The forthcoming resignalling of Cardiff station area is a large complex undertaking and Atkins invited Rail Engineer along to the project offices at Newport to learn about the latest extension planned for the South Wales Control Centre (SWCC).
The Cardiff area was previously resignalled back in 1966 with the commissioning of Cardiff power box, with standard BR Western Region Henry Williams entrance switch/exit button panel for route setting with ‘E10K’ relay interlockings, similar to that at Swindon described in issue 131 (September 2015).
The long panel was split into two sections with the left portion covering the South Wales main line from Marshfield in the east through Cardiff Central station main line Platforms 0-4 (bay Platform 5 no longer exists) to Pontyclun in the west. The right section covers the valley lines from Cardiff Queen Street through Cardiff Central platforms 6 & 7 to Penarth, Cadoxton and Radyr (exclusive).
This equipment is now life expired and is being replaced with three new General Electric (GE), Modular Control System (MCS) workstations covering the main lines, Vale of Glamorgan (VoG), and valley lines respectively which interface with Siemens Westlock interlockings.
Although the Cardiff Area Signalling Renewal (CASR) project is primarily a renewals scheme, capacity improvements are being introduced to cater for the ever-increasing passenger numbers. Today, Cardiff Central is the busiest station in Wales.
The original station layout did not provide for movements from the Down Main to Platforms 1 and 2. Thus, for example, HSTs from London terminating at Cardiff have to do so in platform 3 or 4, then run forward at the west end before reversing into platform 1 or 2 prior to departure back to the east.
This is being addressed by remodelling at the east end and the addition of new routes from the Down Main into platforms 1 or 2, thereby obviating the need for the out and back shunt move, and also freeing up platform 3 for other services. A new through platform 0 was created in 1999 for Up Main local services.
With the decline of heavy industry in the valleys and the increase in office-based businesses in Cardiff, the pattern of traffic has changed dramatically, from a procession of heavy coal trains to the docks to an intensive passenger service for commuters for which the island Platform 6/7 is no longer sufficient.
Accordingly, a new crossover at the east end allows Platform 4 to be used for Up Valley line services, whilst on the Down side a new Platform 8 is under construction. Thus, on completion of resignalling, four platforms will be available for valley services.
The CASR project embraces a wider area than that of the original Cardiff power box. The various phases are as follows:
- Stage 1 – Mar 2013 – Aberthaw & Llantwit (Bridgend Fringe);
- Stage 2 – Sep 2013 – Cardiff Queen Street to Coryton and Rhymney;
- Stage 3 – Jun 2014 – Penarth, and Barry branches to Cardiff West Junction;
- Stage 4 – May 2015 – Main line Marshfield (Newport fringe) to Cardiff (exclusive);
- Stage 5 – Dec 2016 – Cardiff Central entire station area and main line to Pontyclun; panel box decommissioned.
Stages 1-4 are thus complete and controlled by Cardiff Mainline, Cardiff Valley, and VoG workstations. The whole scheme is measured as 669 Signalling Equivalent Units (SEUs), of which stage 5 is the largest, consisting of 241 SEUs. The SEU concept is a method of breaking down a job into the hardware it contains, such as interlockings, point controls, signals and level crossings, and then calculating those into a number of SEUs. The cost per SEU is then fairly constant, and can be used to calculate the value of the whole job.
Atkins runs the project from the depot at Newport, shared with Network Rail. There are 81 staff involved in signalling design, although these are based at Swindon, Birmingham, Glasgow, Plymouth and Bangalore. Signalling construction staff number around 50, and there is a core complement of 20 testing staff, peaking at 90 for commissionings.
Who does what
The project is being carried out under a ‘Hub and Spoke’ contractual arrangement. Network Rail, acting as the principal contractor as well as the client, sits in the hub. The spokes are the tier one contractors, in this case:
- Atkins – design, management and implementation of the signalling for all five phases of the CASR project;
- Atkins – power and distribution;
- Balfour Beatty – permanent way, track, switches & crossings (S&C);
- BIRSE (now part of Balfour Beatty) – Civil engineering;
- Siemens – telecommunications.
Each tier one ‘spoke’ has its own set of subcontractors. In the case of Atkins these are:
- Siemens Automation – Westlock interlockings, Westcad workstations (Newport and Bridgend areas);
- GE Transportation (now part of Alstom) – MCS workstations;
- Unipart – lineside equipment location cases and relocatable equipment buildings (REBs);
- Henry Williams – functional (power) supply points (FSPs).
GE in turn sub-contracts Hitachi for TREsim signalling simulators for signaller training and design verification, and for TREsa Automatic Route Setting (ARS).
