St Brides To Canton Independent Feeder

About the project

Enable Infrastructure (formerly BCM Construction) were contracted as the Tier 1 Principal Contractor to provide independent feeder cables in South Wales as part of the Great Western Electrification Programme (GWEP). GWEP, which began in 2010, has been a landmark programme for Network Rail, with carbon reduction among its key drivers. 

Independent feeder cables such as those required for this project extend from National Grid Supply Points to remote Auto Transformer Feeder Stations (ATFS) – in this instance, from the Bulk Supply Point (BSP) located at St Brides ATFS near Newport to the remote ATFS at Canton in Cardiff.  

Enable Infrastructure successfully designed the new 15km, 25kV high voltage independent feeder (8501) under GRIP 5 (stage 5, ‘detailed design’, of Network Rail’s Governance for Railway Investment Projects). Design support came from Enable Design (another company in the Enable Group, formerly Equate Design). 

We then self-delivered, with Enable Power Systems teams successfully installing, testing and commissioning the feeder. The integration with Enable Design added value in the construction phase by facilitating engineering efficiencies. 

The Welsh independent feeder cables distribute bulk power at 50kV without the requirement for the contact system to be energised. The independent feeder cables are operated as a 2-phase, +25kV, -25kV supply, switched by double-pole switchgear at both ends. Neutral is provided by the common bonded AC traction return earth. Our Enable Power Systems teams conducted the final pressure test over one weekend, allowing Network Rail to energise the feeder and determine through soak testing that the application could sustain the continuous load. 

Among the innovations Enable Infrastructure successfully introduced on this project was the use of a new link box. The old link boxes used were of the 3-phased buried type and were not maintenance-friendly. Our 2-phase Link Box is not buried and allows better access for maintenance. 

Drawing on the experience of our Enable Power Systems team, we also built efficiencies into the design by introducing surge voltage limiters at every 3,600m, instead of 1,000m, thus reducing both maintenance requirements and the overall cost. 

In addition to the electricals work, Enable Infrastructure were responsible for the civils scope of the installation, including all associated construction of the haul roads providing access to the St Brides ATFS substation site.  

As a result of engaging with the customer and obtaining feedback through using the PRISM framework during this project, we gained vital knowledge of the Network Rail team. We are now making use of this knowledge on subsequent projects.  

We invested in training and skill development for our own staff during the project and have subsequently successfully retained these highly competent personnel – another ongoing benefit of our involvement.  

The challenge

The need for several contractors to deliver projects collaboratively as part of the wider GWEP programme. Our project took place simultaneously with the installation of overhead line equipment (OLE) by others: the installation of the catenary wiring meant we had only limited access throughout the length of the route. 

The solution

We undertook detailed, integrated planning of the delivery of the project. Since we had to work around new piling and stanchions, both the design and the installation were planned to include co-ordination with other contractors and the integration of respective methodologies. To overcome the constraints, all cables were installed using Road Rail Vehicle (RRV) working between OLE team worksites. Network Rail benefited from this strategy, as we required less interface with the OLE team mitigating the programme integration risk between projects.  

Enable Infrastructure provided a dedicated access planner to assist with Network Rail’s planning of possessions. 

The deliverables

The installation consisted of:    

• 6,188m TTS 200 ground route & 6,585m Arco raised route post route 
• 4 x under RRAP crossing; 3 x under track crossings; 1 x over track crossing gantry 
• 29,900m 1-core 630mm² cable 
• 66 x inline joints; 34 x shield break joints; 19 x link box installations & surge voltage limiters; 19 x spider plates 
• 118 x sheath testing; pressure-testing; associated bonding; Form E commissioning.