C2C - designing a UPS solution

14 January 2021
Image of a rail traffic control light on green.
When interruptions to the signalling power supply on the C2C route in Network Rail’s Anglia region became unacceptable, Amey Consulting was tasked with designing a UPS solution

The C2C line, a busy commuter route from Essex into London, was experiencing interruptions to the signalling power supply, creating problems such as signal blackouts and SPADs (signals passed at danger). The Network Rail route asset manager (RAM) for the Anglia region asked Amey Consulting to design a UPS (uninterruptible power supply) solution to regulate the current and manage sudden drops in power.

Electricity for railway infrastructure is supplied from a distribution network operator (DNO) via principal supply points (PSPs), where the supply is converted to the 650V distribution voltage used by the railway. For safety reasons, as well as meeting customer service targets, it is clearly important that power to the signalling is continuously maintained. However, the supply from the DNO in the C2C region is notoriously unreliable, and it was decided the best way to regulate the current was to retrofit AEG Protect 1.M UPS units into PSPs at 10 critical sites.

Amey’s bespoke signalling power analysis tool was used to model the PSPs, from the electrical source to the point at which the supply enters the feeder network. The biggest challenge was the age of the infrastructure. Brand-new equipment was being connected to old equipment, which created issues around the interfaces. The situation was exacerbated by the client’s stipulation that the existing PSP architecture should be retained wherever possible. The designers had to model numerous scenarios to determine that plugging in the UPS units would work as intended, without causing new problems.

Although not contractually required to do so, the Amey designers carried out site visits to the PSPs to check that the technical information supplied was accurate and to fill in any gaps. It was important to ensure that the design would work in practice, which involved close collaboration with AEG, Network Rail’s maintenance team, Amey’s own civil engineers, and the Amey Inabensa joint venture team responsible for the installation.

It was inevitable that issues would arise during the installation process. For example, it was discovered that a manual bypass switch was sealed within the AEG unit and could not be accessed without dismantling the box. Following discussions with AEG the unit was upgraded to include an external switch, and Amey’s design was amended to incorporate the change.

The project had beneficial side-effects which were greatly appreciated by Network Rail. While modelling various scenarios to ensure plugging in the UPS units would work as intended, the Amey designers identified opportunities to improve the efficiency of the power supply system and make it safer. Local domestic equipment was reconfigured where this could increase the capacity on the signalling power transformer, while MCCBs (moulded case circuit breakers) were added to protect against faults on the feeder cables.

The nature of the task meant that Amey had to manage the expectations of various parties while producing a design that met the client’s requirements. Ultimately the collaborative nature of the project and Amey’s continuous quest for excellence produced an effective solution that not only solved the basic problem but added value to a critical Network Rail asset.