Atkins offered an innovative new product, not previously used on the UK network, as an efficiency saving under the CASR scheme at time of tender. Frauscher digital axle counters (FAdC) with type RSR123 wheel sensors have been installed throughout the CASR area.
Although axle counter products are common in resignalling schemes, the wheel sensor RSR123 has the advantage that it is fitted to the rail by a clamp so it can be fitted on-site in a matter of minutes since drilling the rail is eliminated. No trackside interface module is required further reducing staff time on-site, and it has a comprehensive diagnostic support system.
The clamp installation feature also provided the team with a solution for the Cardiff west station throat. A very cramped four-way divergence with eight sets of double slips, much bespoke point operating iron work in the S&C, which is not being renewed at this stage, meant that drilling the rails was not an option.
A plan was drawn up at the single option development stage (GRIP 4) for the installation of 109 track circuits in the station area which would involve a lot of rail drilling for bonding and the fitting of rail end-post insulations with a significant installation time.
There was a lot of concern about maintaining robust track circuit electrical separation within the bonding and rails of the moving point operating rods and stretcher bars.
After further consideration, Network Rail and Atkins concluded that the Frauscher axle counters, with their much smaller interference area around the head, more compact design, and clamp-on feature, was the ideal solution for the station area.
Overall, CASR uses 832 Frauscher wheel sensors (a total of about 600 train detection sections), of which 252 are in the Stage 5 area. Sensors consist of two detector coils which enable direction to be determined. A single RSR123 may act both as exit counter for the rear section and as entry counter for the forward section.
Sensors are connected into ring transmission circuits, which are linked via nodes into the Fixed Telecomms Network (FTN), communicating with IP protocol utilising Westermo ethernet switches and modems. Thus, if the system detects a fault with part of the lineside cabling, messages are automatically re-routed.
A handshake, via the evaluation boards of adjacent sensors, determines the clear/occupied status of the section which is fed into the signalling system via standard Solid State Interlocking (SSI) Track Function Modules (TFM) in an adjacent location case.
All the ring circuits are connected into the South Wales Control Centre (SWCC) where the diagnostic support system provides technicians with detailed information on the condition of all sensors and train detection status to facilitate efficient faulting.
Points and signals – ‘Plug and Play’
Many existing point operating devices will remain and be re-controlled by the new signalling with the exception that surviving older Westinghouse Type M3 point machines will be replaced. Points will be operated by a mixture of Alstom HW2000 machines, which are AC-immune DC machines for 110V operation; the comparatively recent Alstom Hy-Drive system, which was developed following a review of point operating mechanisms after the Potters Bar derailment; In-Bearer Clamp locks and conventional Rail Clamp Point Lock mechanisms, both from SPX.
New HW machines come with a set length of tail cable with a plug coupler end which should reach the cable troughing route. For existing HW machines that don’t have cables fitted with plug couplers, the machines are opened up and the existing cable replaced with a new piece of standard length, terminated at one end on the harness and the other end with a plug coupler reaching the cable route. Connecting to this, a further cable with a plug coupler on one end is terminated in the existing location in the traditional way.
Meanwhile, a new pre-measured length of cable with plug couplers on both ends is run from the cable route to the new location case. Under a possession, the cable to the existing location is disconnected, swapped with the cable to the new location and rehearsal tested with detection tests, correspondence tests, and contact break tests. When done, the cabling is swapped back to the old location. On commissioning the new cable is once again swapped back into service but this time permanently, following which all that needs to be done is a function test. For the central station area there are about 100 points being treated in this way, each of which is a separate design pack.
In fact, cables with plug couplers are used for everything as far as physically possible, including signals, AWS, TPWS and Frauscher sensors. As an example of the principle, AWS magnets come with a 25 metre lead with a plug coupler on the end. The philosophy is that the lead from every magnet should reach the troughing route within 25 metres. A pre-measured cable with plug couplers at each end connects between the plug coupler of the tail cable in the troughing route and plug coupler connection panel in the controlling location case. The latter cables are all made to measure and care has to be taken to ensure there is not too much slack as several plug couplers are connected on each plate.
Whilst this methodology involves a significant amount of accurate measurement work, the benefit is that a location case can be connected up in about an hour compared with a conventional wire-by-wire termination undertaken by an installer on his knees peeling back the individual cable cores. The pre-measured and labelled cables arrive on site on a drum, hopefully with cables wound the right way round so that male/female ends correspond on the ground!
