Western 650V Cable Renewals - meaningful carbon reduction

22 April 2021
Amey Consulting’s optioneering for the renewal of signalling power supply infrastructure included proactive use of the RSSB Rail Carbon Tool to identify meaningful carbon savings

A large number of signalling functional supply points (FSPs) along the Great Western route in Somerset and Devon had been previously upgraded by Network Rail, but there were issues around the ageing feeder cables. FSPs are safety-critical assets, responsible for converting the 650V incoming power supply to a voltage suitable for use by signalling equipment. The power supply must be reliable with no unacceptable volt drops. Amey was tasked with assessing the condition of the principal supply points (PSPs), FSPs and cabling along 74 kilometres of track, providing renewal options where necessary and producing outline designs.

The Amey Consulting team saw an opportunity not just to identify the best options in terms of cost and functionality, but to promote a sustainable and environmentally-friendly approach. Cost is understandably a high priority for clients like Network Rail, but Amey hoped to demonstrate the value of including environmental protection and proactive carbon assessments at the early design stage.

The team began with a detailed survey of the signalling power distribution system. This included ecological walkover surveys in areas marked for potential disturbance, identifying issues such as the presence of badger setts and the suitability of the habitat for reptiles, great crested newts, hazel dormice and nesting birds. A comprehensive environmental assessment was included alongside the final survey report.

Next Amey Consulting worked with the client to model different options for improving the system and managing potential volt drops, with cost analyses undertaken for each option. Initially Network Rail expected to install new PSPs as well as renew existing FSPs and cabling. Amey’s detailed modelling, however, identified options that avoid the need for new PSPs or DITAs (distribution interface transformer assemblies) and the expensive infrastructure and environmental impact that comes with them, yielding significant cost and time savings.

In line with new mandatory requirements for projects valued at more than £1 million, the team also included detailed carbon assessments using the RSSB Rail Carbon Tool. This is a web-based resource designed to help calculate the carbon footprint of rail infrastructure projects. Since the tool is relatively new and product libraries are limited, Amey took the initiative, consulting with product suppliers and construction teams to create new product carbon packages based on detailed carbon calculations.

This allowed the team to gain a realistic insight into the carbon impact of materials, including the extraction and processing of raw materials into products, machinery and fuel used during site construction, transportation of materials and products to work sites, and transportation of staff. A Resource Efficiency Workshop was also held to identify opportunities to cut down on the materials used, design out waste and introduce recycled and more sustainable products.

This process produced many positive outcomes for the client, the project and the environment. For example, the conventional method for protecting trackside cabling is to enclose it in concrete troughs. Concrete, however, has well-known drawbacks – it is heavy, requires more workers to handle it, and embodies high levels of carbon in its manufacture and transportation. The workshop identified glass-reinforced plastic as an alternative, which is not only less carbon intensive but is lighter and cheaper to manufacture, transport and handle.

This option not only significantly reduces labour and transportation costs but saves approximately 0.5 million kilos of equivalent CO2 compared to a conventional solution.

The workshop also analysed cabling requirements. A major issue on the railways is the theft of copper cables, which have a high resale value. Aluminium is currently worth around a quarter the cost of copper and is more conductive. Replacing copper cables with aluminium wherever possible is not only cheaper and more efficient, but discourages thieves, producing another win-win for the client.

The project was completed on time with the handover of detailed designs for the construction and commissioning of 83 kilometres of new signalling power feeders, 57 kilometres of new cabling and several Class II FSP upgrades.