30.08.18
Building resilience on the Brighton Main Line
Source: RTM Aug/Sept 2018
SPONSORED INTERVIEW
Andrew Swanson, head of signal engineering at Kier Rail, talks about a key rail signalling project for his team.
The Brighton Main Line (BML) is one of the most congested commuter lines on the UK railway network. It connects Gatwick Airport and the south coast with London, and is used by 300,000 people every day. A quadruple track for much of its length, it reduces to a double-track section between Balcombe Junction and Haywards Heath.
The signalling on the line was commissioned in the 1980s, with the northern section (Victoria signalling centre) between 1982 and 1984 and the southern section (Three Bridges ASC) between 1984 and 1986.
For many years this section had been operating a simplified bidirectional signalling system during periods when only a single track was available. This allowed only one train in the reverse direction approximately every 10 minutes. Section capacity was further reduced by trains stopping at Balcombe station.
Passing traffic in both directions meant the capacity was at best three trains per hour either way. In addition to signalling operating issues, the poor condition of Balcombe Tunnel meant that major works would be required. Solutions were needed to keep the service running smoothly during periods of ‘reverse’ working. The nature of the line, with many rail connections on flat junctions, means it is very susceptible to delays.
Train operations required a minimum of six trains per hour in each direction utilising one line; in 2015, Kier facilitated this by providing full bidirectional working between Balcombe Junction and Haywards Heath. This resulted in a significant operational improvement on the BML under perturbed working and was a welcomed success.
This visible success had a hidden technological secret which laid the cornerstone for the future Haywards Heath to Brighton section of line: the Siemens Westplex System.
The Westplex equipment is a safety-critical microprocessor-based data transmission system designed to interface directly with signalling relays. It was originally intended as a replacement for Vital Reed FDM equipment currently in service. However, as Westplex meets safety integrity level (SIL) 4, it offers much more and provides a positive impact on sustainability, maintenance and train operations.
Westplex comprises a family of modules, which can interface to many types of signalling systems. The entire system is based on easily replaceable modules that are extremely robust and designed for the rail environment. Westplex can be installed in conventional location cases with no need for any special cooling requirements. One of the key features of Westplex is that the system configuration data is stored in an EEPROM within the interconnecting connector. This allows the maintainer to replace modules without the need for the downloading/configuring of site-specific configuration data. This has the positive benefit of faster fault rectification time and reduces spares holding requirements.
Due to the distance between Preston Park and Haywards Heath interlockings, there are several long line signalling sections which use a large number of repeat circuits involving additional relays and power supplies. This in turn requires a significant number of lineside main signalling cable, typically several 48core cables. These circuits are therefore vulnerable to failure due to the cable condition and the large amount of equipment in each circuit.
Cable faults are time-consuming to repair and test, involving large teams of staff to get long and heavy cables to site, install, test, commission, and recover redundant cables where necessary. Having long cascading relay line circuits is not ideal and is one of the weak links in any signalling system.
By installing Westplex, all the lineside main cable is replaced with a 6pr telecoms cable. Signalling controls and indications are transmitted safely via the Westplex transmission system using the telecoms 6pr cable. The existing lineside infrastructure is maintained and controlled from the Westplex modules. In the event of cable failure, diversity is provided through the FTN system.
Kier was awarded the project to install the Westplex system to replace all the main lineside cables in the long bidirectional section between Keymer Junction and Preston Park. The opportunity will also be taken to simplify the remote-control systems in the area by moving existing FDM functions to Westplex.
The original scheme design relied heavily on the use of reed track circuits and section loops. This equipment is now obsolete, as the loops were becoming unreliable and causing signal aspect reversions and consequent delays. The project will replace the reed track circuits and loops and double rail AC track circuits between Haywards Heath and Preston Park with the modern EBI 200 track circuits.
The old-style filament signals between Haywards Heath and Preston Park will be replaced with modern LED equivalent type. These were chosen for their increased reliability, ease of maintenance, and lower fault attendance. Standardising these signal types presents a better profile to drivers.
Due to the adverse environmental conditions in Clayton Tunnel, provision will be made for the future implementation of dual detection using axle counters.
All 650V location equipment and cabling will be replaced with new incoming feeding arrangement and FSPs for nine feeders between Haywards Heath and Preston Park. Minor power works will be completed on the Haywards Heath North feeder.
All the above improvements on the BML, especially completing the introduction of Westplex between Haywards Heath and Brighton, will provide a more resilient signalling system for years to come.
At Kier, we have a long history in the rail sector with a specialist team of signalling engineers. Our design solutions for each project always reflect what is best for each location to ensure the client’s needs are met by increasing the asset life and providing value for money over the long term.
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