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Electrical excellence – The importance of attention to detail

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Amongst all of the other resignalling schemes that are underway at present – Cardiff, Bristol, North Wales, Derby, Norwich Yarmouth Lowestoft, Waterloo, Birmingham and Cornwall amongst others – there is one that is often overlooked.

Siemens Rail Automation was awarded a contract by Network Rail for the Victoria 2: Sutton to Wimbledon resignalling project in August 2016. The project called for the decommissioning of life-expired relay interlocking systems at Sutton, Mitcham Junction and Wimbledon, and for them to be replaced by two new Siemens Trackguard Westlock computer-based interlockings, at Sutton and Wimbledon.

All the signalling equipment between Sutton and Mitcham Junction was to be completely renewed, with signalling control being moved from a conventional NX panel at Victoria Area Signalling Centre to a Siemens Controlguide Westcad control desk at Three Bridges Rail Operating Centre (ROC).

The project also included the complete renewal of the CCTV level crossing at Mitcham Eastfields with axle counters replacing all conventional track circuits for train detection.

Enhanced negative bonding

As part of this project, Siemens asked AM1 Projects to carry out the design, installation and commissioning of the enhanced negative bonding that would be required. AM1 Projects, based in Chatham, Kent, had previously undertaken similar projects in Control Period 5 for Network Rail on the East Sussex, Poole to Wool and Victoria Area Phase 2a Re-signalling Schemes (Streatham).

Conversion of signalling track circuits to axle counters requires the existing traction negative bonding to be changed to enhanced negative bonding in accordance with CRE (conductor rail equipment) work instructions. Using the signalling scheme plans, AM1 Projects designed the enhanced negative bonding for the different areas of the scheme in house.

As much of the bonding as possible was installed in advance in preparation for the conversion to axle counters over the 2018 Easter weekend commissioning. This included renewal of DC negative feeders at substations and TP (track paralleling) huts.

During the commissioning weekend, AM1 Projects permanently connected the new enhanced bonding and recovered redundant impedance bonds and cables.

E&P Work

Some of the traction locations on the scheme were classified as ‘hot sites’. This was nothing new, as AM1 Projects had previously provided design and construct solutions for ‘hot sites’ throughout the South East of England for Network Rail Route Maintenance and Investment Projects, having worked at over 20 substations over the past three years.

Sutton substation, a critical location for the scheme, was a classified ‘hot site’ and AM1 Projects was contracted to design and build a solution to declassify the site, enabling the access restrictions at the location to be lifted.

The chosen solution used earth interlinks between the 11kV and 33kV substation buildings. Existing earth legs were refurbished and several new earth legs installed in a no-nonsense solution that resolved immediate traction location earthing issues. This enabled Sutton substation to be declared a cold site and access restrictions were lifted, allowing work to be carried out within the substation and surrounding area.

AM1 Projects was also contracted to design and renew the point heating trackside components at various points on the scheme and to carry out the conductor rail alterations that would allow the new signalling equipment to be located.


Winchfield substation

A little further out from London, at Winchfield station in Hampshire on the line between Waterloo and Basingstoke, a DC contactor failed, causing damage to the adjacent DC switchboard. As a result, train services were disrupted, so Network Rail instructed AM1 Projects to design, install and commission two new DC Modules into service at Winchfield substation on a tight timetable.

With the challenging timescales, the new DC modules had to be located near the existing substation. With extremely limited space available, AM1 Projects designed the layout and configuration of the DC modules, concrete module bases and DC and LV cable routes to suit these location restraints and enable construction to start.

DC cables and switchgear

AM1 Projects was instructed to double-up the DC track feeder cables for the four-track layout and designed the routeing through tracks using cable management sleepers.

The four DC interconnector cables from the original Bournemouth Electrification 2MW H&H traction rectifier set had been damaged beyond repair when the DC contactor failed. To enable connection of six new 1,000sq mm aluminium cables to the existing rectifier output busbar, AM1 Projects proposed the use of 500sq mm copper LUL cable and lugs, working with suppliers to produce bespoke size-reducer connectors and busbar lugs to enable this interface, which Network Rail approved.

Network Rail provided two DC Modules and AM1 Projects re-configured the DC busbar to enable connection of the supply from the existing rectifier to the eight electrical sections.

A new DC interface marshalling cabinet was installed, to enable connection from the new DC modules to the existing GEC supervisory control equipment and HV switchgear, and the existing LV supplies were also modified to enable LV supply to the new DC modules.

Construction and commissioning

The site was cleared and concrete bases and cable routes constructed in time for delivery of the two DC Modules in an abnormal possession. AM1 Projects delivered the modules to Winchfield and used a Kirow crane to manoeuvre the 11-tonne modules into position.

With four weeks to go, connection of the DC modules commenced in preparation for the commissioning of the DC switchgear and cables during a 52-hour possession.

AM1 Projects had pre-commissioned the DC modules at a Network Rail storage depot prior to delivery to Winchfield. High-current testing was carried out on the DC circuit breakers on site before commissioning, to ensure there would be no control or equipment problems later.

The supervisory control and protection wiring was installed and pre-commissioned with Eastleigh ECR (electrical control room) before the planned possession.

The DC track feeder cables were successfully installed and commissioned into service during the 52-hour possession, which enabled train service restrictions to be lifted after delays over just 12 weeks.

Finally, the DC interconnector cables were connected to the rectifier and DC modules after the possession and were commissioned into service once the damaged rectifier protection equipment was repaired.

Both of these projects, at Sutton and at Winchfield, benefited from the collective experiences of AM1 Projects, gained within the rail industry over many years.

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