Signals are either Unipart Dorman Integrated Lightweight Signals (iLS) for straight post signals or conventional Dorman LED for gantry mounted heads. New signal gantries are to electrification standards. Cables for gantry signal heads are measured so that the plug couplers are staggered down the side of the structure and are not bunched up. From here the measured cables with plug couplers connect back to the location case.
Complex interlockings interfaces
The Siemens Westlock interlockings for CASR consist of eight Central Interlocking Processors (CIPs). A Westlock CIP has a much greater capacity than an SSI – the eight CASR CIPs are equivalent to about 19 SSIs. However, Westlock is compatible with SSI Trackside signals, while items such as points are driven by SSI Track Function Modules (TFMs) which communicate with the interlocking using SSI data link telegrams.
Trackside Interface (TIF) units are connected to the interlocking cubicle and incorporate SSI Data Link Modules (DLMs) or Long Distance Terminals (LDTs) to enable communications with lineside TFMs via the external data links. CASR has 19 TIF areas and hence 19 data links.
The GE MCS signallers’ workstations interface with the interlocking via a Control System Gateway (CSG) which provides the protocol converter between the CIP and the MCS.
Generally, one CSG is required to link workstation to interlocking. However, Cardiff Central station is treated operationally as two separate stations – main lines and valley lines. Separate signallers will operate the two parts, replicating the segregated panel arrangement within the existing signal box. Also, there are separate CIPs for main and valley line tracks.
However, the track layout at each end of the station facilitates movements between the two portions and so the system will allow either signaller to set a route across the boundary. To achieve this, both the main and valley lines MCSs need to interface with both sets of CIPs for which, in a world first, duplicated CSGs are provided. This arrangement also complicates the data for the interlockings, Automatic Route Setting (ARS) groups, SPAD management, and signal emergency replacement groups.
To date ARS has been provided only on Stage 2 valley lines. However, come Stage 5, ARS will be live on all CASR workstations. Hitachi TREsa ARS plugs into the GE MCS.
Testing and commissioning
Much of the new outdoor equipment can be installed, set to work and tested in advance of the commissioning. Location cases manufactured by Unipart can be brought into the depot at Newport and verification (known as Mod 3) testing undertaken in a safe and dry environment.
The complexity of Stage 5 is such that four new interlocking CIPs will be brought into service but the other four CIPs of CASR, plus Port Talbot SSI, and two relay interfaces between adjoining box electronic interlockings, are affected by the changes.
24 hours have been allocated purely for the data changes, during which time the new S&C work will be progressing on the ground. Inevitably, trains will not be able to run through Cardiff at this time and a complete shutdown between Newport and Swansea is planned for Christmas 2016.
During Stage 4 commissioning, although interlockings and workstations were tested separately in advance of commissioning, it was found that, when the systems were put together, communications issues and error messages occurred. Learning lessons from this stage, an integration test centre is being set up within the equipment room at SWCC, facilitating eight to nine months of offline data testing by Atkins, Siemens and GE. A new piece of test gear supplied by Siemens contains four interlockings CIPs that enables the changes to four ‘in-use’ interlockings to be tested ‘off-line’.
A 650V AC ring main, connecting suites of location cases, is fed via FSPs which take in the supply from the electricity board. If the power goes off, a UPS holds up supply during changeover until the generator fires up and is ready to take the load. Auxiliary Supply Points include a UPS to provide a supply for a certain amount of time but don’t have a generator. Allen Bradley power supply monitors are located at SWCC.
There are three CCTV and one AHB crossings controlled by GE VHLCs (Vital Harmon Logic Controller). Although Automatic Lowering has been installed at Rhoose, it is currently not operational. There is some debate as to whether it should be used at St Fagans level crossing, given the heavy 7,500 vehicles a day that use it. A level crossing simulator enables the logic controllers to be tested offline. On the day, it is a case of plugging it all in and function testing.
Wales Rail Operating Centre
Unusually, the signalling centre featured in this article has two names. Conceived as a control centre for South Wales, the SWCC appellation appears in print on thousands of signalling schematics and wiring diagrams of the CASR project and also the previously completed Newport Area Signalling Renewals (NASR) scheme.
However, as part of roll-out of Network Rail’s National Operating Strategy, it has been decided that the centre shall control the whole of Wales plus the route via Shrewsbury linking south and north Wales. In 2013 a Shrewsbury North workstation was added to control the line between Shrewsbury and Crewe. It is likely that workstations for the Port Talbot area will be added next, and then a start made on resignalling the North Wales main line. Thus the control centre has now officially become the Wales ROC.
Thanks go to Conor Linnell, Atkins practice director, for facilitating this article and Paul Carney, Atkins senior engineering manager, for describing the technical details.
Written by David Bickell