a compact V2A stainless steel housing, engineered to ensure continued operation even in the event of rockfall or vandalism.
• Both directions of travel, one housing: Up to two TVM components monitor both directions using a single unit – requiring less installation work and taking up less space than two separate devices.
• Safely isolated voltage ranges: Highly insulating isolation zones between the voltage ranges and between the operating and signalling voltages prevent flashover.
• One monitoring point instead of two: in an emergency, a single glance at a central unit is enough to assess both directions of traffic – reducing the time required and minimising the potential for errors compared with two separate devices at different locations in the tunnel.
• Can be extended to meet higher security requirements: Optional time-window-based synchronisation of the threshold signalling for both TVM components.

How the TVM system works

The TVM system consists of a very compact housing made of V2A stainless steel, in which up to two analogue voltage monitors (voltage signalling relays) of the WITT-TVM type are installed – one for each monitored direction of travel. Within the housing, several voltage ranges are separated from one another by highly insulating zones to prevent arcing; the internal wiring and terminals are additionally designed to ensure that there is a separate insulating barrier between the operating voltage and the signalling voltage. Each of the two TVM components operates in the same way as the standalone TVM component – in analogue mode, without an external auxiliary voltage – and signals via potential-free changeover contacts as soon as the factory-set threshold values are exceeded or fallen short of (for basic technical data, see the TVM traction voltage relay). The TVM system is supplied fully pre-configured.

TVM System Special Application: Enhanced Safety Requirements

For applications where monitoring by a single component is insufficient, the two analogue TVM components in the TVM system can be calibrated so that they signal the set threshold values within a defined time window.